Transmission and actuator OEMs sourcing precision plastic gears injection molding need more than tooth count on a drawing — shrink, concentricity, and wear behavior across humidity swings drive field failure.
Engineering requirements for molded gears
- Profile and pitch accuracy on CTQ diameters
- Material — POM, PA, PBT; lubricated grades for dry wear
- Concentricity relative to bore and mounting face
- Flash control at parting line on tooth flank
- Dimensional correlation batch-to-batch at production temp
Deuchi application: precision mechanical transmission parts.
DFM decisions that affect gear quality
| Design choice | Molding impact |
|---|---|
| Uniform wall at hub-to-web | Reduces sink shifting pitch |
| Gate at hub vs tooth tip | Weld line away from load path |
| Semi-crystalline grade | Directional shrink — tool compensation required |
Run DFM before steel — gear tools are costly to re-cut.
Validation before production release
- First article on tooth CTQs and bore pattern
- Mesh fit with mating pinion / worm in assembly fixture
- Noise and backlash check at operating temp
- Wear sample if application is high-cycle
FAQ
Are molded gears always weaker than machined?
Not for many moderate-load applications — correct material and tooth design win on cost and noise at volume.
Can you mold internal gears?
Yes with collapsible cores or split tooling — disclose in RFQ for accurate tooling quote.
Next step: Request gear molding review with STEP and load spec.