CNC Processing Cost: What to Expect

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  Key takeaways
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  The 7 cost drivers and how much they move the price
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  Material: the first thing that moves CNC processing cost
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  Tolerance and finish: where machine time doubles
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  Size, geometry and the number of setups
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  Volume, MOQ and how the quote changes with quantity
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  Certifications, inspection and what to expect in the paperwork
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  Lead time, shipping and the cost of a late part
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  Post-processing and finishing costs
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  What to expect: 6 steps from RFQ to a firm quote

Stock price sets a floor that no amount of clever programming can beat. Aluminium 6061-T6 and POM machine fast and cost little per kg, so the material line stays small. Swap to 17-4PH stainless or TC4 titanium and you pay more for the billet, more for the tool wear, and more for the slower feeds.

Machinability matters as much as the invoice price. Inconel and magnesium AZ91D behave very differently on the same machine. Inconel needs low surface speeds and generous coolant; magnesium cuts quickly but needs chip control because fine swarf is a fire risk. Both raise the hourly rate the shop must charge.

There is also scrap risk. A part cut from a 200 mm titanium billet that fails final inspection costs the shop the billet, the machine time and the re-setup. Shops price that risk into exotic material work. If your design allows 6061 or 6082, saying so early usually saves more than any negotiation on hourly rate.

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  Cheapest per part6061, 6082, 5052, POM, ABS
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  Middle band303/304 stainless, 1045, 4140, brass C36000
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  Highest riskInconel, TC4, beryllium copper, magnesium

A general tolerance of ±0.1 mm lets the operator run at full feed and check with calipers. Tighten a bore to ±0.005 mm and the same feature needs a finishing pass at reduced depth of cut, a temperature-stable setup, and a CMM check. That single callout can add 30–50% to the cycle time on that feature.

Surface finish follows the same logic. Ra 1.6–3.2 μm comes off the tool as machined. Ra 0.8–1.6 μm usually needs a lighter finishing pass. Ra 0.2–0.8 μm often means polishing or a dedicated finish operation after machining, plus handling between steps.

The mistake we see most often is a tight tolerance applied to a feature that does not need it. A mounting face at ±0.05 mm and a bearing bore at ±0.005 mm are both fine. Making the whole part ±0.005 mm is not. Mark only the features that carry function and let the rest run loose.

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  As machinedRa 1.6–3.2 μm, general tolerance
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  Fine finishRa 0.8–1.6 μm, adds a finishing pass
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  PolishedRa 0.2–0.8 μm, separate operation

Every setup costs money before the first chip. Fixture design, zero-point setting and trial cuts run 30–90 minutes on a simple part. A part that needs five sides machined on a 3-axis machine may take four setups. The same part on a simultaneous 5-axis center can be done in one, which is why the higher hourly rate often wins on complex geometry.

Size cuts both ways. Small parts under a 200 mm envelope fit any machine and can be nested several per billet. Large parts up to 4,000 mm need a big-travel machine, longer warm-up, and more careful handling. Deep pockets and thin walls add another cost: lower feeds, extra support, and sometimes a stress-relief step between roughing and finishing.

Undercuts, deep bores and features that need long-reach tooling are quiet cost multipliers. Long tools deflect. The shop must slow down and take lighter cuts. If a design change moves a feature closer to the spindle, it can cut that feature's cycle time noticeably.

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  One setupBest case, 5-axis or simple prismatic part
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  Two to three setupsTypical for 3-axis mill work
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  Four or moreComplex parts, check the 5-axis option

At one piece you are buying programming and setup, not parts. At 10,000 pieces you are buying cycle time, and setup is a rounding error. This is why unit price falls steeply between quantity 1 and quantity 100, then flattens. If a supplier quotes the same unit price at 10 and 1,000 pieces, ask why.

Minimum order quantity is a separate question from price. Some shops refuse runs under 50 pieces because the fixture cost cannot be recovered. We take work from a single prototype to 10,000+ part runs, so the quote reflects the actual quantity rather than a minimum billing floor.

Tooling is the third variable. Custom fixtures and gauges are one-time costs. Spread them over a small run and the unit price jumps. Spread them over a large run and they almost disappear. Ask the shop to show tooling as a separate line so you can compare it against another supplier fairly.

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  1–10 piecesSetup and programming dominate
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  100–1,000 piecesBalance point, fixture cost amortized
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  10,000+ piecesCycle time and material dominate

A certification is only worth paying for when your part or your customer needs it. ISO 9001:2015 covers general quality management. IATF 16949:2016 applies to automotive production parts. ISO 13485:2016 covers medical devices. ISO 27001:2022 covers information security, which matters if you are sending CAD files for regulated products.

Inspection depth follows the same rule. Standard work is 100% inspection before shipment with raw material check, in-process monitoring and final inspection, and reports on request. A first-article inspection report with dimensional results is a step up. Full PPAP or a validated medical documentation package is another step, and it costs engineering hours, not machine hours.

Ask for the inspection scope in writing before you order. Vague promises like full quality control tell you nothing. A named report, a sampling plan and a stated tolerance band give you something to check against the parts when they arrive.

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  Standard100% inspection before shipment, reports on request
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  AutomotiveIATF 16949 records, PPAP where required
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  MedicalISO 13485 documentation package

Machining price is only part of what you pay. A cheap part that arrives late can stop an assembly line, and that cost dwarfs the per-piece saving. Ask what to expect on timing before you compare prices. We quote with a free DFM analysis within 12 hours, production can start within 24 hours, and parts ship in 3–5 days.

Rush work costs more. Overtime, machine re-scheduling and expedited freight all land on the invoice. If your schedule is tight, say so at the quoting stage rather than after the order. A shop that knows the deadline can often re-sequence work at a smaller premium than a last-minute rush.

Freight and customs are real line items on cross-border orders. Incoterms decide who pays what and when risk transfers. Ask for the term in writing, and check whether the quoted price includes export packing. Bubble wrap and a wooden crate are not free.

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  Quote and DFMWithin 12 hours
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  Production startWithin 24 hours
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  ShippingParts ship in 3–5 days

Finishing is quoted separately at most shops, and it can be a large share of the total on visible parts. Anodizing in clear or colour is common on aluminium. Hardcoat anodizing wears better but costs more because it runs longer in the tank. Electroless nickel, zinc, silver and gold plating follow the same pattern: the more controlled the process, the higher the price.

Cosmetic requirements are the hidden driver here. A bead-blasted internal bracket and a brushed front panel may use the same base machining, but the panel needs careful handling, masking and inspection for scratches. Powder coating and black oxide are cheaper per part but limit how tight a tolerance you can hold afterward.

Laser marking is usually cheap and easy to add, with a minimum character height of 1.5 mm for legibility. Plan the finish before machining starts. Changing an anodizing colour after the parts are made is not a rework you can do at the bench.

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  Functional finishBlack oxide, zinc plating, tumbling
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  Cosmetic finishAnodizing, powder coating, brushing
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  MarkingLaser engraving, minimum character height 1.5 mm