What is Design for Manufacturing (DFM)?
Design for Manufacturing (DFM) is the practice of designing parts so they are easy and cost-effective to machine or mold. A good DFM review catches issues like impossible geometries, overly tight tolerances and hard-to-reach features before production starts, saving time and money.
At JIANGCHENG, our engineers review every drawing for free and suggest improvements that reduce cost without affecting function.
Why DFM Matters
- Lower Cost — simpler parts machine faster and need fewer setups.
- Shorter Lead Time — fewer revisions and rework cycles.
- Better Quality — designs that match machining capabilities produce more accurate parts.
- Fewer Failures — catching issues early avoids scrap and delays.
DFM Guidelines for CNC Machining
| Feature | Design Guideline |
|---|---|
| Internal corners | Use a radius (R≥1mm) rather than sharp corners; end mills are round. |
| Deep pockets | Keep depth under 4x the tool diameter. |
| Thin walls | Keep walls above 0.8mm (metal) or 1.5mm (plastic). |
| Holes | Use standard drill sizes and keep length under 4x diameter. |
| Undercuts | Avoid when possible; they need special tooling. |
| Text & engraving | Use simple fonts and a minimum stroke of 0.5mm. |
Material Selection Tips
- Choose the cheapest material that meets your strength and environment needs.
- Aluminum 6061 is the best all-rounder for most machined parts.
- Use POM or Nylon for low-friction plastic parts.
- Specify heat treatment or finishing only when required.
Tolerance Guidelines
Specify tolerances only on critical features. Over-tight tolerances raise cost significantly. Typical guidance:
| Application | Suggested Tolerance |
|---|---|
| General features | ±0.1 mm |
| Mating features | ±0.05 mm |
| Precision features | ±0.01 mm |
| High-precision (5-axis) | ±0.005 mm |
Common DFM Mistakes
- Sharp internal corners that cannot be milled.
- Walls that are too thin and deflect during cutting.
- Unnecessary tight tolerances on non-critical faces.
- Deep pockets that break small tools.
Get a Free DFM Review
Send us your drawing and our engineers will review it for manufacturability and suggest cost-saving improvements at no charge.
Send Your DrawingFrequently Asked Questions
What is the biggest DFM mistake?
Specifying sharp internal corners or overly tight tolerances on non-critical features, both of which drive up cost unnecessarily.
Do you review drawings for free?
Yes, our engineers provide a free DFM review and cost-saving suggestions with every quote.
What file formats do you accept?
STEP, STP, IGES, IGS and XT for 3D, plus DWG and PDF for 2D drawings.
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