Two Possible Materials for Casing

Two possible materials for the casing would be

a. Polypropylene or

b. An aluminium 1/3 per cent silicon-casting alloy (LM6).

Conclusions

 (i) Polypropylene is a relatively strong and tough thermoplastic of low cost, which can be formed into complex shapes easily by injection moulding. It is electrically insulating and of low density. Casings could be produced in large quantity by injection moulding. The separate parts of the casing could be assembled by means of 'clip-fit' assembly or the use of setscrews or a combination of both methods.

(ii) Aluminium alloy LM6 is an excellent die-casting alloy, which can give strong precision castings of simple or intricate shape. The low density of aluminium will give a lightweight product at comparatively low cost (though more expensive than the polypropylene alternative). The method of manufacture would be pressure die-casting for large quantity production.

Either material would be suitable but polypropylene would give the lower cost. Aluminium will give a more robust product and would be better for heavy duty industrial tools while polypropylene is more suited for the domestic market.