Here we will discuss the research on the automatic production line of fireworks granules. The paper establishes the overall process of the production line, creating geometric models of the stacking components and assembling them using Pro/E solid modeling software. The Pro/E motion simulation is also used to verify the feasibility of the mechanism design, while dustproof, explosion-proof, and antistatic materials and equipment are selected during the design process. The article also covers establishing the pneumatic system for the stacking components, utilizing AMEsim pneumatic simulation software for simulation analysis. Furthermore, the robot control system of the stacking components is designed based on the Mitsubishi PLC, achieving automatic robot control. Lastly, the production monitoring system is created based on the configuration king, meeting the requirements of real-time monitoring and data management.

ABSTRACT

Fireworks deeply affect Chinese people, and it has been indispensable to all kinds of celebrations and festivals. Apart from happiness, fireworks also cause injuries to people. Carelessness in production always causes injuries; carelessness in storage and transportation often causes accidents; carelessness in setting off fireworks causes big fires. Terrible accidents happen, especially in the process of production. Nowadays, fireworks production is mainly manual operation while the mechanization degree is not high. Therefore, it is imperative to realize the automation of fireworks production. This paper studies the more dangerous production techniques in the production process: powder weighing, granulation, palletizing, drying, and mixing. Analyzing the fireworks production process, we explore the most suitable production methods and establish the entire production process.

Meanwhile, the palletizer component is studied in detail. Firstly, the paper discusses the action the palletizer should complete according to the technique. The palletizer system components model is worked out based on Pro/E. The whole system mainly contains five parts: a salver conveyor, a salver supplier machine, a filling conveyor, a shelf conveyor, and a palletizer. After that, this paper confirms the rationality of the mechanism motion by establishing the motion simulation based on Pro/E; it also confirms the operability of the circuit by establishing a pneumatic circuit simulation based on AMEsim. Then, in this paper, the palletizer system control circuit (robot) is designed. Based on the Mitsubishi PLC, the robot control system has been worked out, and according to Kingview, the monitoring system is set up. A friendly human-computer interaction interface has been designed. Thus, the design work of the palletizer system is completed.

KEYWORDS: fireworks, palletizer, automatic production line, pneumatic simulation, monitoring system.

Chapter 1: Introduction

1.1 Introduction

1.1.1 Background and Significance of the Research

As one of the three ancient civilizations in the world, China has a glorious and brilliant civilization with a vast and profound cultural history. The Chinese people have left a distinct mark on the history of world civilization. China is composed of 56 ethnic groups with diverse cultural forms and customs. Among them, fireworks and firecrackers, one of ancient China’s four great inventions, have played an important role in history. The activity of setting off fireworks and firecrackers is a traditional folk activity that represents people’s pursuit of happiness and good fortune and their desire to ward off evil. It is a way for people to welcome the future and pray for good luck, and it represents people’s pursuit of joy, peace, and auspiciousness.

Fireworks and firecrackers have a long history in China, with traces of their use appearing as early as the Spring and Autumn Periods. In ancient times, people used firecrackers to drive away ghosts and evil spirits, hoping to bring peace for the coming year. As recorded in the “Firecracker Song”: “One or two sounds frighten a hundred ghosts, three or four sounds make the devil’s nest collapse. Ten sounds calm the gods, and peace prevails in all directions.” A legend about firecrackers has been passed down: a long time ago, there was a fierce beast called “Nian,” which would appear on the night of the Chinese New Year and harm people and livestock. People burned bamboo sticks before their doors to stop this Nian beast while hanging up red items or using red items. Since bamboo sticks have air inside, they expand when heated and burst with a loud sound, scaring away the Nian beast. Later, with the invention of gunpowder, firecrackers made of gunpowder replaced the bamboo stick firecrackers.

As time passed, the activity of setting off fireworks and firecrackers gradually became a traditional folk custom and a way for people to express their joy with their own unique cultural characteristics. The original superstitious content has also gradually faded away. Nowadays, people set off fireworks and firecrackers not only to welcome the New Year but also to celebrate festivals or happy occasions, such as the Double Ninth Festival, the Mid-Autumn Festival, the Lantern Festival, the opening of shops, weddings, and building houses, to express their good wishes. It can be seen that fireworks and firecrackers are an important part of Chinese culture and customs, beloved by people, and have become one of China’s unique characteristics, with a worldwide influence.

Fireworks and firecrackers are a part of China’s national culture and an indispensable witness. Under the influence of Chinese culture, other countries in the world also have a great fondness for fireworks and firecrackers, making the artistic products of this pyrotechnic industry more widely spread. Since China’s accession to the World Trade Organization, the market trend for fireworks and firecrackers has become increasingly clear. The popularity of fireworks and firecrackers has made China a major producer, consumer, and exporter of fireworks and firecrackers. However, while bringing joy to people, fireworks and firecrackers also bring harm. Personal injuries caused by careless production, major accidents caused by improper storage and transportation, and fires caused by careless use are common occurrences, especially in the production process, and such accidents frequently appear in the media in this information age.

Fireworks and firecrackers produce various splendid effects mainly due to the pyrotechnic material. The pyrotechnic material can react under isolated air, and its main characteristics and uses are combustion and explosion. From raw materials to finished products, fireworks production is dangerous and flammable. China has strict requirements for fireworks and firecrackers and controls them strictly (robot). A small mistake in the production of fireworks can lead to a major accident. However, some low-level mistakes often occur during production, such as violating procedural operations, collisions during production, and failure to use the specified equipment. These are key factors in causing fireworks accidents. To reduce the probability of accidents occurring during production and minimize the losses caused by accidents, it is important to mechanize each link in the production of fireworks.

Figure 1.1: Fireworks Powder and Finished Product

The market prospects for fireworks and firecrackers are vast, as our country has enormous consumption capacity. On festive occasions, sales points for fireworks and firecrackers are always crowded with people. Figure 1.1 shows the raw materials and finished products of fireworks. Some large cities, such as Beijing, have introduced measures to ban the use of fireworks and firecrackers, but this has not significantly impacted the sales market for these products. Furthermore, the sales prices of fireworks and firecrackers have remained high. From low-end firecrackers to high-end display shells, their prices are much higher than their raw material costs (money). The main reason for this is that producing fireworks and firecrackers involves significant risks and is inefficient. Therefore, the trend toward mechanized production of fireworks and firecrackers is inevitable.

As an important part of the logistics field, palletizing machines can improve fireworks production lines’ automation level and efficiency. Palletizing machines can automatically stack various materials or pack them according to certain requirements and patterns, making it easier to handle the materials. There are many types of palletizing machines, each with various functions.

• This paper establishes the process of the automatic production line of fireworks granules.
• Geometric models of stacking components’ parts are created using Pro/E solid modeling software.
• Pro/E motion simulation verifies the feasibility of the mechanism design.
• The pneumatic system of the stacking components is established, and AMEsim software is used for simulation analysis.
• The robot control system is designed based on Mitsubishi PLC for automatic control.
• The production monitoring system includes real-time data collection, historical data inquiry, production dynamic screens, manual point control, and alarms, meeting the requirements of real-time monitoring and data management.

1.1.2 Common Problems in Fireworks Production

Fireworks and firecrackers are an indispensable part of folk celebrations, and their industrial development has benefits such as promoting economic growth, increasing export exchange rates, and providing more job opportunities. However, the production of fireworks and firecrackers is also a high-risk industry with a high level of danger. In recent years, many major and extremely serious accidents have occurred, including explosions and fires caused by safety issues or improper storage during production and accidents caused by poor product safety and quality. Therefore, fireworks and firecrackers production is a high-risk industry that can threaten personal and property safety.

Explosions and fires characterize fireworks and firecrackers production accidents. There are many reasons for accidents during the production process, such as violations of regulations, excessive production, misuse of workshops, use of prohibited drugs and formulas, use of items and tools that can easily produce sparks from impact or friction, presence of fire sources in production areas, high temperatures in storage facilities, failure to comply with clothing requirements for production personnel, and incorrect posture during operations. Generally, the direct causes can be summarized into two categories: unsafe mechanical materials or storage environments and unsafe human behavior. However, the vast majority of accidents are caused by human violations.

Due to the diversity of materials used in fireworks and firecrackers, their overall performance is quite sensitive, and unexpected situations can ignite the chemicals, causing terrible consequences, such as friction, high temperatures, static electricity, and impact. Among them, friction is inevitable and the main risk in the production process. The reasons are as follows: firstly, the drugs commonly used today have high friction sensitivity; secondly, friction is generated whenever there is movement, and its universal presence causes highly sensitive drugs to ignite or explode; thirdly, human factors are involved, and personnel involved in production may not have a high awareness of danger, and the universality of friction causes people to overlook this issue.

Due to the production of explosives, automation is strongly required. Similarly, the development of automated equipment for explosives is affected. Hazards are everywhere in the production process, which causes people to doubt the development of automation. Can safety be guaranteed, and how to investigate responsibility after an accident all hinder the development of automatic fireworks production lines?

1.2 Domestic and International Research and Status

1.2.1 Overview of Domestic Development

China is the birthplace of fireworks and firecrackers; as one of the traditional arts, fireworks and firecrackers has undergone three stages of development, from burning bamboo knots to saltpeter and now to fireworks. The use of burning bamboo knots as firecrackers lasted for more than 2,000 years. With the invention of gunpowder, one of the “Four Great Inventions,” burning saltpeter gradually replaced bamboo knots and became widely used. Around the 6th century AD, people began filling bamboo tubes with black gunpowder and lighting them with a fuse. The resulting sound was louder, and the explosion stronger than burning bamboo knots, making it a true firecracker.

Fireworks, as the name suggests, refer to the smoke and fire produced by the combustion of gunpowder and are collectively called smoke and fire. They are also called “fireworks” or “pyrotechnics.” The inside of the fireworks is filled with explosives and wrapped in paper. When lit, they release colorful sparks, some of which can even fly into the air in various shapes. They were very popular during the Song Dynasty.

With the progress of society, fireworks gradually evolved into a form of art called “firework display.” It cleverly combines light, movement, sound, and color to provide people with a beautiful artistic experience. During festivals, fireworks are set off to celebrate, adding an exquisite touch to people’s lives.

In the mid-20th century, China’s fireworks and firecrackers industry experienced rapid development. Large and medium-sized enterprises had reached over 7,000, distributed in various provinces, with the main production areas in Jiangxi, Hunan, Fujian, and other provinces. The number of people engaged in related industries related to fireworks and firecrackers could reach 400,000, not including some small individual businesses and illegal operators. As of 2007, the production value of fireworks and firecrackers in China had reached as high as 20 billion yuan, with over 4 billion yuan in export value. More than 20,000 enterprises were engaged in the wholesale of such products.

While experiencing rapid development, problems have also become apparent in China’s fireworks industry. From 1985 to 2003, there were 8,448 accidents in the industry, with an average of over 400 accidents occurring each year [8]. It means, on average, such accidents occur every day, sounding an alarm for us that the safety situation in China’s fireworks industry is very serious. Although China has increased its control over the fireworks industry in recent years and has cracked down on illegal individual operators, the number of casualties has not decreased. It has resulted in a phenomenon where the number of accidents has decreased, but the severity of accidents has increased, with major accidents occurring in China every year.

