How design affects cost
Design decisions directly impact manufacturing cost. Complex features, tight tolerances, and special material requirements all increase machining time and cost.
Simple design changes can often reduce costs by 15-30% without affecting part performance.
Design reviews with your supplier often identify cost-saving opportunities that are not apparent in the original design.
Corner radii and tool access
- Add radii to internal corners — sharp corners require EDM or hand finishing
- Use larger radii where possible — allows larger tools, reducing machining time
- Consider tool access — ensure cutting tools can reach all features
Avoid sharp internal corners on milled parts. A small radius (0.5mm) is often sufficient and reduces cost significantly.
Wall thickness and material usage
- Avoid excessively thin walls — thin walls increase machining difficulty and cost
- Optimize material usage — choose standard bar sizes where possible
- Consider material removal — reducing the amount of material to remove saves machining time
Hole and thread design
| Design factor | Recommended practice | Cost impact |
|---|---|---|
| Hole depth | Up to 5x diameter | Standard |
| Thread engagement | 1.5x diameter | Standard |
| Standard vs custom | Use standard sizes | Lower cost |
| Blind holes | Avoid deep blind holes | Reduce cost |
Specifying unnecessarily tight tolerances. This is the single largest driver of cost in CNC machining.
Tolerance and surface finish
- Use general tolerances — specify ISO 2768-m for non-critical dimensions
- Only specify tight tolerances where required — each tighter step adds cost
- Loosen surface finish requirements — standard as-machined is sufficient for most parts
Design review process
- Request DFM feedback from your supplier — most suppliers can identify cost-saving opportunities
- Review all dimensions and tolerances — confirm each is necessary
- Consider alternate materials — sometimes a different material reduces cost
Frequently Asked Questions
How much can design changes reduce cost?
Design changes can often reduce CNC machining costs by 15-30% without affecting part performance.
What is the most cost-effective design practice?
Avoiding tight tolerances and sharp internal corners. These are the largest cost drivers in CNC machining.
Should I request DFM feedback?
Yes. DFM feedback from your supplier can identify cost-saving opportunities that may not be apparent.
Can material selection reduce cost?
Yes. Choosing a more machinable material can reduce manufacturing cost significantly.