Plastic Part Cosmetic Defect – Gas Burn | Definition, Causes & Inspection Criteria | Justway

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Plastic Part Cosmetic Defect – Gas Burn | Definition, Causes & Inspection Criteria

Last updated on Jul 22, 2026

1. Definition

Gas burn describes scorched discoloration that appears on molded part surfaces during injection.

2. Formation Mechanism

Burn marks occur at melt flow end positions, most often associated with inadequate mold venting.

3. Typical Risks

Impairs surface appearance, local mechanical performance and perceived quality by customers. Severe cases are accompanied by carbonized traces.

Inspection Focus Points

Prioritize checking flow ends, corners and wall thickness transition zones

Confirm discoloration depth and affected area

Retain defective samples

Timely escalate venting concerns for mold optimization

Plastic Part Cosmetic Defect Training – Simple Reference for Quality Inspectors

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