Abstract

In the fireworks making process extremely easy to occur.The dust exceeds the standard and, slightly carelessly, will occur the explosion, causing human casualties and huge economic loss.

The problem has been bothering the fireworks industry, which also always restricts the development of itself, is considered to be risk huge industry, young people don’t want to join, practitioners have 45 years old, now faces the situation of the industry and the absence or.

Although some parts of fireworks making have realized mechanical and automatic production, the efficiency of is low,the process is not standardized, and it is not safe and reliable enough.This paper proposes a safe and controllable process of small dust so that all links of are seamlessly connected and controllable. The specific work and achievements are as follows:

(1） Based on the current powder fill open transport links the characteristics of dust, pollution bigger, the store USES the oxidant, the reductant, division of the initial big sheng feeder pipeline – controllers such as transportation (shipping) and ferry wait for a link, realizes the oxidant, the reductant, no leakage, no dust conveying independently of the package process, and according to the engineering mechanics properties of the material and function requirements, completed the design of the structure.

(2） To avoid the “triad trinity” of traditional artificial easily in the powder fill mixed process of the low effect, the dust concentration exceeds bid, electrification, explosion, and other issues, this paper adopts synchronous cylinder valve – Y type pipe – static mixer – 2 levels of the vibrating screen/aggregate bin, implements the mix uniform consistency, and according to the engineering mechanics properties of the material and function requirements, completed the structural design of the components and power element selection design.  

(3） Based on the current powder fill more open points in the process of powder of dust explosive, uniform consistency, pollution, poor characteristics, this paper designed a feed through the central tube – dial – points of material scraper coneporous dislocation rotating disc tremie pipe and other components, implements the powder uniform consistency, and accordance with the requirements of engineering mechanics properties of the material and effect, finished parts, holes, and hole and connecting pipe of continuous seamless and smooth cohesion and dynamic element matching selection design.

(4） The filling of the traditional manual work to overcome the fireworks powder in the feed, mix powder, powder time-consuming, beats can’t continuous characteristics, this paper designed a software, accordance with the requirements of operation control and effect, can independently complete the powder fills the conveying and mixing powder, powder of time allocation and process control.

(5） Multiple links characterize the mechanical and automatic production of powder filling, complex in grasping the beat, and limited space. In this paper, the structural parameters and process parameters of each link and component of the whole line are adjusted, matched, and optimized through experiments to ensure the safe and efficient operation of the whole line.

Keywords: Fireworks: powder filling, Structural design, Electrical control, Automation

Chapter 1: Introduction

1.1 Research Objectives and Significance

The history of fireworks and firecrackers in China can be traced back to the Spring and Autumn Period and the Warring States Period. Fireworks and firecrackers belong to the traditional crafts industry and play an indispensable role in national celebrations and important festivals [1]. After decades of vigorous development and technological breakthroughs, hundreds and thousands of varieties of fireworks have emerged, with a faster cycle of new product updates. Fireworks bloom with magnificent brilliance in the night sky, possessing a profound historical appeal and dazzling beauty, and are loved by people worldwide [2-3]. The unique colors of fireworks are widely applied worldwide [4]. With years of technological progress, the fireworks and firecracker industry has become an important pillar industry of China’s national economy, and fireworks are now sold in various countries around the world [5]. According to statistics from relevant departments, over 700 fireworks making enterprises are distributed in Hunan, Jiangsu, Jiangxi, Guangxi, and other regions in China. Among these regions, Hunan and Jiangxi have the largest production volume, producing a total of approximately 20 million boxes each year, accounting for 80% of China’s total fireworks making[6-7].

The production of fireworks mainly involves gunpowder, which is used for burning or producing sound through the explosion. Gunpowder is one of the Four Great Inventions of ancient China and is a source of pride for the Chinese nation. The appearance of fireworks and gunpowder has created countless splendid histories for the world’s development [8]. The production process of fireworks cannot be separated from the incorporation of gunpowder. Many accidents occur during the manufacturing process of fireworks, and the production involving gunpowder has a dual nature [9]. Gunpowder is an indispensable raw material, but slight negligence can lead to an explosion. According to investigation reports, between 2011 and 2014, there were more than 40 serious accidents in China’s fireworks and firecracker industry, resulting in the loss of 233 lives. The main cause of these accidents was the illegal operation of fireworks and firecrackers. The peak season for fireworks is the fourth quarter of each year, which is also a period of frequent accidents. This magnificent art of fireworks brings joy to people but also inflicts unforgettable injuries. The actual manufacturing process of fireworks has inherent risks of combustion and explosion, and even a slight carelessness by the workers can trigger fire and explosion accidents, ranging from minor fires to casualties. Especially in production and processing, new workers who perform incorrect operations, violate operational norms and procedures, and fail to carry out corresponding pre-processing preparations increase the possibility of accidents. According to statistics, These parameters account for most accidents [10].

However, the causes of accidents in the fireworks production process vary. Firstly, China’s fireworks and firecracker enterprises are mainly concentrated in remote mountainous areas, with scattered workstations and imperfect industry standards and specifications. Private enterprises account for most accidents and the most serious ones [11]. Secondly, the fireworks and firecracker industry comprises small and medium-sized enterprises, mainly producing mid-to-low-grade fireworks. Most of the production is done manually, resulting in a high density of personnel. The education level of most employees is not high, and they lack basic safety awareness, thereby increasing the risk in the fireworks production process. Fireworks and firecrackers belong to a special and hazardous industry, and ensuring safety in production is the top priority [12-14]. Therefore, it is common to see the words “safety measures” in fireworks and firecracker enterprises. However, “safety” cannot be guaranteed one hundred percent, whereas the burning and explosion of guns.

Currently, in producing fireworks and firecrackers, only a single process has been mechanized, but the automatic filling of explosives has not been achieved. Suppose the fireworks and firecrackers industry adopts fully automated production methods. In that case, it will fundamentally solve the difficulties in labor, greatly reduce labor intensity, reduce accidents, improve the standard of fireworks displays, lower the cost of fireworks production, ensure safety during the production process, and avoid dangers faced by workers during production. The automation of fireworks production is a major trend in the 21st century. The future’s main direction is designing and developing more automated fireworks packaging systems and mechanized production equipment to free up labor and achieve green and sustainable production [18]. Through the research of this project, the risks associated with the filling process of fireworks explosives will be systematically addressed. Through mechanical automation, the entire process will automate high-risk processes such as delivering, mixing, and separating explosives, eliminating the need for human involvement and avoiding accidents such as combustion and explosions during the mixing process. It ensures the grade of fireworks and firecrackers, reduces losses, improves production efficiency, and makes the fireworks production industry for green and sustainable development with profound social significance.

We propose a revolutionary approach focusing on powder filling to address these challenges. Our innovative solutions include the following:

1.   Dust-Free Conveyance: Independent transport of oxidants and reductants, ensuring no leakage or pollution during transportation.

2.   Uniform powder Mixing: Utilizing synchronous cylinder valves, Y-type pipes, static mixers, and vibrating screens to achieve consistent and safe powder mixing.

3.   Seamless powder Distribution: Designing components such as central tube feeds, rotating disc scrapers, and dislocation tremie pipes to ensure uniform powder consistency and smooth cohesion.

4.   Streamlined Automation: Introducing software for controlled powder filling, eliminating manual work and enabling efficient powder conveyance, mixing, and process control.

5.   Optimal Production Line Efficiency: Adjusting and optimizing structural and process parameters to enhance the overall efficiency and safety of the line.

By implementing these groundbreaking solutions, the fireworks industry can mitigate dust-related risks, improve consistency, and foster growth and innovation.

1.2 Development History and Current Situation of Fireworks Production Machinery

1.2.1 Development History

Fireworks and firecracker production machinery originated in the last century. China’s fireworks and firecracker industry has developed from being led by township enterprises in the fireworks and early 1980s to being dominated by private enterprises today. It has evolved from manual manufacturing that has existed for thousands of years to the use of simple manufacturing tools in the 1970s and now to the large-scale use and research application of machinery.The first successful inventions were the fusing and rolling machines, which were successfully promoted and applied in enterprises. Later,paper-cutting machines, fully automatic paper-cutting machines, tube-cutting machines, bottoming machines, pill-pressing machines, shell-pressing machines, drilling machines, fuse-inserting machines, fully automatic whipping machines, and packaging line machines [19-20] appeared successively, sparking a revolutionary change in the fireworks and firecracker industry. 

In the fireworks production process, dust exceeding safety standards can lead to explosions, casualties, and economic losses. However, the industry has lacked effective dust control measures, hindering its development and attracting young talent. Existing production methods lack consistency, safety, and efficiency.

1.2.2 Current Research Status

In China, during festivals and celebrations, fireworks are often set off to express joy and happiness [21-22]. Currently, only a few researchers or design units are optimizing and improving fireworks and firecracker production machinery [23], and some progress has been made, but the pace is still relatively slow. With the increasing attention of the general public to the fireworks and firecracker industry, China has been increasing its research investment in fireworks and firecracker machinery. A series of fireworks machinery has emerged and been put into actual production. First, the rolling machine, the first type of fireworks machinery, was developed for the rolling process and achieved wide promotion and successful application in fireworks production enterprises. Then, paper-cutting machines, pill pressing and loading machines, fuse-inserting machines, tube-cutting machines, fully automatic weaving and tying machines, through-hole machines, and others [24-25] were developed, causing a significant breakthrough in the fireworks and firecracker industry [26]. As a major fireworks producer, China needs to learn from foreign countries to apply new technologies and develop new processes [27].

In foreign countries, fireworks and firecracker production companies pay more attention to the research and development of fireworks and firecrackers. They invest a large amount of manpower and resources in in-depth investigation and research on the formulation of fireworks explosives, as well as optimize the production and processing techniques of fireworks. In the process of mixing the explosives, they achieve separation between people and explosives to increase the speed of the mixture and apply new vacuum drying technology and infrared drying technology to the drying process of fireworks and firecracker explosives, attempting to reduce the reaction time of the explosives during production. In the early 17th century, fireworks and firecracker manufacturers (and packaging machine manufacturer for automated packaging systems with efficient production process) emerged in Japan, where the raw material for fireworks and firecrackers was black powder. It was not until 1880, when a new type of fireworks and firecracker explosive called potassium chlorate was introduced from Europe that the formula for fireworks explosives was improved, and Japan began to master the production method of colorful fireworks and firecrackers. In the mid-20th century, the fireworks and firecracker industry in the United States experienced rapid development and established a group of companies. The foreign fireworks industry has shown obvious characteristics of grouping, technological advancement, and centralization. Countries like Europe and America rely on their advanced industrial technology, strong scientific and technological capabilities, and processing equipment to achieve high automation levels in production. A significant portion of the processes are fully automated, utilizing artificial intelligence and online real-time monitoring. With the continuous development of automation and control technology, the production cost of fireworks has been reduced, and an increasing number of global fireworks and firecracker manufacturers are adopting mechanical automation methods for production.

1.3 Research Progress on Fireworks Filling Equipment

Fireworks belong to hazardous materials, and even slight negligence during the production process can easily lead to explosions and cause casualties. Filling fireworks explosives in the production line (automated involves high-risk parameters such as high temperatures, open flames, dust, static electricity, and collision pressure. Therefore, the processes of delivery, mixing, and separation of explosives are high-risk procedures, and these key processes are crucial factors in determining the class of fireworks. Therefore, in the design process, the principles of explosion prevention, antistatic measures, spark prevention, and automatic control must be considered for the fireworks making line.

1.3.1 Explosion Prevention

When an explosion occurs, a sudden and drastic change in pressure in the surrounding area is accompanied by a loud noise, causing a certain degree of mechanical damage. Fireworks and firecrackers belong to high-risk industries, and even slight negligence during production can easily lead to explosions. The process of filling fireworks explosives is considered a hazardous process, and any oversight in the entire process can result in combustion or explosion accidents due to the mixing of oxidants and reducing agents. Therefore, explosion prevention measures must be implemented throughout the production process of fireworks filling. The main explosion prevention measures used in the actual production process of fireworks filling include:

(1) Eliminating the material conditions that may cause explosion hazards by storing oxidants and reducing agents in separate sealed compartments, effectively preventing the occurrence of explosive chemical reactions and avoiding explosions.

