Investigation of fibre modified ceramic moulds for investment casting

The incorporation of nylon fibres in a water based silica binder to replace the costly liquid polymer addition in investment casting mould were investigated in this work. Ceramic moulds produced with fiber modified binder were found to be 13% thicker at flat section and 40% thicker at sharp edges and radii than polymer modified system. The firing strength after fiber and polymer burn out was comparable for both systems. The extra shell thickness in the fibre system, especially at edges, gives a higher load bear capacity. This has the advantage of resisting cracking during de-wax and mould wall movement during alloy casting which lead to costly defects. A much higher mould permeability at casting temperature of fibre modified system also proves advantageous to complete mould filling. The unique properties of fibre modified system lead to a promising alternative for the standard investment casting industry.