In the face of the bright prospects but rough road ahead for China’s fireworks market, fireworks production can be described as “three highs and three lows.” The “high threshold” refers to the fact that most fireworks production still adopts traditional techniques. There is no relatively systematic modern manufacturing system, so it requires a relatively high entry threshold to enter this industry truly. The “high risk” refers to fireworks production being a high-risk industry with high labor intensity. It does not have a relatively advanced automatic production system, which makes personnel participation significant in the production process. However, fireworks’ flammable and explosive nature makes safe production a difficult problem that many people are unwilling to touch. Accidents involving personnel injuries occur every year in fireworks production. The “high profit” refers to the relatively low capital required for fireworks production but the high profits obtained, and the current domestic fireworks are in a state of supply shortage.

The “low production efficiency” is because an automatic assembly line production has not been formed. The production process is still mainly manual, with lagging middle links and personnel participation, which does not ensure production efficiency. The “low quality of employees” is because China’s fireworks production enterprises are mainly distributed in sparsely populated rural or suburban areas. The quality of employees is generally low, and there is no unified management system. The “low quality of the working environment” is due to the low sealing of equipment and the lack of a sound ventilation system during fireworks production, resulting in a large number of gunpowder particles in the factory building. Long-term work in such an environment will significantly impact human health; even if personnel wear protective equipment, working in such an environment full of gunpowder is still a huge challenge to life safety.

An automatic production line has a palletizing system. Palletizing can be divided into manual and mechanical automatic palletizing [9]. In situations where the process is convenient and the labor intensity is low, manual palletizing can be performed. In situations where the labor intensity is high, the process is complex, and the repeatability is high, mechanical automatic palletizing is required. Mechanical automatic palletizing has many advantages. It not only reduces the labor intensity of personnel and improves production efficiency but also reduces direct contact between personnel and materials, reducing accidents caused by personnel errors and making production safer. Another advantage is that mechanical movements can be replicated, whereas human movements cannot. The consistency of products obtained by machine operation in the same batch is better, facilitating unified management.

As a new high-tech product integrating machinery and electronics in the field of logistics [10], palletizing machines can realize block, box, and granular stacking molding according to different routes, levels, and size requirements to facilitate overall logistics operations. In the 1960s, breakthroughs in palletizing machines were made in countries such as Europe and the United States, and semi-automatic and fully automatic equipment was developed. Through continuous updates and iterations in practice, palletizing machines have been widely used in many fields of industry and agriculture, such as food, chemical industry, engineering machinery, petroleum, medical supplies, etc. Although China started relatively late in palletizing machines, they have been widely used in practice.

There are many types of palletizing machines, and they have a wide range of applications. According to the complexity of the completed movement and the types of tasks performed, they can be divided into cement automatic loading and palletizing machines, robots, palletizing manipulators, palletizing machines, etc. [5]. Palletizing robots, as a technology with high automation and strong flexibility in palletizing, are highly favored. They have many advantages, such as a small footprint, high flexibility, wide working range, and low cost (money), making robotic palletizing a development direction of palletizing technology. Currently, large enterprises are equipped with palletizing robots [11] for palletizing, which can improve production efficiency and realize flexible production. See Figure 1.2.

Due to China’s technological innovation, the application scope, product performance, and quality of the palletizing machines produced in China have been greatly improved. Many research areas have gradually caught up with the world’s technological level. Overall, the performance can already meet the needs of enterprise material palletizing and logistics. However, there is still a gap compared to the world’s advanced products. The quality of the basic components used in palletizing machines is generally low, the palletizing efficiency is not high, and the controller’s stability is low.

After understanding the development overview of China’s palletizing technology, it is known that the future of palletizing machines in design, manufacturing, and usage is very promising. After years of development, China has a research team dedicated to the development of palletizing technology. After years of exploration and practice, they have accumulated a lot of experience and laid a solid foundation for realizing more efficient, stable, and flexible palletizing technology. With China’s increasing emphasis on manufacturing, China’s mechanical production and manufacturing level has greatly improved, resulting in the quality improvement of basic components and the branding of control elements, all of which have laid a good foundation for the rapid development of palletizing machines.

1.2.2 Overview of Foreign Development

As the rise of fireworks abroad is all rooted in China, their manufacturing process was essentially the same as that of China for a long period. In modern times, due to the rapid development of industrial technology abroad, there have been innovations in producing fireworks, leading to improved effects from both pharmaceutical production and ignition. At the same time, due to the socialization of production and the relative concentration of resources, fireworks companies have realized that joint production and unified management can reduce costs and improve their competitiveness, thus making group and industrial chain production a common form of organization abroad. However, due to the relatively low dependence on fireworks abroad, the output value of the fireworks industry is not very high, and a portion of fireworks is imported from China. Also, the number of sectors engaged in their production abroad is not too high due to the danger of fireworks. Nevertheless, given the higher level of industrial automation abroad, there are some mechanized production processes in the field of fireworks manufacturing as well.

Foreign palletizing technology is relatively mature. In recent years, with the rapid development of technology and the acceleration of the social pace, the demand for higher production levels has been continuously increasing, which has accelerated the pace of the development of automated production and provided ample space for the development of palletizing machines. With the potential market demand increasing, research (find) on palletizing technology has become more enthusiastic globally, and the fierce competition among countries has greatly promoted the rapid development of palletizing technology. Among them, the United States, Germany, and Japan are at the forefront of palletizing technology, and palletizing products have a significant market share.

1.2.3 Trends in Fireworks Production

Regarding the current technology and overview of the fireworks production industry, the trends are toward high safety, high efficiency, and high automation.

1.   High safety requires reliable equipment operation and minimizing contact between personnel and materials. Isolation equipment should be set up to prevent injury to personnel and chain reactions caused by chemical explosions. Additionally, monitoring technology should be combined with online detection and real-time monitoring of processes to reduce the probability of accidents.

2.   High efficiency refers to improving the efficiency of equipment production, thereby increasing the company’s production capacity to meet the potential consumption capacity of the market.

3.   The entire production process is based on mechanical operation, and the existing process flow should be improved to achieve uncrewed operation. Similar processes should be combined to achieve multi-station automation.

1.3 Main Research Content of this Thesis

1.3.1 Research Objectives

Fireworks hold an important position in China and have always been beloved by the general public. However, their production faces many problems. Through research on the weighing and mixing, granulation, stacking, and drying processes of the fireworks production line, our research group aims to improve the industry’s safety production technology level and reduce and prevent the occurrence of fireworks and firecracker explosions accidents. From an economic perspective, this will transform the previously restricted industry into a normal and encourage continuously developing one. The implementation of this technology not only has broad operational prospects but also can generate significant economic and social benefits.

In the existing stacking machine’s operation process, the rapid start and stop often cause significant impact and friction forces, leading to problems in specific environments. In the case of the production line for explosives, large impact and friction forces during transportation can cause explosions and severe accidents. In this thesis, we use an electromagnetic proportional valve to control the lifting cylinder and attempt to achieve a smooth start and stop of the lifting cylinder by setting the proportional valve’s electrical signal. It will eliminate hard impacts during the start, stop the process, and reduce or avoid soft impacts [14].

Expected Results: Our research group aims to study the entire process of mixing gunpowder to dry bright beads without human involvement. We aim to achieve this by placing raw materials into the weighing equipment, pouring the materials into the feeding equipment on the conveyor belt according to the set mass, mixing the materials in the mixing machine, and then transporting them to the granulating machine. The granulated product will then be formed into plates, stacked by the stacking machine, and finally sent to the drying machine for drying. The stacking machine mainly consists of three parts: the feeding mechanism, conveying mechanism, and the stacking mechanism. The tray is sent into the conveying mechanism through the feeding mechanism, the drug particles are loaded onto the tray through the conveying mechanism, and then the tray is sent to the stacking machine for stacking. Finally, the tray is sent to the drying machine for drying. Due to the quantitative constraints in each production workshop and the relatively slow pace of the mixing, granulation, and drying processes, the stacking section can achieve a one-to-many supply. This thesis mainly studies the stacking machine’s design, the control program’s preparation, and the movement’s simulation to achieve automation.

1.3.2 Research Content and Methods

This paper focuses on mixing gunpowder to dry the finished product using a rotary drum dryer. The process includes weighing, mixing, granulating, stacking, and drying, particularly emphasizing the stacking process. This paper systematically designs the mechanical structure, pneumatic system, robot electrical control system, human-machine interface, and simulation for the stacking process. The specific research contents of each chapter are as follows:

Chapter 1 Introduction: This chapter mainly introduces the current production status and development trends of fireworks and explains the significance of studying the mechanized production line for fireworks.

Chapter 2 Overall Design of Fireworks Production Line: This chapter analyzes the working mechanism and production process of the fireworks production line and provides an overall design for weighing, mixing, granulating, stacking, and drying.

Chapter 3 Design of Stacking Machine Components: This chapter designs the stacking machine’s mechanical structure and pneumatic system. It uses PRO/E to model and simulate the motion of the stacking components and AMEsim to analyze the pneumatic process.

Chapter 4 Electrical Control System Based on Configurator and PLC for Stacking: This chapter establishes a real-time monitoring human-machine interface based on Configurator and PLC for the stacking process (robot control system).

Chapter 5 Conclusion and Future Directions: This chapter summarizes the main achievements of this study and proposes future research directions.

Chapter 2: Overall Design of Fireworks Production Line

2.1 Introduction

The automatic fireworks production line mainly realizes the automation of gunpowder weighing, mixing, granulating, stacking, and drying. This chapter will establish safety requirements for fireworks production and introduce each component’s working principles and selection.

2.1.1 Design Requirements for Fireworks Production Line

The biggest problem facing fireworks production is safety, which involves gunpowder and can cause explosion accidents at any stage. Therefore, the production process must strictly adhere to the following conditions:

1.   Each independent production process is produced in a separate workshop.

2.   Conductive, wooden, copper and new materials are selected for production equipment.

3.   Explosion-proof facilities are installed.

4.   Adequate heat dissipation is provided.

5.   The number of personnel participating in production is less than three.

6.   The temperature in the production workshop does not exceed 20 degrees.

7.   Real-time monitoring and immediate shutdown are implemented.

8.   Explosion-proof panels, partition walls, etc., are set up.

9.   The amount of a single process’s medicine should not exceed 5 kilograms.

10.   The medicine particles’ thickness in the tray should not exceed two particle thicknesses.

11.   The temperature during the drying process should not exceed 60 degrees.

Under these conditions, the production line is preliminarily designed with small-scale and high-efficiency principles. The total amount of gunpowder is set at 5 kilograms per batch, and since mixing and granulating require a certain amount of time, 5 batches per hour are tentatively set.

2.1.2 Composition of Fireworks Production Line Process

The production process of fireworks mainly includes mixing raw materials, producing bright pearls, drying bright pearls, producing shells, wiring, loading launch powder, packaging, etc. In this process, raw material mixing, granulation, and drying are extremely dangerous, involving issues such as friction, squeezing, and heating of gunpowder. Therefore, this project mainly focuses on designing these three parts. To achieve automation in production, improve production efficiency, and reduce human involvement, a stacking process must be added between these three processing steps. This stacking process mainly involves putting the particles formed from granulation into trays and stacking them into shelves. The shelves are then transported into the drying machine through a conveyor belt. Therefore, this project can be divided into four parts: weighing and mixing, granulation, stacking, and drying.

After analyzing the overall production process, a fireworks production model was established based on Pro/E, as shown in Figure 2.1. Gunpowder is weighed and mixed through the dispensing system, and the mixed powder is then sent to the granulation system. The granulation system turns the powder into pellets, which are then loaded onto trays and stacked by the stacking system. The trays are then sent to the drying system, where the pellets are dried. The unloading system then unloads the pellets into a recovery box, completing the entire production process.