(2) When mixing oxidants and reducing agents, they are mixed in a static mixer with no violent molecular movement.

(3) Limiting the amount and inventory of hazardous materials as much as possible, ensuring that each mixing process involves a specific quantity, thus preventing the accumulation of excessive explosives and eliminating potential explosion risks.

1.3.2 Anti-static measures

Static electricity is one of the serious safety hazards in the production process of fireworks and firecrackers. Electrostatic sparks can cause the combustion and explosion of fireworks, leading to dangerous accidents. Due to the characteristics of electrostatic attraction between opposite charges and repulsion between like charges, especially with dust, it is easy for dust to aggregate, reducing the flowability of fireworks powder and causing uneven distribution of fireworks components, resulting in substandard  products. According to statistics on accidents in fireworks production in China before the 1970s, accidents caused by static electricity accounted for 6.6% of the total accidents. Therefore, fireworks production enterprises should pay attention to the hazards of static electricity and implement anti-static measures. It is important to avoid mixing and stirring chemical substances with fireworks powder to prevent the generation of static electricity. During transporting fluids and powders, friction with the pipe walls can easily generate static electricity. In such cases, measures such as reducing the flow rate and minimizing the degree of curvature of the conveying pipelines can be taken, and if necessary, increasing the diameter and avoiding vibrations can also be considered. In addition, there are other anti-static methods as follows:

(1) Anti-static grounding of production equipment. All metal parts in the production equipment that may generate static electricity should be properly grounded.

(2) Control of human static electricity. Anti-static devices should be installed at the entrances and exits of production operation rooms to eliminate human static electricity. Workers should touch the anti-static devices with their hands when entering the working area to eliminate static electricity and avoid working while charging.

(3) Increase the relative humidity of the production environment. Spraying, watering, and using air humidifiers can increase the production workshop’s environmental humidity and reduce static electricity generation.

(4) Grounded conductive rubber mats should be placed on the charging workbench.

1.3.3 Dust prevention

We all know that when the concentration of flour or cornstarch in a room is high, and it encounters an open flame, it can cause an explosion. Both reducing agents and oxidizing agents used in the fireworks production process are combustible powders. Therefore, corresponding dust prevention measures should be taken in fireworks production. The main dust prevention measures used are as follows:

(1) Sealed operation. In mechanized and automated packaging line for fireworks production, fully sealed manufacturing is adopted, and corresponding sealing devices are installed at positions where different components contact each other to prevent dust generation.

(2) Use of automated production lines. Fireworks making lines can completely replace manual operations, avoiding the involvement of workers. It not only improves safety but also greatly increases production effectiveness.

1.3.4 Issues to be addressed in mechanized production of mixing and filling fireworks

In summary, the key components of the automated fireworks mixing and filling are the transportation system, mixing system, and batching system. The following mainly explains the problems and solutions faced by these key components.

(1) Transportation system: The most important raw materials in the automated fireworks making are aluminum-magnesium alloy powder, sulfur powder, aluminum-silver powder, and potassium permanganate powder. Among them, aluminum-magnesium alloy powder, sulfur powder, and aluminum-silver powder are reducing agents, while potassium permanganate is an oxidizing agent. There are several problems in the transportation of powders:

① Storage of raw materials: Accidents of combustion and explosion may occur during the mixing process in fireworks production. Firstly, avoiding excessive storage in the raw material warehouse is important. Additionally, the fineness of these powders ranges between several hundred meshes with extremely fine particles. Excessive powder storage can lead to compression and adhesion between the powders, causing variations in powder looseness and difficulties in material discharge, resulting in compromised accuracy. Furthermore, the angle of the storage vessel for storing the powder material should consider the influence of the angle of repose of the powder on material discharge.

② Quantitative material discharge: It is crucial to focus on discharging the same weight of raw materials each time. Excessive raw materials can lead to accumulation in the equipment, reducing production effectiveness and increasing the risk of combustion and explosion, which is detrimental to subsequent processes. On the other hand, insufficient raw materials can result in phenomena such as misfires or dud fireworks during ignition, leading to a poor customers experience. Therefore, it is necessary to achieve quantitative material discharge by controlling a stepper motor-operated screw feeder.

③ Powder dust: A significant amount of dust is generated during the transportation and mixing processes of the powders. If proper sealing devices are not employed, the powder content in the workshop will increase. Once the airborne concentration exceeds a certain limit, the likelihood of explosion accidents greatly rises. In this study, the powder leakage is prevented by reducing the free-fall time of the powder and installing sealing devices on each spatial channel. Additionally, timely cleaning of the fireworks making is required.

④ Static electricity: The raw material conveying system should avoid friction and collision between powders to reduce static electricity generation. Measures such as using antistatic materials, optimizing the transmission structure, and grounding all devices that may generate static electricity are implemented to reduce or prevent static electricity.

(2) Mixing system: The mixing system occupies a particularly important position in the fireworks making process. The mixing process aims to uniformly blend the four raw materials, and any slight negligence can lead to dangerous accidents (explosions). The mixing process faces the following problems:

① Synchronous mixing: In this process, the raw materials undergo preliminary mixing, requiring the simultaneous arrival of the three reducers and oxidizers in the intersecting space. By controlling the synchronous action of pneumatic butterfly valves, the reducers, and oxidizers enter the Y-shaped pipe intersection at the same time for preliminary mixing. Then, further mixing is carried out in a static mixer to achieve the initial blending of the raw materials.

② Sieve aperture size: The size of the vibrating sieve determines the time and quality of mixing. If the sieve aperture is too small, the dispensing time increases, while if it is too large, the blending of the materials becomes uneven. Simulating the manual “three-to-one” mixing process adds several levels of vibrating sieves, and the aperture gradually decreases from top to bottom, thus achieving uniform mixing of the four raw materials.

③ Vibration issues: Installing a vibrating motor on the vibrating sieve helps accelerate the dispensing process and ensures better blending of the powders. However, if the vibration frequency is too low, the mixing effect is compromised, and if the frequency is too high, it generates excessive noise. Therefore, determining the appropriate vibration frequency and amplitude is necessary.

④ Elastic elements: Elastic elements are used to prevent the vibrations of the vibrating sieve from affecting the connected components. Elastic elements are installed at the upper and lower ends of the vibrating sieve to prevent the propagation of vibrations to other parts, ensuring proper screening and granulation while also providing a sealing function.

(3) Material Distribution System: The main function of the material distribution system is to evenly and consistently distribute the mixed materials into the 61 holes of the firework cakes. The following issues exist in the material distribution system:

① Material Distribution Cone: The height and angle of the material distribution cone have a significant impact on the uniformity of material distribution. If the height of the material distribution cone is too high, it will generate internal airflow and affect material distribution. The angle of the material distribution cone affects the speed of material discharge. The height and angle of the material distribution cone must be designed based on the powder’s process parameters and mechanical properties.

② Material Distribution Pipe: The role of the material distribution pipe is to transport the allocated materials into the firework cakes. The length and bending of the material distribution pipe affect the discharge speed and may cause blockages. Therefore, the required height, vibrator frequency, and amplitude must be calculated to address this issue.

③ Alignment: Improper alignment of the material distribution cone can result in uneven material distribution, with some areas having more and some having less material. During installation, alignment equipment should be used to align the entire apparatus and avoid errors caused by misalignment.

1.4 Main Research Content of this Paper

In the production process of fireworks, the majority of explosive incidents occur during the powder-filling process. Therefore, achieving automated production of powder filling has significant application value in terms of achieving human-machine separation. Currently, few fireworks powder-filling automation devices are available on the market, and they cannot achieve long-term effective automated production, which is highly unfavorable for the automated production and sales of fireworks. This paper mainly focuses on the automation design of fireworks powder filling, truly achieving human-machine separation, preventing accidents, maintaining long-term efficient operation, reduce costs in the fireworks production process, and obtaining higher economic returns. The main contents of this paper are as follows:

(1) Through extensive literature research, combined with the production process of fireworks making lines based on actual production requirements, the influencing factors and relevant constraints of the fireworks making are analyzed. Taking into account the latest research progress in fireworks equipment at home and abroad, a series of appropriate designs are made, including mechanical equipment design, factory layout, selection of electrical components, and human-machine separation.

(2) Due to the complexity of the production process of automated fireworks making lines, the important stations in the production process are determined. Considering each station’s requirements and potential issues, a comprehensive design is carried out, taking advantage of strengths and avoiding weaknesses. Detailed structural design and parameter calculation are performed for material feeding, mixing, distribution, and vibration in the fireworks making line. Three-dimensional modeling, assembly, and verification of assembly correctness and rationality are conducted based on these calculated data. The electrical design adopts an integrated approach, designing a stable and controllable control flowchart based on the process flow, determining the design of PLC, motors, and electrical components, and also designing a user-friendly remote monitoring and human-machine interaction interface.

(3) The assembled fireworks powder-filling automation equipment is operated and debugged. Based on actual production conditions and the characteristics of the raw materials, each process engineering is debugged individually, followed by overall debugging to determine whether there are any interferences in the entire equipment, abnormal mechanical equipment, and robustness of program operation. Good operating parameters are obtained to ensure the efficient and long-term operation of the fireworks powder-filling automation equipment without personnel.

Chapter 2: Design of Fireworks powder Filling Line

2.1 Introduction

There is mechanized production equipment for fireworks without powder processes in domestic and international markets. However, no corresponding mechanized equipment for fireworks production with powderpowder processes exists. The powder-filling process of fireworks production mainly includes three processes: powder delivery, powder mixing, and powder separation. The main problems faced in this important process are difficulties in conveying oxidizers and reducers, uneven powderpowder mixing, uneven powder separation, easy generation of dust, friction-induced static electricity, and explosion risks. To address this series of issues, this chapter utilizes a combination of theoretical calculations and practical methods, following the overall principles of fireworks design, to design the conveying system, powder mixing system, powder separation system, distribution pipelines, and connecting components of the fireworks automation equipment. These designs aim to meet the requirements of fireworks production standards and fulfill the needs of actual fireworks production processes.

2.2 General Design Principles

Fireworks production has evolved from primitive manual craftsmanship to mechanized production in certain stages and now to fully mechanized automated lines. The basic sequence of mechanized production is shown in Figure 2.1. It includes the following steps: placing empty tubes that have passed inspection, powder filling, adding sawdust, sealing paper, sealing quick-setting gelatin, flipping paper tubes, powder filling, adding sawdust, sealing paper, sealing quick-setting gelatin, and secondary packaging line.

Figure 2.1: Schematic Diagram of Basic Sequence of Mechanized Production Line

In the steps of firework production, the placement of empty tubes, filling with sawdust, sealing paper pieces, sealing quick-setting gel, tube flipping, and packaging have been largely mechanized and automated. However, the filling and secondary packaging process for the medication is still unsatisfactory. The main reasons are dust emission during material feeding, uneven mixing, large and unstable material distribution errors, and the risk of explosion. Therefore, achieving dust-free filling, uniform mixing, consistent material distribution, eliminating explosion hazards, and achieving fully automated production are key considerations in the design of the medication filling process.

2.2.1 Medication Selection

The principle of fireworks is to burn the fireworks gunpowder inside the tube, producing splendid colors in the night sky. Firework gunpowder consists of aluminum-magnesium alloy powder, sulfur powder, aluminum-silver powder, and potassium permanganate powder in certain percentages by mass. Here, we select aluminum-magnesium alloy powder, sulfur powder, aluminum-silver powder, etc. as the reducing agents for firework production and potassium permanganate powder as the oxidizing agent. Considering the safety hazards such as excessive accumulation time of reducing agents and oxidizing agents, poor ventilation, powder fermentation, and temperature increase leading to spontaneous combustion, maximizing production capability while ensuring safety is the natural pursuit of every enterprise. We store the reducing and oxidizing agents separately to keep up with the production pace and improve production ability. The design of the charge volume container is based on the amount of powder required for approximately 2 hours of firework production. Additionally, the charge volume containers for the oxidizing and reducing agents should be placed at a distance of no less than 5 meters and not in the same workshop. Firework production requires mixing and filling the reducing agents and oxidizing agents into a single hole. However, even with slight mishandling, explosions can occur. For every firework production company, the goal is to design an mechanized and automated fireworks making line that can keep up with the production pace, meet functional requirements, and minimize property losses in case of an explosion caused by improper operation. This means that there should be only one cake of powder after mixing so that even if an explosion occurs, the blast wave will not be significant. The design of the powder dispenser before filling should be based on a dosage of 366g for large cakes and 183g for small cakes.

