Design for manufacturing with silicone
Rule 1 — uniform wall thickness
Keep wall thickness between 1.0 mm and 3.0 mm, and variation across the part under 25%. A 0.8 mm wall fills well in LSR but cures with high internal stress; a 4.0 mm wall cures evenly but traps voids.
Rule 2 — draft angle on every surface
Minimum 1° on every surface in the mold draw direction, more on soft grades (Shore A < 40). No draft means the part sticks in the cavity on ejection.
Rule 3 — radius every internal corner
Radius at least 0.5 mm on every internal corner. Sharp corners concentrate stress and act as tear-initiation sites in service.
| # | Rule | What it prevents |
|---|---|---|
| 4 | Parting line on a non-critical, non-sealing surface | Visible flash, secondary deflashing operation |
| 5 | Gate on the thickest section of the part | Weld-line voids on thin walls, air trap |
| 6 | Undercuts only on soft grades (Shore A < 50) | Side-action cost, mould wear |
| 7 | Self-mating surfaces carry a 0.05 mm texture allowance | Surface-to-surface sealing after cure shrinkage |
Rules 4–7 at a glance
FAQ — DFM for silicone
How long does the DFM memo take?
48 hours from the moment we receive the drawing.
Is the DFM memo a chargeable service?
No. The DFM memo is part of the quote.
What if my drawing already violates one of the seven rules?
The DFM memo lists the violation and proposes a geometry change.
Can the rules be relaxed for very low volumes?
Rule 1 (wall thickness) cannot. Rules 2–7 can be relaxed on a case-by-case basis.