Figure 2.1: Process Assembly Drawing

2.2 Weighing and Mixing System Design

2.2.1 Weighing System Design

The important components of the weighing mechanism include the material storage mechanism, conveying mechanism, and weighing mechanism [16]. The material storage mechanism is the hopper, the conveying mechanism mainly consists of a stepper motor and a feeding screw, and the weighing mechanism mainly consists of an electronic scale, an electronic scale tray, and a discharge cylinder, as shown in Figure 2.2.

Figure 2.2: Weighing Mechanism

1.   As a material storage device, the hopper needs to have sufficient space to facilitate the manufacturer’s supply of sufficient raw materials during production and allow workers enough rest time during material loading. Additionally, the four walls of the hopper should have a certain inclination angle to facilitate the smooth sliding of powders into the feeder.

2.   The feeder adopts a worm screw feeding mechanism. Its accuracy can be controlled by limiting the number of step angles or adjusting the cross-sectional area of the powder in the screw.

2.2.2 Mixing Principle Analysis

The mixing component is mainly responsible for receiving the raw materials sent by the weighing component and completing the mixing process. The connection between these two parts is made by a drop-off mechanism, which reduces weight loss after weighing and strengthens the overall structure, making it more compact.

The working principle of the mixer is to use its own gravity and mechanical force to mix various materials evenly. Mixing machines are widely used in daily life and various industrial productions. For powder and granular solid materials, there are mainly rotary drum mixers (Figure 2.3), V-type mixers (Figure 2.4), and screw mixers (Figure 2.5).

Figure 2.3: Schematic diagram of a cylindrical mixer

Figure 2.4: V-shaped mixer

Figure 2.5: Screw mixer

1.   Rotary drum mixer:

The mixer consists of a cylindrical container, a guiding device, and baffles. In a single rotary drum configuration, the materials inside the drum blend together. Materials with different parameters have different motion states in the rotary drum mixer. Assuming the same material, there are approximately six motion states under different motion parameters of the drum.

Figure 2.6: Slip

Figure 2.7: Stairs

(1) As shown in Figure 2.6, the material inside the cylinder moves in a slip form, which cannot achieve the mixing effect.

(2) As shown in Figure 2.7, the material inside the cylinder moves in a stair form, which also cannot achieve the mixing effect.

Figure 2.8: Rolling

Figure 2.9: Little waterfall

(3) As shown in Figure 2.8, the material inside the cylinder moves in a rolling form, which can achieve the mixing effect but is not very effective.

(4) As shown in Figure 2.9, the material inside the cylinder moves in a falling (little waterfall) form, which has a more obvious mixing effect.

Figure 2.10: Big waterfall

Figure 2.11: Centrifugal

(5) As shown in Figure 2.10, the material inside the cylinder moves in a falling (big waterfall) form, which achieves the most obvious mixing effect.

(6) As shown in Figure 2.11, the material inside the cylinder moves in a centrifugal form, which cannot achieve an obvious mixing effect.

1.   V-type mixer:

This type of mixer consists of two cylinders connected together, with single V-type and multi-V-type series forms. When the container rotates, the material inside the cylinder will gather at the same top to achieve the first mixing, and then the angle will be rotated. The material will flow back into the two cylinders to achieve the second mixing, and so on. The angle between the axes of the two cylinders is generally 60° or 90°. According to the rotational speed, the material has the following three movement states:

Figure 2.12: Centrifugal

Figure 2.13: Partial Slippage

Figure 2.14: Full Slippage

(1) Centrifugal motion. As shown in Figure 2.12, when the rotating speed of the cylinder exceeds a certain critical value, the material inside the cylinder undergoes centrifugal motion. The material rotates with the top of the cylinder and cannot achieve the desired mixing effect.

(2) Partial slippage. As shown in Figure 2.13, when the rotating speed of the cylinder is relatively high, the material far away from the axis of rotation is still held at the top by the centrifugal force and does not fall. As a result, some of the material at the top cannot be well mixed.

(3) Complete slippage. As shown in Figure 2.14, when the rotating speed of the cylinder is relatively low, all of the material can fall, so the mixing effect can be relatively good.

Screw mixer:

Figure 2.15: Screw Mixer

As shown in Figure 2.15, a helical propeller inside the screw mixer uses gravity and mechanical force to mix the materials. During mixing, the propeller forces the materials to move upward from the bottom, and the materials above fall downward. At the same time, vortex motion is generated throughout the container space, thus repeatedly achieving the purpose of mixing.

2.2.3 Weight-based Mixing Process Design

Figure 2.16: Weight-based Mixing

The working principle of the weight-based mixing structure is shown in Figure 2.16:

1.   The powder is added from the hopper, and the system is started.

2.   After the system automatically detects no faults, the stepper motor starts to operate. The material passes through the feeder and is sent to the tray.

3.   When the weight of the material reaches a certain value, the stepper motor stops working.

4.   At the same time, the cylinder of the electronic scale starts to work, lifting the tray. When the tray is at a certain angle with the horizontal plane, the cylinder stops moving, and the material begins to slide from the tray into the guide pipe, entering the mixing process. The cylinder returns to its original position after the material is completely discharged.

5.   The mixer starts to operate when the material is completely dropped into the mixer through the pipe. When the mixer is fully mixed, the cylinder starts to operate, driving the discharge valve to open and sending the evenly mixed material to the next process.

2.3 Granulation system design

2.3.1 Analysis of granulation principle

As the name suggests, the granulator machine manufactures mixed gunpowder into granules. There are various methods for granulation, including extrusion rolling granulation, reciprocating granulator, rotary granulator, cone gear meshing granulator, boiling granulation, guiding jet granulation, spray drying granulation, centrifugal granulation, rotary drum granulator, disk granulator, etc. [20].

The first few methods mainly use extrusion to granulate, which is unsuitable for gunpowder granulation. The following section will introduce some representative granulation methods:

Figure 2.17: Spray Drying Method

Figure 2.18: Centrifugation Method

1.   The spray drying method [21], as shown in Figure 2.17, uses a nozzle or a circular disk to spray highly concentrated slurry to form smaller droplets. Under the blow of hot air at high temperatures, the droplets quickly dry to form particles. Because the water evaporates quickly, the particles produced have gaps and low hardness. This method has low particle production efficiency and requires large equipment, making the entire production process complex. This method generally produces traditional Chinese medicine preparations and instant foods.

2.   The centrifugal method [22], as shown in Figure 2.18, requires the production of precursor granules before granulation using this method. The precursor granules are then fed onto a centrifugal plate. Under friction force, centrifugal force, and scraper, the precursor granules form a vortex-like particle flow on the plate. At the same time, an atomized binder is continuously sprayed into the particle flow from the nozzle to make the precursor granules adhere to the powder. Meanwhile, the powdered material is regularly supplied to the plate. Hot air is continuously blown into the annular gap of the plate, causing the precursor granules to grow continuously until they reach the target particle size. The advantage of this method is that the particles are uniform, have high hardness, and have ideal sphericity and surface smoothness.

Figure 2.19: Boiling granulation method

Figure 2.20: Disc granulation method

3. As shown in Figure 2.19, the boiling granulation method[23] utilizes airflow to lift the powder particles, making them come into contact and collide with the sprayed concentrated solution from above, forming the formation of granules by adhesion. This method has the highest production efficiency among several methods, but the granules produced have lower hardness, relatively loose structure, and less ideal surface smoothness and sphericity. This method is suitable for producing particles with low production requirements or for pre-processing particles.

4. As shown in Figure 2.20, the disc granulation method[24] involves adding powder material to a rotating inclined disc. Due to frictional force, the disc drives the powder material to move. When the powder material reaches a certain height, it slides downwards. The adhesive is constantly added during this process, allowing the powder material to adhere and roll together, growing into granules.

After comparative analysis, the granules produced by the spray drying and boiling methods are relatively loose, and the centrifugal granulation method requires mother particles. Therefore, the disc granulation machine is selected for granulation.

2.3.2 Granulation Process Design

Figure 2.21: Granulation Process

The granulation process is the second station in the production line. Its specific process is as follows: After the powder is weighed and mixed according to the given ratio, it is sent to the feeding port by the feeder, electronic scale, tray, conveyor belt, and other mechanisms. It then enters the granulation plate through the feeding device. The motor receives a signal to start and begins to work at the set speed. At the same time, the spraying system starts to spray the granulation. The round granulator enters the granulation process. The specific granulation process is monitored remotely by a camera. After granulation is complete, the discharge cylinder and lifting platform cylinder work together to pour the bright beads into the remaining material recovery device. The bright beads that meet the requirements and those that do not meet the requirements, as well as the remaining powder, are separated by the remaining material recovery device. The remaining material and the bright beads that do not meet the requirements slide into the recovery bin, while the bright beads that meet the requirements roll into the tray and enter the stacking process, as shown in Figure 2.21.

2.4 Stacking System Process Design

Stacking is a technique that puts items together and uses the concept of integrated unitization to stack the materials in a certain way. It’s beneficial to achieve various logistics operations for the overall material.

Stacking is a technology in the field of logistics automation, and it has developed rapidly in recent years. Firstly, with the increase in production scale and capacity, the efficiency of stacking must be continuously improved. Therefore, online stacking is developing at high speed. Secondly, as enterprise products flow from the seller’s market to the buyer’s market, the production of enterprises is developing towards multi-variety and small-batch production. Enterprises will use flexible production to produce multiple products on one production line.

Similarly, this requires stacking to have the ability to handle multiple products. In addition, with the emergence of large-scale wholesale distribution centers, delivering according to different customer orders is necessary. Stacking machines must have a wide range of stacking capabilities and strong mixed stacking ability. In these environments, stacking robots have developed very well. Nowadays, there are many varieties of stacking machines on the market, and their automation and flexibility are also very high.

In this production line, the stacking machine mainly completes the following processes: transporting pallet groups, supplying pallets, loading materials, transporting racks, and stacking.

The amount of gunpowder produced in one production run is 5 kilograms. Due to the design requirements of the drying equipment, the 5 kilograms of gunpowder are granulated and then placed in 4 pallets. Therefore, a pallet group consists of 4 pallets, and a rack holds 4. The rack enters the drying box for drying to complete the entire manufacturing process.

The working principle of the stacking component is shown in Figure 2.22:

The entire stacking component comprises six parts: conveyor 1, pallet supplier, conveyor 2, stacking machine, conveyor 3, and conveyor 4. The work performed by each part is as follows: conveyor 1 places the pallet group on top, supplying the pallet group to the pallet supplier. The pallet supplier receives the pallets conveyed by conveyor 1 and then supplies them to conveyor 2 one by one. Conveyor 2 conveys the pallets supplied by the pallet supplier, and the granules are loaded onto the conveyor. Conveyor 3 transports the rack to the stacking machine. The stacking machine receives the rack and stacks the pallets supplied by conveyor 2 layer by layer. Conveyor 4 transports the stacked rack and pallets into the drying box for drying.

Figure 2.22: Stacking working principle

The design of the conveyor can be based on the requirements of the conveyor in the design manual, so the main work of the principle design is on the pallet supplier and the stacking machine.

2.5 Drying System Design

2.5.1 Drying Principle Analysis

The drying component is responsible for drying the stacked gunpowder granules. Currently, the main drying technologies for fireworks production are hot air drying technology (Figure 2.23) [26], vacuum freeze-drying technology (Figure 2.24) [27], and far-infrared drying technology (Figure 2.25) [28].

