On the design and application of Huichuan frequenc

2022-08-17
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Brief discussion on the design and application of Huichuan inverter in gravure printing machine

1. Introduction

gravure printing machine is named for its layout characteristics, and plays an important role in the flexible packaging industry with its exquisite printing quality. It is generally composed of unwinding device, unwinding traction, host, rewinding traction and rewinding device. According to different configurations, it has three motor systems, five motor systems and seven motor systems

the general gravure printing machine is basically equipped with three motors: main machine, winding traction and unwinding traction. The unwinding tension is controlled by the magnetic powder brake, and the winding tension is controlled by the torque motor or magnetic powder clutch, which is a basic three motor system. If the unwinding and winding tension is controlled by the motor controlled by the frequency converter, it is a five motor system. For the duplex position winding and unwinding system with automatic roll change, it constitutes a relatively advanced seven motor system at present

when printing coiled materials, a certain tension is required to tension the materials into the printing unit, and ensure the stability of the tension during the operation, so as to ensure the accuracy of overprint of various colors and exquisite patterns. Tension control is the core of gravure printing control technology. If the tension control is stable and the tension fluctuation is small, the overprint accuracy and printing speed of the machine will be high

because of the high requirements for chromatic accuracy in the high-speed printing process, the tension control accuracy in the whole process is very high. For a long time, the driving part of the seven motor gravure press has been the world of imported frequency converters, and the higher-grade shaftless transmission system is realized by servo controllers. In recent years, domestic vector converters have been launched one after another, but due to the complex algorithm of vector control, domestic vector converters still have some gaps compared with imported converters in terms of performance, mainly in terms of speed stability accuracy and dynamic response characteristics. Some domestic high-end frequency converters have occupied an important position in the printing and packaging industry, but they are generally used in applications with low requirements such as compound machines and slitting machines. The gravure printing machine with seven motors, which can best reflect the high level requirements, has been dominated by imported frequency converters for a long time, but it cannot be shaken

the MD320 series vector control frequency converter and md330 special tension frequency converter launched by Shenzhen Huichuan Technology Co., Ltd. integrate high-end performance and powerful functions. Using its unique synchronous control and tension control functions, it effectively makes up for the slight gap between the performance and the imported high-end frequency converter, and has been successfully applied to the seven motor gravure printing machine system. This paper compares and analyzes the application scheme of Huichuan frequency converter in seven motor gravure press with the scheme in the current industry

2. Scheme introduction

2.1 the tension control of the traditional scheme

system is to control the tension stability by controlling the constant linear speed of the system. At present, the industry mostly uses high-grade PLC to control the constant linear speed, sends the feedback signal of the winding and unwinding traction and the swing roll potentiometer of the winding and unwinding device to PLC, carries out PID control and winding diameter calculation through PLC, and transmits the result to the vector frequency converter through analog quantity in the future work. The frequency converter is only an actuator in the whole control system. This requires that the PLC operation speed is fast and more a/d and d/a modules need to be expanded. Moreover, due to the influence of PLC operation speed and signal transmission, the dynamic response of the system becomes slower, so we can only use the most high-end brand of vector converter, which requires that the analog input port of the converter has high resolution, the dynamic response of the converter is fast and the speed stability accuracy is high, so as to make up for the delay caused by the lack of solutions

2.2 Huichuan inverter scheme:

(1) introduction to Huichuan vector inverter

Huichuan vector control inverter is a newly launched domestic high-end inverter in recent years. There are mainly MD300 simple vector converter, MD320 general vector converter and md330 special vector converter for tension control. MD300 has simple functions and is mainly used in occasions with low functional requirements and high performance requirements. MD320 has powerful functions and can realize closed-loop vector control, which can meet the requirements of most industries for the function and performance of frequency converters. Md330 is a special inverter controller for tension, which mainly integrates the special functions of tension control such as coil diameter calculation, tension taper and pre drive, and realizes the simplification of tension control. The tension control of md330 has torque mode and speed mode. The speed mode is generally used in the occasions with high requirements for tension control accuracy, and the torque mode can be used in the occasions with low requirements for tension control accuracy. The system structure is simple and the debugging is convenient

(2) the system composition of Huichuan frequency converter

the system is controlled by seven motors, which are composed of two winding (md330), two unwinding (md330), host (MD320) and winding and unwinding traction (MD320), in which winding, unwinding and winding and unwinding traction are closed-loop tension control with tension feedback, and the frequency converter works in speed mode. Because the middle part is the printing part, which requires high chromatic accuracy, the host and the winding and unwinding traction work in the closed-loop vector control mode with encoder. As shown in the attached figure

attached Fig. 7 Schematic diagram of motor gravure printing machine

(3) control points

it is required that the tension of each section is constant and the swing amplitude of the swing rod is small. However, due to the continuous change of coil diameter in the process of winding and unwinding, the speed change caused by the change of coil diameter must be considered in the adjustment of PID, otherwise the swing bar will swing too much

intermediate chromatic printing is very sensitive to tension changes, so it is required that the swing of the front and rear traction swing bars should be very small, and the main motor source, computer and printer of the experiment should be turned off, otherwise it is easy to chromatic inaccuracy. This requires high speed stabilization accuracy and fast response speed of the system in dynamic state

the speed is stable during automatic roll changing, and the swing of the swing rod is small, so as to minimize the scrap rate

