Craftsman spirit green innovation
Introduction of new high-efficiency inversion molding sheet air pressure thermoforming equipment

Yang Weiguang Zhang Junbo Zheng Xushan
(Guangdong Dacheng Technology Co., Ltd.)

Abstract: This article introduces the current situation and technological process of the production of air pressure thermoforming machines at home and abroad in recent years, and focuses on the green innovation of the equipment, which is reflected in the equipment structure, key technologies, and manufacturing processes. Finally, it points out that the plastic Development direction of sheet air pressure thermoforming machine equipment.

Key words: plastic sheet air pressure thermoforming machine; tilting overturning, plastic sheet heating, mold forming.

I. Production status of plastic sheet air pressure thermoforming machines at home and abroad

Plastic sheet air pressure thermoforming machine is a kind of plastic products processing and forming equipment. Suitable for PP, PS, PE, PVC, ABS, starch-based degradable materials, photobiodegradable materials, etc., for making jelly cups, yogurt cups, disposable drinking cups, instant noodle bowls, lids and other disposable plastic light containers. Extensive and efficient. The process molding method is to heat the thermoplastic plastic sheet to soften, and under the gas pressure, rely on the compressed air to stretch and press the heated and softened plastic sheet to make it close to the surface of the mold, and then it becomes a product after cooling and shaping. At the same time, it can repeat the production cycle according to a certain procedure to manufacture the exact same product.

my country began to manufacture plastic sheet air pressure thermoforming machines in the early 1990s. For example, Guangdong Dacheng Technology Co., Ltd. designed and manufactured the first SZR61-25 plastic sheet air pressure thermoforming machine in 1998. With the accumulation of manufacturer's experience and the improvement of technology, the products are constantly upgraded, but the traditional cam direct drive mechanism or hydraulic cylinder drives the mold table to move up and down directly, with slow running speed, low output, high energy consumption and complicated operation.

At present, in the foreign air pressure thermoforming machine industry, the German plastic sheet air pressure thermoforming machine is the most famous. Since the 1950s and 1960s, the plastic sheet air pressure thermoforming machine has been launched and sold all over the world, most of which are driven by traditional cam direct-acting type; It was not until the early 1990s that the tiltable reversible plastic sheet air pressure thermoforming machine was launched. With automatic stacking and other equipment, the United States, China and other countries have also successively launched tiltable reversible plastic sheet air pressure thermoforming units. It has various power forms and structures, and its purpose is to realize tiltable overturning and improve stability and production efficiency.

2. Introduction of new high-efficiency inversion molding sheet air pressure thermoforming equipment

How to carry out green innovation in equipment, increase equipment output, reduce energy consumption, simple operation, adapt to the development of the times, realize the development concept of "innovation, coordination, green, openness and sharing", and achieve equipment digitalization, intelligence and networking. Automatic control promotes the rapid development of domestic plastic sheet air pressure thermoforming equipment. Guangdong Dacheng Technology Co., Ltd. has launched a new type of high-efficiency inversion molded sheet air pressure thermoforming equipment. The details are as follows:

1. The production process is as follows:

The sheet is automatically uncoiled through the unwinding rack—the preheating of the sheet—the radiant heating of the sheet electric furnace—the sheet stretching—the positive pressure forming of the sheet—the in-mold shearing of the product—the inversion of the die table—the automatic top cup ejecting the product - Automatic cup stacking - Automatic cup push count - Conveyor belt output products - Waste film winding or online crushing

2. Advantages of new high-efficiency inversion molding sheet air pressure thermoforming equipment

The unique reversing mold design is integrated, punching, shearing and stacking are integrated to realize the automatic stacking and counting functions of cups in the machine. Efficient automatic production, greatly save labor, improve product quality and production efficiency. The main principle of tiltable overturning is to use two groups of swinging conjugate cam linkage mechanisms, one group of which performs the direct upward movement of the die table, and the other group of which the movable die table descends and tilts over. Since the movable mold table is tilted during the descending process after demoulding, the up and down stroke of the mold table is greatly shortened, generally about half of the linear movable table, and the cup is laterally discharged after the mold table is turned over. With automatic stacking and counting equipment, it is easy to realize automation. Production is the mainstream direction for the development of air pressure thermoforming machines. The ordinary linear table is to use the cam mechanism or hydraulic cylinder to drive the mold table to move up and down directly to realize the opening and closing of the mold. The movement stroke is greater than the height of the product by about 80MM. Since the increase in the stroke of the die table affects the running speed of the molding machine, and it cannot be equipped with an automatic stacking system, the degree of automation is not high.

