At present, the new electric control technology has been widely used in domestic sheet-fed offset printing presses, such as PLC, touch screen, frequency converter, etc. These new sheet-fed offset printing presses have the advantages of high reliability, energy saving, high efficiency, and perfect functions compared to the old-style equipment several years ago. However, in many current printing companies, old-fashioned sheet-fed offset printing presses are still Has a considerable amount. If they are modified, all PLC and touch screens are used, and a large number of lines need to be changed, which is almost equivalent to remaking the electrical control system. If only the inverter is used for the main transmission part of the sheet-fed offset printing press, the circuit changes little and the workload is small. It not only retains the simple and practical characteristics of the original relay contact control, but also gives full play to the advantages of inverter reliability and energy saving, and the cost-effective transformation is high. The following is about the application of the inverter in the transformation of the domestic single and double color sheet-fed offset printing machine.
1. Technological characteristics of printing machine operation control
In order to make the inverter-driven inverter motor be well applied to the printing machine and meet the requirements of the production process, we must first understand the technological characteristics of the operation control of the printing machine, what kind of requirements does it put on the function of the inverter, and then choose which model Inverter, and how to specifically modify and connect the original line.
The operation of the sheet-fed offset printing press is driven by the motor through the belt drive, gear drive, and chain drive. The mechanical interaction between the rollers, tooth rows, and mechanisms is coordinated, so the motor that controls the main drive is Controlled the running state of the whole machine. In mechanical adjustment, inspection, installation and removal of PS version and blankets, and cleaning of the machine, it is necessary to manually control the machine to run in the reverse direction. A speed of about 4r / min is more appropriate. During the printing pause, in order to ensure that the PS plate is not damaged and the ink is not dry, the machine must be run at the same speed for a long time. When the machine started formal printing production, it had an initial speed of about 3,000 rpm. When the paper feeder starts to feed paper, it can be accelerated to make the machine produce at a higher speed, generally 6000 to 8000 rpm. In order to adapt to different production speed requirements, a high-speed potentiometer can be used to adjust the high speed, and the actual value of the speed can be indicated by the speedometer. There are two cases from the high-speed printing to the initial printing speed. One is the manual button to slow down, and the other is that paper faults are detected during the printing process, such as crooked sheets, no paper, double sheets, etc., which causes the printing machine to automatically decelerate, and various parts make coordinated actions accordingly, such as pressure release and water stop. , Remove ink, stop paper feeding, etc. At the end of production, press the stop button, and the machine stops smoothly in corresponding free stop mode. In addition, in order to ensure personal safety, a safety protection switch or an emergency stop button is installed in the dangerous part of the printing machine. As long as these switches are activated, no matter what state the machine is in, it must be stopped immediately and the whole machine is braked.
2. Requirements for the functions of the inverter
(1) There must be three-stage speed control and direction control functions to meet the requirements of positive and negative spotting, positive low speed, initial printing speed and high speed;
(2) The speed value of high-speed operation is variable, and it is best to adjust the speed steplessly by manually adjusting the potentiometer to adapt to different process requirements;
(3) There must be speed indication during the operation of the machine to make the operator know the current operation status;
(4) The acceleration and deceleration process of the machine should be stable, the speed is appropriate, and the speed change should be smooth and without impact in a timely manner. When the inverter itself is faulty, the whole machine should be stopped.
3. Parameter selection of the inverter
According to these requirements, it can be seen that most inverters can be satisfied. For the occasions used, choose a universal inverter. The selection of voltage capacity is based on the connected power supply and the motor used by the original machine. The inverters of 400V grade, 5.5kW for single-color machines and 11kW for two-color machines are used here. There are many types of inverters on the market. Generally, mainstream products with good quality are selected, such as Mitsubishi A540 series, Yaskawa G5, and Delta Although the price is higher, the quality is guaranteed.
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