Figure 2.23: Hot Air Drying Machine

Figure 2.24: Vacuum Freeze-drying Machine

Figure 2.25: Far-infrared Drying Machine

1.   Hot air drying is a common drying method in modern times. Objects are placed in a drying chamber or box, and hot air is blown to accelerate airflow and evaporation. Hot air is heated around the heat source and blown by a fan onto the surface of the object being dried, and changing temperature and airflow can improve the drying efficiency.

2.   Vacuum freeze-drying, also known as sublimation drying, is different from hot air drying in principle. The object to be dried is placed in a closed drying chamber, and the air in the chamber is evacuated while the object is heated. It causes water molecules in the object to escape and be removed from the chamber, achieving the drying goal.

Far infrared drying is a method that utilizes thermal radiation for drying. Far infrared radiators emit electromagnetic waves, whose frequency is similar to the molecular vibration frequency of the object being dried, causing resonance and intense vibration of the molecules in the object, which generates heat to achieve drying.

It is worth noting that compared with hot air drying and vacuum drying, far infrared drying technology has the following advantages:

(1) Energy-saving, infrared heating technology achieves the corresponding absorption of the spectrum, greatly reducing unnecessary waste.

(2) With high production efficiency, direct manipulation of molecules results in low heating inertia and fast heating rates.

(3) The product quality is high because infrared heating can achieve uniform heating both inside and outside, improving the quality of the product.

(4) The structure is simple and requires less investment. The compact structure of the infrared heater does not require a large amount of auxiliary heating equipment and pipeline systems, reducing capital costs.

(5) It is easier to achieve continuous production. Therefore, the drying equipment in this production line uses far-infrared drying.

2.5.2 Design of Drying System Process

The drying and unloading system consists of two parts: the drying part is responsible for conveying the shelf and drying the material in the tray placed on the shelf. In contrast, the unloading part is responsible for conveying the shelf and dumping the material in the tray onto a collection box to complete the unloading process. The system structure is shown in the figure. The specific working process is as follows: after the granules are made and placed in the tray, they are stacked and placed on the shelf through the stacking part. Then, the shelf is conveyed to the drying part, and the robot control system controls the motor to make the conveyor belt of the conveyor run, driving the shelf to move. The drying machine system consists of three drying boxes. The temperature of the first drying box is set to 45°C, the second to 60°C, and the third to 45°C. The shelf will be dried in each of the three drying boxes for 10 minutes, completing the drying of the granules. Then, the shelf enters the unloading link, and the cylinder in the unloading part tilts the shelf to complete the unloading. After unloading, the shelf is returned to the stacking part to be reloaded. Figure 2.26 shows the working diagram of the drying and unloading process.

Figure 2.26: Schematic Diagram of Drying and Unloading Work

1.   Working Principle of Drying System: The drying process combines far-infrared and hot air to dry the fireworks particles. Far-infrared drying is the main method, and hot air drying is supplementary. When the far-infrared electric heating plate in the drying box is turned on, it begins to heat up. The surface temperature of the far-infrared electric heating film increases, and when it reaches a certain temperature, it emits far-infrared rays. After the particles on the tray absorb the far-infrared rays, the internal molecular motion intensifies. The internal and external temperatures of the particles begin to rise uniformly, starting the drying process. At the same time, the axial flow fan supplies air to the drying box, producing a certain amount of hot air to dry the particles. The inlet and outlet ducts form a circulation ventilation system through the action of the axial flow fan, which makes the heating of the particles more uniform and can effectively collect the dust in the drying box, preventing safety accidents and achieving the effect of recycling. The drying process uses a PID temperature robot control system, which can freely set the temperature and has an automatic adjustment function. The power of the far-infrared electric heating plate can be adjusted to meet the temperature requirements between room temperature and 150°C. An emergency stop switch is installed on the drying box to ensure safety during the working process.

2.   Working Principle of Unloading System: When the conveyor delivers the shelf to the unloading system, the front and rear cylinder systems push the unloading rack to clamp the shelf to prevent the shelf from flipping. Then, the upper and lower cylinder systems lift the unloading conveyor and the shelf. The edge of the tray has a tilt angle, which can meet the unloading requirements of materials at a certain tilt angle. After detecting that the material has been unloaded, the upper and lower and front and rear cylinder systems return to their original positions. Then the conveyor delivers the shelf to the next link.

3.   Design Considerations: (1) Safety issues should be the primary consideration during the drying process, as safety is the primary guarantee in the entire fireworks production line design process. Therefore, explosion-proof motors should be selected in the design, and all wires should not be exposed and should be sealed to prevent contact with powder and fine particles. In addition, the external surface temperature of all parts in the system should not exceed 80°C. Finally, the system should be equipped with an alarm device. (2) The second issue is to ensure sealing. Heat loss should be minimized during the drying of the particles in the drying box. In addition to insulation materials, the sealing of the front and rear “doors” should be ensured after the shelf enters the drying box. (3) Ensure that all parts are in place. Each part should reach the specified position through the detection of sensors and the control of the robot control system. (4) For the unloading section, complete unloading should be ensured. One way is to determine the maximum time of the unloading process through experiments, and the robot control system can be set to the maximum time. The second way is to capture the tray image with a camera and compare it with the image of the tray when there are no particles to ensure complete unloading.

 2.6 Summary of this Chapter

This chapter divides the automatic fireworks production line into four parts and selects and designs the process for each part. A spiral mixing machine is used for mixing, a disc granulator is used for granulation, special simple equipment is used for stacking and far-infrared drying technology is used for drying.

Chapter 3: Design of the Stacking Machine System

3.1 Introduction

The stacking component of the fireworks automatic production line is mainly responsible for transportation and stacking, consisting of a series of movements. Therefore, when designing the mechanism, it is necessary to fully consider the friction and collision between the movements and adopt movements with low and stable frictional forces. For metal structures, copper plating should be used on the surface, and objects (such as pallets) in direct contact with gunpowder should be made of wood or special antistatic materials.

This chapter mainly constructs the stacking component model based on Pro/E5.0, performs parts assembly, conducts Pro/E motion simulation, and analyzes the feasibility of its motion. Based on the stability and reliability of the motion, the pneumatic system is simulated based on AMEsim to verify whether the application of the cylinder is reasonable.

3.2 Design of the Stacking Mechanism

Pro/E is a powerful 3D software that uses parametric technology. It has a great influence in the field of 3D modeling and is widely used worldwide. It can perform various operations such as 3D modeling, engineering drawing production, analysis calculation, and simulation.

In this design, the function of the stacking component is to load the particles into the pallet and place the pallet on the shelf. Therefore, a pallet machine is required to supply the pallet, a belt conveyor is used for transportation, and finally, the stacking machine is used for stacking.

3.2.1 Design of the Pallet Machine

A pallet group positioning device and a supply device are required on the pallet machine to complete the action of receiving and supplying the pallet group. The positioning device can be completed with a stop block or a baffle, and the supply device requires several coordinated actions.

First, design the pallet:

When gunpowder burns, the reaction equation is as follows:

2KNO3 + S + 3C = K2S + N2 (gas) + 3CO2 (gas) — (3.1)

The proportion between reactants is potassium nitrate 75%, sulfur 10%, and charcoal 15%. Density: potassium nitrate ρ1 (2.1093 g/cm), sulfur ρ2 (2.03 g/cm), charcoal ρ3 (0.43 g/cm) [32].

The theoretical density calculation formula for black powder:

Due to the addition of some luminescent agents, colorants, binders, etc., during the production of the grains, the density varies depending on the composition, making it impossible to know the actual density. After consulting relevant materials, it was found that the density of the grains is ≥1.23 g/cm, calculated using the minimum value of 1.23 g/cm.

Total weight: 5kg, volume: 4.1763 x 10 mm.

Each grain has a diameter of 10mm, a radius of 5mm, and a volume of (4/3) x π x (5mm)^3 = 523.43 mm^3. The depth of the tray can be determined from the figure below: only one layer of grains with the thickness of one grain can be placed on each tray. Therefore, when loading the tray, to scrape off the top layer of grains, the outer wall of the tray should be lower than the middle position of the top layer of grains, i.e., the height should be less than 12.07mm, which is rounded to 12mm. The modeling is shown in Figure 3.1.

Figure 3.1: shows the model of the tray

The shelf is designed with four layers, each accommodating one tray. Six rollers are placed on each layer to allow the tray to slide smoothly, and a stopper is placed at one end to position the tray. The model is shown in Figure 3.2.

Figure 3.2: Shelf Modeling

Design of Supply Tray Machine Base:

The tray group is conveyed to the base of the supply tray machine. During this process, there are three issues regarding whether the placement direction of the tray group is accurate, whether the tray group can reach the designated position by inertia when it leaves the conveyor, and whether it can stop when it reaches the designated position.

The diagram shows that stopper 1 ensures the tray group is properly positioned when it enters the base. The roller gives the tray group the power to continue moving forward when it leaves the conveyor, and stopper 2 positions the tray group when it reaches the designated position. The model is shown in diagram 3.3.

Diagram 3.3: Modeling of the Base

Here is a proposal for the supply tray device:

Option 1: Using a mechanical hook, modeled as follows:

It consists of a regular cylinder, a swing cylinder, and a hook. The regular cylinder is responsible for vertical lifting. The swing cylinder and the hook are connected by a gear rack [33, 34] and are responsible for horizontal movement. The working principle is: the hook lifts the second tray and the tray above it to a certain height. Another cylinder pushes the bottom tray out to complete the supply of one tray. The hook then releases the tray and repeats the above operation to complete the tray supply. See diagram 3.4.

Figure 3.4: Supply Plan 1

This plan has the following disadvantages: 1. The connection between the hook and the swinging cylinder is relatively complex. 2. This plan operates at a slower speed.

Plan 2: Use a bottom plate lifting mechanism modeled as follows:

The bottom plate lifting mechanism and the cylinder expansion and contraction cooperate in supplying the pallets. The scissor-type lifting device is used to achieve stable lifting of the bottom plate, with the power source coming from the lifting cylinder. The pallet supply cylinder pushes out the first pallet above the pallet group, and the lifting cylinder lifts one pallet’s height. The pallet supply cylinder continues to push out the second pallet and so on, to complete the pallet supply. In order to prevent friction from moving the lower pallets during the pallet supply process, a stopper is set on the pallet supply machine base to prevent the second pallet from moving. The stopper on the lifting frame remains stationary and can always block the movement of the second pallet. See Figure 3.5.

Figure 3.5: Supply Plan 2

This plan has the following drawbacks: the single lifting cylinder has four positioning points in its stroke. If the mechanical structure is used for positioning, the structure will be more complex. If directional valves are used for control, specific parameters must be simulated through experiments.

3.2.2 Conveyor Design

A conveyor is a mechanical device transporting materials along a certain route. Its history dates back to ancient China, where it was used for water lifting with the turning drum cart, which is the prototype of modern conveyors. The operating routes of conveyors vary, such as inclined, horizontal, long-distance, and short-distance. They have a large carrying capacity and a wide range of applications, making them widely used in various industries.

Conveyors come in various types, such as belt conveyors, screw conveyors, roller conveyors, chain conveyors, mesh conveyors, etc. [35]. This conveyor is used to transport pallets and shelves, so the commonly used belt conveyor is selected.

Belt conveyors are the main equipment for bulk material transportation. They have the advantages of a wide range of feed types, strong conveying capacity, flexible and changeable transport routes, low maintenance costs, and high reliability. In some specific fields, belt conveyors have replaced vehicle transportation, which has greatly improved production efficiency. It is worth noting that belt conveyors powered by electric rollers have unique advantages and potential markets.

