CNC machining: a cost-effective solution
This guide is for engineers and buyers comparing quotes for machined parts. We break down where the money actually goes, which part shapes suit CNC, and when another process wins on cost. Read it and you can judge a quote instead of just comparing totals.
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Five things to settle before you compare quotes
When CNC machining is a cost-effective solution, and when it is not
Cost per part at 100 pieces, 6061-T6, 80 × 60 × 25 mm bracket
| Process | Best quantity band | Typical tolerance | Cost trap |
|---|---|---|---|
| CNC machining | 1 to 10,000+ | ±0.005 mm | Thin walls under 0.8 mm deflect |
| Die casting | 5,000+ | ±0.1 mm | Tooling cost sits in the mold |
| 3D printing (SLS) | 1 to 200 | ±0.2 mm | Surface is grainy as built |
| Sheet metal | 50 to 5,000 | ±0.1 mm | Only for constant wall parts |
| Injection molding | 10,000+ | ±0.05 mm | Steel tool takes weeks to cut |
The verdict on CNC cost
CNC machining is a cost-effective solution when your part is prismatic, your volume is past a handful of pieces, and your tolerances are applied only where they matter. Below that, printing or casting usually wins.
Where the money goes in CNC machining a cost-effective solution
A CNC quote is not one number. It is setup, programming, material, cycle time, tooling wear, inspection and finishing stacked together. On a 100-piece run of a simple aluminium bracket, setup and programming can be 30 to 40 percent of the total. On a 5,000-piece run of the same part, that share drops under 5 percent. This is the single biggest reason CNC machining is a cost-effective solution at volume and an expensive one at low volume.
Cycle time follows material removal rate. Aluminium 6061-T6 cuts at roughly 300 to 500 m/min surface speed with carbide tooling. 304 stainless drops to 120 to 180 m/min. Ti-6Al-4V drops to 40 to 60 m/min and needs more coolant and shorter tool life. The same pocket that takes 4 minutes in aluminium can take 20 minutes in titanium. Part price follows that ratio closely.
Tolerance is the second lever. A part held to ±0.05 mm runs on standard three-axis machines with normal fixturing. A part held to ±0.005 mm needs finer passes, temperature control, and CMM checks on a sample. That inspection time is real cost, and it does not shrink with quantity the way setup does.
Finishing is often quoted separately. Anodizing is priced per batch and per surface area. Laser marking needs a minimum character height of 1.5 mm to stay legible. If you can drop a cosmetic requirement or move a marking to a flat face, the quote usually moves with it.
- 1Setup spreadProgramming and fixturing paid once, divided by the run size.
- 2Material removal rateAluminium 6061 is the cheapest common metal to cut.
- 3Tolerance bandEvery step tighter than ±0.05 mm adds inspection time.
Which part shapes suit CNC, and which do not
CNC wins on prismatic parts: brackets, housings, plates, manifolds, and turned shafts. These have flat faces, clear tool access, and features that can be reached from a few directions. A 5-axis machine can reach the back side of a part in one setup, which removes a second fixture and the alignment error that comes with it.
CNC struggles with three shapes. Very thin walls below 0.8 mm deflect under cutting force and need multiple light passes. Deep narrow pockets with a depth-to-width ratio past 4:1 need long reach tools that chatter. Organic lattice or hollow internal channels are better printed, because no tool can reach inside.
Size matters too. Our largest travel is 4,000 × 400 × 150 mm, and we run a Ø400 mm rotary table for round parts. Anything past that envelope has to be split into sections or made another way. Sending a drawing that fits the machine avoids a redesign after the quote.
If your part is under 200 pieces, has a few critical features, and needs to be in hand next week, CNC is usually the shortest path. If it is a hollow shell with no critical dimensions, printing it will cost less.
How to judge a CNC supplier on cost, not just price
The lowest quote is not always the cheapest part. Ask what is included. Does the price cover material certification, first article inspection, and final inspection reports? A shop that quotes machining only will send a second invoice for inspection and finishing.
Check the machine list against your part. A shop with only three-axis mills will farm out 5-axis work or split it across setups, and both add cost and error. Ask how many simultaneous 5-axis centers they run. We run 16, alongside 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers.
