At Packserve, we understand the frustrations that can arise when blow moulding PET bottles. Achieving consistent quality and efficient production is crucial, and encountering problems can disrupt your entire process. Based on our extensive experience, we’ve compiled this troubleshooting guide to help you identify and resolve common issues you might face with your PET bottle blowing machine.
Problem 1: Poor Transparency of PET Bottles
- Possible Causes:
- Thermostat temperature too high.
- Compressed air contains moisture.
- Excessive heating time.
- Opaque PET preforms.
- Inappropriate preform design.
- Low inflation rate.
- Solutions:
- Reduce thermostat temperature.
- Use a dryer to remove moisture from compressed air.
- Decrease heating time.
- Use higher quality, transparent PET preforms and ensure raw material dryness.
- Redesign PET preform dimensions.
- Increase inflation rate.
Problem 2: Pearly Luster or White Colour on PET Bottles
- Possible Causes:
- Thermostat temperature too low.
- Uneven PET preform wall thickness.
- Insufficient heating penetration due to thick preforms.
- Solutions:
- Increase thermostat temperature or decrease rotation speed.
- Use higher quality PET preforms with consistent wall thickness.
- Reduce preform thickness or enhance heating device coverage.
Problem 3: Off-Centre Nozzle at Bottle Bottom
- Possible Causes:
- Premature blowing.
- Incomplete stretch rod descent.
- Misaligned stretch rod.
- Uneven preform injection density or wall thickness.
- Inconsistent heating.
- Solutions:
- Delay blowing time or increase stretch rod descent speed.
- Adjust magnetic pole switch position.
- Realign stretch rod.
- Use higher quality PET preforms.
- Check preform rotation and improve heating conditions.
Problem 4: Uneven Bottle Wall Thickness
- Possible Causes:
- Off-centre stretch rod.
- Asymmetrical blowing holes.
- Low stretching or expansion ratios.
- Lack of preform rotation in heating furnace.
- Uneven preform wall thickness or injection density.
- Solutions:
- Adjust stretch rod position.
- Adjust blowing hole position and diameter.
- Increase inflation or stretching ratio.
- Verify preform rotation mechanism.
- Use higher quality PET preforms.
Problem 5: Thick Upper Portion of Bottle
- Possible Causes:
- Low temperature in upper oven section.
- Vent too far from upper oven section.
- Insufficient stretching ratio.
- Low inflation ratio in upper bottle section.
- Slow stretch rod speed.
- Solutions:
- Increase temperature of upper heating tubes.
- Adjust vent position.
- Increase stretching ratio.
- Modify bottle shape.
- Increase stretch rod speed.
Problem 6: Thin Bottle Bottom
- Possible Causes:
- Premature blowing.
- High bottom temperature.
- Thin preform bottom.
- Solutions:
- Delay blowing time.
- Reduce bottom temperature.
- Use preforms with thicker bottoms.
Problem 7: Obvious Bottle Clamping Line
- Possible Causes:
- Insufficient clamping force.
- Premature sealing.
- Mould issues.
- Mismatched preform neck and mould.
- Solutions:
- Increase clamping pressure and adjust clamping support rod angle.
- Adjust mould clamping stroke switch.
- Inspect mould assembly and repair if necessary.
- Adjust mould teeth position.
Problem 8: Material Accumulation at Bottle Bottom or Neck
- Possible Causes:
- Excessive delayed blowing time.
- Uneven rolling.
- Low material accumulation temperature.
- Unstable action air pressure.
- Solutions:
- Decrease stretch rod descent speed or shorten delayed blowing time.
- Reduce gas volume on one side of reel bottle.
- Increase preform heating temperature.
- Add gas storage tank or shorten air supply pipeline.
Problem 9: Stretching and Perforating Bottle Bottom
- Possible Causes:
- Insufficient temperature and penetration.
- Excessive delay stretching time.
- Large stretch ratio.
- Thin preform bottom.
- Sharp stretch rod head.
- Solutions:
- Increase heating temperature.
- Shorten delay stretching time.
- Reduce stretch ratio.
- Use preforms with improved bottom design.
- Trim and adjust stretch head.
Problem 10: Bottom Blasting
- Possible Causes:
- Insufficient blowing delay.
- Short delayed mould opening time.
- High temperature.
- Malfunctioning exhaust valve.
- Solutions:
- Increase stretch rod descent speed or lengthen delay blowing time.
- Extend mould opening time.
- Reduce temperature.
- Clean exhaust valve.
Problem 11: Incomplete Bottle Bottom
- Possible Causes:
- High bottle bottom temperature.
- Inadequate or uneven vent holes in mould bottom.
- Incomplete stretch rod descent.
- Mismatched stretch head and preform bottom.
- Inadequate blowing pressure.
- Insufficient blowing valve flow.
- Poor bottle bottom curve design.
- Solutions:
- Lower bottom heating zone temperature or use damp cloth to cool preform bottom.
- Increase and evenly distribute vent holes.
- Ensure complete stretch rod descent.
- Replace stretch head.
- Increase blowing pressure.
- Clean blow valve.
- Improve bottle bottom curve design.
Problem 12: Uneven Preform Thickness
- Possible Causes:
- Preform design issues.
- Mould exhaust problems.
- Uneven preform heating.
- Poor mould bottom design.
- Solutions:
- Improve preform design.
- Increase vent size at mould bottom.
- Improve heating conditions.
- Enhance bottom design.
Problem 13: No Sealing and Stretching Action
- Possible Causes:
- Incorrect clamping stroke.
- Broken mould clamping stroke switch.
- Loose wiring.
- Damaged delay stretch time relay.
- Damaged solenoid valves.
- Blocked or closed throttle valves.
- Solenoid valve failure.
- Incorrect delay stretch time setting.
- Solutions:
- Adjust clamping block.
- Replace mould clamping stroke switch.
- Reconnect wiring.
- Replace time relay.
- Replace solenoid valves.
- Check throttle valve openings.
- Check solenoid valves.
- Correct delay stretch time setting.
Problem 14: Stretch Rod Fails to Return
- Possible Causes:
- Incorrect magnetic pole switch position.
- Excessive stretching rod speed.
- Solutions:
- Adjust magnetic pole switch position.
- Reduce stretching rod speed.
This guide covers many common issues. If you’re still experiencing problems, don’t hesitate to contact Packserve. Our team of experts is ready to assist you in finding targeted solutions for your specific blow moulding needs. Contact us today for further support.