Selection of conveyor belt: As this conveyor is used in an environment where gunpowder is transported, the belt needs to be explosion-proof and antistatic. According to the manual, the CC cotton canvas core should be chosen for the core, and CR chloroprene rubber should be selected for the cover [35].

Calculation of electric roller power: The power is generally composed of the power required for running under no-load conditions, the power required for horizontal transport load, and the power required for lifting load. The following empirical formula can be used for calculation:

After consulting the manual [25] and according to the design requirements, the parameters in the formula can be determined as follows:

Length of conveyor belt: 4L tray + 540mm reserved + 2000mm loading = 4.5m

L=4.5m; C=7.6; f=0.03; belt width based on one pallet = 4900mm, B=500mm; Gm=26; belt speed tentatively set to 0.25m/s; V=0.25m/s; Qt is based on completing a stacking of 5kg of gunpowder every two minutes,

= (20.9 + 5) x 30 = 0.78t Qt; lifting height H=0.

Substituting the values into formula (3.3), P0 = 0.098KW.

Electric motor power:

With η = 0.9 and K = 1, we can derive P = 0.098/0.8 = 0.122KW. The power level of the electric drum is selected according to the standard of 0.25KW.

Calculation of maximum tension:

Refer to the manual to select: μ = 0.35, φ = 3.19; choose a wrap angle of 190 degrees.

Calculation of the number of layers of the conveyor belt.

Refer to the manual to select: n = 8, σ = 56 N (mm·layer).

The calculation result is:

Round to the nearest integer, Z = 3.

Create component models of the conveyor, such as the tensioning device, rollers, supports, and motorized drum, based on Pro/E. The assembly model of the conveyor is shown in Figure 3.6.

Figure 3.6: Conveyor modeling

3.2.3 Stacking Machine Design

The stacking machine needs to perform the following actions: receive shelves from the conveyor, stack pallets into the shelves, and then push the shelves onto the conveyor to the drying machine. The design concept of the stacking machine is similar to that of the feeding machine. The shelves need to be positioned correctly when they are transported and need to be located when they reach the designated position. The pallets need external power to be transported into the shelves, and the shelves need to lift and lower so that the next pallet can enter another shelf layer.

According to the action requirements, the stacking machine is designed and modeled as shown in Figure 3.7.

Shelf positioning mechanism: The shelf is positioned by the positioning baffle, and the roller provides power to the shelf to continue moving forward until it collides with the positioning baffle and stops. When the pallet enters the shelf, roller b provides power to the pallet to enter the shelf, and the bottom plate drops a certain height to allow the second pallet to enter, and so on, completing the stacking process.

Figure 3.7: Modeling of the Palletizing Machine

3.2.4 Setting of Sensors

As the name suggests, a sensor is a device that transmits sensing signals. Specifically, it can detect the measured info and convert various measurement info into signals or other required methods according to the specified changing rules, achieving the transmission, storage, recording, conversion, control, and other requirements of info. It is the first step to achieve automated detection and control. There are many types of sensors, which can be divided into velocity sensors, displacement sensors, temperature sensors, pressure sensors, and gas sensors according to the different physical quantities input. During the operation of this palletizing system, it is necessary to detect the position of the cylinder rod, the position of the pallet, and the position of the shelves.

Measurement of the position of the cylinder rod: The lifting cylinder starts and stops several times during the lifting process. If a mechanical positioning structure is used, the mechanical structure will be more complicated. Therefore, a displacement sensor should be selected for real-time measurement. After comparison, a wire rope displacement sensor was chosen. The wire rope displacement sensor has a sophisticated structure and combines the advantages of a linear displacement sensor and an angle sensor. It has a clever structure of a linear displacement sensor. It is a compact and precise sensor with a small installation size and a large measuring stroke, ranging from a few hundred millimeters to more than ten meters. According to the actual situation, the KS-1000-008-G-24 wire rope displacement sensor was selected with a measuring range of 1000mm, a resolution of 0.008mm, digital signal output, absolute value type, and a power supply voltage of 24V. The shape of the sensor is shown in Figure 3.8, and the installation position is shown in Figure 3.9, with the pull head fixed below the bottom plate.

Figure 3.8: Sensor Type

Figure 3.9: Wire Rope Displacement Sensor

Figure 3.10: Pallet Group Positioning

Figure 3.11: Palletizing Positioning

Figure 3.12: Shelf Positioning

To advance the cylinder, it is only necessary to determine the upper and lower positions. Therefore, choose one with a magnetic ring directly when selecting the cylinder.

For tray position measurement: A limit switch can be used when the tray assembly enters the supply plate machine base plate and collides with the baffle. Place the limit switch at the extreme position. When the tray reaches it, it will emit a signal. Choose the XCJ-110 model. The shape is shown in Figure 3.8, and the installation position is shown in Figure 3.10, placed in the middle of the baffle.

When stacking, the tray is conveyed to roller 3, conveyor 2 stops, and roller 3 starts. A limit switch is needed here. When the tray is conveyed to the roller, press the long flat operating lever to output an electrical signal to the PLC to enter the next step. Choose the XCJ-126 model. The shape is shown in Figure 3.8, and the installation position is shown in Figure 3.11, placed next to roller 3. When a tray is conveyed over, the long flat operating lever of the limit switch is pressed down, and the signal is transmitted.

When the shelf is conveyed to the bottom plate of the stacking machine, the principle is the same as when the tray assembly is conveyed to the bottom plate of the supply plate machine. Choose the XCJ-110 model. The shape is shown in Figure 3.8, and the installation position is shown in Figure 3.12, placed in the middle of the baffle.

3.3 Assembly and motion analysis of the stacking system: In this design, the method of establishing all parts models and assembling them one by one is adopted. Based on the selected cylinder, establish the complete structure of the mechanism. The mechanical assembly of the feeding system is shown in Figure 3.13.

Figure 3.13: Mechanical equipment structure diagram – Pyrotechnics Assembly Lines and Palletizers

3.3.1 Overall Assembly and Motion Steps

In the Pro/E assembly process, it is necessary to determine the connection method of each component [36] to achieve the subsequent motion simulation. Pro/E provides users with 10 types of constraints, and each connection type is involved in this assembly. After step-by-step modeling and assembly, the complete model of the mechanism is established. The overall assembly effect of each part is shown in Figure 3.14.

Figure 3.14: Overall equipment diagram – Pyrotechnics Assembly Lines and Palletizers

The motion steps are completed sequentially according to the designed action sequence, which is a decomposition of the action loop that helps to analyze the entire work process. The mechanism action sequence diagram is shown in Figure 3.15:

Figure 3.15: Mechanism action sequence diagram

3.3.2 Mechanism Kinematic Simulation

Pro/E motion simulation is a simulation analysis and design tool based on modeling. Through kinematic analysis of the model, data such as product speed, acceleration, displacement, critical position, etc. can be obtained [37]. The Pro/E motion analysis module can define motion conditions in the model, such as pin, cylinder, sliding rod, plane, etc., and then perform interference analysis directly, which is convenient and fast. The analysis results can provide guidance and be used as the basis for structural design modifications, making the product more reasonable [38].

The motion simulation steps are shown in Figure 3.16:

Figure 3.16: Motion simulation steps

Defining the servo motor: In the operation interface diagram, when defining the servo motor, select the mechanism motion as uniform motion, with a vertical speed of 10mm/s and a horizontal speed of 100mm/s for observation.

Figure 3.17: Operation interface for motion analysis

3.3.2 Kinematic Simulation of Mechanisms

Pro/E motion simulation is a simulation analysis design tool based on modeling. Through the kinematic analysis of the model, data such as the product’s speed, acceleration, displacement, critical position, etc., can be obtained [37]. The Pro/E motion analysis module can define motion conditions in the model, such as pin, cylinder, sliding rod, plane, etc., and then perform interference analysis directly, which is convenient and fast. The analysis results can provide guidance and serve as the basis for structural design modification, making the product more reasonable [38].

The steps of motion simulation are shown in Figure 3.16:

Defining the servo motor: In the operation interface diagram, when defining the servo motor, select the mechanism motion as uniform motion, with a vertical speed of 10mm/s and a horizontal speed of 100mm/s for observation.

Figure 3.17 Motion Analysis Operation Interface

Establishing motion analysis: The operation interface is shown in Figure 3.17. Select the motor and determine the operating time for each motor. Based on the motion dimensions of each action, the overall operating program is compiled as shown in Table 3.1.

Table 3.1: Operation Program Table

Table 3.1 (continued): Program Execution Table

Running the above program will enable motion simulation. The mechanism action is obtained as follows:

Table 3.2: Transfer Tray Mechanism Action

Image 3.18: Transfer Tray

Table 3.3: Supply Tray Mechanism Action

Image 3.19: Supply Tray

Table 3.4: Conveyor Rack Mechanism Action

Image 3.20: Conveyor Rack

Table 3.5: Palletizing Mechanism Action

Image 3.21: Palletizing

Table 3.6: Transfer to Drying Machine Mechanism Action

Table 3.6 (continued): Transfer to Drying Machine Mechanism Action

Image 3.22: Transfer to Drying Machine

In this simulation result, graphics can be created for observing a set of motion analysis results.

Image 3.23: Lifting Cylinder of Supply Tray Machine

Image 3.24: Advancing Cylinder of Supply Tray Machine

Image 3.25: Lifting Cylinder of Palletizing Machine

Image 3.26: Advancing Cylinder of Palletizing Machine

3.23. To observe the time-motion diagram of the lifting cylinder of the tray feeder, it can be seen that the cylinder rises four times, with the first time being 20mm and the following times being 24mm (the height of one tray). The curve descends 98mm, indicating that all four trays have been pushed out to complete the feeding, and the cylinder returns to its initial position.

Figure 3.24 shows the time-motion diagram of the advancing cylinder of the tray feeder. It can be seen from the figure that the cylinder lifts and lowers uniformly four times, corresponding to four feeding actions, and finally returns to the initial position.

Figure 3.25 shows the time-motion diagram of the lifting cylinder of the palletizer. From the figure, it can be seen that the cylinder descends four times, with the first time being 60mm and the following times being 70mm (the height of each layer of the shelf). The curve rises 270mm, indicating that all four trays have been transferred to the shelf and pushed out by the tray feeder to complete the palletizing, and the cylinder returns to its initial position.

Figure 3.26 shows the time-motion diagram of the advancing cylinder of the palletizer. It can be seen from this figure that the advancing cylinder has only one extension and contraction action, which pushes the shelf to the palletizer, and the cylinder returns to its initial position.

Through motion simulation and analysis, it can be concluded that the model design of the palletizing components meets the motion requirements, and the simulated motion meets the design requirements. It can realize the overall palletizing requirements, and the results are consistent with the actual design requirements, which can be applied to practice. At the same time, it improves the targetedness of subsequent design improvement work and achieves the design purpose.

3.3.3 Assembly Interference Inspection

Interference inspection [30] proves whether the assembly of components in the simulation is correct. The virtual assembly structure of the palletizing mechanism is subjected to interference inspection, which can initially determine whether each structure is reasonable. At the same time, when unreasonable structures are found, they can be modified promptly, providing a more theoretical basis for practice. Using the analysis function of Pro/E, a global assembly interference inspection is performed on the already assembled mechanism. The interference dialog box is shown in Figure 3.27.