Three, the spirit of craftsmanship is reflected in the product structure, and the characteristics of green innovation are as follows

1. The structure of the equipment

1) Unwinding rack: automatic feeding, unwinding by motor pinch, photoelectric eye tracking closed-loop control, simple and convenient feeding, user-friendly operation;

2) Host (core component)

A. Sheet feeding device: Servo-driven conveying of plastic sheets, positioning of toothed chains, accurate sheet feeding, chain track with cooling water circuit, cooling edge sheet temperature, to ensure that the double-row roller chain with sharp teeth can accurately drive plastic sheets When entering the heating area, the chain rail is opened and closed with an electric control device to ensure that the sag of the plastic sheet is within the control range; and it has a backward function, the mold table can be automatically raised and lowered, and the mold replacement is convenient and safe

B. Heater: The heating elements are imported from Germany with far-infrared ceramic heating elements with thermal insulation. The upper and lower heaters advance and retreat at the same time using photoelectric eye tracking closed-loop control, which is safe and efficient;

C. Cam drive structure: When the conjugate cam rotates, the inner and outer contours are in contact with the pendulum rod to drive the connecting rod to raise the lower die table. When the lower die table descends, another group of cam drives drives the overturning and tilting. The application of the conjugate cam and the link mechanism can improve the Clamping force and motion accuracy;

D. Lifting device of the upper die table: the chain drives the column nut to complete the lifting action of the upper die table, and adopts a bladder-type air cylinder and a pneumatic locking device above the die table, which is easy to adjust;

E. Plastic sheet stretching device: the servo motor drives the stretching structure, and the ball screw is driven by the servo motor to rotate forward and reverse to complete the stretching and return movements of the punch.

F. Lubrication device: equipped with imported automatic oil supply lubrication system, which can supply oil and lubricate the machine regularly and quantitatively through PLC control;

3) Waste rewinding device: the rewinding form is friction rewinding, which is simple and practical;

4) Flip cup receiving device: servo-driven cup receiving manipulator, three-dimensional movement of the product, accurate control of the position

A. Driven by servo motor, the products are picked up by reciprocating motion;

B. The cup-sweeping plate is lifted and lowered, driven by a servo motor, and can be positioned and lifted quickly;

C. Use the servo motor to drive the cup sweeping plate to sweep the product onto the conveyor belt;

D. The conveyor belt is lifted and lowered, and the ball screw is driven by the servo motor to drive the conveyor belt to rise and fall;

5) Intelligent remote control technology: PLC integrated control technology, touch screen digital display, convenient control.

Through the server IDC center industrial data center and industrial data collection and analysis software, remote monitoring network equipment, standard motor health detection and analysis system, equipment energy management optimization system, etc., the equipment in the customer's factory can be remotely monitored and various process data collection. And storage, and process data analysis, optimize the production process formula. Including temperature acquisition control system, power drive control system, water cooling control system, pneumatic control system, etc.

2. Demonstration of key technologies

Turning technology of die table

The flip structure is driven by a swinging conjugate cam link mechanism. The two swing bars swing in parallel around the fulcrum. When the conjugate cam rotates, the contact point between the outer contour and the swing bar will change with the change of the swing bar, making the contour of the conjugate cam change. The design and processing are difficult, which directly affects the stability of the mechanism. In the design, computer simulation design and software technology are used to improve the stability of operation, and the manufacturing process adopts German precision machining center, supporting high-strength conjugate cam and connecting rod mechanism materials. The guide mechanism of the upper and lower die tables adopts the 4-column alloy steel structure, which has good rigidity, accurate guiding performance and wear resistance, which helps to prolong the service life of the die notch;

Sheet heating system

The heating system part of the traditional plastic sheet air pressure thermoforming machine is controlled by zone, that is, the upper and lower heaters are divided into certain temperature zones. Therefore, for the entire heating system, the temperature decreases from the highest to the two in the middle, resulting in insufficient heating of the sheet. uniform, product yield decline and resource waste. At present, foreign advanced plastic sheet air pressure thermoforming machines all use matrix heating systems. The company cooperated with Xi'an Jiaotong University to analyze the heat flow coupling problem affecting the three parts of the heating system of the plastic sheet air pressure thermoforming machine (ambient air, heater, heated material), and established a model analysis, using the finite element method to establish the plastic sheet pressure The thermal field distribution model of the matrix heating system of the thermoforming machine, and the temperature distribution of the heating area under the uniform and non-uniform heating modes is simulated based on the software. The heating area is basically a linear temperature distribution, and the variation range is less than 2 degrees, and the heating effect on the material is much greater than that of the uniform heating mode.

