CNC Machined Aluminum Enclosures & Housings

What a machined enclosure actually is

Most machined enclosures are a two-piece job: a base that holds the electronics and a lid that closes over it. The base gets milled pockets to clear the board, internal bosses tapped or counterbored for standoffs, bored holes for connectors and cable glands, and a flat sealing face around the rim. The lid carries its own pockets for display windows, buttons, and vents, plus the matching bolt pattern. Because every feature is cut from solid aluminum, walls, ribs, and mounting points go where the model puts them.

That is the difference from a plastic project box you drill out by hand. The connector openings, the standoff heights, and the PCB outline all live in one CAD model, so the print can carry every one of them. Grounding bosses, heat-sink pads, and gasket grooves are features of the part, not afterthoughts.

Machined from solid vs die-cast

Die casting is a process of forcing molten metal under high pressure into a mold cavity, and aluminum is one of the common alloys for it (source 1). Every die-cast surface parallel to the opening direction of the die needs draft so the casting can be ejected (source 1).

A machined enclosure is cut from solid, so there is no die to make before the first part and no draft requirement: walls stay vertical where the design wants them. When the board changes, a revision starts from the new model and a new toolpath. That is the difference to weigh for low-volume electronics enclosures and robotics housings, along with the quantity you need.

Materials, sealing, and finish

6061 aluminum is the usual starting point: it is one of the most common aluminum alloys for general-purpose use and stays resistant to corrosion even when the surface is abraded (source 4). Stainless resists corrosion through a thin passive film of chromium oxide (source 5), and the 316 stainless page covers the grade for chloride exposure. Other alloys and plastics quoted on request. Name the grade on the print.

For a gasket or O-ring seal, the groove and a flat sealing face are machined around the rim to the print. Put the groove width and depth, and the O-ring cross-section or gasket thickness, on the print instead of leaving a guessed slot.

Type II is a sulfuric-acid anodize that takes dye (source 2). The oxide grows into the surface and out from it by equal amounts (source 2), and powder coating can build a much thicker film than liquid paint (source 3), so say on the print whether a cutout dimension applies before or after finish. An anodized surface is insulating (source 2), so a face that must stay bare for grounding is marked on the print, and masking is quoted with the part. A finish called out on the print is quoted with the part.

What to put on the print

Connector and display cutouts are where fit is decided, so tolerance them on the print. Typical machined tolerance is ±0.005 in; tighter cutouts and mating faces are quoted from the print. A note on which face is the datum keeps the base and lid mating true. Position, perpendicularity and runout callouts are quoted from the print.

Spell out standoff and boss callouts: thread size, depth, and whether a threaded insert goes in after machining. If a boss needs a threaded insert, put it on the print; the insert is supplied and installed to the print. Name the wall thickness on the print, and say where a connector will be torqued so the free design review can look at that wall. An enclosure usually needs a bezel, a mounting bracket, or the knobs on its front panel to go with it, which the custom machined parts index covers.

Sources

All accessed 4 October 2026. Where a figure here differs from your print, the print governs.

1. Wikipedia, "Die casting": en.wikipedia.org/wiki/Die_casting (forcing molten metal under high pressure into a mold cavity; aluminium among the common non-ferrous alloys; surfaces parallel to the opening direction of the die require draft for ejection).

2. Wikipedia, "Anodizing": en.wikipedia.org/wiki/Anodizing (the anodic layer is insulative; the oxide grows into and out from the surface by equal amounts; sulfuric acid anodizing produces a porous surface that accepts dyes).

3. Wikipedia, "Powder coating": en.wikipedia.org/wiki/Powder_coating (can produce much thicker coatings than conventional liquid coatings without running or sagging).

4. Wikipedia, "6061 aluminium alloy": en.wikipedia.org/wiki/6061_aluminium_alloy (one of the most common aluminium alloys for general-purpose use; resistant to corrosion even when the surface is abraded).

5. Wikipedia, "Stainless steel": en.wikipedia.org/wiki/Stainless_steel (a thin surface film of chromium oxide; forms a passive film that protects the material and can self-heal when exposed to oxygen).