Figure 3.27: Interference Dialog Box

When selecting collision detection settings in the playback options, checking the global collision detection option will detect interference between all components in the entire assembly when simulating playback results. When the system detects interference, the affected area will be highlighted. By checking for interference and finding none in the assembly, it indicates that the mechanical assembly is reasonable, and as long as the part processing technology is ensured, it can be smoothly assembled without various problems that may occur during actual assembly, improving design efficiency and quality.

3.4 Pneumatic System Design

3.4.1 Overview of Pneumatic Technology

Pneumatic technology[39] is one of the important technical measures applied to mechanization and automation. Its full name is pneumatic transmission and control technology. The main difference between pneumatic technology and hydraulic transmission is that the medium used is air, which is highly compressible. Compared to hydraulic transmission, it has unique advantages and is widely used in light industry machinery and food industries. Since the 1960s, pneumatic technology has developed rapidly and has become an increasingly important field in related industries. Nowadays, research on pneumatic systems has become a specialized field.

Pneumatic transmission has the following unique advantages:

1.   The medium used is air, which is readily available and does not require cost consideration. The material is easily obtainable, requires no post-treatment, and can be directly released into the atmosphere without causing pollution, thus eliminating the need for recycling pipelines.

2.   The viscosity coefficient of air is small, making flow smooth, suitable for long-distance transmission and centralized gas supply, and convenient to use.

3.   It has a fast response speed, is easy to maintain, and the working medium does not require replacement.

4.   It has a wide range of applications and can be used in harsh environments such as dust, flammability, and electromagnetic fields.

5.   It can withstand certain overloads without easily overheating.

However, the pneumatic transmission also has its own disadvantages:

1.   Due to the large compressibility of the medium, the accuracy of precise positioning achieved during movement is not high, and the stability of speed during operation is poor.

2.   Pneumatic transmission equipment such as air compressors and exhaust devices generate high noise levels and require muffler installation.

3.4.2 Pneumatic Circuit Design

This project mainly uses pneumatic devices as the execution mechanism. Pneumatic transmission systems usually include four major parts: air source devices, pneumatic auxiliary components, pneumatic control components, and pneumatic execution components[40], as shown in Figure 3.28.

Figure 3.28: Pneumatic transmission system

The pressure robot control system of this project uses the basic circuit of the secondary pressure control loop, which consists of an air compressor, check valve, air storage tank, relief valve, and pneumatic tripartite components (water separator, pressure reducing valve, and oil mist device), etc. [39]. The control part consists of three-way, four-way directional valves. The execution part consists of SI standard cylinders, which respectively realize the lifting of the dish supply machine, tray supply, stacking machine lifting, and shelf supply.

The corresponding three-way controls the lifting and moving actions of each cylinder, four-way solenoid valves, and the control signals of the solenoid valves are sent out by the PLC according to the logical sequence of the program. After starting, the signal of solenoid valve 1 moves to the right, connects the dish supply’s lifting cylinder and rises by 20mm. When it reaches the designated position, the signal of solenoid valve 1 moves to the left, stays in the middle position, disconnects the connection of the lifting cylinder, and the lifting cylinder stops. At the same time, the signal of solenoid valve 2 moves to the right, and the tray-pushing cylinder is connected, pushing forward. When it reaches the designated position, the signal of solenoid valve 2 moves to the left, and the tray-pushing cylinder moves back. Solenoid valves 1 and 2 continue to repeat the above actions until all four trays are supplied. The signal of solenoid valve 1 moves to the left, the lifting cylinder of the dish supply descends to the initial position, and the connection of the lifting cylinder to the dish supply cylinder is disconnected. When the first tray enters the first layer of the shelf, the signal of solenoid valve 3 moves to the left, and the lifting cylinder of the stacking machine descends by 60mm. When it reaches the designated position, the signal of solenoid valve 3 moves to the right, stays in the middle position, disconnects the connection of the lifting cylinder, and the lifting cylinder stops. When the first tray is passed to the first layer of the shelf, the signal of solenoid valve 3 moves to the left, and the lifting cylinder descends by 70mm. When it reaches the designated position, the signal of solenoid valve 3 moves to the right, stays in the middle position, disconnects the connection of the lifting cylinder, and the lifting cylinder stops. Solenoid valve 3 repeats the above actions until all four trays are passed into the shelf. The signal of solenoid valve 4 moves to the right, and the stacking machine pushes the cylinder forward. When it reaches the designated position, the signal of solenoid valve 4 moves to the left, and the stacking machine pushing cylinder moves back to the initial position. Solenoid valve 3 receives the signal and moves to the right, and the lifting cylinder of the dish supply rises to the initial position, and the connection of the lifting cylinder to the dish supply cylinder is disconnected. Due to the use of pneumatic transmission, the system considers the issues of pressure adjustment, speed control, buffering, and safety, so appropriate auxiliary components such as pressure-reducing valves and speed control valves are added. The schematic diagram of the pneumatic circuit is shown in Figure 3.29.

Figure 3.29: Pneumatic Circuit

3.4.3 Cylinder Design

To establish a complete pneumatic circuit, it is necessary to determine the pneumatic indicators based on the on-site conditions. Based on mechanical modeling, the actual working stroke values of each cylinder are determined as follows: 120mm for the lifting cylinder of the feeder, 300mm for the pushing device cylinder of the feeder, 270mm for the lifting cylinder of the palletizer; and 300mm for the pushing device cylinder of the palletizer. The speed of the lifting cylinder cannot be too fast, although there is no requirement for the speed of the pushing cylinder as long as the material is supplied in a timely manner. The output force of the cylinder is related to whether the action can be completed. Based on calculations, a pallet weighs 2.1kg, a shelf weighs 15kg, the base plate of the feeder machine weighs 12.5kg, and the base plate of the palletizer weighs 13kg. Generally, the output force of the cylinder is sufficient, and no special requirements are made here. The design process is shown in the simplified flowchart in Figure 3.30.

Other requirements: all cylinders are controlled by solenoid valves, and each cylinder has a stroke limit switch. In the case of mechanical interference, point control can be implemented separately.

Environmental requirements: anti-electromagnetic interference and reliable performance. Main pneumatic components: four double-acting cylinders; four 3-position 4-way solenoid valves.

Figure 3.30: Flowchart of Cylinder Design

The main parameters and dimensions of the cylinder include cylinder diameter, piston rod diameter, cylinder wall thickness, cushion stroke, and the size of the cylinder inlet and outlet ports. As we have selected a standard cylinder, determining cylinder diameter and thrust size is the most important parameter. Other indicators can be selected based on the manufacturer’s provided data and may not need to be calculated.

The energy conversion principle of the cylinder is to convert the pressure energy of air into mechanical energy. Based on the analysis that all cylinders move in a straight line, the method of selecting the cylinder is basically the same. Taking the lifting cylinder for the supply disc machine as an example, the selection process is explained below.

First, calculate the cylinder diameter D. Since the load of the lifting cylinder can be obtained from the actual working process, the working load is known, and the cylinder diameter D is calculated using the following formula:

D = (4F/(πP))^(1/2)

Where:

D is the cylinder diameter in millimeters

F is the working load in Newton

P is the pressure of the compressed air source in Pascal

π is a mathematical constant (approximately 3.14)

After the cylinder diameter is calculated, other parameters, such as the piston rod diameter, cylinder wall thickness, cushion stroke, and the size of the cylinder inlet and outlet ports, can be selected based on the manufacturer’s provided data without further calculations.

F: External load on the cylinder (N)

FZ: Resistance during cylinder operation (N)

P: Working pressure of the cylinder (Pa)

Common simplified formula (V=0.2-0.5m/s):

Main support for the lifting cylinder: pallet group + supply disc machine base = 20.9kg = 204.82N;

Substituting P=430000 Pa into the formula, we get D≈0.0304m and choose the standard cylinder diameter of 32mm.

After determining the cylinder diameter, the calculation of thrust size is carried out, which directly affects whether the cylinder can operate under normal conditions.

Thrust calculation formula:

F is the cylinder thrust (N);

P is the operating pressure (Pa);

D is the cylinder diameter (m);

When the data is substituted into the formula, the thrust value is 345.65N, which is greater than the total load of the lifting cylinder motion of 204.82N.

After determining the main dimensions, other factors such as cylinder series, stroke, installation form, cushion form, and magnetic switches need to be considered.

According to the product manual, select the cylinder model SI-32×150-S. Other cylinder models can be selected similarly.

The cylinder models are calculated and analyzed based on the parameters as follows:

Supply plate lifting cylinder model: SI-32×150-FB, rubber cushion, two-side rubber cushion, no need for oil, working pressure range 0.1-1.0 MPa, double acting.

Supply plate advancing cylinder model: SI-32×350-S-TC, rubber cushion, two-side rubber cushion, no need to give oil, working pressure range 0.1-1.0 MPa, double acting, with D-Z73 inductive switch.

Pallet lifting cylinder model: SI-63×350-FB, rubber cushion, two-side rubber cushion, no need for oil, working pressure range 0.1-1.0 MPa, double acting.

Palletizing push cylinder model: SI-32×350-S-FC, with rubber cushioning on both sides, does not require oil input. The operating pressure range is 0.1-1.0 MPa, double-acting, with a D-Z73 proximity switch.

3.4.4 Selection of Pneumatic Auxiliary Components

The model of the electromagnetic control valve is often selected based on the size of the connected piping of the actuator or the size of the actuator itself. In this pneumatic system design, the main function of the solenoid valve is to control the direction of gas flow and the opening and closing of the gas flow.

The main function of pneumatic auxiliary components is to ensure the normal operation of the pneumatic circuit system. Before compressed air enters the actuator, it usually needs to undergo water removal and filtration and control its pressure, flow rate, and flow direction. In addition, pneumatic components also need to add lubricants or mufflers at the exhaust port to extend their life of pneumatic components and reduce maintenance costs. Therefore, pneumatic auxiliary components that can complete these auxiliary functions need to be added to the pneumatic system. In this pneumatic system, after the gas is released from the gas source, it needs to flow through the AC2000-02D filter regulator, which mainly filters and reduces the compressed air and delivers clean, low-pressure air with a pressure of 4 kg to the actuator. In addition, the directional control valve needs to be integrated into the module to save space, so the SS5Y5-20-04 module is selected. Other accessories include various types of mufflers, quick couplers, and various diameter pipelines [41].

3.5 Pneumatic System Simulation of Palletizing Machine

3.5.1 Pneumatic System Modeling

AMESim (Advanced Modeling Environment for Simulation of Engineering Systems) [42] is an analysis software promoted to the public by the French company IMAGINE in 1995. It has a wide range of applications, and users can build complex simulation and modeling systems based on this platform for in-depth analysis and complex calculations. AMESim provides users with a modeling environment in both the time and frequency domains. Users can use existing models or establish new models through a model library to build the desired structures. The standards adopted are easy to recognize, with simple and intuitive icons and diagrams, which makes it easy for users to simplify complex models. At the same time, the system also provides specific application examples in various fields. Users can achieve model building, parameter simulation, dynamic simulation, and curve drawing by simply changing them. The operation interface is friendly and easy to operate. AMESim has been successfully applied in engineering machinery, aerospace, ships, vehicles, and other fields, covering mechanical, fluid, electrical, magnetic, thermal analysis, control, and other aspects.

The AMESim pneumatic modeling system is a top-down modeling method, as shown in Figure 3.31.

