Molded geometry differs from machined geometry
Thermoplastics cool and contract in a cavity. Thick sections can leave sink on visible faces while large flat areas can distort. Uniformity and controlled transitions generally matter more than merely adding mass.
An engineer should locate the parting line, ejection direction and cosmetic surface early; a late draft correction can change both the assembly envelope and tool complexity.
Ribs and mounting bosses
Structural ribs can stiffen a wall without building unnecessary thickness. Their root and intersection require inspection for sink, weld lines and local stress.
A screw boss must match the chosen fastening strategy. Evaluate screw diameter, pilot geometry, torque, surrounding ribs and possible cosmetic read-through.
Gate, flow and venting
Gate placement affects weld lines and cosmetic vestige. Holes and inserts can split the flow front; venting and gate strategy should be discussed near functional loads.
Do not copy an arbitrary universal wall thickness or draft value into a controlled drawing without a resin grade and moldability study.
Working review table
| Issue | Design or procurement action |
|---|---|
| Parting line | Identify visible edges, sealing surfaces and direction of pull. |
| Draft | Evaluate textured and deep wall conditions as a separate design decision. |
| Wall design | Core out heavy zones and manage wall transitions. |
| Mounting features | Model mating fasteners, bosses and snap deflection. |
| Sample plan | Record critical characteristics and the acceptance owner. |
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Before you send the RFQ
Document the current design revision, expected service conditions, the part receiving this component and who will approve samples. Discuss technical exceptions openly rather than burying them in a general note.