Application of V80 series PLC in printing machine

The application of V80 series PLC in the control system of printing machine

1 introduction

printing machine is a machine with high precision. The quality of printed matter depends on the machining and installation accuracy on the one hand, and on the balance of waterway and ink path and the accuracy of pressing on the other hand. In order to stabilize the performance of the printed products, a control scheme with V80 PLC as the main controller is adopted

2 system structure

v80 series PLC is a general-purpose and cost-effective small programmable controller developed by haiweishen Technology Co., Ltd. It adopts 32-bit high-performance CPU chip and high-speed logic analysis ASIC chip. The program scanning speed is fast, and each basic instruction only needs 0.2 μ s. I/o control points up to 256 points, large user storage space, stable and reliable performance

due to the large number of input and output points of the two-color printing machine, the dual machine communication is adopted. The upper computer adopts the V80 series product m40dr+e16d+e4da2, which is mainly responsible for the control of the main drive, the clutch pressure control of each unit, as well as the control of the air pump and air valve. The lower computer adopts the V80 series product m40dr+e8ad2, which is mainly responsible for the control of the water roll motor, the speed regulation output of the main drive, the data acquisition of the version adjustment motor, etc. At the same time, an eview touch screen is selected, which is mainly responsible for the speed display of the water roller motor, the version adjustment display, and the whole machine fault display

the system structure is shown in Figure 1:

among them, the upper computer and the lower computer adopt RS485 communication, and the communication protocol adopts Modbus protocol. In the design, each unit should consider the safety control, including the emergency stop and safety button of the unit; It is also necessary to consider the convenience of operation, including that each unit should have on-time and anti point buttons. This leads to a lot of input points on the one hand; On the other hand, the wiring is also very inconvenient. Therefore, using dual computer communication can solve this problem well

each color group of the two-color machine has water and ink devices. In order to facilitate the adjustment of water roll speed, each water roll is controlled by a frequency converter. At the same time, the speed of the main motor also needs to be adjusted by the frequency converter. Because "the person in charge of the market of a foreign-funded chemical enterprise at the scene told the author that in order to realize multi-channel speed regulation, v80-e4da2 analog output module is adopted, which converts the digital quantity given by the PLC party into 0~10v DC voltage output according to the corresponding algorithm, which well realizes the requirements of multi-channel speed regulation

for multicolor machines, version adjustment is a relatively cumbersome process, and the accuracy of each group of versions will have a great impact on the printed products. If the overprint is not accurate, the printed matter will appear literal overlap or unclear image. Generally speaking, the axial adjustment range of the printing plate is -2mm~+2mm, and the circumferential adjustment range is -1mm~+1mm. If you use manual version adjustment, it will waste a lot of time, and the accuracy is not high. In order to realize automatic plate printing, a potentiometer is installed on the plate roller, and the analog quantity is transmitted to v80-e8ad2 through the potentiometer. After PLC processing, the rotation accuracy of the plate roller can be well controlled within the plate printing range

through the touch screen, users can freely combine words, buttons, graphics, numbers, etc. to process or monitor and manage information that may change at any time, and can clearly indicate and inform the operator of the current situation of the machine and equipment, making the operation simple and vivid. Using the touch screen can also standardize and simplify the wiring of the machine, reduce the i/o points required for PLC control, reduce the production cost, and relatively improve the added value of the whole set of equipment

3 system design

3.1 paper feeding design

the overall electrical design of the printing machine has strict requirements on time. Proximity switches are installed in many places of the machine to detect different time points. In the printing process, the quality of paper is an important link that affects the quality of the machine. The so-called quality of paper walking refers to the absence of skew sheets, double sheets and other phenomena. If there is skew sheets, double sheets and other phenomena, under the condition of high speed, the worn paper will be involved in the machine, thereby damaging the rubber and causing great losses to users

the flow of the paper feeding process is shown in Figure 2:

according to the program prepared according to the above process, after the speed increases to 7000r/h, there will be skew and locking, which is mainly caused by the reaction time of the bare head and the lag of the magnet action time. In order to advance the output of the electromagnet, the input and output refresh command of the interrupt programming command is used to make the output of the electromagnet execute immediately, which advances the action time of the electromagnet, and can lock the faulty paper well even at the speed of 12000r/h

3.2 clutch pressure design

the accuracy of clutch pressure has a direct impact on the quality of prints. Pressing too early will pollute the imprint roller and bring a lot of inconvenience to the operation; If the pressure is released too early, the last piece of paper will not be printed with a complete pattern, resulting in a waste of paper

when printing, the plate roller and the rubber roller are pressed first, and then the rubber roller and the embossing roller are pressed. Since the printing speed is multi-stage speed, between 3000~12000r/h, different speeds can be selected according to the needs of users. However, due to the pneumatic device used for closing the low elastic modulus, each cylinder has an action time, and the gear rotation angle is certain. Therefore, when the machine speed is different, the closing time is also different. In order to solve this problem, according to the theoretical calculation value, find out the delay time of the machine for different machine speeds. Using the comparison command, when the machine segment speed is equal to the theoretical value, delay the corresponding time to make the imprint roller and the rubber roller press accurately

4. Conclusion

using the control scheme of V80 series PLC, the system is reliable, easy to maintain, simple and intuitive to operate, which greatly improves the grade of the offset press and is highly praised by users