Figure 3.31: Modeling Method

AMEsim usually modularizes and specifies real and complex systems, using a rich model library to build systems with graphic symbols and natural language, and constructs module and simulation models according to actual physical systems [43]. The pneumatic simulation module in this study [44] consists of commonly used modules, each corresponding to one or more mathematical models for describing component characteristics. After analysis, the feeding mechanism system in this study mainly consists of the following components: power source, generally an air pump; valve control components, including solenoid valves, check valves, and throttle valves; and actuating components, including ordinary air cylinders. As each component is a pneumatic standard component [45], pneumatic models are built within AMEsim’s pneumatic library, as shown in Figure 3.32

Figure 3.32: Pneumatic Model

3.5.2 Pneumatic Circuit Simulation Analysis

Based on the actual cylinder parameters and different loads, the motion parameters of each cylinder are set. Since we are not concerned with the fine motion process of the cylinder, and such research is also very complex, modeling with standard components can avoid this type of complexity. However, to ensure the correctness of the cylinder model, the influence of the flow coefficient of the inlet and exhaust and the relevant factors of leakage between cylinders must also be considered. Taking the lifting cylinder as an example and combining with the cylinder parameters and actual working environment, the valve port area, working frequency, current, cylinder working load, cylinder diameter, starting position, piston rod diameter, and working temperature of the solenoid valve are set. The default pressure at each outlet is 1 bar [47], where 1 bar = 0.1 MPa, and the piston rod diameter and cylinder diameter are set directly based on the calculated values, as shown in Figure 3.33.

Figure 3.33: Parameter Settings

Based on the above settings introduction, taking the pneumatic lifting of the disk drive as an example, the pneumatic states of the solenoid valve and cylinder are analyzed, respectively. The pneumatic flow and pressure change curves mainly reflect the static characteristics of the solenoid valve. In contrast, its dynamic characteristics are reflected by the response time of the solenoid valve. According to the technical specifications, the simulation time is 10 seconds, and the printing interval is 0.001 seconds.

Figure 3.34: Pressure Curve of Solenoid Valve P and T Ports

Figure 3.34 displays the pressure curves for an electromagnetic reversing valve’s P and T ports. As shown in the figure, the P port is connected to a constant pressure source, and the pressure remains at a constant value of 4.052 bar (0.4 MPa). The T port is connected to the outside atmosphere, and the pressure is also constant at 1.013 bar (0.101 MPa), which meets the requirements.

Figure 3.35: Pressure curve of the cylinder port

Figure 3.35 shows the pressure and cylinder rod acceleration curves of cylinder ports 1 and 2. If leakage is ignored, the pressure changes at ports 1 and 2 are basically consistent with the air pressure changes at electromagnetic valve ports A and B. The figure shows that the amplitude of the changes in ports 1 and 2 is small, and their differences are also small. It is mainly because during the cylinder’s motion, the cylinder’s motion distance is short (20-24mm)/cycle, and the motion time for each stage is 1 second, which makes the cylinder’s motion speed low, about 0.02m/s. At the same time, due to the increased influence of cylinder friction and gas compressibility, the pressure at ports 1 and 2 will exhibit unstable fluctuations, causing acceleration to be positive or negative. It cannot ensure smooth movement of the piston, resulting in the phenomenon of crawling [48]. The appearance of crawling is mainly due to the low speed of the cylinder. Since the cylinder has four strokes, the mechanical positioning structure is relatively complex. In situations where positioning accuracy is not high, real-time sensing can control the electromagnetic directional valve for positioning. However, if the cylinder speed is high, the positioning will be difficult, and the magnitude of the positioning changes will increase, making it impossible to achieve the required accuracy. Meanwhile, the cylinder’s travel distance is short, and the required time is not long, meeting the overall palletizing time requirements.

Figure 3.36: Shows the cylinder rod displacement curve

Figure 3.36 shows the displacement diagram of the cylinder lever. The lifting cylinder of the tray machine needs to rise 4 times and descend 1 time. Therefore, in the simulation process, the cylinder is set to rise 4 times, stop 4 times, and descend 1 time, to observe the stability of the cylinder displacement curve.

As shown in the figure, when the cylinder receives the signal to rise, it will exhibit a crawling phenomenon due to its slow speed. When stopped, the cylinder will still rise a certain distance and fluctuate within a certain range. The maximum peak and valley values of the fluctuation at the point of stopping are compared in the figure, and it is found that (2)-(1)y_1=0.0027m, which is 2.7mm. The range of fluctuation up and down is not very large.

Since the motion precision requirement of the palletizing system is not high, it is only necessary to reserve a fluctuation range of 3-5mm to eliminate this problem during assembly. The specific operation is as follows:

Figure 3.37 – Improvement 1

Figure 3.38 – Improvement 2

Figure 3.39 – Improvement 3

Figure 3.40 – Improvement 4

1.   As shown in Figure 3.37, the height of the conveyor 1 belt is 5mm higher than the height of the supply disk machine bottom plate to prevent the supply disk machine bottom plate from being too high, which would make it impossible for the pallet group to be transported onto the supply disk machine bottom plate.

2.   As shown in Figure 3.38, the height of the conveyor 2 belt is 5mm lower than the height of the third pallet on the supply disk machine bottom plate (i.e., the supply disk machine bottom plate is 67mm below the conveyor belt) to prevent the supply disk machine bottom plate from being too low, which would make it impossible for the pallet to be pushed onto the conveyor belt.

3.   As shown in Figure 3.39, the height of the conveyor 3 belt is 5mm higher than the bottom plate of the stacking machine to prevent the shelves from being unable to be transported above the stacking machine’s bottom plate.

4.   As shown in Figure 3.40, the height of the conveyor 2 belt is 5mm higher than the height of the first layer of shelves on the stacking machine bottom plate (i.e., the height of the conveyor 2 belt is 125mm higher than the stacking machine bottom plate) to prevent the pallet from being unable to be transported into the shelves.

3.6 Summary of this Chapter

This chapter introduced the modeling and simulation of the mechanical and pneumatic movements of the stacking system. The motion and pneumatic systems were simulated and analyzed based on two simulation software, Pro/E, and AMESim. This can further verify the correctness of the design of the mechanical structure and pneumatic circuit, provide a lot of reference and help for the actual platform building and theoretical experiments, and give many suggestions for the further improvement of the system.

Chapter 4: Electrical System Design

4.1 Introduction

This chapter mainly constructs the palletizing system’s control structure, including the PLC control unit [49], monitoring system, and other auxiliary circuit control systems (robot). The accuracy of the robot control system design plays a crucial role in whether the system can operate according to the design requirements and also provides a reference basis for the debugging of the prototype [50].

4.2 Control Circuit Design

The core requirement of the robot control system [51] is to transport the workpiece in an orderly manner. The PLC (robot) mainly controls four conveyor motors’ start and stop four cylinders’ expansion and contraction, and three rollers’ rotation and stop.

1.   The main circuit design is shown in Figure 4.1:

Figure 4.1: Main Circuit Diagram

In the main circuit, contactors KM1-KM4 control the motors of four conveyors (robot), relays FR1-FR4 provide overload protection for the motors, fuse FU1 provides short-circuit protection, and power switch QF implements short-circuit protection for the main circuit.

1.   The control circuit design is shown in Figure 4.2:

In the robot control circuit, there is a power indicator light that displays the working status of the motor. The contactor coil and limit switch provide the triggering signals for each process, respectively. The circuit also includes manual control buttons for equipment debugging.

4.3 Working Principle and Selection of PLC

4.3.1 Working principle of PLC

PLC is mainly used in industrial design[55]. It is a logic controller (robot controller) that uses digital manipulation. It has good stability and can maintain high anti-interference ability even under complex and changing conditions. It has good dependability. The storage used by PLC can be programmed to store internal programs. It has a variety of portable instructions, such as timing, sequential control, arithmetic, counting, logical operations, etc by a robot control system. The robot can control various types of machinery to complete specified actions through analog or digital signals. It is the command center of industrial robot control equipment.

PLC adopts a cyclic working mode, which can be divided into three stages: input sampling stage, program execution stage, and output refreshing stage[56].

When the PLC is internally processed, it checks whether the hardware of the CPU module is operating normally and resets the monitor. When it is in a stopped state, it only performs communication service operations and its internal processing. When running, it performs internal processing communication, program input, program execution, and program output. The working principle of PLC is shown in Figure 4.3.

Figure 4.3: PLC Operation Principle

According to the design requirements, the PLC should meet the following requirements:

1.   The number of input and output points should reach the number of control signals (robot).

2.   The number of internal timers and counters in the PLC.

3.   The operating speed of the PLC is related to the system’s scanning time.

4.   The program storage space of the PLC.

4.3.2 Selection of PLC

Mitsubishi’s PLC was one of the early brands to enter the Chinese market. The FX2N model is a small, high-functioning integrated machine that has been promoted in recent years. The FX series has many similar models and a wide range of varieties. There are 9 types of basic units: FX0, FX0N, FX0N, FX1, FX1S, FX2, FX2C, FX2N, and FX2NC. Each type has different specifications for storage points and different output forms, which are divided into relay output, transistor output, and thyristor output [49].

Mitsubishi’s FX2N model PLC is one of its excellent works in the small and high-energy category. The maximum number of I/O points its system allows is 128, which can be expanded to 256 points after adding expansion units. When executing instructions, the FX2N model has a speed of 0.48μs per step, and the user’s program storage capacity can be expanded to 8K steps. In China, the use of the FX2N model PLC is relatively common. After comparing and understanding the working principles and performance of various PLCs and combining them with actual requirements, the FX2N model PLC was selected for this design.

Based on the requirements, it can be determined that 22 input points are needed. During manual operation, there are 11 manual buttons used for routine system inspection and maintenance, 1 off button, emergency stop button, and 1 start button. During automatic operation, there are 9 input points for sensor signals.

In summary, this design chose Mitsubishi’s FX2N-48MS PLC. Relative to other PLCs, this type has good usability, low cost, and a low probability of failure. The project also has room for expansion in case of future needs.

4.3.3 Resource Allocation for PLC

Figure 4.4 shows the resource allocation chart for the PLC [57].

Figure 4.4: PLC Resource Allocation Chart

Table 4.1 represents the meanings of the inputs and outputs of each interface in the Resource Allocation Chart.

Table 4.1: Resource Allocation

Table 4.1 (continued): Resource Allocation

4.4 PLC Software Design

4.4.1 Determine PLC Flowchart

The following modules are divided based on the action sequence and requirements: cylinder action output, fault display, touchscreen operation, host operation control (robot), and parameter setting. The flowchart is shown in Figure 4.5.

Figure 4.5 shows the workflow diagram of a PLC (Programmable Logic Controller)

4.4.2 PLC Program Compilation

According to the above workflow diagram, the control state (robot) transition diagram for the stacking movement sequence [49] is compiled. Figure 4.6 is an important basis for the compilation of PLC ladder diagrams. This diagram has the following characteristics:

1.   Complex processes or tasks are divided into several operations. No matter how complex the sequential control process (robot) is, it can be divided into small operations, making implementing a structured program design easier.

2.   The robot control tasks are simplified relative to a specific operation, making it more convenient to compile the entire program.

3.   The overall program is the synthesis of local programs. As long as the conditions for each operation are established, the conditions for operation transition, and the specific directions are clear, this type of diagram can be designed.

4.   The sequential control state transition diagram (robot) is easy to understand and has strong readability, which can more clearly reflect the global robot control process.

