Analysis of Technical Challenges and Solutions in Bag-Making Machines

1. Inconsistent White Bag Length
   Possible Causes:
   1. Poor servo traction tension;
   2. Material dragging difficulty;
   3. Diameter error in the rubber roller.
   Solutions:
   1. Adjust the servo traction curve;
   2. Check if the rubber roller is slipping, clean it, or reduce the unwinding air pressure tension;
   3. Replace the rubber roller.
2. Excessive Positioning Error (>2mm) in Punching of Self-Standing Bags
   Possible Causes:
   1. Excessive swing amplitude of the servo traction floating roller, causing severe bouncing;
   2. Film stretching;
   3. Slipping of the rubber roller.
   Solutions:
   1. Reduce the servo tension compensation coefficient or raise the floating roller to limit its swing range;
   2. Lower the heat-sealing temperature of the film, and check if the servo traction and heat sealing are synchronized. If not, adjust the main servo blade-lifting angle to ensure it is close to 90 degrees relative to the high-position signal angle;
   3. If the rubber roller hardness exceeds 75 degrees, replace it with a softer roller. Check for dust between the roller and the film, and clean it.
3. Frequent Stops During Bag Making
   Possible Causes:
   1. Excessive main motor speed or unstable voltage;
   2. Incorrect Hall signal angle or poor contact;
   3. Servo drive alarm.
   Solutions:
   1. Set the correct pulses for the main servo drive and check the servo transformer voltage;
   2. Adjust the blade-lifting and high-position Hall switches to the correct 90-degree position, and align the Hall switch with the signal detection rod;
   3. Check the corresponding alarm code on the servo drive and troubleshoot step by step.
4. Main Motor Fails to Start
   Possible Causes:
   1. Servo system malfunction;
   2. Computer signal interruption;
   3. Faulty main motor contactor or broken contactor control circuit;
   4. PLC error alarm.
   Solutions:
   1. Check if the servo system and motor are functioning properly;
   2. Reconnect the signal cable;
   3. Replace the contactor;
   4. Check and restore the control circuit, and resolve the PLC error alarm.
5. Poor Heat Sealing
   Possible Causes:
   1. Uneven sealing blade;
   2. Broken heating control circuit of the sealing blade;
   3. Damaged control circuit or thermocouple;
   4. Insufficient sealing blade pressure.
   Solutions:
   1. Grind the sealing blade flat on a grinding machine;
   2. Replace the heating plate and check its connections;
   3. Inspect, repair, or replace the thermocouple; replace the temperature control module if necessary;
   4. Adjust the spring pressure of the sealing blade.
6. Wrinkling When Passing Through the Middle Rubber Roller
   Possible Causes:
   1. Poor back seal cooling effect;
   2. Uneven pressure on the middle rubber roller;
   3. Excessive air pressure on the floating roller;
   4. Excessive dust on the middle rubber roller;
   5. Excessive heat-sealing temperature.
   Solutions:
   1. Improve the chiller’s cooling effect and lower the chiller temperature;
   2. Adjust the left and right air pressure of the rubber roller based on the film characteristics;
   3. Reduce the floating roller pressure;
   4. Clean the rubber roller;
   5. Lower the heat-sealing temperature of the sealing blade.
7. Excessive Error in Bag Length Positioning System
   Bag length is divided into blank bag length and printed bag length. Both types of positioning systems consist of a heat-sealing/cutting linkage system and a film feeding system, coordinated by an electric eye. If there is an error in linkage or coordination, it will cause deviations in bag length dimensions.
   Focus on inaccurate electric eye tracking. The reasons for tracking inaccuracy include:
   1. Electric Eye Issues: Improper adjustment or selection of the photoelectric eye’s working mode. First, confirm if the electric eye is properly adjusted and whether reflection or transmission mode is correctly selected. Also, verify whether edge control is set to leading edge or trailing edge (i.e., polarity), and confirm the tracking mode, such as scanning mode (i.e., completing the fixed length first, then scanning the mark) or fixed-length positioning mode (i.e., checking the mark position after completing the fixed length to see if it is over or under the target).
   2. Issues with Mark Printing or Spacing: Inconsistent printing or spacing of marks.
   3. Unreasonable Mark Design: The scannable area is too narrow, or the contrast between the mark and the surrounding area is insufficient.
   4. Variations in Mark Spacing: Inconsistent spacing between marks.