Troubleshooting starts with evidence, not guessing

Common Injection Molding Defects and Solutions

A visible defect can come from part design, mold construction, material preparation or process settings. Record the location, cavity, timing and conditions before selecting a correction.

Real trial issues shownDesign/tool/process separatedCorrection loop documentedSpecialist guides linked

Common Defects and the First Checks

Defect	What it may indicate	First evidence to collect
Sink / local depression	Thick intersections, packing, gate freeze, cooling or resin shrinkage	Wall map, gate location, settings, section and timing
Warpage	Uneven shrinkage, orientation, cooling, ejection or constraint	Geometry, material, cooling layout, sample timing and datum
Flash	Parting damage, fit, vent depth, clamp or pressure	Exact location, cavity, mold condition and process record
Short shot	Flow restriction, venting, temperature, speed, pressure or shot size	Fill pattern, gate/runner, settings and material condition
Burn / gas mark	Trapped air, excessive speed or degraded material	Fill end, venting, melt history and settings
Knit or weld line	Flow fronts meeting around holes, inserts or multiple gates	Gate/flow path, temperature, venting and appearance zone
Fit or dimensional issue	Shrinkage, datum, tool dimension, process drift or mating-part variation	Drawing, measurement method, both mating parts and settings

Project Evidence: Three Different Problem Types

First-trial molded toy sample with a local visible step — **Tool/geometry correction**Buyer feedback marked a step that was not accepted against the approved model, creating a correction and re-check.

Wall-thickness analysis for a dense PA6 bristle part — **Predicted shrink/warp risk**DFM identified thick areas and deformation risk before the first sample.

Flexible magnetic backing fitted to a molded holder — **Assembly and flatness**Magnetic fit and flat contact were checked as part of the assembled-product correction loop.

A Disciplined Troubleshooting Loop

Describe

Photograph and mark the defect; record cavity, sample and time.

Reproduce

Confirm whether it repeats under the same material and settings.

Isolate

Change one design, tool, material or process factor at a time where practical.

Verify

Retest the corrected condition and preserve the acceptance record.

Defect FAQ

Can every defect be fixed by changing process settings?

No. Some issues are driven by part geometry or mold construction. A process-only correction can also create another defect.

Why does the same tool make different parts on another machine?

Machine response, material preparation, auxiliaries, environment and settings can change the process window. Transfer records help, but re-validation may be needed.

What should I send for troubleshooting?

Send the drawing, resin grade, defect photos, cavity identification, sample history, molding settings and the acceptance standard.

Turn a Defect Into a Testable Problem

Share clear photos, part data, resin, cavity, settings and the acceptance requirement.

Ask About a Molding Defect