Prototype Parts Ltd - UK - Vacuum Casting

Prototype Parts Ltd - UK - Vacuum Casting

Prototype Parts Ltd - UK - Investment Casting

Vacuum casting is a simple method of generating a number of Polyurethane mouldings from an original master model. A master model is generated using either SLA or FDM technology and finished to give a good appearance and to assist with mould removal. The master is suspended in a box with runners & risers attached, after which silicone is poured around it and left to harden. The master is then cut out of the fully cured mould. The re-assembled mould is inserted into a vacuum chamber with both "A" and "B" components of the Polyurethane resin and the air is evacuated (Fig. 1). The "A" & "B" components of the Polyurethane resin are mixed together under vacuum and introduced into the mould cavity (Fig. 2). Atmospheric pressure is then re-applied (Fig. 3). Finally, after a period of time & heat to cure the PU resin, the mould cavity is opened and the cast part removed (Fig. 4).


Fig. 1	Fig. 2	Fig. 3

Once a mould has been made, depending on the geometry of the component and the materials being cast, it is possible to create 20 - 40 mouldings before the mould begins to degrade. Although normally sufficient for prototyping purposes the piece part figure can be a multiple of this when multi-cavity moulds are created. This however increases the mould cost due to increased mastering costs, size of mould and degree of venting & porting required.

Fig. 4