Read the part. A defect is evidence, not a diagnosis. Start with the visible symptom, understand the mechanism, and test one explanation at a time.
All symptoms Filling & packing Surface & material Shape & release
INVESTIGATION 01
Short shot Part of the intended geometry is missing.
What can be happening The cavity is not completely filled before flow stops or the melt freezes.
A useful investigation sequence Check fill consistency and material supply. Compare cushion, temperatures and flow restriction. Review venting and the resin-specific process window. Celanese · further reading INVESTIGATION 02
Flash Thin unwanted plastic appears along a joint or shut-off.
What can be happening Melt enters a clearance at the mould boundary. Tool condition and process conditions can both contribute.
A useful investigation sequence Inspect parting surfaces and mould closure. Compare shot size, pressure and clamp conditions. Celanese · further reading INVESTIGATION 03
Sink marks Local depressions appear over thicker regions.
What can be happening Cooling contraction is not sufficiently compensated by incoming melt before the feed path freezes.
A useful investigation sequence Compare local thickness and gate placement. Review packing continuity and gate-freeze timing. Celanese · further reading INVESTIGATION 04
Burn marks Brown or black areas occur near the end of filling.
What can be happening Air trapped during filling can heat strongly as it is compressed.
A useful investigation sequence Inspect the affected region's venting. Review where and how quickly trapped gas is compressed. Celanese · further reading INVESTIGATION 05
Weld line A visible seam occurs where melt fronts meet.
What can be happening Divided melt streams reunite with a locally different bond and orientation.
A useful investigation sequence Locate flow splits and meeting fronts. Review venting and material-specific temperature conditions. Celanese · further reading INVESTIGATION 06
Warpage The part twists, bows or departs from its intended shape.
What can be happening Uneven cooling, shrinkage or mechanical distortion produces a nonuniform final shape.
A useful investigation sequence Compare mould temperature balance. Observe ejection and post-ejection handling. Celanese · further reading INVESTIGATION 07
Splay / streaks Streaks trail along the flow direction at the surface.
What can be happening Gas, incompatible material or incompletely melted material can disturb the flow front; appearance alone does not identify moisture.
A useful investigation sequence Check resin drying against its specification. Review overheating, air entrainment and contamination. Compare nozzle and manifold temperatures. Eastman · further reading INVESTIGATION 08
Jetting A curled or snake-like flow trace is visible.
What can be happening A narrow free jet advances into the cavity before spreading across its walls, leaving a partly frozen trail.
A useful investigation sequence Inspect the gate's entry direction. Review the initial flow speed and whether melt contacts a cavity surface. Eastman · further reading Keep a controlled record. Record the material grade and condition, cavity identity, defect location, cycle data and the exact change being tested. Compare repeatable observations before deciding that a setting was the cause. Resin-specific processing guidance takes priority over generic defect advice.
Inspection and adjustment inside a moulding cell require the applicable machine procedures and isolation measures. The atlas explains mechanisms; the equipment manual defines how work is performed safely.
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