Raspberry Pi Aluminum Alloy Case: Design and Machining Basics

• 1
  Key takeaways
• 2
  What a Raspberry Pi aluminum alloy case actually has to do
• 3
  Wall thickness, standoffs and the tolerance stack
• 4
  How the case moves heat away from the SoC
• 5
  Port cutouts, screw bosses and assembly
• 6
  Surface finish and what it costs you
• 7
  CNC, die casting or sheet metal: which one fits
• 8
  Enclosure process comparison

A Raspberry Pi aluminum alloy case is not a cosmetic shell. It holds a 85 × 56 mm board in a fixed position, keeps every connector reachable, and pulls heat out of a chip that can run near 80 °C under load. Get any of those wrong and the enclosure becomes the problem.

The board itself has two mounting holes on a 58 × 49 mm pattern, and the port cluster sits on two edges. Any enclosure has to respect that geometry. Aluminum gives you stiffness at 1.5–3 mm wall thickness, which plastic cannot match without ribs and extra volume.

We machine these enclosures in 6061-T6 or cast them in ADC12. Both take anodizing well. The choice usually comes down to quantity and how much post-machining the port openings need.

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  Board fitClearance around the PCB edge, typically 0.3–0.5 mm per side.
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  Standoff heightEnough for the tallest bottom-side component plus solder joint.
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  Port accessCutouts aligned to the connector centerline, not the board outline.

Start with the stack, not the drawing. Board thickness on a Raspberry Pi 4 is about 1.6 mm, and the mounting holes are plated. A standoff that is 0.1 mm short lets the board flex when you tighten a screw. A standoff that is 0.1 mm tall leaves the port cluster sitting high in its cutout.

For machined enclosures we hold standoff height at ±0.05 mm and hole position at ±0.05 mm. That leaves room in the stack for board variation, screw seating and coating thickness. If the case gets anodized, add 10–25 μm per surface to your clearance numbers.

A common mistake is designing the lid clearance from the top of the tallest connector. The microSD card and the camera ribbon cable both sit outside that envelope. Measure the real assembly, or leave 1.5 mm of headroom and a slot for the ribbon.

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  Standoff height±0.05 mm on machined parts.
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  Hole position±0.05 mm relative to the enclosure datum.
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  Coating allowanceAdd 10–25 μm per anodized surface.
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  Headroom1.5 mm above the tallest connector or cable.

An aluminum case works as a heat spreader when there is a real path from the chip to the metal. Air gaps kill that path. A thermal pad of 1.0–1.5 mm, compressed about 30 %, gives contact without stressing the board.

Wall thickness matters less than contact area. A 2 mm floor directly under the SoC outperforms a 4 mm wall on the far side of the case. If the enclosure has a lid, tie the lid to the body with a machined lip or a screw boss so heat has somewhere to go.

Vent slots help, but they mostly move air across the board. They do not replace a conduction path. On a passively cooled unit running at 60–70 % load, a metal case with a pad typically holds 10–15 °C lower than the same board in a sealed plastic box.

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  Thermal pad1.0–1.5 mm thick, compressed about 30 %.
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  Contact areaAt least the full footprint of the SoC package.
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  Lid couplingMachined lip or screw boss, not a loose snap fit.

Port cutouts are where most enclosures look cheap. USB, Ethernet and HDMI connectors sit at slightly different heights, and the openings need to clear the plastic overmold on a cable, not just the metal shell. Add 0.5–1.0 mm around the connector body.

We hold cutout position at ±0.10 mm against the mounting datum. That is tight enough that a standard cable seats without scraping, and loose enough to keep the part economical. Chamfer the inside edge 0.3–0.5 mm so the connector does not catch.

Screw bosses need enough thread depth. For M2.5 in aluminum, 4–5 mm of engagement is safe. For M3, 5–6 mm. Do not run a screw into a 1.5 mm wall without a boss; the thread will strip on the second assembly.

If the case is opened often, use threaded inserts or a captured nut. They cost more per unit but survive repeated service far better than tapped aluminum.

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  Cutout clearance0.5–1.0 mm around the connector body.
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  M2.5 engagement4–5 mm of thread depth in aluminum.
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  Edge chamfer0.3–0.5 mm on the inside face.
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  Service accessThreaded inserts if the lid comes off often.

Anodizing is the default for these enclosures. Clear anodize keeps the machined look, and hardcoat adds wear resistance on the edges. Both add thickness, so mask the standoffs and any grounding contact if you need electrical continuity.

Powder coating gives more color options and hides tool marks. It also adds 60–100 μm, which is enough to close a tight port cutout. If the design has 0.5 mm clearance, powder coat is fine. If it has 0.2 mm, use anodize.

Bead blasting before anodizing produces a matte, even surface. Brushing leaves visible lines and shows handling marks sooner. For a case that sits on a desk, bead blast plus clear anodize is the low-risk choice.

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  Clear anodizeKeeps the machined look, adds 10–25 μm.
• 2
  HardcoatBetter edge wear, mask grounding points.
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  Powder coatAdds 60–100 μm; check cutout clearance.
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  Bead blastEven matte surface before anodizing.

CNC is the right answer for prototypes and low volume. A milled 6061-T6 case gives you ±0.005 mm on critical features, no tooling cost, and changes are a program edit. Lead time for a first article is short because there is no mold to cut.

Die casting takes over when volume justifies the tool. ADC12 flows well into thin walls, and the per-part cost drops. The trade-off is draft angle, parting lines and a small amount of post-machining on the port openings and screw bosses.

Sheet metal works for flat, folded enclosures where the board sits on a tray. It is cheap at volume but harder to make rigid without extra bends. For a Raspberry Pi case with tight port alignment, CNC or die casting usually wins.

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  CNC1 to 500 units, no tooling, tight tolerance.
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  Die castingAbove 5,000 units, lower part cost.
• 3
  Sheet metalFlat tray designs, cheap at volume.