The shaftless rotary corrugated printing control system uses PLC as the main control system. The printing plate roller, ink roller, paper feed roller, and electronic cam are all servo driven, the stepper motor adjusts the gap, the man-machine interface is centralized monitoring, and the field bus collects the transmission signal. Combined with high-precision reducer, coupling, encoder, slide screw, synchronous belt and other mechanisms, the speed and phase synchronization of each roller under high-speed operation are realized. The phase adjustment function of the system makes the adjustment simple and easy. All of these have greatly improved production speed, overprint accuracy and ease of operation.

System Components

The system consists of a paper feed section and a four-color printing section. The paper feed section mainly includes an electronic cam vacuum suction paper feed mechanism and a paper feed roller. The electronic cam vacuum suction paper feeding mechanism uses the negative pressure generated by the fan to make the paper board closely adsorbed on the paper feeding platform. Two electronic cam servo motors drive the paper feeding platform to reciprocate synchronously between the upper and lower positions of the paper feeding, and cooperate with the paper feeding roller and paper feeding. The rollers complete the cardboard transfer in sequence. On the basis of the stable friction coefficient of the rollers and the pressure of the cardboard, the paper feeding timing is related to the position of the one-color printing plate and the production speed. At a certain speed, when the one-color printing plate turns to a certain position, the paper starts to be fed to another position Stop the paper feed to ensure that the printing plate can accurately print the pattern on the corresponding position of the cardboard every time. For different specifications of cardboard, the timing of feeding / stopping of the paper also changes accordingly. The operator only needs to adjust the material number on the man-machine interface, and the system will automatically adjust it immediately to ensure the printing position is accurate. The action, speed and rotation angle of the two electronic cam motors must be completely the same to ensure the continuous and stable operation of the motor and mechanism, and the straight out of the cardboard. Here, we use the two-axis simultaneous motion linear compensation function to achieve real-time synchronization of the two axes. In addition, the cam motor must also meet the needs of long-term frequent reciprocating forward and reverse operation. The system is required to select a high-response servo system and adjust the servo parameters in conjunction with the load to give full play to the high-speed high-response characteristics of the servo system and minimize the transmission links and various The link is delayed, and at the same time, the system heating and recovery protection issues must be fully considered to make the motor work in a light load state (schematic diagram of equipment and system composition is as follows).

After the cardboard is sent out, it enters the four-color printing section. Each color section is controlled by printing plate rollers, ink rollers, support rollers, pick-up rollers, and air cylinders. Adjust the roller gap and position with the encoder.

The shaft diameter of the printing plate roller is usually very large, and the running speed is very fast, and the accuracy of printing overprinting is high. Therefore, the slight speed difference between the printing plate rollers will cause the overprinting in a short time. Set the speed difference of any two printing plate rollers at any time as △ V, the system speed loop adjusts the speed difference within △ t time, because the transmission mechanism delay is very small, set to 0, then the speed difference is set within △ t The deviation caused by △ V is set as ε, and the formula can be summarized as follows:

ε = ∫0 △ t △ Vdt

It can be seen that the smaller the speed difference ΔV between loads, the faster the system response (that is, the shorter Δt), the smaller the overprint deviation ε generated. This requires on the one hand to improve the mechanical accuracy, such as better installation concentricity, uniform load inertia, etc .; in addition, the system must be fully considered to match the load when selecting the system, while providing sufficient load torque, but also to provide sufficient response capacity. At the same time, debugging work is also very important, to combine the load to make the system play the best performance. In this regard, the automatic detection function of the servo system can be used to detect the load condition first, and then match the parameters according to actual needs (such as increasing the response or reducing the overshoot, etc.), and further fine-tune until the conditions are met. At the same time, because each load and its transmission mechanism are not the same, the parameters of each servo will also be slightly different, and the difference in the mechanical transmission coefficient of the load should be compensated electrically.

The system uses the PLC motion control function to control the servo system in real time. It uses a separate high-speed processor, and the calculation is independent of the CPU. The combination of the servo system meets the needs of high precision and fast response. In addition, the encoder signal of the load shaft end is collected to detect and correct the running status of the load, so as to eliminate the influence of the transmission error, and is beneficial to analyze and find the problem.

The linear speed between the rollers must be the same to avoid the paperboard slipping, and at the same time the ink on the ink rollers will be uniform and colorless. In addition, the action of the ink roller cylinder is also very important. When starting paper feeding, the air cylinder drives the ink roller to drop in sequence, inking the printing plate. The timing of falling and lifting is determined by the position of the printing plate to ensure the inking position and amount of ink on the printing plate of the ink roller, thereby ensuring the printing quality.

Due to the large number of specifications and models of cardboard, the process and control must be adjusted accordingly for different specifications of cardboard printing. At the same time, equipment cleaning, maintenance, and versioning are often carried out, which will inevitably cause human errors. The adjustment of the phase is realized in the program. The operator only needs to adjust the material number and the correction value on the man-machine interface without making any changes to the equipment. The operation is simple and the work efficiency and flexibility are greatly improved.

In addition, in the course of practice, we have summarized a set of simulated registration test methods to cooperate with the debugging work. Servo feedback and encoder signals are detected by PLC, and statistical analysis is performed to calculate the phase difference (pulse value) of each printing plate roller at any time, and then converted to length (mm) to measure the mechanical registration accuracy. There is no need to inking and cardboard, saving a lot of materials, but also shorten the debugging time.

Performance and characteristics

1. Due to the use of servo drive, its high-speed, high-precision and high-response characteristics greatly increase the production speed. Traditional equipment usually has a maximum production speed of 80 sheets / min. This system can double the production speed of the equipment to 160 sheets / min. .

2. The closed-loop design and quick response capability of the system enable the equipment to maintain extremely high control accuracy under high-speed production, with overprint deviation ≤ ± 0.25-0.4mm (depending on mechanical conditions).

3. The electronic cam vacuum suction paper feed mechanism changes the traditional push-back paper feeding method, which will not cause the cardboard to bend or even fail to feed the paper, and also avoid the inaccurate positioning of the cardboard, thereby ensuring the accuracy of overprinting. speed. In addition, the application of electronic cam makes the transition production very simple, without any adjustment of equipment.

4. System adaptive synchronization control, only need to change the speed of the paper feed roller or any printing plate roller, the remaining rollers will automatically follow up, always keep the linear speed and phase synchronization, and the paper feed frequency and feed / stop timing will also change. Ensure overprint accuracy and location.

5. The electronic cam and formula function make the transition production very simple, without adjusting the mechanical mechanism, as long as the production material number is changed on the man-machine interface, it can be easily achieved.

6. Before each operation of the equipment, the printing plate roller must find its initial phase. Traditional equipment usually uses high-precision encoders for positioning. This system can save this investment and simplify the work through the program. The operator only needs to follow The prompt on the man-machine interface can be operated. In addition, the initial phase shift caused by versioning or installation and maintenance can also be adjusted at will on the man-machine interface without stopping or power-off.

7. The application of the fieldbus system saves the equipment a lot of cumbersome installation and wiring work and takes up space, ensuring the stability, speed and accuracy of signal transmission, and enhancing the maintainability of the system.

Conclusion

Because the system has the above characteristics, especially its advantages of high efficiency, high precision and high flexibility, it has attracted the attention of many packaging and printing companies after being applied to the equipment. However, only a few of these technologies are currently adopted in the country, and most of them are imported or joint venture technologies. There is no independent intellectual property rights. Their high price also makes many enterprises, especially small and medium-sized enterprises, prohibitive. Therefore, we hope to promote the promotion of this technology in China and create better benefits for more enterprises.

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