Certifications tell you what paperwork you will get without asking. ISO 9001:2015 covers general quality systems. IATF 16949:2016 is for automotive. ISO 13485:2016 is for medical devices. ISO 27001:2022 covers information security, which matters if your drawings are sensitive.
Ask for the DFM notes, not just the price. A supplier that flags a 0.5 mm wall or an unreachable feature before cutting saves you a scrapped batch. We return a quotation and free DFM analysis within 12 hours.
Finally, ask about lead time risk. A shop that quotes 3 days but has never measured its on-time rate is guessing. Our historical late-delivery probability is below 2 percent, and parts ship in 3 to 5 days.
- 1Quote scopeConfirm whether material, inspection, and finishing are inside the number.
- 2Machine fitMatch the part envelope and axis count to the shop's real equipment.
- 3CertificatesISO 9001, IATF 16949, ISO 13485, ISO 27001 each unlock different paperwork.
What a fair CNC quote should list
A quote you can audit lists material grade and stock size, setup hours, cycle time per part, tooling, inspection level, finishing, and quantity breaks. If it is one lump sum, you cannot tell whether the shop is efficient or just cheap on material.
Quantity breaks matter most. Ask for pricing at 1, 10, 100, 1,000 and 10,000 pieces. The curve shows where setup stops dominating and material and cycle time take over. That is the point where CNC machining is a cost-effective solution for your program.
Watch for missing items. Deburring, thread checking, surface finish calls, and packaging are common omissions. On a medical or automotive part, a missing inspection line is a bigger problem than a higher total.
If a quote comes in 40 percent under the others, ask what was left out. It is usually material certification, inspection, or a tolerance the shop cannot actually hold.
Six steps to a comparable CNC quote
- 1Send STEP and 2D PDF togetherThe STEP carries geometry, the PDF carries tolerances and finish calls. A STEP alone forces the shop to guess which dimensions are critical.
- 2Mark only the dimensions that matterCall out the 3 to 8 features that affect function. Blanket tolerances of ±0.005 mm on every dimension multiply inspection cost for no benefit.
- 3State material grade and temper6061-T6 is not the same as 6061-T4 for strength or machinability. Wrong temper means a re-quote or a scrapped batch.
- 4Give the real annual volumeA 200-piece first order that becomes 20,000 a year should be quoted as both. Setup spread changes the answer.
- 5Ask for DFM notes with the priceLook for flagged thin walls, deep pockets, and tight tolerances. Fixing these in CAD is free; fixing them after cutting is not.
- 6Request inspection reports on the first articleAsk for dimensional reports and material certs on the first batch. Confirm the process before the full run.
Common questions about CNC cost
Is CNC machining cheaper than 3D printing?
It depends on quantity and geometry. For one to five simple brackets, printing can be cheaper because there is no setup. Past about 50 pieces, CNC usually wins on unit price.
For hollow or lattice parts, printing stays cheaper at any volume because no tool can reach inside.
What is the minimum order quantity for CNC machining?
There is no minimum order quantity. We run from one prototype to 10,000+ part runs.
The cost per part at quantity one is dominated by setup and programming, which is why the first piece is always the most expensive.
How tight a tolerance can CNC hold?
We hold ±0.005 mm (±0.0002 in) on critical features when the geometry allows it.
Tolerances that tight need stable fixturing, temperature control, and CMM verification on a sample. They should only be applied to features that affect function.
What materials can be machined?
Aluminium grades including 6061, 7075 and 6082; stainless including 303, 304, 316L and 17-4PH; steels including 1018, 4140 and 4340; copper and brass; titanium including Ti-6Al-4V; and plastics including POM, PEEK and ABS.
Material choice affects cycle time more than any other single decision after geometry.
How fast can parts ship?
Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours of approval, and parts ship in 3 to 5 days.
Finishing steps like anodizing or plating add time and are quoted with the batch.
Are drawings kept confidential?
Uploads are secure and confidential, and an NDA is available on request.
Our ISO 27001:2022 certification covers information security for customer data and drawings.
Send a drawing, get a real number
Upload your STEP and 2D PDF. We return a quotation and free DFM analysis within 12 hours, with the cost drivers broken out.
12-hour quoteNo MOQ100% inspectionNDA on request
More machining notes
We publish setup notes, tooling trials and inspection data from the factory floor.
