China Customized CNC Processing: What to Check Before You Order

Most quotes you receive from China will look similar on price. The difference shows up in the equipment list. A shop that can only run three-axis mills will quote the same part as a five-axis shop, then send it out or split the setup across three fixtures. On a part with compound angles or deep pockets, that shows up as mismatched datums and longer lead time.

GreatLight runs 127 high-precision CNC machines across 3 wholly-owned plants covering 7,600 m², with 150 technicians based in Dongguan and a second plant in Singapore. The fleet includes 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines and 16 mill-turn centers. That mix matters when your part family ranges from a Ø30 mm bracket to a 4,000 mm frame.

Ask for the travel envelope, not just the machine count. Large parts run on 4,000 × 400 × 150 mm travels. Mid-size work fits 750 × 1,150 × 550 mm or 600 × 600 × 600 mm. Small, high-mix parts run best on 500 × 500 × 450 mm or 500 × 310 × 200 mm machines with a Ø400 mm rotary table. If your part sits near an envelope edge, the fixture design changes, and so does the quote.

A customized CNC processing job with no minimum order quantity is normal for a prototype shop, but it is not normal everywhere. We take runs from one piece to 10,000+ parts, which keeps the same process and inspection plan from first article through production.

Tolerance is a cost driver, not a badge. We hold ±0.005 mm (±0.0002 in) on features that need it, but applying that callout to every dimension on a part triples inspection time and rejects good parts. Put tight tolerance on the fits that matter: bearing bores, mating faces, dowel holes. Leave the rest at general tolerance.

Surface finish follows the same logic. As-machined surfaces land at Ra 1.6–3.2 μm. A high-finish cut reaches Ra 0.8–1.6 μm. Fine finish goes to Ra 0.2–0.8 μm and usually needs a second operation, a different tool, or both. Tell us which face seals, slides or takes a coating, and we will put the money there.

Thin walls, deep narrow slots and sharp internal corners are the three features that push a part out of standard milling. Below roughly 0.5 mm wall thickness on aluminum, chatter and deflection become the limit, not the machine. Deep pockets past 4× tool diameter need reduced feed or a longer reach tool with more runout. These are the points worth a DFM conversation before quoting.

Our quotation and free DFM analysis come back within 12 hours, and production can start within 24 hours of approval. Parts typically ship in 3–5 days. Historical late-delivery probability sits below 2%, which is a record, not a promise on your specific job.

Aluminum is the default for prototypes and most housings: 6061, 6061-T6, 2024, 5052, 5083, 6063, 6082, 7075 and ADC12. Stainless covers 303, 304, 316, 316L, 420, 430, 431, 440C and 17-4PH (SUS630). Steels include 1018, 1045, 4130, 4140, 4340, A36 and tool steel. Copper and brass grades run from C101 and C110 through beryllium copper, C27400, C28000 and C36000.

For higher-load work we machine TA1, TA2, TC4 (Ti-6Al-4V), Inconel and magnesium AZ31B or AZ91D. Plastics include ABS, PC, PMMA, POM, PA, PEEK, PP, HDPE and carbon fibre. Titanium and Inconel cut slowly and wear tooling fast, so expect a different price curve than aluminum on the same geometry.

Finishing changes dimensions. Anodizing adds a few micrometres and hardcoat adds more, so mask threads and bores or cut them undersize. We run clear, colour, hardcoat and conductive anodizing; electroless nickel, zinc, silver and gold plating; powder coating and black oxide; bead blasting, tumbling, brushing and polishing. Laser marking and engraving hold a minimum character height of 1.5 mm.

Bring heat treatment into the same conversation. Annealing, hardening and stress relief all move the part, and the sequence against machining decides whether your final tolerance holds. If a drawing calls for both tight tolerance and hardening, say so at quote time.

Every part gets 100% inspection before shipment: incoming raw material check, in-process monitoring and final inspection. Reports are available on request. Ask for the report format you need up front, because a first-article report and a full dimensional layout take different time.

Our quality system is certified to ISO 9001:2015, IATF 16949:2016, ISO 13485:2016 and ISO 27001:2022. The first two cover general and automotive work. ISO 13485 supports medical device programs, and ISO 27001 covers how we handle your data. If your industry requires traceability to heat lot, tell us at quote time so material certs are gathered before cutting starts.

Uploads stay secure and confidential, and we sign an NDA on request. For most customers the practical protection is simple: keep the CAD and the process sheet under the same access rule, and confirm who inside the shop sees the drawing.

Qualification rate across production runs sits at 99.99%. That number reflects inspection discipline, not luck. If your drawing has a feature that is hard to measure, send the GD&T scheme with the model so we can agree on datums before the first cut.