Molding Defect — Splay Marks

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Molding Defect — Splay Marks

Last updated on Jul 22, 2026

(1) What are Splay Marks? (Visual Defect)

Splay marks refer to the phenomenon where gas or trapped air appears on the surface of molded parts.

The gas originates from decomposition of resin or additives, or contamination by foreign polymer materials. Air is trapped during the metering phase. Moisture is also a contributing factor.

Figure 1: Splay Marks on 120mm Square Flat Plate Gate

Figure 2: Splay Marks on Colored Plate (Approx. 5cm Plate Size) Gate

🔍 Definition

Silvery-white flow streaks, filament-like textures or splash-like appearance on the surface.

🔗 Potential Sources

Gas, entrapped air, moisture, resin degradation, or contamination with foreign polymer materials.

👁 Key Inspection Focus

Pay close attention to areas near gates, along melt flow direction, and regions with localized whitening or bright surface.

Inspection Criteria (Inspection Steps)

☑ Confirm whether textures show silvery-white appearance

☑ Focus inspection on gate areas

☑ Distinguish between flow marks and splay marks

☑ Retain photos for documentation

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Molding Defect — Splay Marks