Loast Foam Casting
The lost foam casting process consists of first making a foam pattern having the shape of the finished metal part. The foam patterns are created from polystyrene beads, similar in size and shaped to sand granules, expanded to the desired shape using aluminium tooling. More complex shapes can be created by gluing a number of patterns together. The assemblies are then attached to a central foam piece or tree.
After short stabilising period, the completed pattern is strengthened by dipping in a refractory material which coats the foam pattern leaving a thin heat-resistant layer which is then air dried. This ceramic coating also provides good surface finish for the finished casting.
After compaction, molten material is poured into the mould causing the foam to burn up and vaporise as the molten metal replaces the foam pattern, exactly duplicating all the features of the original pattern.
After solidification, the container is tipped over and the unbounded sand flows out together with the castings. Because there are no binders or other additives the sand is reclaimable.
Workshop Processes, Practices and Materials - pg 286
No comments:
Post a Comment