2.2.2 Environmental Control

During the process of charging and filling the medication, the excessive temperature can easily reach the ignition point of the oxidizing and reducing agents, resulting in combustion and explosion. Therefore, the indoor temperature during the firework production process should not exceed 60℃.

The humidity during firework production should be appropriate. If the humidity is too high, it will cause the powder to agglomerate, affecting the uniformity of medication mixing and distribution. On the other hand, if the humidity is too low or too dry, it can lead to excessive dust and explosions. Therefore, the recommended relative humidity range during firework production is 45% to 75%.

As mentioned above, if the dust content in the workshop exceeds the standard, explosions are likely to occur. Therefore, the dust content in the workshop should not exceed 50g/m3.

2.2.3 Delivery of Medication

The delivery section of the fireworks automated package loading line consists of the following components:

(1) Initial Feeder

A spiral feeder is chosen as the material container in the fireworks making line. Firstly, three types of reducing agents are mixed uniformly and placed in the spiral feeder, while the oxidizing agent is placed in another workshop’s spiral feeder. Due to the powder’s stickiness and high explosion risk, the raw materials in the spiral feeder are stored only for a one-hour quantity. The spiral feeder dispenses the materials once in a working cycle. To accelerate the feeding speed of the spiral feeder, the top of the feeder is square or circular, while the lower part is designed as a cone with a cone angle greater than the raw materials’ repose angle. There are no steps between the connecting sections of the upper and lower parts to ensure smooth material movement.

(2) Quantifier

① Reducing Agents: The density of the mixed reducing agents is 0.65 kg/L. The amount of material for each large cannon cake is 146.4 g, corresponding to a volume of 225.23 mm3. The amount of material for each small cannon cake is 73.2 g, corresponding to a volume of 112.62 mm3.

② Oxidizing Agent: The density is 0.65 kg/L. The amount of material for each large cannon cake is 219.6 g, corresponding to a volume of 337.85 mm3. The amount of material for each small cannon cake is 109.6 g, corresponding to a volume of 168.62 mm3.

The size of the quantifier is designed based on these data, and the shape of the quantifier can be square or circular. To avoid airflow during the medication quantification process, two gates are set at the upper and lower ends of the quantification container to ensure that the two processes of storing and dispensing materials do not interfere.

The upper gate is open during storage, and the lower gate is closed. After filling, the upper gate is then closed.

During dispensing, the lower gate is opened. After all the medication in the quantifier is discharged under the action of the vibrator, the lower gate is closed, the upper gate is opened, and the next cycle starts.

(3) Conveyor

Since the initial mixing of the reducing agents and oxidizing agents cannot be placed in the same space, there is a distance between the initial mixer and the quantifier, which can be transported by conveyor belt or pipeline.

If a conveyor belt is used, it should have a skirted edge with isolation plates placed between them. The amount of medication transported between two isolation plates is equivalent to the required dosage for one loading. Since the dust content in the workshop does not exceed 50 g/m3, the conveyor belt cannot be left open and must be embedded in a dustproof sealing device with regular cleaning of the conveyor belt. Additionally, attention should be paid to the inclination angle of the conveyor belt, which should not exceed 12°.

If a pipeline is used for transportation, the powder relies on gravity to overcome the static friction force and slide. However, due to the long distance between the initial feeder and the quantifier, the limited indoor space restricts the vertical placement of the pipeline, and it can only be inclined. The inclination angle must be greater than the material’s repose angle to overcome the maximum static friction force and move downward.

(4) Pushing Container

To allow the oxidizer and reducer raw materials to meet in the same space simultaneously, a synchronized cylinder is set up to facilitate the feeding of oxidizers and reducers at the same time.

2.2.4 Mixing of Materials

In the traditional fireworks mixing process, uniform mixing is achieved through the “three sieving and three collections” method. It involves manually sieving several kilograms of oxidizers and reducers through a coarse sieve, collecting them, then sieving the mixture again through a fine sieve, collecting it once more, and repeating this process three times. Through this repeated sieving and mixing, the thorough blending of the reducer and oxidizer can be achieved, and the blended powder is then quantitatively filled into the fireworks casing by the workers. During the aforementioned “three sieving and three collections” process, there is a high risk of exceeding dust concentration, generating frictional electricity, and causing explosions. In the event of an accident, it will undoubtedly result in casualties and significant property damage.

To avoid the above-mentioned issues, the fireworks powder-filling process designed in the text involves automating the mixing step in the line. The oxidizer and reducer are transported through a Y-shaped tube in the dosing device and reach the intersection area for the first mixing. Then, they go through further mixing in the lower static mixer, the second mixing. Subsequently, they enter multiple stages of coarse and fine sieve screens for steps such as sieving, collecting, sieving, and collecting, aiming to achieve a uniform and consistent mixing.

During the automated mixing process, the dosage of the large cannon cakes is 366g, and the dosage of the small cannon cakes is 183g. By going through a series of steps, including transportation through the Y-shaped tube, static mixing in the mixer, and sieving through multiple vibrating screens, the powder mixing achieves natural uniformity and consistency, despite the smaller dosage used in each mixing.

2.2.5 powder Separation

Traditional manual powder filling involves taking well-mixed gunpowder and, based on personal experience, filling a certain amount of powder into the inner tube of the fireworks. After filling 61 holes, the excess amount of powder is scraped off using a scraper to remove the surplus. This process is highly prone to excessive dust, and even a slight mishap can result in an explosion, causing casualties and significant economic losses. So far, no fast and simple method or process has ensured uniformity and consistency in powder separation with low dust generation and safe control. This problem has been a persistent challenge in the fireworks production industry, hampering its growth and development. The industry is considered highly risky, and young people are unwilling to join. Currently, the industry’s workforce is mostly over 45 years old, and it is facing a situation where the fireworks production industry may only disappear with successors.

Based on the aforementioned issues, the text presents a self-designed, fast, and simple method and process for powder separation. This method involves using a feeding device and a conical division method to evenly scatter the powder powder around the division cone, allowing it to fall into the 61 division plate holes surrounding it. To ensure the precision of powder division, a scraping device is further employed to guarantee the uniformity and consistency of the dosage in each hole. The 61-hole plate is seamlessly connected to the conical surface without steps or accumulation, and it is connected to the 61 receiving pipes from above and below without any gaps.

2.2.6 Automated Production and Control

The production proficiency and safety factor are extremely low in the traditional manual process of fireworks powder filling. The mixing and separation processes are time-consuming, and continuous operation is impossible. It cannot meet the huge demand during major festivals or the Spring Festival due to humid and hot weather or dim lighting. Currently, the bottleneck of mechanical and automated fireworks production lies in the automation of powder filling, which includes the automation of transportation, mixing, and separation. If any of these steps are not well connected, it will affect the rhythm of automated production and subsequently impact production. Therefore, the key to the problem lies in the time allocation for each step of powder filling and the seamless integration and connection between each step.

The manufacturer requires fireworks production machinery to be automated, mainly to improve the efficiency of fireworks production, liberate labor, compensate for labor shortages, and enhance both economic and social benefits. Generally, an automated fireworks making line should have a daily production capacity equivalent to 10-15 workers to demonstrate economic benefits; otherwise, the products will be difficult to be accepted by the market. Assuming each person fills 300 cakes with powder per shift, with 15 people filling 4500 cakes daily. If mechanical automation is used for filling, the task can be completed in 10 hours, producing 450 cakes per hour. The theoretical time allocated for filling each cake with powder is 8 seconds.

Next, based on the actual production of fireworks powder filling, the 8 seconds will be allocated as follows:

(1) Loading and unloading through the safety door takes 7-8 seconds.

(2) Each cake has a filling interval of 6 seconds, with a filling time of 2 seconds and a positioning and leaving time of 2 seconds each.

(3) The transfer time from the mixing material hood to the inner cylinder is less than 2 seconds.

(4) The retention time on the powder conveyor belt is less than 4 seconds.

(5) The cylinder driving time is less than 1 second, and the back-and-forth cycle is shorter than 2 seconds.

The automated production time for filling one cake with Pyrotechnic composition is 8 seconds, while the manual filling time for one cake is 8 * 3600/300 = 96 seconds. The efficiency of automated production has increased by 96/8 = 1200%. It greatly improves labor productivity and economic benefits while also achieving the goal of safe production.

Based on the time allocation and connection of each step in the Pyrotechnic composition-filling process, the characteristics of the oxidizer and reducer, as well as the limited space environment, the corresponding design calculations are carried out to achieve the required structures or components for each step.

2.3 Design Conditions

2.3.1 Technical Requirements

The technical specifications for the automation of Pyrotechnic composition filling are as follows:

(1) Dust content in the operating space ≤ 50g/m3;

(2) Uniformity of mixed Pyrotechnic composition ± 0.5%;

(3) Uniformity of divided Pyrotechnic composition ± 3%;

(4) Working cycle ≤ 8 seconds;

(5) Height ≤ 4.2 meters.

2.3.2 Design Parameters

The automated fireworks making line involves two types: large cannon cakes and small cannon cakes, as shown in Figure 2.2.

Figure 2.2: Cannon Cake 3D Model

The design parameters for the cannon cake in the fireworks making line are shown in Table 2.1.

Table 2.1: Design parameters of the cannon cake

Fireworks involve design parameters in addition to the design parameters of the burst charge. They include the following:

(1) Hopper 1, Hopper 2, Hopper 3, and Hopper 4 filling capacities: Large cakes correspond to 73.2g, 36.6g, 36.6g, and 219.6g, respectively, while small cakes correspond to 36.6g, 18.3g, 18.3g, 109.8g respectively.

(2) Hopper 1, Hopper 2, Hopper 3 capacities should not exceed 30kg, and Hopper 4 should not exceed 10kg.

(3) The conveyor belt has a skirt and grating to prevent falling and ensure no loss. A receiving hopper is placed below it.

(4) The piston should not extend beyond its mouth, and a gate is set at the piston port.

(5) All devices, such as the conveyor belt, distributor, vibrator, connectors, and pipes, are enclosed and dust-free.

(6) All connectors use flexible connections, and the height is temporarily set at 2cm.

(7) The cone angle of the distributor, whether it is a positive cone or an inverted truncated cone, should not exceed 40°.

(8) The mixing device’s total height is 2.6m.

(9) The loading and unloading of propellant through the safety door takes 7-8 seconds.

(10) The interval between each charge is 6 seconds, the loading time is 2 seconds, and the positioning and departure time are 2 seconds.

(11) The time for mixed materials to flow from the pipe hood to the inner cylinder is less than 2 seconds.

(12) The retention time of the powder conveyor belt is less than 4 seconds.

(13) The cylinder’s pushing time should not exceed 1 second, and the back-and-forth cycle should be shorter than 2 seconds.

2.3.3 Raw Material Parameters

The four raw materials required in the fireworks inner cylinder production process have the following parameters:

(1) Aluminum-magnesium alloy powder

The mass fraction of aluminum-magnesium alloy powder required in the automated fireworks production line is 20%, defined as material 1. It is a silver-white powdered substance. The particle size range is 30-300 mesh (0.6-0.05mm), and the bulk density is 0.4-0.85 g/cm3. It emits a dazzling white light when burned. See Figure 2.3 for aluminum-magnesium alloy powder.

Figure 2.3: Aluminum-Magnesium Alloy Powder

(2) Sulfur Powder

The required mass fraction of sulfur powder in the automated fireworks production line is 10%, defined as material 2. The mass percentage of S is 99.5% to 99.95%. Different sulfur grades are available, such as industrial grade and refined grade, depending on the S content. Sulfur products widely used vary in particle size, including 200 mesh, 400 mesh, and 500 mesh. Sulfur is chemically active and easily reacts with oxygen in the air, and it can undergo combustion or explosion under severe conditions. Therefore, it should be stored in a sealed, cool, and dark environment. The specific gravity of sulfur powder is 2.0, and the bulk density is 0.5 to 0.9 g/cm3. Refer to Figure 2.4 for sulfur powder.

