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Ripples (Wavy Flow Marks) | Definition, Causes & Inspection Criteria

Last updated on Jul 22, 2026

(1) What are Ripples (Surface Defect)?

Ripples refer to continuous wrinkled traces visible on the surface of molded parts.

They typically occur under conditions of low injection speed, where the surface layer solidifies faster than the advancing molten resin front.

Figure 1: Ripples on Handle Test Sample

Gate

Figure 2: Ripples on Handle Test Sample (2)

Gate

Definition

Regular or continuous wrinkled wavy marks on the part surface.

Prone Conditions

Low injection speed; premature solidification of surface layer; obstruction to subsequent molten resin advance.

Inspection Criteria

Focus inspection on areas near gates, sharp corners, and long flow path regions.

Inspection Criteria (Inspection Steps)

☑ Observe the orientation of texture patterns

☑ Compare against acceptable reference surface

☑ Pay close attention to areas near gates ☑ Take photos for record retention


Plastic Part Cosmetic Defect Training – Simple Reference for Quality Inspectors