What buyers should verify first
A reliable decision starts with evidence that matches the drawing, production volume and business risk. Use the table below during RFQ review; replace assumptions with named documents, owners and acceptance criteria.
| Review area | What good control looks like | Buyer action |
|---|---|---|
| Deep narrow pocket | Long tools chatter and cut slowly | Open geometry or reduce depth |
| Sharp internal corner | Rotary cutters require a radius | Use the largest functional radius |
| Thin wall | Clamping and cutting cause distortion | Thicken or support |
| Tight tolerance everywhere | Extra finishing and inspection | Limit to CTQs |
| Multiple orientations | More fixtures and datum transfer | Consolidate access |
1. Design around tool access
Visualize how a rigid cutter reaches each surface. Increase internal radii, avoid extreme depth-to-width ratios and provide clearance around walls and bosses.
For sourcing approval, convert this point into a written requirement: identify the responsible party, evidence to retain, acceptance rule and response when the rule is not met. This keeps a sample success from being mistaken for a capable production system.
2. Reduce setup count
Features machined from different directions require refixturing, datum transfer and verification. Align features where function allows.
For sourcing approval, convert this point into a written requirement: identify the responsible party, evidence to retain, acceptance rule and response when the rule is not met. This keeps a sample success from being mistaken for a capable production system.
3. Treat walls and floors as structures
Thin sections move under clamp force, heat and residual stress. Add ribs, increase thickness or sequence roughing and stress relief.
For sourcing approval, convert this point into a written requirement: identify the responsible party, evidence to retain, acceptance rule and response when the rule is not met. This keeps a sample success from being mistaken for a capable production system.
4. Use standard details
Standard hole sizes, thread forms, corner radii and stock thicknesses reduce special tools and procurement delays.
For sourcing approval, convert this point into a written requirement: identify the responsible party, evidence to retain, acceptance rule and response when the rule is not met. This keeps a sample success from being mistaken for a capable production system.
5. Separate function from appearance
Identify cosmetic faces, allowable tool marks, grain direction, protected threads and post-finish dimensions instead of demanding premium finish everywhere.
For sourcing approval, convert this point into a written requirement: identify the responsible party, evidence to retain, acceptance rule and response when the rule is not met. This keeps a sample success from being mistaken for a capable production system.
Practical buyer scenario
Changing a deep rectangular pocket to include larger corner radii can allow a shorter, stiffer end mill and faster material removal without changing enclosure function.
The useful output is a controlled plan, not a promise. Record the drawing revision, assumptions, open questions, required evidence and approval gate in the RFQ or purchase order. For critical applications, obtain engineering, quality and regulatory review appropriate to the product.
RFQ checklist
- Controlled 3D model and 2D drawing with matching revision
- Material grade, condition or temper, and any certificate requirement
- Quantity per release, annual demand and target delivery date
- Critical-to-quality characteristics and agreed measurement method
- Surface finish, cosmetic zones, masking and post-finish dimensions
- Packaging, labeling, Incoterm and destination
- First-article, sampling, traceability and corrective-action expectations
Frequently asked questions
When should DFM happen?
Before the design is frozen and again before production tooling or fixtures are committed.
Does a looser tolerance always reduce cost?
Only when it changes the process, inspection or scrap risk; discuss the actual feature.
Why are deep holes expensive?
Chip evacuation, tool deflection, peck cycles and special drills add time and risk.
What files help DFM?
A native or neutral 3D model plus a controlled 2D drawing with CTQs and notes.
Sources and further reading
Technical note: Examples in this guide are planning guidance, not a universal manufacturing specification. Final capability, certification, tolerances, treatment and acceptance criteria must be confirmed for the exact drawing and contract.
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