Your Thermoforming Reference

Thermoforming Troubleshooting Guide

Every defect in thermoforming has a pattern. Every pattern reveals a cause. Every cause can be fixed. This free thermoforming troubleshooting guide contains 15 chapters and 300+ described defects, process failures, root causes, and corrective actions — created by engineers with 10+ years of hands-on factory experience. We are gradually posting all the information about the bugs and their fixes. The full PDF version of the guide, including all chapters, defects, root causes, and corrective actions, is available for download below.

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The Ultimate Thermoforming Troubleshooting Guide by THERMOFORA
15+
Chapters
300+
Defects
10+
у. Experience
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Nipples from Vent Holes in Vacuum Forming — Why They Form and How to Stop Them

Overheated plastic forced into mold vent holes by atmospheric pressure creates nipple defects. Fix: shorten heat cycle, keep holes under 3 mm, redrill oversized vents.

June 15, 2026
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Why Does the Plug Leave a Mark? Sheet Overheating and Plug Assist Imprints Explained

Excessive melt fluidity at plug contact permanently displaces the sheet surface before it can recover. Felt wrapping, delayed plug entry, and heater profiling eliminate the defect.

June 15, 2026
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Corner Tearing in Vacuum Forming — Causes and Fixes

Corner tearing in vacuum forming is caused by over-softened sheet losing tensile strength at sharp radii. Learn how to fix it with heat control and mold design. THERMOFORA

June 15, 2026
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Sheet Sag and Pre-form Collapse in Vacuum Forming — Causes and Prevention

Sheet sag in vacuum forming happens when melt strength drops under excessive heat, causing pre-form collapse and uneven material distribution. Causes and fixes.

June 15, 2026
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Orange Peel Texture in Vacuum Forming — Diagnosis and Prevention

Orange peel texture in vacuum forming is caused by prolonged heat soak that degrades surface quality. Learn how to identify it and eliminate it through heat control and zoning.

June 15, 2026
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Surface Gloss Change in Vacuum Forming — Why It Happens and How to Fix It

Surface gloss change in vacuum forming is caused by overheating that makes the sheet too fluid before forming. Learn how to restore consistent surface appearance through temperature control.

June 15, 2026
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Surface Boiling Effect in Vacuum Forming: Causes, Prevention and Solutions

Learn what causes the surface boiling effect in vacuum forming and thermoforming. Discover how extreme overheating creates pitted surfaces, texture defects, and material degradation, and how to prevent them.

June 15, 2026
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Microbubbles in Vacuum Forming — Causes and How to Eliminate Them

Microbubbles in vacuum forming result from polymer degradation at excessive temperatures, not moisture. Learn how to identify the difference and fix it through heat and regrind control.

June 15, 2026
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