Application of VFD in Renovation of Printing Machine

The rapid development of technology has improved the manufacturing process of printing machines, and frequency converters play an important role in various printing machine processes. Today, I will take you into the equipment accessories to learn more about the application of frequency converters in the process of printing press transformation.

At present, the new technology of electrical control has been widely used in domestic sheet-fed lithographic printing machines, such as PLC, touch screen, frequency converter and so on. These new sheet-fed offset printing machines have the advantages of high reliability, energy saving and high efficiency, and complete functions compared with the old equipment several years ago. However, in many current printing companies, the old models of sheet-fed offset printing machines are still have a considerable amount. If they are transformed and all PLCs and touch screens are used, a large number of lines need to be changed, which is almost equivalent to remaking the electrical control system. If only the main transmission part of the sheet-fed lithographic printing machine is modified with a frequency converter, the circuit changes are small 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 reliability and energy saving of the frequency converter, and the cost performance of the transformation is high. The following is the application of frequency converter in the transformation of domestic single and double-color sheet-fed offset printing machines, and some experience.

1. Process characteristics of printing machine operation control

In order to make the frequency conversion motor driven by the frequency converter can be well applied to the printing machine and meet the requirements of the production process, first of all, it is necessary to understand the process characteristics of the operation control of the printing machine, what requirements it puts forward for the function of the frequency converter, and then choose which type Inverter, and how to specifically transform and connect the original line.

The operation of the sheet-fed lithographic printing machine is driven by the motor through the belt drive, gear drive, and chain drive. The cylinders, tooth rows, and mechanisms are coordinated by mechanical connections, so the motor that controls the main drive is Control the running state of the whole machine. During mechanical adjustment, inspection, installation and removal of PS plates and blankets, and cleaning of the machine, it is necessary to control the forward and reverse rotation of the machine by manual pointing, and the 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 should be run at the same speed for a long time. When the machine starts formal printing production, there is an initial speed of about 3000 rpm. When the paper feeder starts to feed paper, it can be accelerated to make the machine produce at a higher speed, generally 6000-8000 rpm. In order to adapt to different production speed requirements, the high speed can be adjusted through a speed regulating potentiometer, and the actual value of the speed can be indicated by the speedometer. From the high speed of printing to the initial printing speed, there are two situations. One is the manual button to slow down, and the other is the detection of paper faults during the printing process, such as crooked sheets, no paper, double sheets, etc., so that the printing machine will automatically slow down, and each part will make coordinated actions accordingly, such as pressure release, water stop , from ink, stop feeding paper, etc. At the end of production, press the stop button, and the machine will stop smoothly in a free stop mode. In addition, in order to ensure personal safety, safety protection switches or emergency stop buttons are installed on dangerous parts of the printing machine. As long as these switches are activated, the machine will stop immediately no matter what state it is in, and the whole machine will brake in an emergency.

2. Requirements for the function of the inverter

There must be three-stage speed control and direction control functions to meet the requirements of forward and reverse pointing, forward low speed, printing initial speed, and high speed; the machine must have a speed indicator to make the operator clear the current operating state; the acceleration and deceleration process of the machine It should be stable, the speed should be appropriate, and the speed change should be smooth and without impact in time. When the frequency converter itself fails, the whole machine should be stopped.

3. Parameter selection of frequency converter

According to these requirements, it can be seen that most frequency converters can meet the requirements, and general-purpose frequency converters are selected for the occasions used. The choice of voltage capacity depends on the connected power supply and the motor used by the original machine. Here we use 400V class inverters, 5.5kW for single-color machines and 11kW for two-color machines. There are many types of inverters on the market, and mainstream products with good quality are generally selected.