(4) implementation process

the system speed is controlled by the host, which can be set by potentiometer or through man-machine interface. The operating frequency signal of the host frequency converter is input to the PLC through AO1. The PLC calculates the outgoing speed signal according to the plate diameter (diameter of the printing shaft) input on the touch screen, and outputs it to the winding and unwinding traction and unwinding frequency converter in the form of analog quantity, which is input to the frequency converter through the AI2 port. For the unwinding part, because the change of coil diameter is one of the factors causing the change of linear speed, the frequency converter will automatically calculate the coil diameter according to the current front-line speed, and then superimpose the influence of coil diameter on the speed, give the corresponding main frequency to ensure basic synchronization, and use PID as the auxiliary frequency for fine adjustment. This PID feedback system is a tension swing rod, and the feedback signal is input to the frequency converter through the Ai1 port. Because PID can ensure synchronization only by fine tuning, the swing rod fluctuation is very small, and the start and stop are stable. At the same time, the linear speed signal of PLC is also input to the winding and unwinding traction frequency converter through the Ai1 port of the frequency converter as its main frequency source. Because there is no change in the winding diameter in this link, the adjustment is relatively simple. There is no need for a special frequency converter for tension, and a general frequency converter can be used. The speed control is also adjusted by the superposition of the main frequency source Ai1 and the auxiliary frequency source PID. PID feedback is input to the frequency converter through the AI2 port. After PLC conversion, the transmission ratio of the host and traction is the same, so here the PID can be synchronized as long as it is fine tuned. In the process of automatic roll change, because the current winding diameters of the two reels are different, the linear speed is different at the same frequency. Direct switching will cause a sudden change in speed, causing the swing rod to swing greatly, and in serious cases, the material will be broken. The line speed of the shaft to be replaced must be consistent with the line speed of the current system through pre drive, so as to ensure that there is no impact during automatic roll change and make the swing rod stable

(5) scheme advantages of Huichuan frequency converter

from the above process, it can be seen that the PID, winding diameter and pre drive that originally need to be calculated by PLC can be completed by using the functions of the frequency converter itself. The speed adjustment is completed by the frequency converter itself, which is the most direct and has fast dynamic response. It can meet the requirements of the system for high speed stability accuracy of the frequency converter, high analog resolution and fast response of the frequency converter to the PLC output signal

during automatic roll change, the md330 itself has a pre drive function, so that the linear speed of the empty reel is consistent with the linear speed of the system operation, ensuring the stability of the swing rod during switching

3. Common and noticeable problems in debugging

(1) because the vector control mode has a great dependence on the parameters of the motor, it is recommended to identify the motor parameters before debugging, so that the copper plastic plate and other frequency converters used for changing doors and windows, furniture, kitchen and bathroom can obtain more accurate motor parameters, so as to obtain better control effect

(2) the phenomenon of converter overcurrent caused by encoder signal is often encountered in the process of realizing closed-loop vector. The expression is that the open-loop vector works normally, but when it works in the closed-loop vector, the motor speed is very slow and the current is very large. One reason is that the A and B of the encoder are connected reversely, and they can be adjusted interchangeably., Another reason is that the encoder loses pulse, and check whether the encoder is firmly connected; Whether there is single-phase pulse loss

(3) in order to make the swing amplitude of the swing rod of the winding and unwinding traction small, it is necessary to debug the main frequency of the winding and unwinding traction. When the main frequency device operates at the maximum frequency, the linear speed of the transmitted material should be equal to the maximum linear speed of the system. During debugging, as long as the exhibition is an excellent platform for self presentation and self promotion, look at the maximum linear speed value corresponding to the output 10V of PLC, and then calculate the frequency required to reach the linear speed according to the transmission ratio and the diameter of the transmission shaft as the maximum frequency of the winding and unwinding traction frequency converter

(4) the initial winding diameter of two unwinds can be input with the same analog quantity. This is because the initial winding diameter value is valid only at the moment when Di input is reset. Therefore, the difference in the reset time of the two sets can be used to distinguish which one the initial winding diameter is for. The source of the initial winding diameter is defined as AI2. Pay attention to their corresponding relationship when programming PLC

(5) in order to reduce the adjustment amount of traction PID, the auxiliary frequency source range selection parameter f is set relative to the maximum frequency, and the auxiliary frequency source range f is set to 8% (50hz*8%=4hz), which can effectively prevent overshoot, and when the linear speed is 0, the PID still works, ensuring constant tension at zero speed

(6) the coil diameter must be reset when rewinding and refueling, otherwise the swing rod fluctuation becomes larger when starting

(7) due to the sudden change of coil diameter during unwinding and refueling, the coil diameter filtering time should be set to be small, so that the frequency converter will quickly calculate the coil diameter as soon as the system runs; Make the system stabilize quickly

(8) during operation, observe the swing law of the swing rod to adjust the PI parameters to obtain satisfactory results

4. Conclusion

Huichuan vector inverter has been successfully applied in seven motor gravure printing machine by using its unique powerful function and excellent performance, through the ingenious combination with the scheme and the function of the inverter. The workload of PLC is effectively reduced, and the logic is clear and the circuit is simple. Compared with the original system, the cost of frequency converter is greatly saved. In this scheme, both the rewinding and the traction have tension feedback, and both the host and the traction use speed sensor vector control; Tension feedback and most control signals are directly input to the frequency converter, so it has the characteristics of high control accuracy, fast dynamic response, low cost, low failure rate, convenient maintenance and so on. It is a cost-effective scheme. (end)

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