Figure 2.4: Sulfur Powder

(3) Aluminum Silver Powder

The required mass fraction of aluminum silver powder in the fireworks making line is 10%, designated as Ingredient 3. It has a relative density of 2.55 and a bulk density ranging from 0.6 to 1.25 g/cm3. The appearance of aluminum silver powder is shown in Figure 2.5.

Figure 2.5: Aluminum Silver Powder

(4) Potassium Permanganate Powder

The required mass fraction of potassium permanganate powder in the fireworks making line is 60%, designated as Ingredient 4. It has a bulk density ranging from 1.6 to 2.703 g/cm3. The appearance of potassium permanganate powder is shown in Figure 2.6.

Image 2.6: Potassium Permanganate Powder

Among them, aluminum-magnesium alloy powder, sulfur powder, and aluminum silver powder serve as reducing agents, while potassium permanganate powder serves as an oxidizing agent. These four powders are mixed in a certain mass ratio, with Ingredient 1 accounting for 20%, Ingredient 2 accounting for 10%, Ingredient 3 accounting for 10%, and Ingredient 4 accounting for 60%. The density of the mixed material ranges from 0.96 to 1.16 kg/L. Several materials similar to reducing agents and oxidizing agents have bulk density and angle of repose, as shown in Table 2.2.

Table 2.2: Bulk Density and Angle of Repose of Several Similar Materials

2.4 Design of Main Components of Fireworks Filling Line

2.4.1 Working Principle

During the fireworks filling process, the photoelectric sensor is immediately triggered when the metering device is empty. At the same time, the initial feeder’s gate and the metering device’s upper gate are opened, and the lower gate of the metering device is closed. The spiral feeder conveys the material to the metering device. After the metering device is full, the upper gate of the metering device is immediately closed. After the loading die of the firework cake is in place, both cylinders open the lower gate of the metering device simultaneously. The material is then sequentially transported through the Y-shaped pipeline to the static mixer, the second-level vibrating screen/aggregate hopper, the concentric tube, the feeding device, the material distribution cone, the porous mismatched rotating disc, the scraping blade, the discharge pipe, the firework cake, etc. After this process is completed, the loaded firework cake leaves the mixing chamber, and the next firework cake enters the mixing chamber, repeating the above operations for the next cycle.

2.4.2 Composition of the Complete Equipment

The fireworks filling automation equipment mainly includes the feeding system, mixing system, dispensing system, and control system, among others. The entire fireworks automation equipment operates through electrical control automation. During the initial stage of designing the entire equipment, two options were considered. Option one is shown in Figure 2.7, and option two is shown in Figure 2.8.

Figure 2.7: Scheme One Structure

Figure 2.8: Scheme Two Structure

1.   Seasoning dispenser

2.   Quantitative dispenser

3.   Material bin bracket

4.   Material chute

5.   Material delivery pipe

6.   Pneumatic butterfly valve (flanged connection)

7.   Flexible connection (clamp ring)

8.   Dust cover

9.   Vibrating screen

10.   Vibrating pneumatic motor

11.   Material blocking pipe

12.   Outer circular platform

13.   Inner circular platform

14.   Material distribution plate (connecting shaft, mounting base)

15.   Explosion-proof motor

16.   61-hole circular ring

17.   61 connecting pipes

18.   Connecting plate for 61 vibration board

19.   61 pipe fixing plate

20.   Firework cake limiting mold

21.   Firework cake conveying system

22.   Integral rigid bracket (bolts, mounting base, etc.)

The main components of Scheme 1 include a spiral feeder, conveyor belt, linkage cylinder, static mixer, vibrating screen, material cone, material pipe, and vibrating motor. Scheme 2 consists mainly of a spiral feeder, conveyor belt, Y-shaped pipe, pneumatic butterfly valve, vibrating screen, static mixer, material pipe, and vibrating motor.

The comparison between the two schemes is as follows:

In Scheme 1, the cylinder pushes the reducing agent and oxidizer, allowing them to mix preliminarily. In Scheme 2, the reducing agent and oxidizer are mixed preliminarily as the materials pass through the Y-shaped pipe, which the pneumatic butterfly valve opens. However, the pushing process of the cylinder in Scheme 1 has several problems:

(1) During the movement of the cylinder, it continuously causes friction with the material, which easily generates static electricity. It needs to be avoided in the design.

(2) The cylinder is prone to wear and tear due to long-term use, leading to material accumulation inside the cylinder, resulting in variations in the transported material quantity and affecting the quality of the firework cake.

(3) During the assembly of the cylinder, if it is not in the same horizontal plane or has slight deviations, it is prone to jamming during movement, resulting in downtime.

(4) The cylinder has a certain stroke distance and a time difference at the extreme position. Considering that the entire operation time is 7 seconds and the estimated running time of the cylinder is 3 seconds, such a long time is not allowed.

(5) The cost of the cylinder is higher than that of the pneumatic butterfly valve, and the cylinder occupies a larger space, making maintenance more complicated.

Considering factors such as time efficiency, time cost, and quality assurance, Scheme 2 is ultimately chosen for the automated line of firework filling.

2.4.3 Transmission System

The feeding system of the fireworks making line consists of a spiral feeder, volumetric bin, and conveyor belt. The specific parameters and design are as follows:

(1) Spiral Feeder

The spiral feeder contains 4 types of raw materials. Based on the performance parameters of these materials and equipment requirements, the materials should be able to freely fall under the influence of gravity. Therefore, the downward force must be greater than the static friction force. In other words,

f (downforce) ≥ f (static frictional force)

Mgsine α ≥ μstatic frictional force . mgcosα

Further, tanα ≥μstatic frictional force

Assuming the maximum static friction angle is equal to the angle of repose, i.e.,

μmaximum static friction force = tan75° = 2.7475, and the height of the silo is given by h = h1 + h2 = 0.2m + 1.0m = 1.2m (with the upper part being a cube and the lower part a regular square pyramid):

For materials 1, 2, 3, and 4, and the silo with a consecutive connection to the large disk (Ф39cm) (inverted square pyramid), the cross-section of the base is as follows:

The length and width of the base are given by l1 l1 (0.0728 0.0728m), and the height is 0.2m. The length of l1 can be calculated as follows:

l1 = sqrt(0.0728 * 0.0728)

l1 ≈ 0.0728m

Therefore, the side length l1 is approximately 0.0728 meters.

Therefore, calculate the upper volume 1 (pyramid) V1 (consisting of 4 pieces) and the volume 2 (consisting of 4 pieces) of the upright shape (cube) on the upper part of Bins 1 and 4. The height is 1.0m. Where:

V1 = 0.072m3, V2 = 0.36m3, thus obtaining the total volume V = V1 + V2, which is the capacity for storing the raw materials.

Of course, the fixed volume method can also adopt the structural form of a rotating impeller, sandwiching an equal volume between the two blades.

(2) Fixed volume bin

The fixed volume bin is connected below the screw feeder, and its cross-section is square. Based on the parameters of the raw materials, the following data is obtained:

① Large cakes:

Cross-section: 44cm, 33cm, 33cm, 44cm;

Height (rounded up to the nearest integer, approximately): 8, 6, 6, 8cm.

② Small cakes:

Cross-section: 44cm, 33cm, 33cm, 44cm;

Height (rounded up to the nearest integer, approximately): 4, 6, 6, 8cm.

The transportation system is shown in Figure 2.9, the screw feeder is shown in Figure 2.10, the fixed volume bin is shown in Figure 2.11, and the skirted conveyor belt is shown in Figure 2.12.

Figure 2.10: Spiral feeder

Figure 2.11: Fixed volume warehouse

Figure 2.12: Skirt conveyer belt

2.4.4 Mixing System

According to the actual situation of the fireworks making line process, the technical specifications and requirements of the mixing system are as follows:

(1) Pipe hood: Diameter Ф0.12m0.24m or 0.12m0.12m0.3m;

(2) Power match: Pneumatic;

(3) Bottom rubber and conical bottom sealing;

(4) Equipped with pulse air flow nozzles for repair, maintenance, and dust removal;

(5) Static mixer: Diameter Ф0.08m0.6m;

(6) Installed using flange matching;

(7) Vibrating screen: Ф100mm*80mm (recommended to use within Ф100, 80-300 mesh, height 60-100mm);

(8) Pneumatic vibration, motor vibration frequency, flexibly connected to other components;

(9) Vibration screen material, anti-static, anti-friction ignition measures, etc. (the screen mesh should be made of 304 stainless steel, connecting parts should use copper screws or aluminum alloy can be used for the frame);

(10) Conical closure at the lower part of the vibrating screen, vibrating together with the vibrating screen;

(11) Material selection, anti-static, anti-friction ignition measures, etc.

Based on the above technical specifications and requirements, the mixing system of the fireworks automated production line consists of a pneumatic butterfly valve, a Y-shaped pipe, a static mixer, and a vibrating screen. The pneumatic butterfly valve acts as a switch, opening during feeding and closing after feeding. The Y-shaped pipe and static mixer facilitate the intersection and preliminary mixing of the oxidizer and reducing agent in the air. The preliminarily mixed raw materials pass through multi-level vibrating screens with a different coarseness to thoroughly mix and evenly distribute the materials. The vibrator accelerates the uniform mixing of the materials. The three-dimensional model of the Y-shaped pipe in the mixing system is shown in Figure 2.13, the static mixer is shown in Figure 2.14, the pneumatic butterfly valve is shown in Figure 2.15, and the three-dimensional model of the vibration system in the mixing system is shown in Figure 2.16. The vibrating screen and pneumatic motor are shown separately in Figures 2.17 and 2.18.

2.4.5 Material Distribution System

According to the actual situation of the fireworks automated production line process, the technical requirements and specifications of the material distribution secondary packaging system are as follows:

(1) Power matching, using a low-speed pneumatic motor, with added pressure reducing valve and speed control throttle valve.

(2) Bottom of the circular platform: diameter Ф0.41m * 0.6m.

(3) Top of the circular platform: circular hemisphere with a diameter of 0.08m and a height of 0.1m.

(4) Circular groove structure: without steps, smooth curved surface.

(5) Connection method between the circular groove and the 61 connecting pipe (61 circular nozzles protruding from the lower part) (the diameter of the connecting pipe inside the pancake is temporarily set at Ф2.0cm with a wall thickness of 1mm, spaced 1mm apart).

(6) Material selection, anti-static measures, anti-friction fire prevention measures, etc.

Two schemes have been developed based on the above technical indicators and requirements. Among them, the material distribution system of Scheme 1 consists of a material distribution cone, upper material distribution plate, lower material distribution plate, top cone, and material distribution scraper. With the combined action of these components, the mixed raw materials are evenly distributed into each hole of the pancake-shaped product. The specific structure is shown in Figure 2.19:

The material-separating system of Scheme 2’s automated fireworks making line consists of a material-separating cone, circular groove, feeding device, transmission shaft, and fixed plate. With the combined action of these components, the mixed raw materials are evenly distributed into individual holes of the firework shells. The inner diameter of the large firework shell is known to be 20mm. Let’s assume the diameter of the material separating tray is R, and the diameter of the 61 holes surrounding it is D1=18mm. The center-to-center distance between two holes is D=24mm, and the angle α1=360°/61=5°, as calculated by the following formula:

sin^2(D/R) = α + 2.5 — (2.5)

The calculation formula for the radius R of the dividing plate is shown as equation (2.6):

1/(1 + 2sin^2(D/R)) = α — (2.6)

From this, it can be concluded that the radius R of the dividing plate is 324.28mm, and the known rest angle α of the material is 60°.

The height H of the dividing plate is determined by the tangent function formula as shown in equation (2.7):

tan(H/R) = α —- (2.7)

Based on the given information and equations, the height of the dividing plate H can be determined as H=561.18mm. The feeding system is illustrated in Figure 2.20.

The feed dispenser, material separator, and circular groove are shown in Figure 2.21, Figure 2.22, and Figure 2.23, respectively.

2.4.6 Distribution System

According to the actual situation of the fireworks automated production line process, the technical specifications and requirements of the distribution system are as follows:

(1) Smooth connection between the connecting pipe and the upper circular groove.

(2) Spatial arrangement of the connecting pipe: no creases, no twisting.

(3) Smooth connection between the connecting pipe and the lower mold 61 holes.

