CNC Machine Manufacturer: 7 Essential Checks Before You Release a PO

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  Key takeaways
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  What to compare across cnc machine manufacturer quotes
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  Machine count and travels
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  Tolerance, finish, and how they are measured
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  MOQ, tooling, and how prototypes are handled
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  Certifications, materials, and finishing under one roof
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  Seven checks to run before you release a PO

Every cnc machine manufacturer will describe itself as precise. The useful question is what is bolted to the floor. Ask for the number of machining centers, how many axes each has, and the travel envelope. Those three numbers decide whether your part fits in one setup or gets moved between three machines, which is where most tolerance stack-up comes from.

GreatLight runs 127 high-precision CNC machines across three wholly-owned plants covering 7,600 m². The 5-axis group is 16 simultaneous 5-axis machining centers. There are also 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers. For parts that need turning and milling in one fixturing, the mill-turn group usually removes a setup and a re-datum.

Travel matters more than tonnage. Our large travel is 4,000 × 400 × 150 mm. Medium machines run 750 × 1,150 × 550 mm and 600 × 600 × 600 mm. Compact machines cover 500 × 500 × 450 mm and 500 × 310 × 200 mm. A Ø400 mm rotary table handles round work that needs indexing.

If a supplier cannot give you a travel table, treat the quote as unverified. You will find out at first article whether the part fits.

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  Ask for axis count per machineA "5-axis shop" with two 5-axis centers and forty 3-axis machines is a 3-axis shop with a niche.
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  Match travel to your envelopeA part 30 mm over the travel limit becomes a two-setup job and a new tolerance budget.
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  Check mill-turn availabilityShafts and housings with cross holes usually come out better on one mill-turn setup.

±0.005 mm is a common headline. It is also meaningless without a feature and a size. A 6 mm bore and a 600 mm bolt circle do not hold the same tolerance on the same machine, because thermal drift and tool wear scale with time and distance. Ask which features get ±0.005 mm, over what length, and on which machine.

Surface finish follows the same rule. Ra 0.2–0.8 μm is achievable, but it usually means a finishing pass with a small stepover, which costs time. Ra 0.8–1.6 μm covers most mating faces and seal grooves. Ra 1.6–3.2 μm is the as-machined baseline and is fine for brackets and covers. Specify finish only where it does a job.

Measurement closes the loop. A tolerance claim without an inspection method is a guess. Ask whether they use a CMM, what the machine's stated accuracy is, and whether the report ships with the parts. Our qualification rate is 99.99%, and we inspect 100% of parts before shipment with raw material checks, in-process monitoring, and final inspection.

One more thing: tolerances tighter than the process can hold will be quoted, then quietly relaxed. Get the capability in writing before the PO.

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  Tie tolerance to a feature listMark the three or four dimensions that actually matter and ask for capability on those only.
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  Do not over-specify finishA Ra 0.4 μm callout on a non-sealing face adds cost and buys nothing.
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  Ask for the inspection reportFirst article plus a final report on the critical dimensions is a reasonable baseline.

Minimum order quantity is a signal about how the shop is set up. A supplier that quotes one piece and a 10,000-piece run from the same process is tooled for flexibility. A supplier that insists on MOQ 500 is telling you the setup cost only amortizes at volume. Neither is wrong, but only one fits a design that is still moving.

We work with no minimum order quantity, from one prototype to 10,000+ part runs. Prototypes are usually machined from billet, so there is no tooling to pay for and no delay waiting on a mold. When the design freezes, the same geometry moves to production machines without a new DFM cycle.

The trap is a quote that hides tooling in a line item called "setup" and then reappears as a change fee when the revision moves. Ask what happens to the setup charge if the model changes by 2 mm. Ask whether fixtures are stored and reused on the next order.

For low-volume work, also ask how they hold the first-article dimensions after the fixture is broken down and rebuilt.

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  No MOQ is a capabilityIt means the shop can absorb setup differently instead of pushing volume on you.
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  Ask where the setup cost livesIf it is buried, it will resurface at the first revision.
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  Confirm fixture reuseRepeat orders should not pay for the same fixture twice.

Certification scope matters as much as the certificate. ISO 9001:2015 covers general quality management. IATF 16949:2016 is the automotive standard and adds traceability and change control. ISO 13485:2016 applies to medical devices. ISO 27001:2022 covers information security, which is what you want if you are uploading CAD for an unreleased product.

Material range is the second filter. Most shops stock aluminium and mild steel. Fewer can machine titanium and nickel alloys without burning tools. We cut aluminium grades including 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12; stainless 303, 304, 316, 316L, 420, 430, 431, 440C and 17-4PH; steels 1018, 1045, 4130, 4140, 4340 and A36; copper and brass C101, C110, C36000 and beryllium copper; titanium TA1, TA2 and TC4, plus Inconel and magnesium AZ31B / AZ91D. Plastics run from ABS and POM to PEEK and carbon fibre.

Finishing is where schedules slip. If anodizing and plating leave the shop, you inherit the vendor's queue. We keep anodizing, plating, powder coating, black oxide, bead blasting, polishing, and laser marking in the same workflow.

Ask one blunt question: who owns the part when it leaves your building?

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  Match certification to industryAutomotive, medical and ITAR-adjacent work each need a different scope.
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  List exotic materials up frontTitanium and Inconel change tooling, speeds and price.
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  Keep finishing in-house if you canEvery external step adds a handoff, a queue and a chance of damage.