What is Design for Manufacturability?
Design for Manufacturability (DFM) is the practice of designing parts that are easier and more cost-effective to manufacture. In CNC machining, DFM principles help reduce cycle time, tool wear, and scrap rates.
Good DFM design doesn't compromise part function — it improves it by eliminating unnecessary complexity.
DFM feedback from your supplier often identifies cost savings of 15-30% without changing part functionality.
Minimum wall thickness
Thin walls are prone to vibration, deflection, and machining difficulty. General recommendations:
- Aluminum — minimum 0.5mm for standard machining
- Stainless steel — minimum 0.8mm
- Plastics — minimum 1.0mm
- Rule of thumb — thicker walls reduce cost and improve machinability
If you have thin walls, consider adding ribs or increasing thickness. It often reduces overall cost by simplifying machining.
Corner radii and tool access
Internal corners require radii because end mills are round. Design considerations:
- Recommended radius — 0.5mm to 1.0mm minimum
- Larger radii — allows larger tools, reduces machining time
- Sharp corners — require additional EDM or hand finishing
- Tool access — ensure tools can reach all features
Specifying sharp internal corners on milled parts. This often requires EDM or hand finishing, significantly increasing cost.
Hole design
| Hole type | Recommended depth | Notes |
|---|---|---|
| Standard hole | Up to 5x diameter | Drilled with standard tooling |
| Deep hole | 5x-10x diameter | Requires special tooling, higher cost |
| Tapped hole | 1.5x-2x diameter | Minimum thread engagement |
| Blind hole | Avoid deep blind holes | Chip evacuation is challenging |
Thread design
- Standard threads — use standard sizes where possible
- Thread engagement — minimum 1.5x diameter
- Thread depth — avoid threads deeper than 2x diameter
- Thread relief — include relief for threaded holes where possible
Tolerance and surface finish
- General tolerances — specify ISO 2768-m for non-critical dimensions
- Critical tolerances — only call out where functionally required
- Surface finish — standard as-machined (Ra 1.6–3.2 μm) is sufficient for most parts
- Design reviews — ask for supplier DFM feedback before production
Frequently Asked Questions
What is the minimum wall thickness for CNC machining?
Minimum wall thickness depends on material. For aluminum, 0.5mm is achievable but 1.0mm or thicker is recommended for cost-effectiveness.
Can CNC machining produce sharp internal corners?
Sharp internal corners are difficult with milling. A small radius (0.5mm) is usually required. For truly sharp corners, EDM is needed.
How deep can a hole be in CNC machining?
Standard hole depth is up to 5x diameter. Deeper holes are possible but add cost and may require special tooling.
Should I request DFM feedback from my supplier?
Yes. DFM feedback often identifies cost-saving opportunities and reduces risk of manufacturing issues.