I. Introduction
Dalian Andy CNC Technology Co., Ltd. has launched a special servo control solution for the domestic heat sealing and cutting machine. It has been successfully applied and widely promoted in a domestic company's bag making machine. The program uses ADSD-S AC synchronous servo drive. , ADSM-S AC permanent magnet synchronous servo motor, touch screen, PLC, frequency converter, frequency conversion motor and other major components; according to the equipment process requirements, the ADSM-S servo motor with low inertia and high speed is selected as the main motion mechanism to ensure the sealing and cutting system. The bag machine has the smoothness and fast response of its own movement under frequent starting load, so that the feeding speed of the servo motor can meet the time requirement of the cutter running up and down. At the same time, the mechanical mechanism is simplified, and the disadvantages of the original mechanical equipment such as low efficiency, low positioning accuracy, high energy consumption, low automation level, and waste of materials are solved.
2. Control principle
The whole process of production process is mainly divided into three parts: lifting knife, positioning, sealing and cutting. The up and down reciprocating motion of the heat sealing knife and the cutter is controlled by the inverter driven variable frequency motor. The positioning of the bag length is controlled by the servo driver to drive the feeding roller, and the photoelectric sensor (also called photoelectric eye), the thermostat and the proximity switch are used. For the measurement and control components, it is responsible for the judgment of time and the issuance of control signals, so that the timing relationship is established between the execution devices. As the carrier of the core program, PLC is responsible for the transmission of pulse signals and the conversion and transmission of various control signals, and finally controls the operation and coordination of various actuators. The touch screen is used as a man-machine interface for parameter setting and overall machine health monitoring. The touch screen can be used to adjust the bag length, clear, reset, jog, etc.; the bag length value and the cumulative number of bags to be processed can also be displayed.
Work flow
1. System power on
Initialize the program, input the length of the bag, adjust the temperature meter, and make the temperature of the sealing knife reach the heat sealing requirement (the temperature of the sealing knife should be set according to the high and low speed of the main motor, and the solid sealing resistance at the sealing of the plastic bag shall prevail. If the temperature of the sealing knife is low, the sealing position of the plastic bag will not be strong. If the temperature of the sealing knife is too high, the sealing of the plastic bag will be hot. Therefore, it should be adjusted according to the speed of the main motor and the length of the sealing time); enter the manual adjustment mode. Check whether the mechanical part, servo system, inverter, etc. can work normally, and adjust the color-coded photoelectric eye so that it can sense the color change.
2. Making a bag
Click the touch screen automatic running button, the main variable frequency motor (1.5KW) works, the mechanical connecting rod drives the sealing knife and the cutter to reciprocate up and down. Each time the cutter moves upward, the servo signal is turned on once, and the PLC sends the pulse to control the servo motor. (1kw) operation, the number of pulses determines the number of turns of the servo motor. The frequency of the pulse determines the speed of the servo motor. The servo motor drives the feed roller through the timing belt. The servo motor must be lowered to the cutting roller. Before the positioning is completed, when the cutter and the sealing knife are cut, the plastic bag is formed. When the number of the cut bags reaches the preset number or the emergency stop button is pressed, the machine is stopped after the current plastic bag is produced, and the cutter and the sealing knife are stopped. Parking at a high position.
