Casting Study: Housing and Base Plate

Originally the housing and base plate frame were sand cast aluminium and finish machined. Machining and assembly time took 3.5 hours per unit. During a redesign, the company set about to reduce costs without sacrificing quality or performance. This led to graphite permanent mould and ZA-12 alloy. Graphite permanent moulding substantially reduces operations by limiting machining to a boring operation, hole drilling and the tapping of one hole. ZA-12’s excellent bearing properties eliminate the need for seven oil impregnated bearings required in the sand-cast aluminium model. Assembly time is also reduced through the use of interchangeable parts and the elimination of multiple handling. The ZA-12 components re produced with +/-0.005 in. tolerance and are completely interchangeable, while the aluminium model had to be machined in matched sets. Graphite moulds permit the indicators to be designed with more appealing style lines and ZA-12’s greater density than aluminium contributes to an increased perception of quality and durability. The cumulative effect of the various cost savings produced by the switch to graphite permanent mould has enabled Mission Industries to hold prices for over four years and maintain its position and profitability in the face of continuous competition.