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Category: investment casting

What Is Lost Foam Casting and How Does It Compare to Lost Wax Casting?

Lost foam casting, also known as evaporative pattern casting, is a metal casting process where a foam pattern is used to create a mould for the final component. Foam beads are injected into the manufactured tooling and are then expanded using steam pressure. The foam pattern is coated with a refractory material, placed into a box or flask, and is then surrounded with unbonded sand.  Molten metal is then poured into the mould, evaporating the carbon foam pattern. The metal cools, leaving behind the desired casting.


  • Surface Finish: Lost foam casting typically results in a rougher surface finish compared to investment casting. The foam pattern can leave behind imperfections or texture on the final casting, typically due to residual polystyrene and/or gas that has been unable to permeate from the mould.


  • Dimensional Accuracy: Achieving tight dimensional tolerances can be more difficult with lost foam casting. The evaporation of moisture from foam pattern during the curing process can cause distortion or impact on the dimensional stability of the final part, leading to less precise results compared to investment casting. Due to the high moisture content in the polystyrene, controlled storage and curing of the pattern is extremely important. Wax patterns are typically more stable and do not need any special curing or storage considerations.


  • Tooling Complexity: Lost foam casting requires specialised tooling and machinery to create the foam patterns. The complexity of the tooling can make the process more time-consuming and is very costly when compared to the cost of tooling for investment casting wax patterns.


  • Environmental Implications: Due to the Styrene content in the foam, the evaporation of the product during casting inevitably produces harmful gases which can be toxic to the environment and health. With the Lost Wax casting process, the wax patterns are melted out of the mould in a controlled environment prior to casting. The wax itself is recycled which further reduces the impact on the environment.


Similarly with Lost Wax Casting, Lost Foam Casting offers great advantages, such as the ability to produce complex shapes, reduced need for machining, and the elimination of parting lines. The choice between Lost Foam Casting and Lost Wax / Investment Casting depends on factors such as part complexity, part quantities, material selection, surface finish requirements, and tooling cost considerations.


If you would like to chat with one of our specialists about investment casting, please call 0116 276 7284.