Multi-color printer control system based on PLC and HMI

As people have increasingly higher requirements on smart printing production methods and diversification of newspaper production, new concepts have also been formed in press management. In this new printing environment, flexibility and consistency are key requirements, and the press control system based on PLC and HMI can fully meet this requirement.

Multi-color printing presses require easy operation and high precision, so they have more input and output points, so dual-machine communication is used. The upper computer is mainly responsible for the control of the main drive, the control of the clutch and pressure of each unit, and the control of the air pump and the gas valve. The lower machine is mainly responsible for the control of the water roller motor, the speed regulation output of the main drive, and the data acquisition of the adjustment motor. The upper computer and the lower computer adopt RS485 communication, and the communication is convenient and reliable. At the same time, a touch screen was selected, mainly responsible for the water roller motor speed display, adjustment display, and the whole machine fault display.

For multicolor machines, safety factors are important. In the design, each unit should not only consider the safety control, including the emergency stop of the local unit, and the safety button, but also consider the convenient operation, including the punctuality and reverse point buttons of each unit. Therefore, on the one hand, the input points increase a lot; on the other hand, the alignment is also very inconvenient. The use of dual-machine communication can solve this problem very well. The alignment of each unit can be in accordance with the principle of proximity and enter the control cabinet close to it, which saves the wiring and facilitates the control.

The quality of the printed matter depends on the precision of machining and installation. On the other hand, it also depends on the balance of the waterway, the ink path, and the accuracy of the pressure. Each color group of the two-color machine has a waterway and ink path device. In order to facilitate the adjustment of the water roller speed, each water roller is controlled by one inverter. At the same time, the speed of the main motor also needs to be adjusted by the inverter. Therefore, in order to achieve multi-path speed adjustment, digital-to-analog converters are needed. The digital amount given by the PLC is converted into a 0~10V DC voltage output according to the corresponding algorithm, and the multi-speed adjustment requirements are well achieved. .

In the printing process, versioning is a more tedious process. Especially for multi-color machines, the accuracy of each set of editions will have a great influence on printed products. If overprinting is not allowed, there will be literal overlap or unclear images. In general, the plate axial adjustment range is -2mm~+2mm, and the circumferential adjustment range is -1mm~+1mm. If you use manual adjustment, you will waste a lot of time and the accuracy is not high. In order to achieve automatic pattern making, we installed a potentiometer on the platen roller and sent the analog quantity to the 4A/D through the potentiometer. After PLC processing, the platen roller's rotation accuracy can be well controlled within the platemaking range.

The application of the touch screen omits some of the original buttons, indicators, counters, tachometers, time relays, and lubrication program control controllers, reducing the failure rate and reducing the wiring work. The screen of the touch screen can provide a large number of alarm information in the form of a scrolling light. It can also design multi-screen PLC input and output status monitoring screens, and can also see the details of the electrical operation and maintenance prompts of the machine in the system help. The electrical system operation, use, and maintenance of the machine are simple and convenient.

After the system was applied to mass production of the press, no major problems were found. PLC is complete in function, reliable and durable, the instruction is simple, touch screen and PLC have very good commonality, can monitor and revise the procedure through the touch-sensitive screen, have brought a lot of convenience to designer and user.