Engineering context
Secondary machining can refine bores, faces or datums after molding when the assembly needs a relationship that is difficult to hold directly from the tool.
The benefit must be weighed against extra handling, fixturing and the possibility of releasing molded-in stress. Machining also changes the datum chain if the gear tooth form remains as molded.
Secondary machining is most valuable when it controls a specific relationship that the molding process cannot hold economically. Typical candidates are precision bores, bearing seats or mounting faces. If the gear is fixtured from a cosmetic outer surface, however, machining may introduce a new eccentricity. The fixture should locate from a stable molded datum that has a known relationship to the teeth.
What the drawing needs to communicate
Identify exactly which feature is machined, which molded surface locates the part in the fixture and which dimensions are inspected afterward.
가능하면 이러한 입력 정보를 관리 도면, 사양서 또는 견적 요청서 첨부 파일에 포함시키십시오. 비공식 메시지에서 이러한 정보를 분리하면 공급업체 비교 및 추후 수정 작업을 더 쉽게 관리할 수 있습니다.
Risk review
Adding a machined bore without a coherent tooth-to-bore datum can improve diameter size but not runout.
Sample acceptance
Use a fixture and inspection plan that references the functional gear datum structure.
For Secondary Machining of Molded Plastic Gears, close the DFM loop by updating the controlled CAD/drawing and sample plan. A recommendation that never reaches the released revision cannot be inspected consistently in production.
From design review to RFQ
Before requesting a price for secondary machining of molded plastic gears, identify the current drawing revision, production quantity, material constraint and the feature that most strongly affects function. Ask the supplier to flag any deviation from those inputs in the quotation so technical alternatives stay visible.
이 결정에 대한 실용적인 설계 검토
Secondary machining can improve a final bore, datum, face or thread, but it changes the process chain. Define the datum used to locate the molded part, expected stock allowance, clamping method and how the machined feature relates to the gear teeth or molded interface.
견적서 또는 견적요청서(RFQ)에 가정 사항을 기록하여 공급업체가 견적을 제출하기 전에 확인할 수 있도록 하십시오. 값이 알려지지 않은 경우, 조립품과 일치하지 않을 수 있는 일반적인 카탈로그 번호를 복사하는 대신 미해결 엔지니어링 항목으로 명시하십시오.
검증 워크시트
- Molded datum used for setup
- Stock allowance
- Machined feature tolerance
- Clamp distortion risk
- Burr / stress / surface requirement
- Final inspection after machining
첫 번째 샘플을 사용하여 치수 증거와 관련 기능 검사를 모두 통해 이러한 사항들을 확정하십시오. 허용된 편차는 재생산 전에 관리 수정 과정에서 기록되어야 합니다.
