Troubleshooting
Packager Seal
Poly Bag does not cut off and separate completely in some areas.
- Back up rubber is not straight. Remove back up rubber and straighten the internal heating element.
- Check seal bar temperature. For polyethylene film the control temperature should be approximately 400-420 F (205-216 C). For polyolefin shrink films, the temperature should be approximately 450-480 F (232-249 C). Adjust seal bar dwell higher or lower.
- Check to see that the seal bars are centered on the Teflon, covered back up rubber.
- Check to see that the seal assemblies grip the film adequately. It should be difficult to pull the film out from between the gripper rubbers when the assemblies are closed.
- For best results polyethylene films should be from virgin resin and contain no more than 2% EVA.
Packaging material builds up on seal bar or Teflon, cloth tape on back up rubber.
- Teflon, coating on seal bar, or Teflon, tape is damaged. Replace seal bar or Teflon, tape. Use a soft cloth only to clean the seal bars. Do not use abrasives.
Back up rubber is brittle, "H" channel is warped, or Teflon, tape slides off back up rubber.
- Back up rubber temperature is too high. Maximum temperature should be 150 F (65.6 C). If you have no pyrometer, it should feel uncomfortable to hold your hand on the surface for more than a few seconds (like the hood of your car on a hot summer day). For most polyolefin shrink film applications, back up rubber heat is not required.
The temperature control is not maintaining heat, is fluctuating erratically, or has an error code read out.
- Thermocouple malfunction: the most common cause is loose or intermittent connection at the heater cable/junction box connector. To check the condition of the heating element and thermocouple, first lift the wiring from the terminal strip in the junction box. Check continuity between thermocouple leads (red and white). If there is a large amount of resistance, the thermocouple is open and the heating element will need to be replaced. Check continuity between the two heating element wires (black and black). Again, replace the heating element if there is a large amount of resistance.
Temperature control problem: To diagnose if the problem is with the control or the heating element, reverse the two controls. If the problem follows the control, it is a control problem. If not, it is a heating element problem.
Electrical Controls
PLC Diagnostics
- If "power" LED is not lit, check power fuse in the PLC base (GE9020 model) or in the power supply module (GE9030 model). If fusing is ok, the power supply module may be defective.
- If "OK" or "RUN" LED is not lit, replace CPU module (upper half of GE9020 model)
Process of elimination to find source of sequencing problem
For every machine motion, low voltage (24vdc) signals are received a the PLC input terminal strip. These inputs trigger PLC logic sequencing which is processed before power can be applied to actuator devices through the PLC output terminals. To diagnose a controls related problem, it must first be determined what series of events leads to the motion that is not happening. It is beyond the scope of this procedure to explain the sequence of your machine. This can be found in the documentation that came with your system. However, the following process of elimination should help isolate the problem.
- Determine which machine function is not happening.
While doing the following electrical checks, turn OFF the air supply to the machinery:
- Review the PLC input and output labels inside the electrical enclosure to become familiar with the machine control device names and how the devices relate to the machine motions.
- Determine which input functions may relate to the problem. Input devices are typically, proximity switches, mechanical limit switches, and electric eye sensors. Next check the condition of the input signal LED's for the devices that are related to the problem. If a particular input LED is off that should be on, check to see if the input device is working. To test a device, turn on the electric power, and actuate it manually while watching the corresponding input LED on the device and on the PLC. If actuating the device does not turn on the input LED, then replace the device.
- If the input device is not the problem, then check the condition of outputs. Outputs typically control actuators such as motors and air cylinders through relays and valve solenoids. Determine which actuator is related to the problem.
- If an output LED is not on when it should be (and the proper inputs are present), check the fuses in the base (GE9020 model) or the output module (GE9030 model).
If the PLC output LED is on, and there is no power at the output device, there may be wiring problems between the device and the main electrical enclosure. If there is power to the device but the device does not respond, the device may be defective. Check continuity of relay coils and valve solenoid coils, etc.
Pneumatic Controls
Turn the air supply to the machine on.
Testing the spool valve
- Use the manual valve actuator on the solenoid to determine if the valve spool is hung up. If the related cylinder does not extend and retract properly when the manual actuator is pressed and released, the spool valve may be defective.
Testing for a worn out cylinder
- When a cylinder lacks power, and its speed slows down, check for 'blow by'. A worn piston seal will allow air to blow by causing lack of air pressure on the piston. Test by applying air on one end of the cylinder while removing the fitting from the opposite end. If air comes out the port, the seal is bad. Replace or rebuild the cylinder.
Cylinder speed control
Between the valve base and the valve body there is a speed control module. An adjusting screw at one end controls the extending stroke, and the screw at the opposite end controls the retracting stroke. The adjusting screws control the flow of air being exhausted from the cylinder ports.