(4) Dimensions of the connecting pipe structure: (provisional diameter of the inner pipe connecting pipe of the large firework is Ф2.0cm, wall thickness 1mm, spacing 1mm).

(5) Material selection, anti-static, anti-friction fire prevention measures, etc.

Based on the above technical specifications and requirements, the distribution system of the fireworks making line consists of 61 connecting pipes and cannon plate connectors. The diameter of the large firework is Φ21.7cm, with 61 holes, each with a diameter of Φ2.17cm. The diameter of the small firework is Φ19.2cm, with 61 holes, each with a diameter of Φ1.92cm. The 61 fine pipes at the bottom of the feeder are inserted into the inner pipes of the large and small fireworks, resulting in provisional diameters of Ф2.0cm and Ф1.85cm for the connecting pipes of the large and small fireworks, respectively, with a wall thickness of 1mm for both. The 61 connecting pipes mentioned above form a circumference, with a total length of the corresponding circumferences of the large and small fireworks being 612.0cm=122.0cm and 611.85cm=112.85cm. Considering the ease of installation, the spacing between the fine pipes is 1mm, requiring 6cm for the 61 pipes. Therefore, the actually required circumferences for the large and small fireworks are 128cm and 119cm, respectively, with corresponding diameters of Ф41cm and Ф38cm.

As mentioned above, the lower circumference of the feeder corresponding to the large and small fireworks is 128cm and 119cm, respectively, with corresponding diameters of Ф41cm and Ф38cm.

Considering a rest angle for the material flow of ≥60°, the calculation formula for the cone height h is as follows:

Tanα = h/4 — (2.8)

The rest angles for fine gray powder and fine white powder are α=60°, and the rest angle for kiln ash is α=75°. The corresponding values of tan 60° and tan 75° are 2.7422 and 3.7222, respectively. Based on this, the specifications for the feeder for the large and small fireworks are as follows:

(1) For the large firework (Ф41cm), the height of the connecting pipe h should be h≧r*=0.76m.

(2) For the small firework (Ф38cm), the height of the connecting pipe h should be h≧r*=0.71m.

The wall thickness of both pipes is 1mm.

The installed connecting pipes and cannon plate can be seen in Figure 2.24.

2.4.7 Connection Component Design

According to the actual situation of the fireworks automated production line production process, the technical specifications and requirements for the connection components are as follows:

(1) The connector should have strength and rigidity and be reliable and safe.

(2) The connector should ensure no damage between the connected parts.

(3) There should be no relative movement between the connectors.

(4) Material selection, anti-static measures, anti-friction ignition measures, etc.

Based on the above technical specifications and requirements, the main connection components for the fireworks filling automated production line include clamps, bolt and nut connections, screw connections, and flange connections. The clamp is shown in Figure 2.25, the flange is shown in Figure 2.26, the bolt and nut are shown in Figure 2.27, and the screw is shown in Figure 2.28.

During the overall assembly process, there is a requirement for coaxiality between the material distribution cone and the material receiving cone. Therefore, a concentric component is designed to ensure the coaxiality requirement for the entire automated production line. The concentric component is shown in Figure 2.29.

Figure 2.29: Heart Components

Chapter 2.5 Summary

Based on the actual process of automating the filling of fireworks with powder, this chapter has completed the initial structural design of the processes of feeding, mixing, and separating, taking into account issues such as explosions, static electricity, uneven mixing, and dust and uneven feeding:

(1) In response to the open transport link’s high dust and pollution characteristics in the current powder-filling process, the initial large feeder-pipeline transport quantifier and other transport-waiting links were used to store oxidizers and reducers separately. It achieves the process of independent and leak-free transportation of oxidizers and reducers without dust, and based on the engineering mechanics characteristics and efficacy requirements of the materials, the design of the above structural components was completed.

(2) To avoid the problems of low efficacy, excessive dust concentration, frictional electrification, and explosions in the traditional manual “three-in-one” powder filling and mixing process, the synchronous cylinder brake valve-Y-shaped pipe-static mixer-2-stage vibrating screen/aggregate hopper and other links were used in this study to achieve a uniform and consistent mixing of powder. Based on the engineering mechanics characteristics and efficacy requirements of the materials, the design of the above components and the selection of power components were completed.

(3) In response to the high dust, pollution, explosion-prone, and poor uniformity characteristics of the current open powder separation process, this paper independently designed a set of components including a heart tube, a feeding device, a separating cone, a porous misalignment rotary disk, a scraping blade, and a discharge tube. It achieves uniform and consistent separation of powders, and based on the engineering mechanics characteristics and efficacy requirements of the materials, the continuous and seamless smooth connection of various components, holes, and holes, and the selection of power components were completed.

Chapter 3: Electrical Control System Design

3.1 Introduction

In the production of fireworks powder filling lines, there are issues such as excessive dust, pollution, high explosiveness, and difficulties coordinating timing. Therefore, the electrical control system is designed to address these problems. Through theoretical analysis and calculations, the design includes the control circuit of the entire electrical system, calculation and design of servo motors, selection of suitable PLC control systems, programming based on the actual process flow of fireworks filling, and configuration software with a user-friendly interface. Through this series of precise and orderly designs, the electrical system of the fireworks filling line achieves coherence, smoothness, and high safety.

3.2 Design Principles

Based on the actual situation of the fireworks powder filling line process, the technical requirements and control parameters for the electrical system of the fireworks filling automation equipment are as follows:

(1) Loading and unloading through the safety door takes 7 to 8 seconds.

(2) The interval between loading each cake is 6 seconds, with a loading time of 2 seconds and positioning and disengaging times of 2 seconds each.

(3) Transferring the mixed material from the hood to the inner cylinder should take less than 2 seconds.

(4) The retention time of the powder conveyor belt should be less than 4 seconds.

(5) The pushing time of the cylinder should not exceed 1 second, and the back-and-forth cycle should be shorter than 2 seconds.

(6) Precautions such as anti-static and anti-friction measures should be taken when using electronic components.

Fireworks belong to the high-risk firecracker manufacturing industry. For the high-risk fireworks production process, the electrical control system needs to be able to implement the actual process and strive to meet the requirements of the production process. The operation of the electrical system should be safe, practical, accurate in motion, easy to maintain and repair, resistant to interference, and simple to operate and maintain. Therefore, the following basic principles should be followed in the design of the electrical control system:

(1) The control system should be in line with the production process

Today, there are many mature and reliable controller products available , such as microcontrollers, PLCs, sensors, etc. The control system of the automation equipment should consider features such as dustproof, explosion-proof, and good safety performance. It should also fully consider the characteristics of the process during the design phase, ensuring that the system can operate correctly, consistently, stably, and efficiently in the long term. 

(2) Simple and Practical

In designing a control system that meets the technical requirements and specifications of the electrical system, the goals should include simplifying operations, ensuring safety in production, and achieving production automation. Based on the actual skill levels of the existing personnel and conforming to their operational habits, the monitoring interface should be user-friendly and easy to understand. Especially for emergency stop and emergency alarm buttons, they should be clearly marked to prevent difficulties in locating them during unexpected emergency situations.

(3) Ensuring the Completeness of Control Functions

During the design process of the control system, the entire system should encompass all the functions medical devices that can be utilized, ensuring the overall integrity of the functionality. It includes effective communication between the upper and lower computers, a user-friendly human-machine interface, a real-time on-site monitoring system, real-time sensing and display of detection results, real-time optical-acoustic alarms, historical records, and self-repair and protection functions for the equipment.

(4) Convenient Operation and Maintenance

For electrical control systems, simplicity of maintenance and a well-coordinated relationship between the mechanical structure and electrical system is required. While ensuring the safe and reliable operation of the system, efforts should be made to enhance its maintainability, making it easier for personnel to inspect and repair the system’s equipment.

3.3 Control Circuit Design

The automation PLC system of the fireworks filling equipment consists of five main components: power supply, control elements, execution elements, detection elements, and display elements, as shown in Figure 3.1.

The working principle of the PLC system is that when the PLC system receives electrical energy from the power and supply chain, the sensing and detecting components detect the signal of the material’s arrival and transmit it to the PLC. The PLC converts the signal into a language the machine can understand, and then the corresponding cylinder makes the corresponding mechanical action. These relevant signals will be displayed on the screen.

3.3.1 Power Supply Design

We know electronic components must work at the rated voltage to function properly. In this fireworks making line, the power source for the conveyor section (tray) is a stepper motor with a working voltage of 380V. The servo motor driver, indicator lights, and other electrical components, such as the DC 24V stabilized power supply has a rated working voltage of 220V. Therefore, the entire electrical control system adopts a three-phase four-wire power supply method, as shown in Figure 3.2.

3.3.2 Transmission Design

The transmission part of the fireworks line consists of a screw feeder and conveyors. The role of the screw feeder is to transport the reducing agent and oxidizer to their respective fixed-volume bins. The speed should not be too fast to prevent changes in powder looseness. At the same time, the speed should be adjustable and high precision is required. The running speed and timing of the screw feeder directly determine the quality of the fireworks. Therefore, a servo motor drives the screw feeder to ensure accuracy, fast response, and timely feeding. One conveyor belt or tray is used to transport powder to the cylinder, while another conveyor belt is used to transport cannon cakes for processing in different stages of production. During the transportation process, both conveyor belts have corresponding position sensors for positioning. Therefore, the running accuracy of the conveyor belt is not very high, but the motor output torque is large. Considering economic costs, a three-phase asynchronous motor is selected as the power source for the conveyor belt.

3.3.3 Servo Motor Design

Considering that there are four types of raw materials in the fireworks automation process, and each type of raw material requires a different mass, it is necessary to design the servo motor based on the corresponding parameters to ensure a discharge time of 1 second during the screw feeder stage. Taking the cannon cake as an example, the corresponding servo motor is designed with the initial design parameters, as shown in Table 3.1.

Table 3.1: Servo Motor Design Parameters

The load inertia J can be obtained based on the above design parameters. The calculation formula for the rotational inertia JX of the ball screw in the X direction is as follows:

The pitch of the ball screw thread is denoted as ΔS. The mathematical expression for the load inertia denoted as JZ, is used to calculate the translation of the servo motor in the X direction.

The calculation formula for the load inertia in the X direction denoted as J, can be obtained from equations (3.1) and (3.2) as follows:

J = Jx + Jz — (3.3)

Based on the previous formulas, the load inertia corresponding to four different servo motors for each material is calculated and presented in Table 3.2.

Table 3.2: Load Inertia of Four Different Servo Motors for Each Material

A motor with a rated speed of 1500r/min is selected to achieve production efficiency. According to the principle of selecting load inertia exceeding 10%, the motor inertias are obtained, as shown in Table 3.3.

Table 3.3: Rotational Inertias of Four Motors

The servo motors selected are as follows. Please refer to Table 3.4 for the specifications of the servo motors.

Table 3.4: Specifications of the Four Servo Motors

In the X direction, neglecting the effect of the acting force on motion, we have Fy = 0N and the friction coefficient μ = 0.2. The formula for calculating the force F in the direction of linear motion is shown in equation (3.4).

F = ma + Wg + μ(y) — (3.4)

Considering that the ball screw is not connected to the motor shaft through gear or other transmission mechanisms, the transmission ratio between them is 1:1. Assuming a driving efficiency of η=0.7, the formula for calculating the load torque TL is shown as equation (3.5).

TL = (F S π ΔL) / (D η) — (3.5)

In the automated fireworks production process, the acceleration time T1 is 0.1s for a servo motor, the rotational speed N0 is 1500r/min, and the formula for calculating the acceleration torque TA is shown as equation (3.6).

TA = (30 N0) / (π T1) — (3.6)

In the automated fireworks production process, for the servo motor, with an acceleration time of T1=0.1s and a rotational speed of N0=1500r/min, the formula for calculating the acceleration torque TA is given by equation (3.6).

The maximum torque T of the servo motor is the sum of the load and acceleration torque, calculated using the formula shown in equation (3.7).

T = TL + TA — (3.7)

After calculating the above equation, the maximum torque of the four servo motors is shown in Table 3.5.

Table 3.5: Maximum Torque Calculated for Servo Motors

The above table shows that the designed servo motor meets the requirements and can ensure the safe production of fireworks.

