Aluminum Die Casting Wall Thickness Rules

Wall thickness controls how metal fills the cavity, how fast the part solidifies and where shrinkage porosity can form. A wall that is too thin may not fill before the metal freezes; a wall that is too thick holds heat and cools unevenly.

In production the effect is visible in cycle time, scrap rate and the machining cost needed to hold critical features. Wall design is therefore a commercial decision as much as a geometry decision.

• Thin walls need higher filling pressure and better venting
• Thick sections cool slowly and can pull shrinkage porosity
• Uneven walls create hot spots and distortion
• Wall design changes usually require a tooling change

For aluminum die casting, general housings and covers commonly use walls between 1.5 mm and 3.0 mm. Small parts with short flow lengths can use thinner walls when the gate, venting and process window are planned for it.

Structural parts and load-bearing housings often sit between 2.5 mm and 4.0 mm. The number should always be confirmed against the flow length, alloy and functional requirement rather than copied from a table.

• 1.5–2.0 mm: small covers and electronic housings
• 2.0–3.0 mm: general housings and enclosures
• 2.5–4.0 mm: structural brackets and load paths
• Confirm the value against flow length and alloy

Abrupt thickness changes create hot spots. Use gradual transitions with generous radii so metal can flow and the part can cool at a similar rate across the section.

Ribs should normally be thinner than the main wall, often around 50–70% of wall thickness, with a radius at the base. Bosses should be supported by ribs or a local pad rather than standing as isolated thick sections.

• Add radii at internal and external corners
• Keep ribs at about 50–70% of wall thickness
• Support bosses with ribs or a pad
• Avoid isolated thick sections

Where a face will be machined, add enough stock to remove casting skin and any local distortion. A common starting range is 0.3–0.8 mm on machined surfaces, confirmed against the drawing and process capability.

Machining stock should be planned together with the datum strategy, because the casting datum and the machining datum decide whether bores, faces and sealing surfaces stay aligned in production.

• Plan 0.3–0.8 mm stock on machined faces
• Define the casting datum before tooling
• Keep critical features on the same datum chain
• Confirm the values during DFM review