💥 Cracks / Rupture
Causes, Solutions & Prevention in Thermoforming
Sheet tears during or after forming. Occurs at mold contact, sharp transitions or demolding. Structural failure risk.
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⚠️Root Causes by Category
⚙️ Process
- Sheet overheated — degradation point exceeded
- Sheet too cold — brittle, insufficient elongation
- Excessive vacuum speed — localized strain
🔲 Mold / Tooling
- Sharp edges or radii too small
- Inadequate draft angles
🧪 Sheet / Material
- Material degraded — regrind % too high
- Moisture in sheet — steam micro-cracks
📐 Design
- Draw ratio too high for material elongation at break
✅Solutions & Corrective Actions
Step 1
- Optimize sheet temperature within forming window
Step 2
- Increase mold radii to min 1× sheet thickness
Step 3
- Pre-dry hygroscopic materials (PC, PETG, PET)
Step 4
- Reduce vacuum speed; use staged application
🛠️Step-by-Step Troubleshooting
Step 1
Optimize sheet temperature within forming window
Step 2
Increase mold radii to min 1× sheet thickness
Step 3
Pre-dry hygroscopic materials (PC, PETG, PET)
Step 4
Reduce vacuum speed; use staged application
❓Frequently Asked Questions
What causes cracks / rupture?
Sheet overheated — degradation point exceeded; Sheet too cold — brittle, insufficient elongation; Excessive vacuum speed — localized strain
How to fix cracks / rupture?
Optimize sheet temperature within forming window
How to prevent cracks / rupture?
Prevention requires systematic process control: verify sheet temperature, maintain mold vents, ensure proper material drying, and document optimal parameters.
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