Chinese CNC prototype: fast and accurate

A prototype order is fast or slow for reasons that have little to do with the spindle. The clock starts when you send a model and stops when a finished part is in your hands. Most of that time is spent on quoting, material sourcing, programming and inspection, not on the cut itself.

Quotation and free DFM analysis come back within 12 hours. Production can start within 24 hours after you approve the drawing, and parts ship in 3–5 days. Those numbers assume a clean 3D model, a defined material and a tolerance callout that matches how the part will be used.

Material is the other lever. 6061-T6, 7075, 303 stainless, POM and ABS are normally held in stock. Titanium, Inconel and beryllium copper take longer because the bar has to be sourced and because tool wear changes the cutting strategy. Tell us the material on the first email and the quote does not have to wait.

Mixing processes into one order also saves time. If a prototype needs a machined housing, a laser-cut bracket and a printed cover, running all three through the same shop removes the shipping gaps between vendors. Three wholly-owned plants in Dongguan and one in Singapore make that easier to schedule.

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  Send step and IGES filesSTEP plus a 2D drawing with tolerance callouts quotes fastest.
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  Name the material and finishAnodize color, hardness and masking notes change the routing.
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  Flag critical featuresMark the two or three dimensions that must hold, not every edge.

Tolerance of ±0.005 mm is achievable on prototype quantities, but it is not a blanket promise on every feature. It applies where the drawing asks for it and where the geometry allows a probe or a gauge to reach. A 0.5 mm wide slot in a deep pocket is a different problem than a 40 mm bearing bore.

Five-axis work reduces error because it reduces setups. Every re-clamp adds a datum shift. With 16 simultaneous 5-axis machining centers, a part with undercuts, compound angles or a contoured surface can often be cut in one or two setups instead of four. Fewer setups means fewer chances for a stack-up to drift.

Inspection closes the loop. Every order gets 100% inspection before shipment, with raw material checks, in-process monitoring and a final report. If you need the numbers, ask for them at quote stage so the inspection plan matches your drawing rather than a generic checklist. The historical qualification rate is 99.99%.

Surface finish is a separate callout from tolerance. Ra 0.8–1.6 μm covers most functional prototypes and seals. Ra 0.2–0.8 μm takes longer, usually needs a finishing pass with a smaller stepover, and is rarely worth it on a part that will be anodized afterwards.

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  ±0.005 mmCall it out on specific features, not across the whole part.
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  Ra 1.6–3.2 μmAs-machined finish, fine for brackets and covers.
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  Ra 0.8–1.6 μmStandard for bearing fits, seal faces and sliding surfaces.

Not every prototype belongs on a 5-axis. A flat plate with a few drilled holes runs faster and cheaper on a 3-axis mill, and the operator can leave it unattended for the roughing pass. The 27 three-axis machines handle that work, and the 12 four-axis mills cover parts that need a single rotary index.

Five-axis pays off when the part has a curved surface that would otherwise need three or four fixtures, or when a feature has to be reached from an angle. Fluid manifolds, impellers, medical instrument bodies and engine brackets fall into that group. The 16 mill-turn centers cover shaft-type parts that need turning and milling in one setup.

Size decides the rest. Travel of 4,000 × 400 × 150 mm covers long rails and frame sections. The 750 × 1,150 × 550 mm and 600 × 600 × 600 mm envelopes take most enclosures and housings. The compact 500 × 500 × 450 mm and 500 × 310 × 200 mm machines are the right home for small, high-detail parts where rigidity matters more than reach.

A Ø400 mm rotary table adds a fourth axis to turned work. If a part has features on both ends of a shaft and a true position callout between them, cutting it in one chucking avoids the runout you get from flipping it.

Aluminium is the default for prototypes because it cuts fast and holds tolerance well. 6061-T6 is the general-purpose grade. 7075 gives higher strength for brackets and fixtures. 2024 machines cleanly but does not anodize to a cosmetic finish. 6082 and 6063 are common in Europe and behave close to 6061.

Stainless is chosen for corrosion resistance or food and medical contact. 303 machines the easiest. 304 and 316L are tougher on tools and tend to move slightly after roughing, so a stress-relief pause helps. 17-4PH can be heat treated to higher strength, which means the prototype goes through a second operation after machining.

Plastics cover the low-load cases. POM and PA are good for gears and sliders. PEEK holds up in high temperature and chemical exposure but costs more per part than aluminium. ABS and PC are common for enclosures. Carbon fibre is used when stiffness-to-weight matters more than surface finish.

Finishing follows function. Anodizing in clear, color, hardcoat or conductive types protects aluminium and gives a repeatable appearance. Electroless nickel, zinc, silver and gold plating cover wear and conductivity. Powder coating and black oxide suit steel. Bead blasting, tumbling, brushing and polishing set the cosmetic baseline. Laser marking needs a minimum character height of 1.5 mm to stay legible.

Send the drawing, not just the model. A STEP file defines geometry but says nothing about which dimensions matter. If the 2D drawing does not exist yet, write the critical dimensions in an email and we will quote against those. That single step removes most of the back-and-forth that stretches a prototype order.

Agree on the inspection plan at quote stage. Some engineers want a full dimensional report. Others want a first article with photos and a note on any deviation. Both are fine, but the request has to arrive before the part is cut, not after.

Confidentiality is a normal part of the order. Uploads are stored securely and an NDA is available on request. For work that involves an unreleased product, ask for the NDA before sending files rather than after.

There is no minimum order quantity. One prototype and a 10,000-part run go through the same quoting process. When a prototype looks likely to move into production, say so early. The DFM notes change when we know the same geometry will be machined again at volume, and it is cheaper to fix a draft angle now than to re-tool later.

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  Quote and DFM in 12 hoursDrawing plus material plus finish, in one message.
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  Start in 24 hoursAfter drawing approval and material confirmation.
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  Ship in 3–5 daysApplies to standard prototype quantities.