CNC Machining
CNC Machining Cost: 6 Factors That Move Your Quote
Six things move your quote. Understand them and you can predict the price before you send an RFQ.
Key takeaways
- Machine time is usually the largest part of a CNC quote.
- Buy-to-fly ratio, or how much stock you remove, drives material and time.
- Every tight tolerance and every extra setup adds cost.
- Quantity spreads setup across the batch, so unit price falls fast at first.
Where the money goes
A CNC quote is built from machine time, material, setup, finishing and inspection. On a typical aluminium bracket, machine time and setup together are often more than half the price.
That is why design changes that save machining minutes matter more than small material savings.
1. Material
Two things matter: the price per kilogram and how much you throw away.
A part cut from a 100 × 100 × 50 mm block that ends up 20 mm thick wastes most of the stock. That waste is paid for twice, once in material and once in the time to remove it.
Choosing a near-net stock size, or a casting or extrusion, can cut both.
2. Setup
Setup covers programming, fixtures, tool loading and the first-article check. It happens once per operation, per batch.
Every additional face you machine usually means another setup. A part machined on five sides can need three or four setups, each with its own fixturing and alignment.
3. Tolerance
Tight tolerances slow the machine and add inspection. Moving from ±0.1 mm to ±0.02 mm on a few features can add 30% or more.
Tolerance on one critical bore is normal. Tolerance on every dimension is a price decision you did not mean to make.
4. Features
Some geometry is expensive no matter how good the shop is.
- Deep, narrow pockets that need long, thin cutters.
- Thin walls that vibrate and need light passes.
- Sharp internal corners where a round cutter cannot reach.
- Text and logos engraved on a machined face.
- Undercuts that need a fourth or fifth axis.
5. Surface finish
As-machined is the baseline. Bead blasting, anodizing, polishing and painting are added operations, often done by a separate supplier with its own minimum charge.
Anodizing also adds handling and masking time. If only part of the surface needs a finish, expect a masking charge.
6. Quantity
Setup is fixed, so the first part carries all of it. The second part carries almost none.
| Quantity | Setup per part | Typical effect on unit price |
|---|---|---|
| 1 | 100% | Baseline, highest |
| 10 | 10% | 40% to 60% lower |
| 100 | 1% | 70% to 85% lower |
| 1,000 | 0.1% | Material and machine time dominate |
This is why a quote for one part and a quote for a hundred can look unrelated. It is the same work, spread differently.
An example breakdown
A 6061 aluminium bracket, 120 × 80 × 25 mm, three setups, ±0.05 mm on two bores, clear anodize, quantity 50:
| Line | Share of price |
|---|---|
| Material | 15% |
| Programming and setup | 20% |
| Machine time | 45% |
| Finishing | 15% |
| Inspection and packing | 5% |
The exact numbers vary by shop and geometry. The pattern does not: machine time dominates, and setup is what makes small quantities expensive.
How to get a lower quote
- Loosen tolerances that do not affect fit.
- Increase internal corner radii to match a larger cutter.
- Reduce the number of setups by designing for one orientation.
- Choose a stock size close to the finished part.
- Combine small parts into one machined plate if the material allows.
- Ask for a quote at two quantities, so you can see the setup effect.
- Send a STEP file and a drawing with the finish and tolerance notes. Missing information adds days, not just cost.
Common questions
Why is one part so expensive?
Because setup, programming and fixturing are charged once and cannot be spread. The second part is much cheaper than the first.
Does a bigger shop mean a lower price?
Not always. A shop that runs your part size every week will usually beat a larger shop that has to learn it.
Can I get a price without a drawing?
You can get an estimate from a STEP file. A drawing with tolerances and finish gives you a real number.
The bottom line
Cost is mostly time, and time is mostly geometry. Design for fewer setups, fewer deep pockets and fewer tight callouts, and the quote will follow.