The application of the hottest electric control in

Application of electrical control in air/gas (liquid) flexible packaging machine

Abstract: taking a single live fish packaging machine as an example, a new control method is introduced. This method is guided by the modular design idea, uses the programmable controller (hereinafter referred to as "PLC" as the control center, integrates various technologies of machine, electricity, gas and light, carries out the optimal combination, and realizes the optimal control of the whole machine. This method is suitable for the automatic control of the air extraction/inflation (liquid) flexible packaging machine

key words: flexible packaging; Control method; PLC； optimization grouping; Optimal control

1 preface

control system is an important part of packaging machinery. Its role is to control and coordinate the whole automatic working cycle, including: making various packaging movements in a certain order; Necessary adjustment and control of pressure, temperature, time and speed; The realization of various quality inspection, automatic safety protection, automatic measurement and counting; Supply and stop of materials, automatic alarm of failure, etc. The fixture should not cause the specimen to fracture at the fixture

conventional control systems include: mechanical, pneumatic (hydraulic) and electronic control. Among them, electronic control is the most widely used. Most of the control methods of these control systems are to accelerate the industrialization of graphene high molecular composites, which is single and has certain limitations. For example, the electronic control mainly adopts the relay contactor circuit and instrument control method. Even the packaging equipment produced by some large enterprises still adopts the switch circuit board or unit combination instrument method (see the control principle), and its control level is low, which has been difficult to meet the control requirements of modern food packaging

in order to improve the comprehensive technical level of our packaging machinery and make our packaging go to the world, we must adopt advanced control technology to improve its automation level. It will be an inevitable trend to develop packaging equipment that integrates high and new technologies such as machinery, electricity, gas and light

through the design and development of a single live fish packaging machine [a continuous multi specification and multi-function single live fish automatic ventilation and oxygenation (liquid) bagging machine], the author adopts a new modular design method, which complements and optimizes the advantages of mechanical, electrical, pneumatic and optical technologies, and realizes the optimal control of the machine. It is the first one at home and abroad, and has been put into use in a fish farm in Singapore with good results. This control method is applicable to the automatic control of air extraction/inflation (liquid) flexible packaging equipment

2 equipment process requirements and control requirements

2.1 process requirements

(1) packaging bag specifications are 3 ", 4", 5 ", 6" And 7 "; (2) the packaging material is non-toxic heat sealing film; (3) because it is a live fish packaging, it is not only required to have water in the packaging bag, but also required to draw the air in the bag to form a vacuum and then fill it with oxygen (liquid preparation) to ensure the storage time of live fish; (4) it is required to work continuously; (5) it is convenient to change the packaging specification; (6) Except for manual fish feeding, all other operations are completed automatically

2.2 control requirements

this machine adopts a multi-functional modular combined design method. The total functions of the machine are divided into nine modules: film supply, molding, quantitative water supply, guidance, traction, longitudinal sealing, photoelectric length determination, transverse sealing and cutting, and output. The composition and function of each functional module and the overall structure of the machine are shown in the author's paper

according to the process requirements of the machine, after optimizing and combining the functional modules according to a certain working order, the working cycle diagram of the machine is obtained, as shown in Figure 1

therefore, the following requirements are put forward for its control system: (1) feeding signal control after manual feeding (FISH); (2) Control of water volume in each bag; (3) Pressure and temperature control of longitudinal and transverse sealing and cutting; (4) Bag length control; (5) Quantitative control of air extraction/inflation (liquid); (6) Action sequence control of each module actuator

3 control method

3.1 overall scheme

this machine adopts modular design method, and the control of each functional module is relatively simple. The key and difficulty of control lies in how to give full play to the technical advantages of machinery, electricity, gas and light, and optimize the combination to make the movements of the actuators of each module coordinate with each other and act in an orderly manner. This scheme adopts PLC as the control of the whole machine, and sets the data setting display unit, which solves this problem well. The control is fast, stable and reliable, and the parameter adjustment is convenient and fast

3.2 mechanical control

realize the automatic control of film supply, molding and finished product output. Among them, the film supply is completed by mechanical devices such as film supply frame, drum support shaft, drum support shaft, drum support block, etc; The forming is mainly completed by the forming lower hopper integrating the hopper and the former; The output of finished products is completed by mechanical devices such as discharge hopper slot

in addition, the heat sealing pressure control of longitudinal sealing and transverse sealing and cutting is realized by adjusting the position of longitudinal sealing head or transverse sealing and cutting head

