Frequently Asked Question

Defect mechanisms

Polymer defects arise from flow, cooling, gas removal, moisture, shrinkage, tool temperature, packing, and material history. Sink marks and voids indicate local volumetric contraction that was not compensated; weld lines indicate meeting flow fronts; warpage indicates nonuniform shrinkage or residual stress.

S is linear shrinkage, L_mold is the reference mold dimension, and L_part is the cooled part dimension.

Worked example

If the mold dimension is 100.00 mm and the cooled part is 99.60 mm, S = 0.40/100 = 0.004, or 0.4%. Separate material shrinkage from process drift by repeating measurements across the cycle window.

Engineering check

For Polymer Processing Defects and Controls, maintain traceability from requirement to risk, design output, evidence, and approval. Record the configuration, acceptance criterion, test or analysis conditions, open actions, and residual risk. A method is not complete when the document is filled in; it is complete when the evidence supports the decision and affected controls are updated.

Process-control note

For Polymer Processing Defects and Controls, the calculation is only one part of the manufacturing decision. Define the drawing characteristic and its functional datum, identify the process variable that moves it, establish a measurement method with suitable resolution, and record the material, tool, fixture, revision, and sampling window. Confirm the result with a first-article or capability study representative of production. If the process changes, reassess the underlying failure mechanism instead of carrying old settings forward unchanged.