Troubleshooting guide for Thermoforming Applications
Thermoforming Troubleshooting
Problem
Probable Cause
Suggested Remedy
Temperature Setting
Temperature setting are crucial parameter for proper plastic processing ,hence one should check temperature controller, thermocouple and solid state relay(SSR)
- when you cold start the machine ,wait for 2hours.
Blushing
- Moulding too cold
- Exceeding yield point
- Increase heating cycle time
- Increase moulding speed
Webbing
- Moulding too hot
- Vacuum too slow
- Shorten heating cycle
- Increase area and number of holes for vacuum
Sheet scorched but not plastic
- Higher rate of heating
- Use slow rate of heating
- Use sandwich heating arrangement
Release of moulded product difficult
- Draft insufficient
- Rough mould
- Undercuts
- Shrunk-on mould
- Increase draft, polish mould
- Polish and lubricate mould
- Eliminate undercuts
- Reduce dwell time on the mould
Chill marks
Mould too cold
Pre-heat mould
Plastic bubbles
- Overheating
- Moisture in the sheet
- Entrapped air
- Increase heating cycle but reduce heating rate
- Pre-heat sheet before moulding
- Check for moisture in air if pre-blowing, correct venting or add extra vacuum holes
Cracking
- Stress concentrated
- Poor design
- Increase radius of all angles
- Rework design
Warping
Residual stresses in the sheet
Try slower mould entry and increase moulding temperature
Tearing
- Higher moulding draw down ratio
- Higher moulding temperature and longer heating cycle
- Improper mould clearance
- Redesign the part
- Reduce moulding temperature and heating cycle time
- Check the punching or misalignment
Excessive shrinkage of sheet
Residual stresses in sheet
Reduce heating cycle time and elevate moulding temperature, optimise sheet extrusion processing parameters
