CNC processing in China: welfare and services

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  Key takeaways
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  What to check before you place an order
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  Why CNC processing in China is a capability question first
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  Tolerance, finish and material: the three numbers that drive cost
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  Lead time, MOQ and certification: what the paperwork should prove
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  Finishing and secondary services: where quotes quietly diverge
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  How to read a quotation from a Chinese machine shop
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  Seven steps to qualify a supplier

Most RFQs compare price per hour. That number tells you almost nothing about whether the shop can hold your drawing. A 5-axis machine with a Ø400 mm rotary table can cut five faces in one setup, so the position of a bore relative to a flange stays inside ±0.005 mm. Move that part to a 3-axis mill and you re-fixture it three times. Each setup adds stack-up error you cannot inspect away.

So the first question is not cost. It is which machine will run the part, how many setups it needs, and how the shop will measure the result. If the answer is vague, the price is meaningless.

China has a deep supplier base, which cuts both ways. You can find a shop with 127 high-precision CNC machines and a full inspection room. You can also find a trading company that forwards your file to a job shop and adds 20 percent. The difference shows up in the technical reply, not the brochure.

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  One setup beats threeFewer setups means less stack-up error and a shorter route to first article.
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  Ask for the inspection methodCMM, height gauge or optical. The method should match the tolerance.
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  Materials set the cutting data6061 aluminium runs fast; Inconel and Ti-6Al-4V need slow feeds and rigid tooling.

Tolerance is the biggest cost lever. Going from ±0.05 mm to ±0.005 mm changes the machine, the tooling, the temperature control in the room and the inspection time. It is not a line item you can trim at the end of a negotiation.

Surface finish works the same way. As-machined parts sit around Ra 1.6–3.2 μm. A sealing face or a bearing bore often needs Ra 0.8–1.6 μm, and optical or medical parts can go to Ra 0.2–0.8 μm. Each step down means a different tool path, a different cutter and usually a second operation.

Material choice decides how hard the job is. Aluminium 6061-T6 and 7075 cut cleanly and hold tight tolerances. Stainless 316L work-hardens, so the shop needs sharp tooling and steady feed. Titanium Ti-6Al-4V and Inconel generate heat at the cutting edge, which pushes tool life down and cycle time up. A quote that ignores the alloy is not a real quote.

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  State the tolerance you need, not the one you likeOver-tightening a clearance hole adds cost with no function gained.
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  Group finish calls by functionSealing and sliding faces tight, cosmetic faces looser.
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  Send the alloy grade6061 and 7075 behave differently. So do 304 and 316L.

Lead time has two parts: the quote and the metal. A shop that returns a quotation and a free DFM analysis within 12 hours has read your file. Production can often start within 24 hours, and simple parts ship in 3–5 days. A historical late-delivery probability below 2% is a reasonable benchmark to ask about, but ask how it is tracked.

MOQ is where smaller buyers get filtered out. A shop that runs from one prototype to 10,000+ part runs does not change its process between the two. The setup is the setup. If a supplier quotes a high minimum on a first article, they are pricing risk, not machining.

Certifications should match your industry, not decorate a homepage. ISO 9001:2015 covers general quality management. IATF 16949:2016 applies to automotive and EV work. ISO 13485:2016 is the medical device standard. ISO 27001:2022 covers information security, which matters when your drawings are the product. Ask for the scope statement, not just the logo.

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  Quote and DFM inside 12 hoursA technical reply beats a fast reply with no notes.
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  No minimum order quantityOne piece to 10,000+ with the same fixturing logic.
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  Match the standard to the sectorAuto, medical and general industrial use different certificates.

Two shops can quote the same machined part and land 30 percent apart because one price includes finishing and the other does not. Anodizing, plating, powder coating and black oxide are separate operations with their own lead times. Bead blasting and tumbling change dimensions slightly, so a part that passed inspection before blasting may not pass after.

Laser marking is a good example of a hidden spec. Minimum character height is around 1.5 mm on most systems. If your drawing calls for a 0.5 mm data matrix, say so early and expect a different process.

The practical fix is to list the full route on the RFQ: machining, deburr, finish, marking, final inspection, packaging. Then each supplier quotes the same scope. Without that list, you are comparing different products with the same part number.

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  Name every operationMachining, deburr, finish, mark, inspect, pack.
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  Watch dimension shift after blastingMedia blasting removes material. Tight features need masking.
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  Marking has a size floorMinimum character height around 1.5 mm for laser marking.

A useful quote has four parts: unit price, tooling or setup cost, lead time and assumptions. The assumptions section is the one people skip. It should state the material grade, the tolerance class, the finish, the inspection level and what the price excludes.

Watch for a quote with no assumptions. It usually means the number was built from a weight guess. That number will move once the shop sees the drawing, and the move is rarely downward.

Payment terms, shipping terms and packaging should also be explicit. Ask whether the price is ex-works or delivered, and who handles export documents. These are commercial details, but they decide your landed cost as much as the machining rate does.

Finally, check whether the shop will send a first article inspection report before the full run. On a tight-tolerance part, that report is worth more than a small discount.

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  Demand an assumptions blockMaterial, tolerance, finish, inspection, exclusions.
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  Confirm shipping termsEx-works and delivered prices are not comparable.
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  Ask for the first article reportDimension results before the run continues.