Transformation of film blowing machine based on PLC, touch screen and inverter
Abstract:After China’s accession to WTO, enterprises in the international market is faced with unprecedented competition, aimed at improving product quality and improve production efficiency of technological innovation is imperative. I use the current field of industrial automation more advanced PLC, touch screen and inverter technology for plastic film blowing machine electric automation transformation and upgrading technology to address the traditional industrial control system hardware complexity, electrical circuits and more human-machine communication difficulties, Mechanical speed control system to bring the maintenance of the complex and heavy workload, long hours and poor reliability problems. Also address the complexity of the traditional control system operation, the new product cycle is long and so on,Is conducive to staff training and improve enterprise competitiveness.
Keywords: PLC; touch screen; converter; electrical; application; control; automation;
Chapter 1 Introduction
In the 1980s, the plastic film blowing machine from Taiwan, its temperature control circuit is the way of thermostat and contactor, due to long-term work in the frequent large current off state, the contactor damage rate is very high, and each thermostat can only control a period of temperature, resulting in many thermostat scattered everywhere, the operation is very inconvenient. The control circuit uses the relay interlock mode, the circuit is complex, the maintenance is very difficult, and the reliability is very low. Speed regulation is completed by the mechanical part, mainly by changing the gear reduction ratio to achieve, mechanical wear is very serious and very energy consumption. These backward technologies make it necessary to invest a lot of manpower and material resources for operation and maintenance, and cause long maintenance downtime and high cost of spare parts consumption. In view of the above backward technology can not meet the production needs and make the enterprise in the market in a competitive advantage, I used in recent years in the industry more and more widely used PLC, touch screen and inverter to transform the machine. The new technology uses the method of temperature control module and solid state relay to control the temperature, and solves the problem of parts damage caused by long-term frequent large current outages. The way of frequency converter speed regulation solves the problem of serious mechanical wear and very energy consumption. The use of the touch screen is conducive to the operator’s intuitive understanding of the current state of the machine to solve the problem of complex operation and difficult personnel training. The comprehensive application of the above technology has high reliability, can achieve long-term maintenance free equipment, and solve the problem of difficult maintenance and long maintenance downtime.
Chapter 2 Design ideas and selection
2.1 Control Requirements
Due to the recovery of the world economy, the rapid increase in business orders, product diversification trend, plus the Pearl River Delta region
The situation of “recruitment difficulties” intensified. According to the actual situation, the following requirements are put forward for the control system:
1. The system should be stable and reliable, and can run without trouble for a long time.
2. Can save multiple groups of formula, and can automatically adjust the speed of each motor according to the preset formula.
3. To operate simple, can be centralized control, save manpower.
4. There should be fault alarm and protection device.
2.2 System Analysis
This system is mainly through PLC, touch screen and inverter integrated application combined with the actual needs of the film blowing machine to complete the control requirements. The main design idea is: using PLC temperature control module and solid state relay to control the temperature of each section of the film blowing machine. The speed of each motor is controlled by PLC analog module and inverter. Use the touch screen to complete the setting and display of temperature, speed setting and display, fault setting and display, the realization of formula functions and so on.
2.2.1 Introduction and working flow chart of film blowing machine
Plastic film blowing machine is a kind of granular plastic raw materials into plastic film machine, its work flow is as follows:
The plastic material is added to the inlet, and the main screw and rotating die head are heated at the same time. When the temperature value reaches the set value, the machine is started. At this time, the plastic raw materials after melting at high temperature are extruded by the ring rotating die under the drive of the main screw. The extruded film is led out by the air cooling and water cooling, and then the embossing wheel A and embossing wheel B are embossed and then the introduction wheel is introduced to the crimping wheel.
The flow block diagram and physical diagram are as follows:
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Figure 2.1 Flowchart
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Figure 2.2 Picture of film blowing machine
2.2.2 Control plan and ideas of the renovation project
1. Change the temperature control mode of the original thermostat and contactor to that of PLC, temperature module and solid state relay. Because solid-state relays are contactless control devices, the damage rate is very low, and frequent high current switching for heating is suitable. The way of PLC temperature control module is very stable, temperature control is accurate, and the temperature can be centrally controlled.
2. The original speed regulation mode of changing the gear reduction ratio through the mechanical part is changed to use the inverter to change the motor frequency speed regulation. Inverter speed regulation has the advantages of energy saving and stability. At the same time, the wear and maintenance problems of mechanical speed regulation are solved, and the inverter can be controlled centrally by using the function of PLC analog output, and the operation is simple.
