Why CNC machining costs vary
CNC machining cost is not a fixed number. It depends on design complexity, material choice, tolerance requirements, and order quantity. Understanding these factors helps identify cost reduction opportunities.
Setup and programming costs are fixed per order. Increasing quantity spreads these costs across more parts, significantly reducing per-part cost.
Six strategies to reduce CNC cost
1. Simplify part design
Complex designs increase machining time and cost. Recommendations:
- Avoid unnecessary features — if it's not functional, remove it
- Reduce the number of setups — design parts that can be machined in one or two setups
- Use standard hole sizes and threads — avoid custom sizes that require special tooling
- Increase corner radii — smaller radii require smaller tools and more passes
Ask your supplier for DFM feedback. Most suppliers can identify cost-saving design changes before production.
2. Choose the right material
Material selection significantly impacts cost. Consider both raw material price and machinability:
| Material | Relative Cost | Machinability | Typical Use |
|---|---|---|---|
| Aluminum 6061 | Low | Excellent | General purpose, enclosures |
| Brass C360 | Medium | Excellent | Fittings, electrical parts |
| Stainless 303 | Medium | Good | Free-machining stainless |
| Stainless 316 | High | Fair | Corrosion-resistant applications |
| Titanium | High | Fair | Aerospace, medical implants |
3. Optimize quantity
Per-part cost drops significantly as quantity increases. Typical cost reduction from prototyping to production can be 30-60%.
- Consolidate orders — combine multiple part numbers into one order
- Plan for production quantities — ordering 100+ parts often reduces unit cost substantially
- Consider annual commitments — blanket orders often qualify for volume pricing
Specifying unnecessarily tight tolerances. Tighter tolerances increase cost significantly without functional benefit for many components.
4. Avoid gold-plated tolerances
Each tighter tolerance step adds cost. Only specify tolerances that are functionally required.
- ±0.1mm — standard, no extra cost
- ±0.01mm — moderate cost, suitable for most fits
- ±0.005mm — higher cost, requires precision equipment
- ±0.002mm — high cost, requires Swiss turning or grinding
5. Reduce inspection requirements where possible
Full inspection on every part adds cost. Options:
- 100% inspection only for critical dimensions
- Consider sampling for non-critical features
- Request supplier inspection reports instead of re-inspecting
6. Choose the right supplier
A good supplier offers more than low unit price. Look for:
- DFM feedback to reduce cost before production
- Competitive material sourcing through volume purchasing
- Consistent quality — fewer rejects mean lower total cost
Frequently Asked Questions
How much can I save by increasing quantity?
Per-part cost can drop 30-60% when moving from prototype (1-10 pcs) to production quantities (100+ pcs).
Which material is cheapest for CNC machining?
Aluminum 6061 and brass C360 are among the most cost-effective materials due to low raw material cost and excellent machinability.
Should I choose a cheaper supplier?
Not necessarily. A cheaper supplier may have higher rejection rates, slower delivery, or communication issues. Evaluate total cost of ownership, not just unit price.
How can I reduce cost without affecting quality?
Focus on design simplification, material selection, and tolerance optimization. These changes reduce cost without compromising part performance.