AAA CNC Machining Services Inc: How to Judge the Supplier

The first question is not how many machines a shop owns. It is whether the right machine is free when your job lands. A bracket with holes on four faces is a three-axis job with two setups, or a four-axis job with one. A hydraulic manifold with ports at compound angles is not. Ask which spindle will run your part and how many setups the process needs.

Setup count drives everything downstream. Every re-clamp adds location error, adds labor, and adds a chance of a scrapped feature. A shop running 16 simultaneous 5-axis machining centers can often finish a complex part in one setup, which is why the tolerance stack stays tight. A shop without that capacity will quote the same part across four fixtures and hope the datums hold.

Size matters too. GreatLight machines up to 4,000 mm, with travels from 500 × 310 × 200 mm up to 4,000 × 400 × 150 mm, plus a Ø400 mm rotary table for round work. If your part sits near the edge of a travel envelope, say so early. Tool clearance and clamping often shrink the usable envelope well below the spec sheet.

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  Fewer setupsBest when the part has features on three or more faces.
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  Five-axisUse it when compound angles make re-fixturing risky.
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  Large travelsFrame parts and long housings need the 4,000 mm class.

A ±0.005 mm tolerance is achievable on a rigid setup with the right tool and a stable thermal environment. It is not achievable on a thin wall that flexes under clamping pressure, no matter what the machine can do. Before you accept a tight callout, check whether the drawing gives a datum structure that supports it and whether the feature has enough material around it.

Surface finish follows the same logic. Ra 1.6–3.2 μm comes off the machine with a normal finishing pass. Ra 0.8–1.6 μm needs a lighter stepover or a dedicated finish pass. Ra 0.2–0.8 μm usually means a smaller tool, longer cycle time, or a secondary operation. Specify the finish on the functional surface only, not the whole part.

Cost climbs predictably as you tighten the window. Moving from ±0.05 mm to ±0.005 mm on one bore can double the cycle time for that feature. The practical move is to mark the critical dimensions on the drawing and leave the rest at general tolerance. Shops quote faster and cheaper when they can see which features matter.

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  Thin wallsUnder 1 mm, expect spring passes and light clamping.
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  Deep pocketsLong tools deflect; keep depth-to-diameter under 4:1.
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  Fine finishRa 0.2–0.8 μm is a separate operation on most parts.

Aluminium 6061 and 7075 cut fast and hold tolerance well. 7075 is stronger but more prone to stress movement after heavy material removal, so rough it, let it relax, then finish. Stainless 303 machines cleanly; 304 and 316 work-harden if the tool rubs instead of cuts, so feed and speed need to be right from the first pass. 17-4PH in the H900 condition is a different job from the annealed state.

Titanium TC4 (Ti-6Al-4V) and Inconel sit at the other end. They generate heat at the cutting edge, which shortens tool life and pushes cycle time up. Thin sections can move while cutting. For these materials, plan on more roughing passes and a stress-relief step if the part is critical.

Plastics behave differently again. POM and PEEK hold dimensions but need sharp tools and air blast rather than flood coolant. ABS and PC can chip on exit. Carbon fibre eats tool edges and needs dust extraction. Tell the shop the exact grade, not just the family name.

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  Aluminium6061, 7075, 2024, 6082, ADC12.
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  Stainless303, 304, 316L, 17-4PH, 440C.
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  TitaniumTA1, TA2, TC4, plus Inconel and magnesium.
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  PlasticsPOM, PEEK, PA, PC, PMMA, carbon fibre.

A machine that cuts the part is only half the story. Ask how the first article is verified, what instrument is used, and whether the report ships with the parts. For a ±0.005 mm feature, that means a CMM or a high-accuracy optical system, not a caliper. For a bore, it means a bore gauge or an air gauge.

GreatLight inspects 100% of parts before shipment, with raw material checks at intake, in-process monitoring during the run, and final inspection at the end. Reports are available on request. If your industry needs traceability, say so at quoting stage so the lot structure is set up correctly from the start.

Certifications tell you what system the shop runs, not what it can hold. ISO 9001:2015 covers general quality management. IATF 16949:2016 applies to automotive work. ISO 13485:2016 covers medical devices. ISO 27001:2022 covers information security, which matters if you are sending proprietary CAD files. All four are in place here, but the useful question is which one governs your part.

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  First articleRequest a dimensional report on the first part.
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  In-processAsk how many parts are checked per lot.
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  TraceabilityMaterial certs and lot numbers on request.

A workable flow starts with the STEP file and the 2D drawing together. The 3D model defines geometry; the drawing defines tolerances, datums and finish. If the two disagree, someone has to decide which one wins, and that decision should happen before the first cut.

Quotation and a free DFM analysis come back within 12 hours. The DFM note is worth reading even when you disagree with it, because it usually flags features that will be hard to hold or expensive to inspect. Production can start within 24 hours of approval, and parts typically ship in 3–5 days. Historical late-delivery probability is below 2%, but the ship date depends on material availability and finish selection.

Runs go from one prototype to 10,000+ parts with no minimum order quantity. Each project has a dedicated engineer who handles DFM, fixturing and the inspection plan. Uploads stay confidential, and an NDA is available on request before you send drawings.

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  Quote12 hours, with DFM notes.
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  StartProduction within 24 hours of approval.
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  Ship3–5 days for most parts.
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  VolumeOne piece to 10,000+.