China Aluminum CNC Processing: A Complete Guide

Most aluminum parts we machine in Dongguan fall into two families: 6061 and 7075. The 6061 grades (6061, 6061-T6, 6082, 6063) cut cleanly, weld well, anodize to a consistent color, and hold tight tolerances without much fuss. If your part is a housing, bracket, manifold, or fixture plate and nobody has specified otherwise, start with 6061-T6.

The 7075 grades are noticeably stronger and machine to a better surface finish, but they cost more and they do not anodize as evenly. Use 7075 when the part carries load or sees fatigue. For 2024, expect better strength than 6061 with worse corrosion resistance; it is common in aerospace work where the part gets a protective finish anyway.

For enclosures and panels that need corrosion resistance more than strength, 5052 and 5083 are the practical picks. They bend well and resist salt water. Casting alloys such as ADC12 belong to die casting, not to machining from plate, so do not mix the two when you write a drawing.

One more decision matters early: plate thickness. A part machined from 20 mm plate behaves differently from the same part cut from 60 mm stock. Thicker stock means more material removed, more internal stress released, and a higher chance of movement after machining. We plan roughing and finishing passes around that.

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  6061-T6General purpose. Good finish, good anodizing, stable dimensions.
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  7075High strength, best finish. Higher cost, uneven anodizing color.
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  2024Aerospace strength. Needs a protective finish for corrosion.
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  5052 / 5083Corrosion resistance and formability, lower strength.

Aluminum has a low melting point and high thermal conductivity, so the heat from cutting leaves the chip and enters the tool and the part instead of staying at the edge. That sounds helpful. In practice it makes aluminum sticky. A sharp tool with the wrong rake angle will weld chips to the cutting edge, and the next revolution tears the surface.

The common failure mode is a built-up edge. You see it as smeared, torn pockets and a finish that looks worse after the finishing pass than before it. The fix is not slower feed rates. It is higher cutting speed, a polished flute, and enough coolant or air blast to clear chips before they recut.

Thin walls are the second problem. Aluminum deflects under cutting force, and a 1.5 mm wall will move away from the tool, then spring back and get cut oversize. We rough leaving even stock, then take light finishing passes with reduced radial engagement. On tall thin ribs we sometimes add a temporary support web that comes off in a later operation.

Heat-treated grades such as 7075 and 2024 also release stress when you remove material. A part that measures within tolerance off the machine can move overnight. For tight work we rough, stress relieve or rest, then finish. That sequencing is planned at the quoting stage, not after the first inspection.

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  Sharp, polished toolsPrevents built-up edge and smeared surfaces.
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  High speed, light engagementBetter than slow, heavy cuts on aluminum.
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  Chip evacuationAir blast or through-spindle coolant keeps chips out.
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  Rough, rest, finishControls movement on 7075 and 2024 parts.

Our standard working tolerance on aluminum is ±0.005 mm (±0.0002 in) on critical features. That does not mean every dimension on a drawing should carry it. Tight tolerances on a non-functional edge add inspection time and cost without changing how the part works. Mark the features that matter and leave the rest general.

Surface finish follows the same logic. As-machined aluminum sits around Ra 1.6–3.2 μm, which is fine for brackets and internal faces. Sealing surfaces and bearing bores usually need Ra 0.8–1.6 μm, and optical or sealing-critical faces can reach Ra 0.2–0.8 μm with additional operations. Tell us which face is which.

Anodizing changes dimensions. A hardcoat layer grows both outward and inward, and threads and bores shrink. If a bore must stay within tolerance after hardcoat, mask it or leave stock and machine after coating. We flag this during DFM review rather than discovering it at assembly.

Cosmetic aluminum is its own category. Clear anodizing shows every tool mark and every alloy inconsistency, so a housing that looks fine bare can look blotchy after coating. For visible parts we adjust the finishing pass and, where needed, specify bead blasting before anodizing to give the surface a uniform matte base.

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  General dimensionsLeave at general tolerance unless function requires more.
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  Sealing facesSpecify Ra 0.8–1.6 μm and say why.
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  HardcoatMask bores and threads or plan a post-coat cut.
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  Visible partsBead blast before anodizing for even color.

Aluminum CNC processing in China is competitive on price because of machine density, tooling supply, and a deep pool of operators. Those same conditions make the market uneven. Two suppliers can quote the same drawing at very different prices and both be telling the truth. The difference is usually scrap rate, inspection depth, and how much engineering time they put into the job.

Ask what inspection happens and when. A supplier that checks parts only at final inspection will ship a bad lot and argue about it later. We check incoming material, monitor during the run, and inspect 100% before shipment, with reports available on request. If a supplier cannot describe their in-process checks in one sentence, that is a signal.

Ask how they handle the first article. A machined prototype that measures well on the CMM is the cheapest insurance you can buy. After that, the production setup should mirror the prototype setup. If the supplier plans to move the job to a different machine for volume, ask for a first-article report from that machine too.

Certifications tell you what systems are in place. Depending on your industry, look for ISO 9001:2015 for general quality management, IATF 16949:2016 for automotive, ISO 13485:2016 for medical devices, and ISO 27001:2022 if your drawings and CAD data need information security controls. We hold all four.

Finally, protect your design. Uploads go through a secure channel and an NDA is available on request. If a supplier is vague about who inside the company can see your files, that is worth a follow-up question before you send anything.

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  Inspection planMaterial, in-process, and final checks named in writing.
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  First articleCMM report from the machine that will run production.
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  CertificatesMatch the certificate to your industry, not to the brochure.
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  NDA and dataAsk who can access your files and how they are stored.

Quotation and free DFM analysis come back within 12 hours for most drawings. DFM at this stage is not a form letter. We look at wall thickness, tool reach, thread depth, tolerance stack-up, and whether a feature needs a 5-axis setup or can be done in three operations. That review often removes cost before the first chip is cut.

Production can start within 24 hours of approval, and parts ship in 3–5 days for typical quantities. We run 127 high-precision CNC machines, including 16 simultaneous 5-axis machining centers, 12 four-axis mills, 27 three-axis machines, and 16 mill-turn centers. Maximum processing size is 4,000 mm, and the largest travel is 4,000 × 400 × 150 mm.

There is no minimum order quantity. A single prototype and a 10,000-part run go through the same quoting process. That matters when you are still iterating: you can test one aluminum bracket before committing to a batch.

If your program is schedule-driven, tell us the date the parts need to be at your dock, not the date you want them shipped. Freight and customs add days that are not visible in a machining schedule.

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  12 hoursQuote and DFM analysis.
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  24 hoursProduction start after approval.
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  3–5 daysTypical shipment window.
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  4,000 mmMaximum processing size.