Aluminum CNC Parts Manufacturing

The metal is not one material. The alloy you name on the drawing sets machinability, achievable finish, and how the part behaves after anodizing. 6061-T6 is the default for structural brackets, housings and fixtures because it cuts cleanly, welds, and holds a stable shape after stress relief. For parts that see fatigue cycles, 7075-T6 gives roughly double the yield strength of 6061, but it machines slower and is far less weldable. 2024-T4 cuts well and takes a fine finish, yet its copper content makes it the worst of the three for corrosion resistance unless you anodize or coat it.

Wall thickness matters more than overall size. A 300 mm plate with 12 mm walls is routine. The same plate with 1.5 mm walls will deflect under cutting load and needs light passes, sharp tooling and often a fixture that supports the back side. If your design allows 2.5 mm minimum walls, you keep more suppliers in play and shave cycle time.

Ask one question early: does the part need to be aluminum at all? If the answer is weight, thermal conductivity or non-magnetic behavior, keep it. If it is only cost, a machined aluminum design may still lose to die casting once volumes pass a few thousand pieces per year.

Three-axis work covers flat plates, pockets, slots and drilled holes open to one direction. It is the cheapest path and still holds ±0.005 mm on well-supported features. Most enclosure panels, heat sinks and mounting plates never need more.

A part with features on four sides gains from a fourth axis. Instead of flipping the workpiece and re-datuming, the rotary table indexes the part and keeps one setup. That removes stack-up error between operations. We run 12 four-axis mills and 16 mill-turn centers, which handle shaft-type parts that need turning and cross-drilling in one cycle.

Complex contours, deep angled pockets, impeller-like geometry and undercut faces push you to five-axis. Simultaneous five-axis lets the tool stay normal to a curved surface, so you cut with the side of the cutter instead of the tip. The result is shorter tools, less chatter, and better surface finish on tall features. The tradeoff is programming time. A five-axis program can take several times longer to prove out than the same part in three setups, so it only pays off when the geometry demands it or the volume justifies the setup.

The tolerance callout on a drawing is a limit, not a promise. Aluminum moves with temperature and releases internal stress as you remove material. A thin rib measured right after cutting can shift 0.02 mm once it cools. That is why we rough, semi-finish and finish in separate passes on tight parts, and inspect after the part has settled.

Holes are the usual trouble spot. A reamed Ø6 H7 hole in 6061 is repeatable. The same hole placed 200 mm from the datum, in a wall under 2 mm, will drift. If you can hold a ±0.05 mm position on a long hole pattern instead of ±0.01 mm, you save inspection time and reduce scrap without changing function.

Threads deserve their own note. Aluminum is soft, so fine threads strip easily. For anything that will be assembled and disassembled more than a few times, specify a thread insert or use a coarser pitch. We can cut threads, but on serviceable joints an insert is the better design decision.

Anodizing adds a hard oxide layer and a small dimensional growth, typically a few microns per surface. On a tight bore or a press-fit pin, that growth matters. Tell us the final dimension you need and whether the coating is included in the tolerance. Hardcoat anodizing is thicker and more wear resistant, but it also builds more and can round sharp edges. Clear, color and conductive anodizing are all available.

Bead blasting and tumbling remove tool marks and deburr edges before coating. They also change surface texture, so a part that needs to seal against an O-ring should not be blasted on the sealing face. Laser marking has a minimum character height of 1.5 mm, so plan your part numbers and traceability codes around that limit.