3.3.4 Pneumatic Transmission Design

The production process of filling fireworks with mixed gunpowder requires the use of mechanized automation to increase fireworks productivity while avoiding potential safety hazards. The execution components of the entire automated packaging system will employ a large number of cylinders to achieve mechanical actions in various parts, aiming to achieve high productivity and safe, stable production on the entire automated fireworks making line. Additionally, the design has the following advantages:

(1) The working medium used is air, which is easily obtained. The discharged air can be conveniently processed and does not require the installation of additional containers or pipelines for air recovery.

(2) Pneumatic transmission allows for quick and responsive actions, easy maintenance, and air as a clean medium, avoiding issues of medium deterioration.

(3) The overall cost of pneumatic control is low and can provide automatic protection in case of overload.

3.3.5 Detection Design

Various sensors play a crucial role in the automated production process of fireworks. In the automated production of fireworks filling, optical sensors, temperature sensors, and infrared sensors are mainly used. The optical sensors act as contact switches that transmit signals to the PLC controller when they come into contact with the shell or limit mechanism, enabling the corresponding mechanical actions and ensuring the orderly and efficient operation of the entire automation process. The temperature and infrared sensors are primarily used for temperature detection during equipment startup and to monitor whether anyone is entering or exiting the workshop or if the doors are closed. In case of any abnormalities, they promptly send alarm requests to the PLC, leading to the automatic shutdown of the automation equipment, thereby ensuring safety and reliability during the work process.

3.4 PLC Working Principles and Selection

3.4.1 PLC Working Principles

PLC stands for Programmable Logic Controller. PLC controls digital information through cyclic scanning, implementing highly logical communication control. With the support of hardware and software control in the control system, PLC scans the instructions in the program in a certain cycle time and executes them in sequence. Within one scan cycle, PLC performs tasks such as self-diagnosis, initialization, and communication services in a sequential manner. PLC controls the actions of mechanical structures to achieve automation in the mechanical process. Additionally, it can easily edit and modify programs and monitor the status of devices through peripheral computers or program editors, allowing maintenance and debugging of on-site programs. The ladder diagram programming language is the most commonly used for PLC controllers.

3.4.2 PLC Selection

Due to the complexity of the control system for the fireworks and pyrotechnics filling automation line, we have chosen Delta’s PLC. Delta DVP series programmable controllers are known for their high speed, stability, and reliability, and they can be found in many industrial automation machineries. The DVP-E series is the highest-level host, suitable for more complex applications with increased program and data buffer capacity. It offers advantages such as fast execution of logic operations, a rich instruction set, and high cost-effectiveness.

For the overall functionality of the control system for the fireworks and pyrotechnics filling automation line, we have selected the DVP-E PLC module as DVP-80EH. The main technical parameters of DVP-80EH are shown in Table 3.6.

Table 3.6: Main Technical Parameters of DVP-80EH

The shape of DVP-80EH is shown in Figure 3.3

Figure 3. 3: DVP-80EH

An analysis of the technical requirements for the fireworks filling automation line control system reveals that the entire control system has 33 points of digital input and 22 points of output and requires 4 points of analog input.

3.4.3 PLC Resource Configuration

(1) Digital Input and Output

According to the production process of the fireworks filling automation equipment, the allocation of digital input and output points on the PLC is shown in Table 3.7.

Table 3.7: PLC Digital Input/Output Point Allocation Schedule

The analog inputs of the fireworks filling line’s PLC include temperature sensors for detecting the temperature inside each detection workshop and position sensors for detecting position signals. The allocation of analog input ports is shown in Table 3.8.

Table 3.8: PLC Analog Input/Output Point Allocation Schedule

3.5 PLC Software Design

3.5.1 PLC Control Requirements

Based on the powerful self-checking function, real-time communication, convenient configuration, reliable operation, and stable performance of PLC, the PLC used in the fireworks making line not only operates reliably but also experiences fewer faults. It has the following key operations:

(1) Manual and automatic operation

Manual operation is an essential operating mode during the debugging stage of the firework’s automatic filling equipment. In the debugging and maintenance stages, by pressing the manual operation button, various devices such as motors, conveyors, cylinders, vibrators, sensors, alarm lights, alarm buzzers, and PLCs are individually debugged. The automatic operation mode is used in general conditions. The automated equipment can perform a series of work processes in a loop without human intervention by pressing the automatic operation button. When the system is manually stopped, the entire system will complete a full process cycle before stopping at the starting point. In case of sudden power loss, such as during an earthquake or snow disaster, the system immediately stops but resumes working when the power is restored. The manual and non-manual modes can be controlled using buttons or touchscreen buttons.

(2) Fault diagnosis

Given the high level of self-diagnostic capability of the PLC, the electrical part of the fireworks automatic filling line utilizes the PLC’s own LEDs for diagnosis when the PLC itself or other components encounter faults.

(3) Data display

By installing photoelectric sensors on the line, the fireworks line can detect the number of projectiles passing through the conveyor belt and the number of projectiles filled with the medication. The temperature parameters inside each working studio are also monitored. The received signals are transmitted to the PLC controller for analysis and comparison and displayed through the touchscreen or monitoring software.

(4) Emergency Alarm

Once the fireworks automatic filling operation is running, if the temperature sensor or infrared sensor detects abnormalities, no material comes to the line for a certain period, or if a sensor malfunctions, the PLC receives these signals. The system initiates an alarm, simultaneously activating the alarm buzzer and causing the indicator light to blink continuously.

3.5.2 Fireworks Automatic Filling Process

The entire control system of the fireworks line follows the overall process flow. The process flow of the fireworks automation line is shown in Figure 3.4:

3.5.3 Programming of PLC

The control program ladder diagram for the entire system can be written based on the automated process flowchart for fireworks and pyrotechnic filling. The ladder diagram for the control system is shown in Figure 3.5.

Figure 3.5: Ladder diagram for the control system

3.6 Design of Configuration-Based Monitoring System Structure Model

3.6.1 System Design of the Monitoring System

Based on the entire fireworks making line process, the touch screen interface for fireworks and pyrotechnic filling automation was designed to correspond to the internal memory addresses of the PLC.

3.6.2 Application of Graphical Interface in the Monitoring System

The design of the touchscreen graphical interface is one of the key components of the entire monitoring system. Considering the production process of the fireworks and pyrotechnic filling line and the required technical functionalities, the control screen includes settings for switches, parameter statistics, parameter inputs, current status, and other items to achieve remote online display and control. The functional interface design includes relevant function settings and corresponding component types while incorporating the settings of the control system into the program design. The monitoring system for the fireworks and pyrotechnic filling line primarily achieves the following key functional interfaces:

3.7 Summary of this chapter

Based on the actual control principles of the automated production line for fireworks filling, this chapter has comprehensively considered issues such as explosion, synchronization, and static electricity and completed the design of electrical control systems, including control circuits, PLC, and sensors, as well as ladder diagram software and configuration monitoring software.

(1) Considering the characteristics of easy explosion and static electricity in the fireworks filling process, the article first completes the circuit design of the entire system. Based on the different contents of oxidants and reducers, relevant parameters are calculated to design servo motors that meet the requirements. Pneumatic transmission is designed at the points where oxidants and reducers come into contact. This series of designs completes the circuit design of the electrical control.

(2) According to the production process of fireworks filling, the selection of PLC, resource allocation of PLC, and selection of sensors are completed. With knowledge of the actual process flow of fireworks filling, ladder diagram software with relative positioning is designed to achieve the automation control process of fireworks filling.

(3) Considering the need for human-machine interaction in achieving automated production of the entire system, a user-friendly customers interface is designed on the touch screen based on automatic control, achieving the goal of friendly interaction and realizing remote monitoring of the entire automated equipment.

Chapter 4:Optimization Analysis of the Entire System

4.1 Introduction

In the previous two chapters, detailed theoretical calculations and designs were carried out for each component of the fireworks line, and the overall framework of the automation line has been formed. In this chapter, the optimization design of time synchronization, static mixer, vibrating screen, feeding device, and distribution pipeline in the entire system is conducted in theory. Detailed discussions are also made on issues such as time synchronization, mixing uniformity, and distribution uniformity.

4.2 Technical Requirements of Fireworks Automation Equipment

The technical specifications for fireworks filling automation are as follows:

(1) Dust concentration in the operating space ≤ 50g/m3;

(2) Mixing uniformity ±0.5%;

(3) Distribution uniformity ±3%;

(4) Working cycle ≤ 8 seconds;

(5) Height ≤ 4.2 meters.

4.3 Optimization of the Overall System’s Operation Synchronization

From Chapter 2, the following technical requirements and specifications are known for the entire fireworks filling automation turnout:

(1) Loading and unloading through the safety door takes 7 to 8 seconds;

(2) Each cake loading interval is 6 seconds, loading time is 2 seconds, and positioning and departure time are both 2 seconds;

(3) The transfer time of the mixed material from the tube cover to the inner cylinder is less than 2 seconds;

(4) Residual time on the powder conveyor belt is less than 4 seconds;

(5) The pushing time of the cylinder flow is no more than 1 second, and the back-and-forth cycle is shorter than 2 seconds.

That is, the initial design time beats were as follows: 1 second for the spiral feeder, 1 second for the fixed-volume bin, 2 seconds for the conveyor belt, 1 second for the cylinder, 2 seconds for the vibrating screen, 1 second for the arrival of the firework cake, totaling 8 seconds.

Accurate structural design was conducted in Chapter 2, and each component’s dimensions in the vertical direction are shown in Table 4.1.

Table 4.1: Dimensions of Components in the Vertical Direction

The powder undergoes free fall motion in the tube due to the gravitational force acting on it. The formula for calculating the free-fall time, denoted as t, is given by equation (4.1):

T = sq(2H/g) — (4.1)

By substituting the formula in equation (4.1) with the given data, the final required times for each section are obtained, as shown in Table 4.2.

Table 4.2: Required Times for Each Section

The calculated time from above is greater than 8 seconds, which does not meet the technical requirements for firework design. Due to the time difference between the mechanical and electrical control components, there is a reaction delay, causing an increase in the time for each component. The overall process time far exceeds 8 seconds. After optimization, it was decided to abandon the conveyor belt and cylinder. The raw materials can be directly transferred from the fixed-volume compartment to the mixing system, greatly reducing the number of components and improving efficiency. It allows the entire system to complete a firework-filling process in 8 seconds.

4.4 Optimization of Static Mixer Structure

A static mixer with three mixing elements was used in the initial design. The radial mixing high degree of the static mixer is calculated using the formula (4.2), as shown.

Among them, σ represents the particle size of the powder, while σ0 represents the number of mixing elements. Figure 4.1 shows the static mixer’s relationship between the mixing elements and the radial mixing degree. The figure shows that using more than 5 or equal to 5 mixing elements can achieve a higher mixing degree compared to using 3 mixing elements, resulting in a better mixing effect. The fineness of the particles is directly proportional to the mixing degree, meaning that the finer the powder, the higher the mixing degree.

Based on the calculations from the previous section, the total height of the entire device is currently H1 = 3.39m. The static mixer with three mixing elements has a height of H = 0.6m. By adding two more mixing elements, the height of the static mixer becomes H = 0.8m, and the total height becomes H1 = 3.39m + 0.2m = 3.59m, which is less than 4.2m. Regarding the height of the entire device, using a static mixer with 5 mixing elements meets the design requirements. Therefore, a static mixer with 5 mixing elements is used, which significantly improves the initial mixing effect of the oxidant and reductant.

Figure 4.5: Vibration System Structure Optimization

During the design in Chapter 2, a 100-mesh sieve and a pneumatic motor were designed. During the experimental phase, two issues were discovered:

(1) Uneven mixing of the materials. The materials coming out of the vibrating sieve are not evenly mixed, as evident from the presence of white particles, as shown in Figure 4.2.

Figure 4.2: Uneven Mixing of Materials

(2) Lengthy material discharge time. With a vibrating motor, it took 5 seconds for a complete batch of material, far exceeding the original set time of 2 seconds, greatly impacting the production efficiency of the fireworks automated production line.

To accurately analyze the issues, let’s analyze the vibrating sieve theoretically.

