Start from the mechanism
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.
Inputs to freeze before quotation
Define the gear standard/convention, module or DP, pressure angle, bore datum, mating gear, center distance, backlash target and measurement condition.
ضع هذه المدخلات في الرسم أو المواصفات أو مرفق طلب عرض الأسعار المعتمد، كلما أمكن ذلك. إن إبعادها عن سلاسل الرسائل غير الرسمية يُسهّل مقارنة الموردين وإجراء التعديلات اللاحقة.
What can invalidate the assumption
Overtightening every drawing dimension can increase tooling and inspection cost without controlling the actual mesh.
Verification strategy
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.
Procurement checklist
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.
مراجعة التصميم العملي لهذا القرار
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.
سجّل الافتراضات الواردة في الرسم أو طلب عرض الأسعار حتى يتمكن المورد من تأكيدها قبل تقديم عرضه. عند عدم معرفة قيمة ما، حددها كبند هندسي مفتوح بدلاً من نسخ رقم كتالوج عام قد لا يتطابق مع التجميع.
ورقة عمل التحقق
- 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
استخدم العينة الأولى لسد هذه النقاط بالأدلة البُعدية والفحص الوظيفي ذي الصلة. يجب توثيق أي انحراف مقبول في المراجعة المُحكمة قبل إعادة الإنتاج.
