Aluminum CNC Machining in China — Milling, Turning and Anodized Alloy Parts

CNC machining removes material under program control, so complex pockets, bores, and contoured surfaces repeat from the first piece to production lots. Aluminum’s high machinability usually allows productive feeds and speeds when tooling and coolant are matched to the alloy—making CNC a practical path for brackets, housings, heat sinks, and structural parts where drawings define critical dimensions and finishes.

6061-T6 is a common general-purpose choice: good strength, corrosion resistance, and weldability for many brackets and frames. 7075-T6 offers higher strength for weight-sensitive structures but is less forgiving for certain welding scenarios—often seen in performance hardware. 5052 is work-hardened, non-heat-treatable sheet/plate material with excellent corrosion resistance and formability—common in marine and chemical environments. 2024 is high strength with fatigue resistance in some aircraft-style applications but is more corrosion-sensitive without protection. We align grade to your environment, loads, and finishing plan.

Generally yes, and there is a number behind it. Specific cutting force—the force needed to remove one square millimetre of chip cross-section—is about 700 N/mm² for non-heat-treatable wrought aluminum and about 800 N/mm² for heat-treatable grades such as 6061, 7075 and 2024, against roughly 1,350 to 1,525 N/mm² for annealed plain carbon steel and about 2,450 N/mm² for annealed high-alloy and tool steel. Lower force means lower power and higher removal rates, so aluminum is usually more productive per spindle hour. “Easy” does not mean careless: soft alloys weld to the tool as built-up edge at low cutting speeds, produce long stringy chips, and move thermally during long cycles. The commercial point is that tolerance band and finishing scope move a price more than the alloy does.

Our standard machining tolerance is ±0.05 mm, and for suitable features we hold a precision tolerance of ±0.01 mm. Which one applies depends on part stiffness, feature accessibility, and whether a relationship has to hold across setups—not on aluminum alone—so we quote tolerance bands against the actual geometry rather than publishing one number for everything. Dimensions the drawing leaves unmarked are usually covered by a general tolerance class from ISO 2768-1, in classes f, m, c or v; mark the class in or near your title block and every unmarked dimension becomes a defined, inspectable requirement. ISO 2768-2 does the same job for geometry in classes H, K and L. Call out critical dimensions and datums so inspection matches how you approve parts.

Yes, subject to your specification. Decorative and hard anodize, conversion coatings, passivation for compatible alloys, powder coating, bead blast, and film-adhesive prep are common follow-ons. We coordinate cosmetic stock, edge breaks, and racking-friendly geometry so secondary processing does not undo machined dimensions.

Send a solid model (STEP, STP, IGES, or X_T) plus a PDF or DWG drawing when you have GD&T, threads, surface finish, or notes not fully captured in the solid. Include alloy and temper, quantity, finishing scope, and any inspection or material certification requirements so the quote covers the same scope as production.

Prototype and low-volume runs absorb more engineering and setup per piece; higher volumes amortize fixturing and programming across more units. Material grade, tolerance bands, and finishing also move price more than alloy choice alone. We quote setup, cycle risk, and inspection explicitly so the unit economics match your stage—prototype, bridge, or recurring production.

Standard lead time on aluminum CNC work is 10 to 15 days. The fastest we quote is 7 days, for a mini order, and that assumes the alloy is on hand, the programming is straightforward and the finishing scope is simple. Where a part sits inside that range depends on material availability, programming complexity, finishing scope and inspection level. First articles usually move in the shorter part of the window once alloy, tooling and gauging are agreed. You receive a confirmed date during quoting rather than an open-ended promise after the PO is placed.

Yes—shafts, bushings, spindles, and other round aluminum features run on our turning centers alongside milled work, with lathe-and-mill sequencing planned in the same setup when a part needs both. Turned aluminum is checked with CMM and video measuring equipment against your drawing's critical diameters, concentricity, and length callouts, with dimensional records available when your order specifies them.

CNC milling within 3000 mm long, and CNC turning within 400 mm diameter. Fitting the envelope is the first question rather than the last one, though: at that size the constraints that decide whether a part is quotable are how rigidly it can be held, how many setups the features force, and whether the datum scheme survives being re-fixtured. Choosing as datums the surfaces actually used to hold the part in manufacture ties the inspection result to the process that produced it, which matters far more on a large plate than on a small housing. Note also that a general tolerance class gets looser with size—over 1000 mm, ISO 2768-m already permits ±1.2 mm—so features needing better than that at those lengths have to be individually toleranced.

Yes, and it is the anodizing question that costs buyers the most money. Roughly half of an anodic coating grows into the part and half stands proud of it, so dimensional build-up is about half the coating thickness. A 2 mil (0.002 inch) hardcoat penetrates 0.001 inch and protrudes 0.001 inch, so a 1.000 inch diameter machined feature finishes at 1.002 inch. All machining is completed before anodizing, so on close-tolerance features that allowance is planned into the programmed size in advance. Hard anodize (MIL-A-8625 Type III) also needs an edge radius—approximately 1/16 inch for a 0.002 inch coating—so a hard-anodized part drawn with sharp corners will not come back the way it was drawn. Tell us the type, class and thickness at RFQ and the machining allowance is built in.

The honest answer is that it is set by the geometry rather than by a single number, and the mechanism is worth understanding before you commit the design. Machining leaves residual stress in the surface, and residual stress causes distortion in thin-walled work—a long-standing problem in airframe structure for exactly this reason. With a sharp tool those stresses do not usually reach deeper than about 50 micrometres below the surface; with a worn tool they can reach five to ten times that depth, which is why tooling gets changed on a schedule rather than when the finish starts to look wrong. Plate stock also carries locked-in stress from the mill, which is what the stress-relieved tempers such as T651 and T7351 exist for. Send the model with the height-to-thickness ratios you need and we will tell you what is realistic before anything is programmed.

Yes, and the silicon content is what changes the plan. Cast alloys at or below about 12% silicon behave close to wrought aluminum and take fine-grain uncoated carbide happily below roughly 7 to 8% silicon. Above 12% silicon the alloys are hypereutectic, sit in their own ISO 513 material group, and generally want PCD-tipped tooling with a lower speed and a heavier feed. Cast surfaces and any porosity are a conversation to have on the drawing before the first cut rather than a surprise at inspection, so send the casting specification along with the model and the machining drawing.

Our certified scope is ISO 9001:2015 for quality management, ISO 14001 for environmental management, ISO 13485 for medical device quality management, and IATF 16949 for automotive quality management. Certificates are available on request at order entry, alongside material certificates and traceability when your incoming inspection requires them. If your programme needs a certification outside that list, tell us at RFQ and we will say plainly whether we hold it rather than let a scope gap surface at audit.