Lost wax moves Lotus forward

The latest development in vacuum-casting technology has solved a tooling problem for Lotus, and saved time and money

Engineers at Lotus Engineering needed a realistic facsimile casting to evaluate the redesigned steering-column bearing housing for the Lotus Esprit, before incurring the high expense of die-cast tooling for production.

Machining housings from solid aluminium was ruled out as they would not possess the best qualities of die-cast aluminium. Instead, the company opted for investment casting using an MCP Equipment vacuum-casting system to produce the requisite lost-wax cores. MCP has introduced an electrically heated cup that enables the computerised machines to vacuum-cast lost-wax cores accurately, rapidly and economically. The cup can be fitted to any MCP system.

A master model of the core was made by stereolithography and used for making a split silicone-rubber mould for the machine. After curing, the mould was placed in the machine’s casting chamber and molten wax was poured into it.

The regulated and monitored vacuum in which the process took place ensured that the molten wax penetrated to every part of the mould before solidifying. The core thus became an exact reproduction of the master model. It was removed from the mould and used as the lost wax, as the housing was investment-cast in aluminium. On completion the housing is heat-treated to adjust the hardness.

According to Lotus the process produced housings so close to specification for dimensional accuracy and physical characteristics that they could be regarded as end-product. They were made for a fraction of the cost and in a third of the time that other methods usually take.

After an initial run of 10 housings, the process was employed for another 35.

MCP Equipment Tel: 01785 815651