3. Use the touch screen as the upper computer to complete the temperature setting, frequency setting of the inverter, formula function, alarm display, machine fault and status display. The operation is greatly simplified, saving personnel. The formula function can facilitate the replacement of new products at any time, save the time for new products to go online, and improve efficiency. Alarm display and fault display can inform the fault situation and fault point at any time, which is convenient for maintenance and debugging, while avoiding the expansion of the fault.
The following is the control scheme diagram:
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Figure 2.3 Control scheme diagram
2.2.3 Selection of PLC, touch screen and inverter
(1) Selection of PLC
The current PLC is roughly divided into two schools. One is the Japanese faction, whose representatives include Mitsubishi, Omron and other brands.
The other is the Euro-American faction, which is mainly represented by Siemens, AB, etc. China’s PLC is mainly Japanese faction, there are some such as Xinjie, Fatek, Fengwei, Delta and other brands (Fatek, Fengwei, Delta for China’s Taiwan brand).
PLC selection is mainly determined by function and cost performance, because the stronger the function, the higher the price. The project needs
The PLC has RS485 communication, expandable module, AD conversion, temperature control, analog output and other functions, and requires the PLC to have the corresponding command system and the company must have a supporting module.
According to the principle of economy and practical, FBS-32MAT PLC, FBS-TC6 temperature control module, FBS-4DA analog output module, FBS-6AD analog input module and FBS-CB5 communication template are selected in this project.
(2). Selection of touch screen
At present, there are many kinds of touch screens on the market, and the commonly used brands are FATEK,eView, GE, Proface, HAKKO, WEINVIEW, HITECH and so on.
Like the PLC, the selection of the touch screen is also determined by the function and cost performance, the stronger the function, the higher the price. The functions required by this project can be done by almost all brands, so according to the principle of economic and practical, the project selected FATEK company’s FV070ST-T50 touch screen with a relatively low price.
(3). Selection of frequency converter
Several points to pay attention to when selecting inverter:
1) The purpose of frequency conversion; Constant voltage control or constant current control.
2) Load type of inverter; Such as vane pump or positive displacement pump, pay special attention to the performance curve of the load, the performance curve determines the way of application.
3) Matching problem between frequency converter and load;
I. Voltage matching; The rated voltage of the inverter is consistent with the rated voltage of the load.
II. Current matching; For ordinary centrifugal pumps, the rated current of the frequency converter is consistent with the rated current of the motor. For special loads such as deep water pumps, it is necessary to refer to the motor performance parameters to determine the inverter current and overload capacity with the maximum current.
III. Torque matching; This may occur under constant torque loads or with decelerating devices.
4) When the frequency converter is used to drive the high-speed motor, the output current value increases due to the small reactance of the high-speed motor and the increase of high order harmonics. Therefore, the selection of frequency converter for high-speed motors has a capacity slightly larger than that of ordinary motors.
5) If the frequency converter is to run a long cable, measures should be taken at this time to inhibit the impact of the long cable on the ground coupling capacitance to avoid insufficient output of the frequency converter, so in this case, the frequency converter capacity should be amplified one step or the output reactor should be installed at the output end of the frequency converter.
6) For some special applications, such as high temperature, high altitude, this time will cause the reduction of the frequency converter, the frequency converter capacity should be amplified one gear.
According to the above requirements combined with the actual situation of the project, the inverter selected for this project is Lanhai Huateng V5 series. As shown in the picture below:
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Figure 2.6 Blue Sea Huateng V5 series inverter
Chapter 3 Application design and function realization
3.1 Touch screen and PLC to achieve human-machine dialogue design
In order to realize the man-machine communication between the touch screen and the PLC, it is necessary to ensure the normal communication between the PLC and the touch screen, and the various components of the screen on the touch screen must correspond to the various soft components on the PLC one by one.
3.1.1 Connection description of FBS series PLC and FATEK FV series touch screen
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Figure 3.1 Touch Master setting diagram of FATEk Touch screen software
The screen editing software of FV series touch screen is “Touch Master”. Figure 3.1 above is the setting on the screen editing software “Touch Master” when FATEk Touch screen communicates with FBS series PLC. Figure 3.2 is the detailed wiring diagram of the communication between FV series touch screen and FBS series PLC, which is realized by RS232 communication protocol.
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Figure 3.2 RS232 communication wiring diagram between touch screen and FBS host
3.2 Realization of temperature control
This project requires that the temperature be controlled in a certain precision range, and the temperature value is set with the touch screen input, and the temperature value is monitored through the touch screen screen.
3.2.1 Wiring diagram of PLC temperature control module FBS-TC6
The function of the temperature control module is to convert the temperature signal sensed by the thermocouple into a digital signal sent to the PLC device, the accuracy of the temperature is related to the resolution of the module, and the higher the resolution, the higher the precision. The following is the connection diagram of FBS-TC6.
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