Bag Making Machine Repair Technical Deep Dive: Servo Motor and Drive Replacement Procedure
Servo motor and drive failures are among the most critical repairs in bag making machines, as they affect all motion axes. The replacement procedure requires careful attention to electrical safety, mechanical alignment, and software configuration. The first step is to isolate the machine from power using a lockout/tagout procedure. The defective servo motor is disconnected from the drive and the mechanical load. The motor's coupling is loosened, and the motor is unbolted from its mount. The new motor is identical in model and specifications; its shaft key and coupling are aligned with the driven shaft. The coupling is tightened to the specified torque. The encoder cable is connected to the drive; the drive is powered up, and the encoder's absolute position is verified. If the encoder is of the absolute type, it must be calibrated to the machine's home position. This is done by moving the axis to a known mechanical reference (e.g., a hard stop) and setting the encoder position to the corresponding value. For incremental encoders, a reference mark is aligned. The drive is then configured with the motor's parameters (stator resistance, inductance, flux) – these are often stored in the drive's memory or loaded from a backup. The drive's current, velocity, and position loop gains are set to the values from the previous motor (or from the manufacturer's baseline). An auto-tuning routine is then run: the motor is commanded to perform a series of short moves, and the drive measures the system inertia and friction, adjusting the gains automatically. This is done at low speed and then at higher speeds.
After auto-tuning, the machine is run in manual mode at low speed to check for any vibration or noise. The motor's temperature is monitored; it should not exceed the rated value. The axis is then integrated into the machine's full sequence. A test run with film is performed to verify that the axis produces correct bag dimensions and registration. The position error (following error) is checked; it should be within the machine's specification (e.g., <0.05 mm). If the error is high, the gains are fine-tuned manually. The machine's control system stores the new motor's parameters and the tuning results for future reference. The repair is documented with the date, motor serial number, and the tuning values. The old motor is sent for refurbishment or disposal.
Plastic Bag Making Machine
Drive replacement: If the drive (amplifier) fails, it is replaced with a new unit of the same model. The drive's settings (parameters) are transferred from a backup file or manually entered. The drive's firmware must be compatible with the machine's PLC. The communication bus (EtherCAT, Profinet) is connected, and the drive is commissioned. The motor's encoder is connected, and a test run is performed. The drive's status LEDs are checked for errors. The drive's regenerative resistor is inspected for damage; if the resistor is burned out, it must be replaced.
Safety considerations: Servo motors can generate high torque; during replacement, the mechanical load must be secured to prevent unexpected movement. The machine's safety circuit must be disabled only for the isolated axis, with other axes still protected. The lockout/tagout procedure must be strictly followed. After replacement, all safety functions (STO, SS1) are tested.
Preventive measures: To reduce servo failures, ensure proper cooling of the drive cabinet; the ambient temperature should be below 40°C. The drive's fans should be cleaned regularly. The motor's cables should be inspected for wear. The encoder battery (for absolute encoders) should be replaced according to schedule to avoid losing position data. By following a systematic repair procedure, servo motor and drive replacements are completed efficiently, with minimal downtime and restored machine performance.
