Housings and covers

What characterises the part

A housing is a shell with functions hung on the inside. The shell must be thin and even. The functions — screw bosses, ribs, cable entries, locating pins, gasket grooves — must be anchored in the shell without creating local accumulations of metal.

That conflict decides whether the housing turns out well. Where a screw boss meets a wall, the section suddenly doubles in thickness. That is where the metal solidifies last, and that is where you get shrinkage porosity. The fix is to core out the boss from the back and tie it into the wall with a rib instead of blending it into a lump.

Why casting is right here

• Thin walls and integrated features in one operation. An injection moulded plastic housing can do this too, but gives no EMC shielding, no heat conduction and no fire resistance.
• Dimensional stability. Two halves that meet along a sealing face must hold the same dimensions in every single part. The tool delivers that.
• Metal conducts heat out. Electronics that generate heat can shed it through the housing instead of needing a fan.
• Metal is a Faraday cage. A continuous metal housing shields against electromagnetic interference. A plastic housing has to be metallised to achieve the same.
• Mass can be a function. In audio equipment, weight damps unwanted vibration. Then zinc is the right choice, not a compromise.

When casting is not right here

• The housing is a straight prismatic box in low volume. Press-braked sheet and a couple of welds is cheaper.
• The housing is long with a constant cross section. An extruded profile with end caps is cheaper and lighter.
• There are no EMC, thermal, fire or stiffness requirements and weight must come down. Plastic is right.
• The housing must be transparent or electrically insulating. Metal does not solve that.

Zinc or aluminium for a housing

Zinc gives finer detail, thinner walls, better dimensional accuracy and a surface that is often finished straight from the tool. The tool also lasts considerably longer, because zinc is cast around 380–390 degrees against 680–700 for aluminium. For a customer who owns the tool, that is a direct commercial argument.

Aluminium gives lower weight and better thermal conductivity. If the housing is load-bearing, or sits in something that has to be lifted, aluminium is usually right.

Specific thermal conductivity and tensile figures per alloy are provided on request — we do not publish numbers we have not verified against the alloys we actually run.