In Figure 4.6, which shows the stacking sequence control by a robot, S0 represents the initial state, and S21 to S50 represents the states of each operation. The sequence control robot process is described as follows:

1.   When the PLC starts running, the pulse signal M8002 drives the initial state S0.

2.   When the start button X000 is turned on, the stacking lifting cylinder is in the initial position, the stacking push cylinder is in the retracted state (X004=ON), the supply and lifting cylinder is in the initial position, and the stacking push cylinder is in the retracted state (X007=ON). The working state transitions from S0 to S21 and S23.

3.   S21 and S23 are parallel branches and executed simultaneously. After the state S21 is driven, outputs Y000 and Y001 are turned on, conveyor 1 and roller 1 start to transport the tray group until the front limit (X001=ON), and the working state transitions from S21 to S22. After state S22 is driven, output Y002 is turned on, and the supply and lifting cylinder rises until the limit position (X002=ON). The working states S23 and S24 are similar to the above movements, S21 and S22 complete the transportation of the tray group, and S23 and S24 complete the transportation of the shelf. When the two circuits have completed their respective step points, the working state transitions to S25.

4.   When the state S25 is activated, the outputs Y006 and Y007 are turned on, the cylinder for advancing the tray is extended, and conveyor 2 is started until the front limit switch (X004=ON) is reached. The working state then shifts to S26. When the state S26 is activated, the output Y010 is turned on, and the cylinder for advancing the tray is retracted until the rear limit switch (X004) is reached. The working state then shifts to S27. When the state S27 is activated, the output Y002 is turned on, and the cylinder moves up to the limit switch (X002=ON). The working state then shifts to S28, and the process from S28 to S35 is repeated to complete the supply of four trays to conveyor 2.

5.   When the state S36 is activated, the output Y011 is turned on, and the cylinder moves down to the initial position (X002=ON). The working state then shifts to S37. When the state S37 is activated, the output Y007 is turned on, and conveyor 2 starts transporting the tray until the limit switch (X011=ON) is reached. The working state then shifts to S38. When the state S38 is activated, the output Y012 is turned on, and roller 2 starts until the tray leaves the limit switch (X011=OFF). The state then shifts to S39. When the state S39 is activated, the output Y005 is turned on, and the stacking cylinder moves down until the limit switch (X005=ON) is reached. The working state then shifts to S40, and the process from S40 to S47 is repeated to complete the stacking.

Figure 4.6: Control State Transition Diagram

After driving status S48, outputs Y013 and Y014 are connected, the stacking lifting and advancing cylinder extend, and conveyor 3 starts until the front limit (X006=ON) is reached. Then the active status transitions to S49. After driving status S49, output Y015 is connected, the stacking advancing cylinder retracts until the rear limit (X007=ON), and the active status transitions to S50. After driving status S50, output Y016 is connected, and the stacking lifting cylinder rises until the initial position (X005=ON), completing the process of pushing the shelf out of the stacking machine. The working process ends at this point, and the working status returns to S0 to start the cycle. The PLC programming is shown in Appendix A.

Section 4.5 establishes a monitoring system based on the configuration for the stacking system. After establishing the monitoring system, four types of info can be provided to the operators: real-time on-site working status screen, production data, historical trend curve, timely fault alarm and fault point, and real-time regulation.

The monitoring system is developed based on the configuration software, and the monitoring configuration software is a platform for data acquisition and monitoring, with a wide range of applications and powerful functions. General configuration software has two characteristics: openness, allowing users to expand it as needed, which is also a key issue of concern to users, and management robot control integration, achieving data analysis and management and combining management system and data control (robot).

The monitoring system can be divided into five modules:

1.   Graphic module: uses simulated screens and animations to reflect the actual production status, providing operators with vivid “live broadcasts.”

2.   Real-time database module: completes real-time data collection, sorting, and other work, which can directly reflect the production situation with data and provide a data foundation for other modules, an important resource.

3.   Communication module: this module is the foundation for data exchange, assuring the system to read data from external devices and robot control the working of external devices.

4.   Historical database module: stores various data info generated during the production process, such as output and working time.

5.   Data report module: displays data info in chart form and also provides users with functions such as printing and saving reports.

4.5.1 Configuration framework design for monitoring system

Developing a monitoring system based on configuration software can be divided into four parts: graphic interface configuration, real-time database configuration, robot control loop configuration, and report configuration [59].

The graphic interface configuration can be divided into three parts: animation connection configuration module, interface production module, and data file management module. The interface production module is used for creating and editing graphics elements and is the core of the visual configuration system. The animation connection module is completed by establishing the relationship between the graphic elements and the field I/O variables through the graphic configuration. The data file management module provides the data info required to operate the graphic interface.

The real-time database system needs to define and process the monitored data objects, a real-time control system (robot). This data must have real-time characteristics, store each process point, and have data management functions. According to different data types, the monitoring point database configuration is divided into analog input/output, switch input/output, and computation quantity. The robot controller continuously stores the newly collected data in the real-time database, which can directly reflect the state of the robot controlled object in the field. At the same time, it provides real-time data for the output module, graphic interface module, and historical curve module. After calculation, the results obtained by the database can provide a basis for using other modules by placing them in the real-time database.

The robot control circuit is a specific control function achieved by connecting functional modules of the robot control algorithm using a certain method. The robot control circuit configuration includes display info, control circuit type, alarm info, control information, and circuit status. Display information refers to the name of the control circuit. The control circuit type is determined based on the variable type of the circuit and decides the data required in the configuration project. Alarm information is based on the input point and corresponds to the collected sensor information. Control information refers to the action and reaction between input and output quantities. Circuit status indicates the working state of the control circuit and can be either manual or automatic.

A report refers to displaying historical curves as graphs on a touch screen, facilitating user browsing and printing. The key parameters for report configuration include the following:

1.   Report data collection time: the starting time of the report to be printed, which is the time when historical data is collected.

2.   Report data end time: the period for automatic printing from data collection to the end time of the report and the cutoff time for collecting historical data.

3.   Data source: specifies which data group from the database will be printed (e.g., production output, fault points) to extract the data from the database.

4.   Data type: specifies the type of data to be obtained in the report (e.g., average value, maximum value, minimum value).

5.   Display format: specifies the display width of numerical characters.

4.5.2 Graphic Interface Design for Monitoring System

Configurator King is a new industrial automation system development software [60]. It adopts a standard software and hardware platform as its basis, making it widely applicable, highly open, operationally stable, and with a short open cycle. Based on Configurator King, a graphic interface for the monitoring system is established, including the main monitoring interface, production process monitoring interface, monitoring point monitoring interface access, fault alarm interface, and historical curve interface.

Main Monitoring Interface:

As shown in Figure 4.7, the main interface is a two-level submenu system, and users can enter different menus according to their needs to access and observe the corresponding working status. The management page is used for editing and parameter modification of the screen, and this page can only be accessed in the shutdown state.

Figure 4.7: Main Interface

Figure 4.8: Production Process Monitoring Interface

Production Process Monitoring Interface:

As shown in Figure 4.8, this interface displays the overall picture of the palletizing robot system with animated effects. The working conditions of the entire palletizing process are synchronized with the animation and displayed through simple animation effects.

Monitoring Point Monitoring Interface:

As shown in Figure 4.9, users can set or modify the delay time for each cylinder action. By setting the system, the continuity and coordination of the actions can be adjusted to ensure production efficiency. If a fault occurs, the troubleshooting purpose can also be achieved by modifying the delay time.

Figure 4.9: Point Control Interface

Figure 4.10: Historical Curve

As shown in Figure 4.10, the workload data curve can be used to track the production output within a day. Users only need to click here to input the query date to view the record of the day and check the workload situation.

Fault alarm interface:

As shown in Figure 4.11, due to the large number of limit switches and contactors for each cylinder, faults are inevitable during the production process, affecting the efficiency of the entire production line. To promptly deal with faults, this interface will display the fault cause and location when a fault occurs, prompting users to troubleshoot. The cylinders and other auxiliary mechanisms are monitored in real-time and displayed as indicator lights. Once a fault occurs, the indicator light turns red and displays the cause, guiding users to troubleshoot and greatly simplifying the troubleshooting process while improving work efficiency.

Figure 4.11 – Alarm Interface

4.6 Summary of this Chapter

This chapter establishes the robot control system for the stacking components and elaborates on the selection and allocation of resources for the PLC and the programming process. Based on the configuration king, a monitoring system is established to make the stacking process more reliable during operation.

Chapter 5: Conclusion and Future Prospects

This paper has designed an automatic fireworks production line by carefully analyzing the fireworks production process. The paper analyzes the working principles of four major parts of the fireworks production process, namely powder weighing and mixing, particle production, stacking, and drying. It provides a systematic design analysis of the stacking components.

“Revolutionizing Fireworks Production with an Automated Production Line: Pro/E Solid Modeling Software and Mitsubishi PLC Integration”

This article showcases the groundbreaking research work that established the overall process of the automatic production line of fireworks granules. The feasibility of the mechanism design was verified through the use of Pro/E solid modeling software and AMEsim pneumatic simulation software. At the same time, the selection of dustproof, explosion-proof, and antistatic materials ensured the safety of the entire process. With the Mitsubishi PLC as the foundation of the robot control system, the production monitoring system was also created, meeting the requirements of real-time monitoring and data management. Discover the impressive innovations that have transformed the fireworks production industry forever.

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5.1 Summary

The research work of this paper is as follows:

1.   Established the automatic production line of fireworks granules’ overall process and assembled the geometric models of the stacking components’ various parts in the Pro/E solid modeling software and assembled them. Based on the motion requirements, the Pro/E motion simulation of the stacking components was established, further verifying the mechanism design’s feasibility. Dustproof, explosion-proof, and antistatic materials and equipment were selected during the design process.

2.   As the supply plate in this paper is mainly driven by pneumatic pressure, the pneumatic system of the stacking components was established, and the AMEsim pneumatic simulation software was used to conduct simulation analysis. The simulation results showed that the system can meet the requirements of multi-stroke and multi-point positioning of the cylinder, and the positioning accuracy is within the allowable range.

3.   The Robot control system of the stacking components was designed based on the Mitsubishi PLC, including PLC selection, circuit diagram drawing, flow chart compilation, and control program compilation, which realized automatic control.

4.   Based on the configuration king, the production monitoring system was created, including real-time data collection, historical data inquiry, dynamic production screens, manual point control, and alarms, meeting the requirements of real-time monitoring and data management.

5.2 Future Prospects

This paper has made some achievements in the preliminary design of the automatic fireworks production line and the stacking components. However, due to time and energy constraints, we find that there are still many issues that need further research, including the following:

1.   Improve the smoothness of the stacking components’ motion and the accuracy of cylinder motion to make their movement more reliable.

2.   Establish a more comprehensive fault diagnosis system to reduce the accident rate.

3.   Based on the overall analysis of the automatic fireworks production line, make the connection between the components closer and the actions more coherent. In addition, this research only covers the process from powder mixing to granule drying, and further work is needed to improve the process of pressing, loading, and packaging.

Appendix A

PLC Program

Reference

• Display Fireworks Manual
• 2021 Fireworks Annual Report
• Giving your own firework display – How to run and fire it safely
• SITE IMPROVEMENT PLAN-Public Display of Fireworks
• Regulation of Fireworks and Fireworks Displays
• Regulation of fireworks
• Federal Explosives Law and Regulations
• Organising firework displays – Explosives
• Ignite Fireworks of Action through Climate Initiatives
• Town of Edgecomb Fireworks Ordinance
• Pyrotechnics Industry – Fireworks Display
• Control of Outdoor Fireworks Displays – First Edition