What matters
- Start with a material-specific range, then test the actual flow length and geometry.
- A gradual transition is safer than a sudden thick-to-thin step.
- Core thick regions and use ribs when stiffness, not solid mass, is the goal.
Why a single minimum is misleading
A short, simple part in a high-flow resin can fill thinner than a long housing with many ribs and a remote gate. Pigment, glass fiber, flame retardant, surface texture, and the available injection pressure also change the window.
Published thickness tables are screening tools. Confirm the chosen grade with its supplier data and review the complete flow path with the molder before freezing the design.
What wall variation does to the part
| Condition | Likely consequence | Design response |
|---|---|---|
| Very thin region | Short shot, hesitation, high pressure | Shorten flow or thicken locally |
| Thick mass | Sink, void, long cooling | Core out and rib |
| Abrupt transition | Differential shrinkage and warp | Use a gradual transition |
| Uneven opposing walls | Unbalanced cooling | Restore symmetry where possible |
Ribs and bosses do not get a free pass
A rib that is nearly as thick as the parent wall creates a local mass at its base. The visible opposite face may sink as the center cools. A boss can do the same thing, particularly where several support ribs meet.
Make these features only as thick as their load requires, core bosses, radius the base, and keep heavy intersections away from cosmetic surfaces. Exact ratios depend on resin, finish, and molding conditions, so treat any generic percentage as a starting point for DFM rather than a guarantee.
A wall-thickness review that catches real risk
- Map minimum, maximum, and transition regions on the final solid model.
- Check flow length from each proposed gate, not just the global part dimensions.
- Identify cosmetic faces opposite ribs, bosses, clips, and thick corners.
- Review cooling access and the ejection temperature for heavy zones.
- Use simulation when the pressure, sink, weld-line, or warpage margin is unclear.
Use this as a design review, not a production release
These guides support early planning. The selected resin supplier, toolmaker, and molder still need to confirm the final geometry, process window, tolerances, safety factors, validation plan, and commercial assumptions for your application.