12/08/2026
Why does PET sheet crack during thermoforming?
When a PET roll starts cracking, the first reaction is often to adjust the machine.
But sometimes the problem starts with the sheet.
Cracking at deep corners, sidewalls, trim areas, or after cooling can point to very different causes. Sheet thickness, material distribution, forming conditions, roll consistency, and even a recent supplier change can all matter.
One thing we always look at as a PET sheet manufacturer is this:
What happens to the material after it leaves the roll and becomes the finished package?
A 0.8 mm PET sheet on the quotation does not mean every area of the formed part will still have the same thickness.
In our latest article, we look at:
• Why PET cracks at deep corners
• How sheet thickness affects weak areas
• Why the same thickness doesn't always mean the same forming behavior
• What to check when changing PET sheet suppliers
• How to tell a material problem from a process problem
• What information to send your PET sheet supplier when troubleshooting
If you're dealing with PET sheet cracking during thermoforming, this is a good place to start.
Read the full article: Why Your PET Sheet Cracks During Thermoforming (And How to Fix It)
PET sheet cracking during thermoforming can come from thickness, material distribution, heating, or sheet consistency. Learn how to find the cause and fix it.