(1) Material Parameters

The density of the reducing agent and oxidizer mixture is 0.65 kg/L, and the diameter of the vibrating sieve is 120 mm. The material undergoes a throwing motion to reduce wear on the sieve surface, with a selected value of D=1.52.5, forward sliding index Dk=1, backward sliding index Dq=1, and vibration intensity K=35.

(2) Angle of Inclination and Direction of Vibration

For linear motion, the angle of inclination α0=0; for throwing motion, when the vibration intensity K=4.5, the optimal direction of vibration is δ=30°.

(3) Amplitude and Number of Vibrations

Using a pneumatic motor, the amplitude λ is selected as 5~6 mm, and the vibration frequency can be calculated using Equation (4.3).

Substituting the given data into the equations, we can calculate the vibration frequency as n=668~732 r/min. Let’s assume n=700 r/min. The calculation formulas for vibration intensity K and throwing index D are as follows:

Vibration intensity K can be calculated using Equation (4.4).

K = λ × n / 1000

Substituting λ = 5~6 mm and n = 700 r/min, we get:

K = 56 × 700 / 1000 = 3542

Throwing index D can be calculated using Equation (4.5).

D = Dk × Dq

Substituting Dk = 1 and Dq = 1, we get:

D = 1 × 1 = 1

Substituting the data, the calculated vibration intensity is K = 2.74, and the throwing index is D = 1.37.

(4) Average velocity of the material

With the previously calculated vibration intensity K = 2.74, referring to the table, the corresponding detachment coefficient is obtained as iD = 0.96. The theoretical formula for the average velocity of material motion is shown in equation (4.6).

By substituting the data, the calculation yields vD=8.46 m/s. Therefore, theoretically, the vibrating screen will not have problems such as a long discharge time.

To address the above two issues, a two-stage vibrating screen is used, with a material collection cone placed below each stage of the vibrating screen to gather the scattered material from all sides into the middle section of the lower-stage vibrating screen, increasing the blending degree of the material. The upper-stage vibrating screen uses an 80-mesh screen, while the lower-stage vibrating screen uses a 150-mesh screen.

Based on the above vibration frequency and vibration motor amplitude, the pneumatic motor model GT-20 is selected. The vibration frequency is adjustable, with a maximum of 2000r/min, a vibration force 4000N, and a control volume consumption of 325 per minute. Adding a vibration motor also increases the air pressure. The optimized structure is shown in Figure 4.3. These two measures are highly effective, achieving uniform mixing of the material and greatly improving work efficiency.

4.6 Material Discharger Structure Optimization

Two experiments were conducted During the material discharging system’s design phase. A cone and a sphere were placed on top of the material discharger cone for material discharging, as shown in Figure 4.4 and Figure 4.5, respectively.

From the two graphs, cone-shaped material distribution aligns more with the actual situation. With ball-shaped material distribution, a large amount of material accumulates on the top of the sphere, affecting the projectile’s quality of the project and may also pose safety hazards.

Since the powder has small and agglomerating characteristics, the particles tend to adhere to each other. At the same time, influenced by equipment and airflow, the flowability of the powder deteriorates, ultimately leading to powder adherence at the outlet, which is not conducive to uniform distribution of the powder in the material separation process. Therefore, installing a material discharger on the material separation cone is necessary. The purchased material discharger is shown in Figure 4.6.

Figure 4.6: Material Feeder

When using the material feeder available on the market for material feeding, the results obtained are not ideal, as shown in Figure 4.7, with a biscuit effect.

Figure 4.7: Diagram of Shell Biscuit Effect

The diagram of the shell biscuit effect in Figure 4.7 shows that the amount of propellant in each hole is highly uneven, with some having more and some having less. The analysis indicates several potential issues:

(1) The rotation speed of the feeder is too fast, causing the propellant to shift to one side.

(2) The feeder rotates steadily but leans to one side, resulting in propellant deviation.

(3) During the rotation of the feeder, airflow is generated in the enclosed and narrow space, causing uneven distribution of the materials.

To avoid the aforementioned problems, a redesign of the feeder is proposed by adding a cover on top. The material enters the feeder through the central hole, and the centrifugal force within the feeder evenly disperses the material to the periphery of the feeding plate. This optimized feeder effectively solves these issues, significantly improving the uniformity of material distribution. The optimized feeder is shown in Figure 4.8, and the construction diagram of the feeder with the cover is shown in Figure 4.9.

Figure 4.8: Optimized Feeder

Figure 4.9: Feeder building Diagram

4.7 Optimization of the Delivery Pipeline

During the initial experimental process, the length of the delivery pipeline was designed to be 76mm. The installed delivery pipeline is shown in Figure 4.10.

Figure 4.10: Distribution Pipe

The installation diagram of the distribution pipe shows that there are large bending angles in some areas, causing an accumulation of raw materials, which can lead to pipe blockage and affect the quality of fireworks. By increasing the length of the distribution pipe and adding a vibrator, along with the reduction of bending angles in the pipe, additional external forces are applied, causing intense movement of materials in the pipe under gravity and external forces, thus avoiding material accumulation.

Chapter 4 Summary

In this chapter, the following optimization designs were carried out for various key components of the automated fireworks production line, addressing issues such as compatibility, uniform mixing, and uniform distribution:

(1) Considering the time cycle of the entire control system is 8 seconds, theoretical calculations were performed to identify areas where optimization is possible. Conveyor belts and pneumatic cylinders were eliminated to achieve system compatibility, controlling the cycle within 8 seconds.

(2) To address the initial uneven mixing of oxidizer and reducer, it was theoretically determined that increasing the mixing elements in the static mixer would improve the degree of mixing. Therefore, the number of mixing elements in the static mixer was increased from 3 to 5, achieving uniform mixing of the raw materials in the initial mixing stage while maintaining the overall height of the equipment.

(3) Due to the long discharge time and uneven mixing of the vibrating screen, the vibrating screen’s rotational speed, amplitude, and feeding speed were calculated. The number of vibrating screens increased, and suitable pneumatic motors were selected to rapidly and uniformly mix the raw materials.

(4) The powder dispenser available in the market does not evenly distribute the powder during the fireworks filling process. Therefore, the dispenser was redesigned, greatly improving the uniformity of powder distribution. Additionally, a vibrator was added to the distribution pipe, reducing the overall operation time of the equipment and enhancing the quality and efficiency of the entire automated production line.

Chapter 5: Prototype Testing and Application of Fireworks Automated Production Line

5.1 Introduction

In the previous chapters, detailed parameter calculations and structural designs were conducted for the entire fireworks automated production line. Considering the hazards such as dust, frictional electrification, and explosions during fireworks production, theoretical analysis was performed to address these issues, and experimental methods were used to suppress them at the source. The separation of oxidizers and reducers was implemented. Key components of the fireworks filling line, such as uniform mixing of ingredients, even distribution, and precise timing, were optimized through experiments to achieve the best results. Building upon the previous chapters, this chapter assembles the scattered components of the fireworks automated production line mechanically and electrically and performs debugging on both the mechanical parts and the electrical control section, ensuring that each component operates smoothly and efficiently, thereby achieving high efficiency, safety, and stability in the fireworks automated production line.

5.2 Installation of Automated Equipment

The automated equipment for fireworks filling includes a spiral feeder, batching silo, conveyor belt, cylinder, Y-shaped pipe, static mixer, pneumatic butterfly valve, vibrating screen, vibrating tube, receiving cone, discharging cone, a dispensing device, partition plate, partition tube, and electrical control system. During operation, the oxidizer and reducer are separately fed from their respective sealed chambers to the batching silo. At this time, the upper door of the silo is open while the lower door is closed. When the time comes, the upper door and the lower door open, allowing the materials to enter the conveyor belt with a sealed cover. The conveyor belt delivers the oxidizer and reducer separately to the cylinders. When the two cylinders receive the signal indicating the completion of material delivery, they start simultaneous action to ensure the oxidizer and reducer intersect in the air and enter the static mixer together. After preliminary mixing, the powder undergoes vibration through the vibrating screen to achieve uniform mixing and accelerate the blending process. The mixed powder is evenly dispensed onto the partition plate by a dispensing device placed on the discharging cone. The powder then enters the firework cake through the partition tube, completing the mixing process for one firework cake. Two upper doors are installed on the fixed-volume silo to ensure equipment sealing during material feeding and discharging, reducing unnecessary errors based on different working conditions.

Powder transportation and packing is carried out using a V-shaped belt conveyor, with a material collection baffle added at the end of the conveyor belt for overall sealing and a powder recovery outlet.

The feeding cylinder and sealing cylinder share the same air path, utilizing the characteristic of different pressure requirements for the cylinders to ensure that the sealing cylinder always moves before the feeding cylinder.

The intersection in the Y-shaped pipe is sealed with a rubber bottom and a cone-shaped bottom, and a pulse air nozzle is installed for maintenance and dust removal purposes.

The vibrating screen uses pneumatic vibration and is flexibly connected to other components. Considering anti-static, anti-friction, and fire prevention issues, 304 stainless steel is used for the vibrating screen material, copper screws are used for the connectors, and the outer frame is made of aluminum alloy. The lower part of the vibrating screen is tapered and vibrates together with the screen.

The distributor achieves the powder’s diversion and adopts a logarithmic spiral shape. A low-speed pneumatic motor controls the speed, and the air circuit includes a pressure-reducing valve and a speed-regulating throttle valve.

The material distribution plate is designed with a circular groove, specifically without steps and with a smooth surface. It is connected to 61 material pipes at the lower end.

The installed fireworks production line is shown in Figure 5.1 and Figure 5.2.

Figure 5.1: Site Plan 1

Figure 5.2: Site Map 2

5.3 Debugging of Automated Equipment

5.3.1 Pneumatic Circuit Debugging

Before debugging the pneumatic transmission of the fireworks filling automation equipment, ensure that the throttle valve and shut-off valve are closed and the pressure of the pressure-reducing valve is 0. Ensure no operators are in the fireworks production workshop and start debugging the pneumatic circuit. The specific steps are as follows:

(1) Start the air compression and wait for the air pressure to reach the required specified pressure.

(2) Start the shut-off valve, but the solenoid valve of the throttle valve is not connected.

(3) Wait for the pressure to rise until it reaches the rated pressure for normal operation.

(4) Connect the throttle valve and adjust the pressure to determine the working status of the pneumatic motor and pneumatic motor.

(5) Use the manual button on the three-way five-port solenoid valve to check for any electrical valves with reversed air paths.

(6) Turn off the power.

The pneumatic control box, automatic control cabinet, and corresponding fireworks filling automation equipment monitoring facilities are set up in a dedicated studio away from the work site. This layout allows centralized management of all production lines and avoids live electrical hazards on the production site using a flexible layout approach. It ensures the safety, reliability, and efficiency of the fireworks automated production line during the production process. The pneumatic solenoid valves and electrical control cabinets are shown in Figures 5.3 and 5.4, respectively.

Figure 5.3: Pneumatic Solenoid Valves

Figure 5.4: Electrical Control Cabinet

5.3.2 Equipment Operation and Debugging

The fireworks making line process involves the PLC control and sensor system for process monitoring and on-site situation detection and monitoring.

The PLC control system receives signals from photoelectric sensors and temperature sensors to adjust the operation of the entire automated line, thus automating the entire equipment. After turning on the main power supply, the PLC first initializes the entire equipment and checks whether there are people in the workshop and whether the workshop doors are closed; and once these are confirmed, the fireworks are in place, and the entire equipment operates automatically. During the on-site debugging process, the automated fireworks filling equipment operates stably, with stable working conditions, minimal vibration of pneumatic motors, uniform mixing of materials, and uniform distribution, meeting the technical requirements of the automated fireworks filling equipment. The entire automated process can meet the requirements, and the operation of the fireworks making line is normal.

5.4 Main Evaluation Criteria during the Experimental Process

During the prototype testing phase of the fireworks making line, comprehensive evaluations are mainly conducted on aspects such as the occurrence of explosions, dust content, uniformity of mixing, uniformity of distribution, compatibility, and work efficiency.

5.4.1 Dust Explosion

Throughout the entire debugging process of the fireworks making line, there were no instances of dust splashing or explosions caused by the mixing of oxidizers and reducers, and the following measures were taken:

(1) Careful selection of materials ensures that friction and collision during material transportation will not generate static electricity.