The temperature control system adopts intelligent temperature control module, and the whole machine adopts PCC (industrial control computer) to centrally set and control temperature control parameters and operating parameters; and 100 sets of parameters can be stored in the computer for calling at any time. When the voltage fluctuates, it can Automatic tracking compensation to keep the set temperature parameters and operating parameters constant. Therefore, the operation is convenient and the quality of the product is greatly improved. The heating plate adopts the ceramic heating plate imported from Germany, which has high thermal efficiency, low energy consumption and long service life.

Die stretch forming technology:

The three major technologies of positive and negative pressure forming, heat balance and knife edge die shearing ensure that the products are beautifully formed and achieve high-quality craftsmanship.

1) Drawing head design and motion precision control, the ball screw is driven forward and reverse by servo motor, and the die punch is driven to complete the working cycle of downward stretching and upward parking. It plays the role of overshoot protection, with fast stretching speed, stable stretching force, accurate stop position, improving the uniformity of the wall thickness of the product, and reducing the impact of the stop of the punch on the quality of the product. The stretching stroke and speed adjustment are convenient and fast, and can be set directly on the PCC panel. No impact on equipment, low noise;

2) The flow rate and blowing time of the upper mold blowing port are controlled;

3) Exhaust area and distribution of exhaust ports (the number and size of exhaust channels and the width of exhaust grooves are required to be large enough to ensure rapid exhaust and avoid leaving traces on products)

4) In-mold gas sealing technology;

5) Cooling control technology of the upper and lower mold tables; through the heat balance calculation, it is ensured that the temperature and pressure of the hot/cold medium match the heat transfer of the sheet, and the mold temperature is consistent, so that the product quality is stable.

6) The upper and lower die edges cooperate with shearing technology;

7) Rapid mold replacement structure technology.

3. Reflection of manufacturing process

1) The main components (base, mold table) are manufactured by German Demag five-axis machining center to ensure manufacturing accuracy;

2) The selection of components is exquisite, the base mold table is made of high-strength ductile iron, and the transmission shaft is made of high-strength and high-torsion materials, which improves the stability and durability of the equipment;

3) The equipment adopts advanced motion control system to ensure the precise control and cooperation of the high-response die table;

4) The equipment is introduced into industrial design, and comprehensive research is carried out in terms of manufacturing, operation and appearance design, so as to improve the simplicity of operation and the grade of equipment;

5) The important parts use 12.9-grade ultra-high-strength screws to ensure the connection strength;

6) After the flatness of the die table is finely ground, the shovel scraping and grinding treatment, and the shaft guide column adopts the cylindrical fine grinding to ensure the manufacturing accuracy;

7) Strict requirements for heat treatment and surface treatment, improve product reliability and durability;

8) Strict quality inspection process and system to ensure that every part is a high-quality product.

Four. Development direction of plastic sheet air pressure thermoforming machine

The development of the plastic machinery industry depends on the development of the plastic raw material industry and the plastic product processing industry. Today, with the rapid development of the plastics industry, the field of plastic sheet molding is expanding, and the status of plastic sheet air pressure thermoforming machines is becoming more and more important. The general development trend of China's plastic machinery is toward serialization, standardization, and intelligence. It is necessary to meet the requirements of energy saving, environmental protection and high efficiency, so as to meet the needs of cost saving of plastic raw materials and plastic products processing enterprises. The plastic sheet air pressure thermoforming machine equipment is developing towards thick sheets and high efficiency, as follows:

1. The equipment is developing towards large layout, high efficiency and convenient operation.

1. Increase the molding area, increase the number of molds on the layout, and the maximum molding area reaches 780*480MM;

2. Improve the operating efficiency, the number of modules per minute, the theoretical maximum operating efficiency reaches 50 modules per minute;

3. Reduce the height of the die table, which is convenient for operation;

4. Optimize the heating structure to save energy loss.

V. The development of thick sheet thermoforming.

At present, most of the thick sheet forming users use imported machinery from Germany. Its energy saving, production efficiency, and high difficulty of thick sheets have become the bottlenecks in the development of thick sheet thermoforming equipment. There are very few thermoforming equipment manufacturers that can replace German machinery, and some thick sheet products are still blank.

With the growing maturity of plastic sheet air pressure thermoforming technology of Guangdong Dacheng Technology Co., Ltd., it is believed that Dacheng's equipment will compete with foreign high-end German thermoforming machines in the near future.

The author of this article: Guangdong Dacheng Technology Co., Ltd. Yang Weiguang, Tel: 13802330365 stywg@163.com