Comece pelo mecanismo.
A useful gear tolerance plan focuses on the characteristics that control the mesh and mounting relationship.
Bore-to-tooth runout, tooth-to-tooth variation, overall geometry and the center distance in the assembly all influence working performance. Molding adds material shrinkage and process variation that should be reflected in datum and inspection choices.
Consider an assembly where the bore locates on a steel shaft and the mate is fixed in a molded housing. A tight outside-diameter tolerance on the gear does little if bore runout or housing center distance dominates the mesh. The drawing should therefore distinguish tooth geometry from mounting geometry and place the inspection datum on the feature that actually locates the gear in service.
Dados a serem congelados antes da cotação
Define the gear standard/convention, module or DP, pressure angle, bore datum, mating gear, center distance, backlash target and measurement condition.
Inclua essas informações no desenho controlado, na especificação ou no anexo da solicitação de cotação, sempre que possível. Mantê-las fora de conversas informais facilita a comparação entre fornecedores e revisões posteriores.
O que pode invalidar a suposição?
Overtightening every drawing dimension can increase tooling and inspection cost without controlling the actual mesh.
Estratégia de verificação
Combine dimensional gear checks with an assembled roll or functional test when that better represents the mechanism.
For Injection Molded Gear Tolerances, 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.
Lista de verificação de compras
Before requesting a price for injection molded gear tolerances, 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.
Análise prática do projeto para esta decisão.
Tolerance should be allocated from the assembly backward. Start with required working backlash or position, then include center-distance variation, tooth-to-bore runout, shaft/bearing clearance, material movement and measurement uncertainty. Tightening every free-part dimension can increase cost without protecting the assembled condition.
Registre as premissas no desenho ou na solicitação de cotação para que o fornecedor possa confirmá-las antes de enviar a proposta. Quando um valor for desconhecido, identifique-o como um item de engenharia aberto, em vez de copiar um número de catálogo genérico que pode não corresponder à montagem.
Folha de verificação
- Working rather than nominal clearance
- Bore-to-tooth or rack-to-mount datum relationship
- Mating-part tolerance
- Inspection temperature / conditioning
- Functional roll, mesh or position check
- Acceptance method agreed before sampling
Utilize a primeira amostra para concluir esses pontos com evidências dimensionais e a verificação funcional relevante. Qualquer desvio aceitável deve ser registrado na revisão controlada antes da produção de nova amostra.