(2) Grounding measures were implemented for components that may generate static electricity.

(3) Design of components that the raw materials pass through based on the static friction force and the angle of repose of the materials to avoid material accumulation in the production line and reduce the accumulation of oxidizers and reducers.

(4) Sealing treatment was applied to the connection points of the conveying system, mixing system, distribution system, and dispensing system to prevent dust overflow in the production line.

(5) The automated fireworks making line is equipped with temperature sensors, infrared sensors, etc., to detect the temperature and presence of personnel in the workshop in real-time.

(6) The entire automated fireworks making line has a remote monitoring system to promptly handle any detected abnormalities.

5.4.2 Uniformity of Mixing

During the automated debugging process of the fireworks making line, the situation greatly improved after the improved mixing system for the four different colors of oxidizers and reducers. The mixed powder has no noticeable yellowish particles or white powder impurities, resulting in a uniform and excellent mixing effect, as shown in Figure 5.5.

Figure 5.5: Mixed Uniformity Effect Diagram

5.4.3 Material Distribution Uniformity

During the debugging process of fireworks automation equipment, after optimizing the material distribution system, including the static mixer, feeder, vibrating screen, and material distribution cone, the material distribution is relatively uniform. The error in the size of the fireworks cakes does not exceed ±3%. The large fireworks cakes require 366g with 6g per hole, while the small fireworks cakes require 183g with 3g per hole. The specific experimental data for the size of fireworks cakes are shown in Table 5.1.

Table 5.1: Medication Content of Size of Fireworks Cake

From the above table, it can be seen that the maximum and minimum values of the charge weight for both large and small cannon crackers are within the error range, thus meeting the accuracy requirements of the equipment.

5.4.4 Compatibility

During the automated debugging process of the fireworks making line, through repeated debugging and based on the actual production process, the following improvements have been made to the production process of the cannon crackers. The optimized actual process flowchart is shown in Figure 5.6.

Figure 5.6: Optimized Actual Process Diagram

The improved process flow of the fireworks automated production line is based on pneumatic butterfly valves and is divided into two paths.

The first path is as follows: when the shell cake is in place, the pneumatic butterfly valve opens for 2 seconds, and the vibrator and pneumatic motor start working for 3 seconds. The shell cake stays for 1 second and then departs for 1 second. The other path is as follows: the upper material compartment door opens for 4 seconds, and after the lower material compartment and other pneumatic butterfly valves are closed, they open for 2 seconds to place the materials at the pneumatic butterfly valve, waiting for the arrival of the shell cake. The entire process, including the arrival of the shell cake for 1 second, takes a total of 8 seconds, greatly improving the original manual production efficiency and achieving mechanized and automated production while avoiding accidents.

5.5 Issues in the Experimental Process

During the debugging and operation of the entire automated filling equipment for fireworks, the following problems were discovered:

1.   Large errors: Possible reasons include whether the motor is always on, whether there are remnants of 61 hoses, determining which direction always has more or less mass, whether the alignment is accurate, or if there is a deviation towards one direction. In addition to alignment, the feeding disk must also be kept level; otherwise, it will tilt towards one side, causing an imbalance in the distribution of materials.

2.   Difficulty in discharging materials from the fixed-volume compartment, especially the oxidizer potassium chlorate. The reasons are as follows: when the fixed-volume gate is closed, and the upper gate is opened during volume determination, the raw materials are filled in the cylindrical barrel, and the upper gate is closed. Due to the 8mm thickness of the gate, the raw materials are inevitably compacted, preventing them from freely falling under their own gravity. Applying an impact force on the volume cylinder wall can facilitate the falling of the materials or another structure can be used as a replacement. Since the material hopper contains the raw materials, one of the upper and lower gates is always closed. If the lower butterfly valve is also closed and the lower gate is opened, the falling of the fixed-volume cylinder’s materials will cause compression of the air inside the bent pipe, obstructing the free fall of the materials. It can be resolved by drilling grooves at the edge of the butterfly valve (on the inner side of the bent pipe) to allow free airflow in and out of the bent pipe. The hollow section can be formed in the material feeder barrel, and long and short bars can be welded on the mixing rod. Connecting the outer ends of these bars together will form a spiral helix, creating a stirring screw-feeding effect.

3.   The upper material hopper easily forms a hollow space, preventing the materials from falling. Adding unequal-length material strips (the larger the barrel, the longer the strips) on the material feeding rod at a certain angle improves the feeding into the measuring cylinder. However, due to the angle (relative to the horizontal plane), width, and thickness of the strips, the powdered materials are easily compacted during the feeding process, leaving a certain thickness of densely packed materials on the inner wall of the material hopper. It is recommended to replace the strips with bars placed horizontally, with the length of the bars slightly smaller than the inner diameter of the location. Connecting the ends of the bars forms a variable diameter spiral blade conveyor, and synchronizing the opening and closing of the material feeding with the upper gate will achieve better stirring and feeding effects.

(4) The inner diameter of the measuring cup is 43.7mm without trimming. By setting an air inlet on the wall of the measuring cup, the raw materials fall down with the impact of high-pressure airflow. The existing measuring cup uses two gate valves for quantification. However, due to the clearance in the front and rear chambers (expansion and contraction) of the gate valve tongue, as the tongue continuously expands and contracts, the internal clearance becomes tighter, making it difficult for the tongue to extend to its original position. There is also a possibility of jamming or aiding combustion. A rectangular shape is used, with a length of 240-280mm and a width of 140-160mm. A through-hole with an inner diameter of 100mm is arranged in the middle, and the required volume determines the height. The material is to be determined (if using a polymer, wear resistance and prevention of particle embedment should be considered). Sealing strips are set on both sides of the upper surface, and sealing strips are set at the front and rear ends of the tongue expansion and contraction cavity. An elastic material is set on the upper surface to seal the funnel opening when the measuring cup leaves the material container funnel. Several threaded holes M6-M8 (measuring cup opening, front and rear ends of the rectangular shape, side sealing strips, etc.) are arranged in appropriate positions to fix the elastic plate and sealing strips. A coupling is set on one end face of the rectangular shape, connected to the expansion and contraction rod of the gate valve (if the existing gate valve can be modified for use). One or two dovetail grooves are set on the bottom surface of the rectangular shape to ensure that the rectangular shape can slide freely on the track. The change in the volume of the measuring cup can be achieved by adding plates with hollows (100mm hole) on the surface of the rectangular shape.

(5) The existing butterfly valve causes severe material blockage. The butterfly valve has a small aperture (44mm), which causes the powder on one side of the valve to be compacted when it is flipped 90 degrees, blocking the falling of the powder. The material blockage can be reduced by reducing the flipping speed of the butterfly valve and increasing the valve aperture diameter (100mm is appropriate).

(6) The existing mixing is significantly uneven, with distinct layering and clear black-and-white features. Can the previously inclined feeding channels on both sides of the “Y” shape be changed to vertical channels with a discharge port arranged in the middle? An additional material distributor can be added here to facilitate sufficient interaction of the raw materials in the air.

(7) The material blockage in the vibrating screen for mixing is also severe, and the powder cannot come down at all. The vibrating screen and the collection hopper are filled with powder. The blockage problem is basically eliminated by changing the aperture of the bottom layer screen to the same as the upper two layers.

5.6 Experimental Results

During the debugging and operation of the fireworks filling automation equipment, the experimental results and data for small cannon cakes are shown in Figures 5.7 and 5.8, and the experimental results and data for large cannon cakes are shown in Figures 5.9 and 5.10. The data in each hole of the cake represents the filling amount in grams. From the experimental results and data, it can be seen that the entire fireworks making line can meet the requirements.

Figure 5.7: Cannonball Biscuit Experimental Results

Figure 5.8: Cannonball Biscuit Experimental Data

Figure 5.9: Big Cannonball Biscuit Experimental Results

Figure 5: Experimental Data of Top 10 Firework Cakes

5.7 Chapter Summary

This chapter conducted experiments and debugging on the automated fireworks making line, combining pneumatic debugging with equipment operation debugging. The investigation focused on dust ignition, uniformity of mixing and dispensing, and the compatibility of the entire automated equipment. All performance aspects meet the practical production needs, and the problems encountered during the debugging process were optimized in the design. The overall effect of the automated equipment has greatly improved. The results of the automated equipment debugging demonstrate that the automated equipment operates safely and reliably, functions properly, has minimal and controllable impact vibrations in the vibration section, and the pneumatic control system operates smoothly. The control and detection systems exhibit strong robustness and can meet the design specifications of the system’s targets. This automated equipment can satisfy the requirements of the process for filling fireworks materials.

Summary and Outlook

Summary

In today’s society, science and technology continuously develop and shed light on various fields. However, the fireworks industry, which is extremely dangerous, has not yet achieved automation in most parts. With the emergence of problems such as labor shortages and high labor costs, achieving automation in the fireworks industry is an urgent and primary task.

The research object of this paper is an automated fireworks making line being developed by a fireworks manufacturing company. After a series of analysis and designs, the functions of each part are designed based on the actual process of fireworks. Then, the three-dimensional software Solidworks is used to create and assemble models, and an automated control system for the entire equipment is designed based on the determined process flow. Solutions are also found for the difficulties in raw material transportation, uneven mixing of powders, uneven distribution of powders, and synchronization of timing in the fireworks filling line process. Finally, the prototype of the processed product is subjected to on-site debugging and optimization. The main contents and conclusions of this study are summarized as follows:

(1) A brief introduction is provided on the current development status of the fireworks industry, including a detailed explanation of the key problems existing in fireworks machinery.

(2) The fireworks making line is modeled in three dimensions using Solidworks. Considering the potential issues such as static electricity, dust, and collisions that may lead to explosions in the fireworks making process, the design of the automated fireworks making line takes into account practical problems from aspects such as design, calculation, material selection, and on-site layout. Combining relevant theories and optimization design methods ensures the entire automated equipment adapts well to the working environment.

(3) The automated control of the fireworks making line equipment is achieved using PLC controllers. Based on the process of the automated fireworks making line, the selection of the PLC is determined to specify the specific model of the PLC. Suitable electrical components, sensors, and monitoring devices are selected, and the corresponding control circuit diagram, connection process, and program are designed to achieve the automation control of the fireworks making line.

(4) Key factors such as synchronization of time allocation, static mixer, vibrating screen, and distribution pipeline are analyzed and designed theoretically. Rational optimization design is carried out based on theoretical analysis results, ensuring that the entire fireworks filling automated equipment comply with fireworks design specifications.

(5) The designed prototype is assembled and debugged on-site. Manual debugging is conducted first to ensure no components are damaged, and the intended actions can be achieved. Then, automatic debugging is performed to ensure the integrity and smoothness of the entire process, meeting the fireworks making specifications.

Outlook

This article discusses the scheme, structural design, and electrical control system design for the automated fireworks making line equipment. It also theoretically calculates and optimizes the difficulties in filling fireworks powders and carries out prototype debugging for the entir line. The automated equipment can meet the design requirements and be promoted and used in fireworks enterprises. However, due to the complexity of the entire system, limited personal time, and inadequate abilities, the research work of this article is not perfect. In addition to the work completed above, further research is needed in the following aspects:

1.   The implementation in this article is a prototype of the filling process in the first generation of automated fireworks making lines. In future production, the process needs to be iteratively optimized to design more efficient and environmentally friendly automated equipment. The connection with the preceding and subsequent processes needs to be considered, and additional connecting devices need to be designed.

2.   Many parts of the entire control system still need to be optimized. Under the optimization of the entire process flow, prioritize the use of safe and efficient controllers. In the program design process, adopt classical optimization algorithms to enhance the robustness of the control system.

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References

• (PDF) A distributed HW-SW platform for fireworks
• Impact of Fireworks Industry Safety Measures
• Fireworks, Embedded Wireless and Insecurity-by-Design
• Manning Park Spring Fair Case Study
• safe handling, storage, and treatment of waste fireworks
• department of licensing and regulatory affairs
• FIREWORKS: A REVIEW OF THE LAW POLICY PAPER
• Fireworks Law
• Fireworks in Grants Pass
• Federal Explosives Law and Regulations
• Fireworks and Pyrotechnics Special Effects Permit – COA
• Part 2 Fire Prevention and Fireworks Act
• Fireworks — Design Life-Cycle