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12 Industrial Defects Mapped·5 Injection · 4 Extrusion · 3 Blow
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Processing Defects
Source-backed root-cause analysis and step-by-step corrective parameters drawn directly from Rosato's Plastics Processing Data Handbook and Allen & Baker's Plastic Technology.
5 of 12+Injection Moulding Active
3Core Industrial Methods
Source-BackedHandbook Diagnostic Guidance
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5 Defects AvailableStep 2 — Select Defect
5 DiagnosesInjection Moulding · Defect Dossier
Sink Marks
MODERATE Priority
Localized depressions or dimples on the surface of a moulded part, typically opposite thick ribs, bosses, or thick wall intersections.
Primary Root Causes
Insufficient holding/packing pressure — volumetric shrinkage pulls melt away from mould cavity walls
Holding time too short — gate freezes prematurely before cavity is fully packed
Wall section too thick — exterior skin solidifies while molten core contracts inward
Melt temperature excessively high — increased volumetric thermal contraction upon cooling
Gate cross-section too small — extreme pressure drop limits effective pressure transfer
Machine Parameter Corrective Actions
Click to reveal diagnostic loopEngineering Protocol & Rationale:
Raise hold pressure until sink marks disappear. Typical optimum range: 50–80% of peak injection pressure.
1. Baseline:80 MPa
2. Test Target:90–92 MPa
3. Expected Result:Elimination of depression depth on thick wall sections
Tooling & Mould Design Prevention Note
Design internal ribs to 60% or less of the adjacent nominal wall thickness. Position gates directly adjacent to the thickest wall sections.
📚 Literature Source: Rosato — Plastics Processing Data Handbook; Allen & Baker — Handbook of Plastic TechnologyAsk AI Copilot about this defect →