Aluminum Parts Machining: GLC CNC Machining Notes for Engineers

Aluminum is not one material. 6061-T6 is the default for housings, brackets and plates because it welds, anodizes and machines predictably at a moderate price. Its yield strength sits around 276 MPa, which is enough for most enclosures and fixtures.

When stiffness matters more than cost, 7075-T6 is the usual answer. Yield strength reaches roughly 503 MPa, so a thinner wall can carry the same load. The trade-off is machinability: 7075 cuts cleanly but is less forgiving of chatter, and it does not weld.

2024-T4 offers good fatigue resistance for parts that see cyclic loading, though its corrosion resistance is lower and it is normally anodized or painted. 5052 and 5083 show up in sheet-metal work and marine parts. 6082 is common on European drawings and behaves much like 6061.

For die-cast housings that will later be machined, ADC12 is the practical grade. It machines fast but is porous compared with wrought alloys, so do not spec it for pressure-tight or high-fatigue parts. All ten grades above are stocked at our Dongguan plant.

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  6061-T6General purpose, weldable, anodizes well. Best starting point for most parts.
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  7075-T6High strength for thin walls and light weighting. Less weldable, more chatter-prone.
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  2024-T4Fatigue resistance for cyclic loads. Coat it; bare corrosion resistance is low.
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  ADC12Die-cast grade for housings. Expect porosity; not for pressure-tight work.

A three-axis mill cuts from one direction. Prismatic parts with holes, pockets and slots on a few faces run economically on these machines, and we keep 27 of them for that work. The catch is that every new face adds a new setup, and every setup adds a datum shift.

Four-axis machining adds rotation around one axis. A 12-station four-axis mill can cut four sides of a part in a single setup, which is often the cheapest way to hold position tolerance between features on adjacent faces. Shafts, manifolds and long brackets fit this pattern well.

Five-axis simultaneous machining tilts the tool and the part at the same time. Undercuts, compound angles and sculpted surfaces that would need custom fixturing on a three-axis machine can be cut in one pass. We run 16 simultaneous five-axis centers, including a Ø400 mm rotary table for round parts.

Five-axis is not automatically better. For a simple plate with holes on two faces, the programming time and hourly rate make it more expensive than two three-axis setups. Reach for it when geometry, tolerance stack-up or setup count actually demands it.

Aluminum cuts fast, but it also deflects. A 0.5 mm wall on a 100 mm long part will sing and move under tool pressure, no matter how sharp the cutter. Wall thickness of 1.0 mm or more on unsupported sections keeps the part stable and the tolerance real.

Our standard tolerance is ±0.005 mm (±0.0002 in) on critical features, but that number only applies where the drawing asks for it. Chasing ±0.005 mm on every dimension raises the price without adding function. Mark the two or three features that matter and let the rest run to general tolerance.

Deep pockets need clearance for the cutter. A pocket 50 mm deep with a 6 mm corner radius forces a long, thin tool that deflects. Opening the corner radius to 3 mm minimum and keeping depth under four times the tool diameter makes the cut cheaper and more accurate.

Threads, counterbores and tapped holes are all routine. Small features pay attention: laser marking needs a minimum character height of 1.5 mm to stay legible after anodizing. Sharp internal corners are better replaced with a fillet so a standard end mill can reach the floor.

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  Minimum wall1.0 mm unsupported; 0.8 mm is possible if the part is short and stiff.
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  Corner radiusAt least one third of pocket depth, or the tool has to be thin.
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  Tapped holesLeave 0.5 × diameter of full thread at the bottom for a clean tap.
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  Laser marking1.5 mm minimum character height, or the text blurs under coating.

As-machined aluminum lands around Ra 1.6–3.2 μm. A finer pass reaches Ra 0.8–1.6 μm, and polishing or lapping can push to Ra 0.2–0.8 μm on sealing faces and optical mounts. The finish you need should be called out on the drawing, because it directly changes cycle time.

Anodizing is the most common aluminum finish. Clear anodize protects without changing color, color anodize adds a dye, hardcoat builds a thicker oxide for wear surfaces, and conductive anodize keeps electrical paths open. Type and thickness matter: a hardcoat layer grows into the part and shifts tight tolerances.

Other options include electroless nickel for corrosion and solderability, zinc or silver plating for electrical contact, powder coating for outdoor housings, and bead blasting or brushing for a uniform matte look. Each one adds a step, so put it on the drawing only where it serves a function.

Inspection follows the same logic. Every part gets 100% inspection before shipment, with raw material check, in-process monitoring and final inspection. Reports are available on request. Our historical qualification rate is 99.99%, and the late-delivery probability over the same period is below 2%.

Send a STEP file or a 2D drawing and we return a quotation plus free DFM analysis within 12 hours. The DFM note flags thin walls, unreachable corners and tolerances that will not hold, so you can revise before cutting metal rather than after.

There is no minimum order quantity. One prototype and a 10,000-part run go through the same process. Production can start within 24 hours of a released order, and parts ship in 3–5 days for typical aluminum work.

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