The bag making machine generally has two kinds of sealing and cutting methods: blank bag fixed length sealing and cutting and searching for sealing and cutting. When selecting blank bag fixed length sealing and cutting, the color standard photoelectric eye does not work, and the PLC program is based on the length of the cutting bag, the mechanical transmission ratio, and the servo drive. The electronic gear ratio, the number of servo motor encoder lines and the circumference of the feed roller, calculate the number of pulses required for servo system positioning, and then the drive motor drives the servo motor to rotate the feed roller to send a certain length of plastic bag, thus realizing the white bag. Fixed length sealing and cutting; when selecting the marking and cutting, the process is as follows, the servo starting signal is turned on, and the servo motor performs acceleration motion, constant speed motion, deceleration motion and low speed chasing according to the preset motion curve of the PLC program, as shown in Fig. 3. As shown in the figure, when the PLC receives the color-matching signal, it immediately stops the servo motor by the interrupt method. Generally, the color-matching length is 10mm, and the color-matching signal is required to function only in the color-matching range. In other ranges, the interference signal needs to be shielded. When chasing color sealing and cutting, set the constant speed of the servo motor on the man-machine interface, first set the acceleration time and deceleration time, then adjust the low speed chase speed to increase the low speed chase speed as much as possible to keep the color chasing smooth. The accuracy is correct. After adjusting the color-matching speed, adjust the acceleration time and deceleration time, and shorten the acceleration/deceleration time as much as possible, so that the plastic bag and the discharge roller do not slide relative to each other and the color tracking is stable. When the PLC program marks the color-matching signal during the color-cutting and cutting, the PLC stops the operation of each motor and drives the alarm to alarm. At the same time, the PLC program counts the batches. When the batch reaches the warning value, the PLC drives the alarm to give an alarm.
4. Introduction to the servo system
The servo system used in this machine is the ADSD-S series of Dalian Andy CNC Technology Co., Ltd. The drive unit adopts the latest digital signal processor DSP of TI Company of America as the core, and chooses Mitsubishi industrial grade intelligent power module (IPM), and chooses The capacity of IPM is one level larger than other domestic servo products with the same power, so it has the characteristics of strong overload capability, strong anti-load disturbance ability, large starting torque and high dynamic speed. It supports multiple communication methods and standard fully isolated RS485 communication. Module, RS422/RS485, CAN bus or Profibus optional; the drive combines the three control modes of position control, speed control and torque control, and can dynamically switch between the control modes, making it more flexible and flexible; Duoz protection and abnormal display such as speed protection, overcurrent, overload, overheat, main power overvoltage and undervoltage, encoder abnormality, communication error, PID feedback signal abnormality, etc., make the control process clear at a glance. The motor is a three-phase permanent magnet synchronous servo motor with three times overload capability, 3000 RPM rated speed, and 2500 line encoder resolution.
Mechanical parameters:
Mechanical transmission reduction ratio 1:3
Rubber roller diameter 66mm
Accuracy requirements: bag length accuracy is less than 0.5mm, servo motor encoder pulse number is 2500P / R, after four times frequency conversion, the resolution accuracy reaches 10000p / r, that is v servo = 360 ° / 10000 = 0.036 °, motor output to The feed roller has a reduction ratio of 3:1, and the actual detection accuracy is:
Vroll = 360 ° / (10000 × 3) = 0.012 °
The corresponding bag length resolution accuracy is:
Vl roller = πD × (0.012 ° / 360 °) = 207.24 × 0.000033 = 0.0026839mm
Therefore, the error itself is much less than 0.5mm, and the real cause of the large positioning error is that the servo motor starts and stops not smoothly enough and shakes during parking. Therefore, it is necessary to adjust the appropriate speed loop and position loop gain according to the start and stop speed of the servo motor. Acceleration and deceleration time, the debugging process is as follows:
a) Set the position loop gain to a lower value first, and then gradually increase the gain of the speed loop to the maximum without generating abnormal noise and vibration.
b) Gradually reduce the speed loop gain value while increasing the position loop gain. Set the position loop gain to the maximum without overshooting and vibration.
c) The speed loop integral time constant depends on the length of the positioning time. Under the premise that the mechanical system does not vibrate, try to reduce this value.
d) Then fine tune the position loop gain, speed loop gain, and integral time constant to find the best value.
e) Adjust the position command once filter time constant appropriately.
The debugging parameters are as follows:
V. Summary
The heat sealing and cutting bag making machine is modified by using Andy servo control system on the basis of traditional old-fashioned equipment, which has the advantages of improving efficiency, reducing energy consumption, improving product rate, improving sealing and cutting precision, convenient and quick debugging, stable running process and simplifying machinery. Features such as structure, higher technical content and better cost performance, creating more benefits for enterprises.
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