China Customized CNC Precision Processing: What Engineers Should Check

A simultaneous 5-axis center earns its cost on parts with compound angles, deep pockets reached from more than one face, or features that need to stay in true position across a curved surface. One setup means one work offset. That removes the stack-up error you get when a 3-axis part is flipped four times on a fixture plate.

It is the wrong choice for simple prismatic work. A plate with holes and a milled step runs faster and cheaper on a 3-axis machine with a good vise. If a shop quotes five-axis time on that part, ask why. Honest suppliers will tell you when three axes are enough.

At GreatLight we run 16 simultaneous 5-axis machining centers alongside 12 four-axis mills and 27 three-axis machines. The mix matters because the right machine for your part is a cost decision as much as a tolerance decision. Max processing size is 4,000 mm, and the large travel is 4,000 × 400 × 150 mm.

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  Use 5-axis whenCompound angles, contoured pockets, or tight true position across two or more faces.
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  Use 3-axis whenFlat plates, simple steps, holes with a single approach direction.
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  Watch the setup countEvery re-fixturing adds position error, not just time.

A drawing full of ±0.005 mm callouts on every dimension will cost more than the same part with only the critical features held tight. General tolerances can sit at ±0.1 mm while datum features and mating bores carry the fine numbers. That split is normal in precision work and it keeps the price sane.

Surface finish follows the same logic. Ra 0.8–1.6 μm is a typical machined finish. Ra 0.2–0.8 μm needs a finer step-over, a sharp cutter, and often a second pass. Ra 1.6–3.2 μm is as-machined and fine for brackets and covers that only need to look clean.

Send the 3D model and the 2D drawing together. The model defines the shape; the drawing defines what you actually inspect. When the two disagree, the drawing usually wins, so make sure the critical dimensions are on it.

Aluminum 6061 machines fast with good chip clearance. Grades like 7075 cut clean too but cost more and are less weldable. If your part is a housing with no structural load, 6061-T6 is usually the right call and the cheapest path to a good finish.

Stainless is where grade choice bites. 303 is free-machining and holds tolerance well. 304 and 316 gum up more, so cycle times rise. 17-4PH (SUS630) can be machined in the annealed state and then aged to hit strength. If you spec 316L for a bracket that never sees chloride, you are paying for corrosion resistance you do not need.

Titanium and Inconel sit at the other end. TC4 (Ti-6Al-4V) needs slower speeds, more coolant, and sharp tooling. Inconel work-hardens if the cutter dwells, so the toolpath has to keep moving. These parts are machinable, but the process window is narrow and the quote should reflect that.

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  Aluminum6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075, ADC12.
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  Stainless303, 304, 316, 316L, 420, 430, 431, 440C, 17-4PH (SUS630).
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  Steel1018, 1045, 4130, 4140, 4340, A36, tool steel.
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  Titanium / specialTA1, TA2, TC4 (Ti-6Al-4V), Inconel, magnesium AZ31B / AZ91D.

A first article inspection report should list every dimension on the drawing with the measured value, the nominal, and the pass or fail result. If a shop only sends a certificate of conformance with no numbers, you have no data. Ask for the report before the parts ship, not after.

In-process checks matter on long runs. A 10,000-part order that is only inspected at the end can hide a drift that started at part 2,000. We check raw material on receipt, monitor during the run, and do a final inspection before shipment. Reports are available on request.

Certifications tell you what system the shop runs, not whether your specific part is good. ISO 9001:2015 covers general quality management. IATF 16949:2016 applies to automotive work. ISO 13485:2016 is for medical devices. ISO 27001:2022 covers information security, which matters when you send proprietary CAD files.

Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours of PO and drawing release. Parts typically ship in 3–5 days for standard work. The historical late-delivery probability is below 2%, but that is a past figure, not a promise for your specific order.

There is no minimum order quantity. One prototype and a 10,000+ part run both go through the same shop. The difference is fixturing and inspection plan, not whether we will take the job. Prototype work often uses soft jaws and a single setup; production work gets a dedicated fixture and a documented inspection routine.

Uploads are secure and confidential. An NDA is available on request. If your program needs one, say so before you send files, not after. Finishes are quoted separately: anodizing (clear, color, hardcoat, conductive), electroless nickel, zinc, silver and gold plating, powder coating, black oxide, bead blasting, tumbling, brushing, polishing, and laser marking with a minimum character height of 1.5 mm.