Heating defect
Sheet sagging in thermoforming
Also called: Excessive sag
All sheet sags as it heats; excessive or uneven sag means the sheet touches heaters or the tool prematurely, or drapes unevenly, spoiling material distribution before forming even begins.
Why it happens
- Sheet over-heated or held too long in the oven
- No sag control (billow / pre-blow) on large sheets
- Uneven heating across the sheet
- Gauge too thin for the span being heated
How to fix & prevent it
- Reduce oven time/temperature to the material window
- Use pre-blow (billow) to control and support the sheet
- Balance zoned heaters for even heat
- Support long spans and match gauge to part size
How Indu prevents it: Our lines use zoned heating with sag control and pre-blow so large, wide-web sheets heat evenly and stay in position before forming.
Troubleshooting help
Fighting sheet sagging on a part?
Send your drawing, sample or a photo of the issue — our engineers will diagnose the cause and reply with the tooling, material and process fix, usually within 24 hours.
ISO 9001:2015 certified · Most quotes back within 24 hours