3.3 electrical control

realize the automatic control of the temperature of longitudinal seal and transverse seal cutting heat seal. The system is composed of two sets of intelligent data temperature indicating regulators, temperature measuring elements (thermocouples) and heating elements (electric heating tubes). The control principle block diagram is shown in Figure 2

3.4 pneumatic control

realize the automatic control of air extraction/inflation (liquid), longitudinal sealing, pre clamping (before transverse sealing) and transverse sealing and cutting. The pneumatic system is mainly composed of triplet, pressure gauge, solenoid valve, vacuum generator, vacuum filter, cylinder, connector, pipeline, etc. The on and off of the solenoid valve and the action of the cylinder are controlled by PLC. The control principle block diagram is shown in Figure 3

3.5 photoelectric control

realize the fixed length control of bag length. The control principle is: the cylindrical film after longitudinal sealing is pulled downward by the traction wheel. The power of the traction wheel comes from the control motor (permanent magnet low-speed synchronous motor), which can realize instant start, stop and magnetic holding positioning. During the downward movement, the film enters the transverse sealing part after being positioned by the photoelectric color code

in order to ensure the accurate and reliable positioning of the electric color code during work, there are certain requirements for the color code width of the packaging film (the width along the forward direction of the film). The color code is too wide, which affects the second receiving signal of the photocell; On the contrary, if the color code is too narrow, and the color code passing time is shorter than the delay time, it will delay all the time, resulting in out of control

3.6 other controls

include feeding signal control after manual feeding (FISH), control of water volume in each bag, and control of water inlet and outlet of water tank. Among them, the feeding signal control after feeding is realized by Hall switch. The control process is as follows: after manual feeding, press the hall switch sensor, and the hall switch sends a signal to start an automatic working cycle; The control of water volume in each bag is realized by automatic quantitative water tank. The control principle is: open the water inlet valve, the float in the water tank drives the sensor on the hall switch to rise, and the position of the hall switch detection head can be set arbitrarily. When the sensor reaches the detection head, it sends a signal to control the closing of the water inlet valve to complete the quantification of a bag of water; The water inlet and outlet of the water tank are controlled by solenoid valves respectively

3.7 whole machine control - PLC control

this machine uses PLC as the control center to automatically control the sequential action of all module actuators of the machine. A data setting display unit is set to realize screen display operation. In addition, considering the needs of machine debugging and operation, manual/automatic switching is set

plc control principle block diagram is shown in Figure 4

4 main advantages of the new control method

compared with the conventional control method, the new control method has the following advantages: (1) the machine adopts modular design and has high requirements for the action coordination and cooperation of each module actuator. PLC is used as the nerve center of the whole machine to coordinate and control the actions of each module, which solves this problem well; (2) The control system is equipped with a data setting display unit, which has good human-computer interaction. The delay time of some actions can be set directly on the display board, which is convenient and fast to operate; (3) The movement of longitudinal seal, pre clamping seal and transverse seal cutting head is realized by advanced pneumatic components, and the work is stable and reliable; (4) The temperature control of vertical seal and horizontal seal cutting heat seal adopts the negative feedback control principle, which is timely, accurate and stable; (5) Using the control mode of complementary and optimized combination of mechanical, electrical, pneumatic and optical technologies, the control effect is good, a large number of mechanical devices are saved, and the machine structure is simplified; (6) The bag length control adopts photoelectric positioning, PLC control, and the traction wheel is driven by a stepping motor to realize the fixed length control of the bag length. Theoretically, the bag length can be changed steplessly. This control method is much simpler than conventional control

5 conclusion

through the design and development of the control system of the continuous multi specification and multi-function single live fish automatic ventilation and oxygenation (liquid) packaging machine under the guidance of the modular design idea, it is proved that the control system of the air extraction/inflation (liquid) flexible packaging machine adopts the integrated structure of machine, electricity, gas and light under the control of microcomputer, and the control of 43% will be used to replace the old aircraft with good effect, The major equipment manufacturers in the world have been invited to participate in the bidding. The machine has good interaction, flexible and simple operation, stable and reliable work, and has formed an intelligent and flexible automatic packaging system, which meets the new requirements of the development of market economy for packaging machinery and has a good market prospect

reprinted from: China Automation