Precise control of printing presses using Mitsubishi PLC
http://www.factoryautmation.com1, introduction
In PLC control printing presses Mitsubishi recent PLC control printing presses Mitsubishi years, with the improvement of China's automation technology, factory automation is a new step. PLC as an emerging industrial controller, with its small size, complete function, low price, high reliability has unique advantages, in various fields to obtain the wide application.
As the largest printing machine manufacturers - beiren group, in order to make the products stable performance, easy maintenance, we adopt the control scheme based on PLC controller. The double color printing machine for easy operation, high precision, so the input and output points more, so the communication host computer using MITSUBISHI. FX2N-80MR 32EX 4D/A, is mainly responsible for the main drive control, control, each unit clutch and pump, valve control. The machine adopts MITSUBISHI FX2N-64MR 4A/D, is mainly responsible for the control of water roller motor, the output speed of main drive motor, adjustable version of data acquisition. At the same time using a MITSUBISHI 5.7 inch touch screen mainly responsible for water, and the motor speed display, adjustable version, and the fault display. The system is reliable in operation, convenient maintenance, simple operation, can greatly improve the grade of the offset press, praised by users.
2, system structure
Button button the upper machine and lower machine adopts RS485 communication, communication is convenient and reliable. The multi-color machine, safety factor is very important. In the design, each unit is to consider to safety control, including standard unit emergency stop, safety, but also consider the convenience of operation, including each unit should be punctual, counter point. Therefore, on the one hand input point increase a lot. On the other hand, walk the line is also very inconvenient. The communication between two computers can be very good to solve this problem, the unit of the wire can be in accordance with the principle of proximity to leave it is close to the control cabinet, not only save walk the line, convenient control.
Given 4D/A also requires, on the one hand because of the printing machine is a high precision machinery, print quality is the mechanical processing and installation accuracy, on the other hand, also depends on the water ink balance and pressure accuracy. Two-color machine each color group, water and ink device. In order to facilitate water and speed regulation, each root water and with a frequency converter control, at the same time, the main motor speed adjusting inverter. Therefore, in order to realize the multi-channel speed regulation, we use the Mitsubishi digital to analog converter, PLC digital quantity, according to the corresponding algorithm and converted into 0 ~ 10V DC voltage output, it is good to realize the multi speed regulation requirements.
Very good 4A/D transmitted to the -1mm~ -2mm~ to affect the precision in the printing process, adjustable version is a more complicated process. Especially for multi-color machine, each version of the positive prints produced great influence. If misregister, print will literally overlap or image is not clear. Generally speaking, a printing plate axial adjustment range of 2mm. Circumferential adjusting range 1mm. If you use the manual version, will waste a lot of time, and the accuracy is not high. In order to realize the automatic version, the version and install potentiometer, through the potentiometer analog, after processing of the PLC, the version and the rotation precision control in the play version of the range.
As a new touch-screen interface, from the emergence of attention, it is easy to use, powerful function and excellent stability make it very suitable for industrial environment. Users can freely combine text, graphics, buttons, etc. to digital processing or monitor may change at any time with the information. The rapid development of mechanical equipment, the operation interface required by skilled operators to operate, can not improve efficiency. But the use of man-machine interface, can clear instructions and inform the operator equipment present situation, so that the operation is simple and vivid. Use the touch screen, also can make the machine wiring standard, simple, but also can to reduce the PLC control I/O points, reduce production costs, but also relatively increase the added value of the whole equipment. MITSUBISHI touch screen and MITSUBISHI PLC has good versatility, can online monitor and modify the program, do not have Very troublesome duplicate plug and plug interface.
3, software design
Printing machine overall electrical design is more complex, the requirements on time is very strict. In many parts of the machine is provided with a proximity switch, used to detect different time point. Walk in the printing process, the quality of the paper is affect the quality of the machine is one of the important link. The so-called paper is good or bad, that is no crooked Zhang, the double Zhang phenomenon, if have a crooked Zhang, Zhang dual phenomenon, in the case of high speed, will go bad paper, involved in the machine, resulting in the destruction of the rubber, to the user to bring great losses.
In the experiment, we found that in accordance with the procedures of the process, preparation, at low speed is no problem, but the speed increased to 7000r/h, will appear crooked Zhang locked phenomenon. The reason, mainly is because the bald reaction time and magnet action time lag caused. Procedures in the implementation process, the circular scanning mode, in order to keep ahead of the output of the electromagnet, in the design, I used the interrupt and Mitsubishi programming instructions input and output refresh command, make the electromagnet output executed immediately, ahead of the electromagnet work time, even in the 12000r/h speed, a good lock fault of paper, solved a major problem in the paper.
Away from the pressure, pressing in the printing has a very important role. Accuracy of the clutch pressure, to printing quality is good or bad has a direct impact. Pressing prematurely, dirty impression cylinder, to the operation to bring a lot of inconvenience; from the pressure too early, the last piece of paper printed complete pattern, resulting in a waste of paper.
When printing plate roller and rubber roller pressure rubber roller and the first, then the imprinting roller pressure. In our machine, pressing all adopts pneumatic device, each cylinder has an action time. Because of the printing speed is more than speed, between 3000~12000r/h, according to user needs can choose different speed. However, the action time is fixed, the gear to turn angle is certain, therefore, the speed of the machine is not at the same time, pressure and time are different. In order to solve this problem, we according to the calculated value, find out for the different speed of the machine, the machine time delay. By comparing the instructions, when the machine speed and equal the theory of value, the corresponding delay time, the embossing roller and rubber accurate pressure. After many tests, from the pressure, and pressure are no problem.
In the man-machine interface, the design of the 7 pictures, including the overall graphics, fault display, display the speed of the machine and the count, water and velocity show that tone version control. Fault display using the indicator, give out components can realize flashing effect, allows the operator to easily know the fault position, the overall feeling is very good. In the water and the speed display, a histogram, can display content increased in size, only need to press the bar, can increase the amount of water, but also to facilitate monitoring.
4. Concluding remarks
Printing machine design belongs to a set of electrical system design, including hardware, software design, covering a wide range. Here, I simply introduced some part of the more important, there are many other details, here no longer lists one one. Using a set of control system of MITSUBISHI, sense of reliable, convenient batch production in machine in the process, found no big problem. The PLC function is complete, reliable and durable, simple instructions, compared with other products, the overall feel of MITSUBISHI software system interface is friendly to users, programming, maintenance is convenient. The touch screen and PLC has good versatility, can through the touch screen monitor and modify] this is the program, other products can not match and industrial components. In short, MITSUBISHI's designers and users have brought a lot of convenience.