The refractory mould for centrifugal casting is ttypically much smaller and more compact when compared to vacuum casting moulds - most centrifugal moulds contain just a single wax pattern impression. The mould flask for this process is removed from the burnout kiln using tongs, then placed directly into a clamping mechanism at one extreme of a rotating centrifuge arm (the arm may be fixed either to a vertical, horizontal or inclined axis of rotation). A carefully measured out charge is then melted in a crucible adjacent to the mould. Applied heat for melting the charge is usually from an OXY-GAS flame, this being sufficient to melt the small quantities of alloy normally used to fill this type of mould.
Once the charge has been melted, the crucible outlet is aligned with the BUTTON (small cup) inlet to the refractory mould and the safety cage on the centrifuge secured. Simple centrifuges are spring-loaded, after PRIMING the wound mechanism can be released to revolve the arm at speed to force metal into the furthest reaches of the mould's cavity. Alternative centrifuge mechanisms are either hand or motor operated, some advanced machines may also include an integrated melting system.
The sophistication and expense of acquiring all these special casting processes can vary considerably – inevitably the level of financial investment by the foundry in purchasing tooling and quality materials is ultimately reflected in the cost charged per cast.
Using an oxy/gas torch to melt a small
bronze chage in a centrifuge. Note counter
weight to the right of the torch.
(cc ANPP/Crucible Foundry).
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