10 Ways to Reduce CNC Machining Costs
From material choice and internal corner radii to set-ups and batch sizes: practical ways to lower CNC quotes without compromising quality.
Table of contents 11 sections
- 1. Tighten tolerances only where needed
- 2. Add internal corner radii
- 3. Avoid deep, narrow pockets
- 4. Avoid thin walls
- 5. Reduce the number of set-ups
- 6. Use standard hole and thread sizes
- 7. Choose the right material
- 8. Simplify text and engraving
- 9. Separate cosmetic requirements
- 10. Plan batch sizes wisely
- Checklist
Machine time is the biggest driver of CNC prices. Design decisions that reduce machining time, set-ups and scrap, without changing how the part works, can lower your quote noticeably.
In short: relax tolerances, add internal corner radii, avoid deep narrow pockets, use standard sizes and design the part to be machined in as few set-ups as possible.
1. Tighten tolerances only where needed
ISO 2768-m is sufficient as a general tolerance. Apply tight tolerances only to fits and sealing surfaces; each one adds finishing passes and inspection.
2. Add internal corner radii
Milling cutters are round, so internal corners are naturally radiused. Asking for sharp internal corners requires extra operations such as EDM. Keeping the internal radius at least one third of the pocket depth allows a larger, more rigid tool.
3. Avoid deep, narrow pockets
When pocket depth exceeds roughly four times the tool diameter, long slender tools are needed, which means low cutting speeds and chatter. If a deep pocket is unavoidable, consider widening it or splitting the part in two.
4. Avoid thin walls
Thin walls vibrate and deflect during machining. Walls below about 0.8 mm in metals and 1.5 mm in plastics need special precautions.
5. Reduce the number of set-ups
Every new face of the part requires re-clamping on the machine. Grouping features on as few sides as possible reduces both time and the risk of positioning errors.
6. Use standard hole and thread sizes
Standard drill sizes and common threads such as M6 and M8 avoid tool changes and special tooling. Limiting thread depth to 1.5–2 times the diameter is enough for most applications.
7. Choose the right material
Aluminum 6061 machines much faster than steel or stainless steel. If high strength is not truly required, an easier-to-machine material shortens cycle time considerably. Part sizes close to standard stock dimensions also reduce material waste.
8. Simplify text and engraving
Machined text takes a long time with small tools. Where possible, prefer laser marking, labels, or recessed rather than raised text in a larger font.
9. Separate cosmetic requirements
Instead of requiring cosmetic quality on every surface, mark the visible ones on the drawing. Accepting standard machining marks on hidden faces reduces finishing time.
10. Plan batch sizes wisely
Set-up time (CAM programming, fixturing, first-article inspection) is spread across the batch. If you will need the part again, ordering more at once lowers the unit price. Asking for prices at several quantities makes this decision easier.
On Üret Al, describing how the part will be used in the quote notes lets manufacturers suggest design or material changes that reduce cost within their offer.
Checklist
- Tight tolerances only on functional surfaces
- Internal corners have radii matching the tool diameter
- Reasonable pocket depths, no thin walls
- Standard hole and thread sizes
- Cosmetic surfaces marked on the drawing
- Prices requested for several quantities
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