Investment casting procedure: the processHigh-precision complex castings with thin walls can be manufactured from metal materials with close tolerances using the investment casting procedure. This involves several steps that are all completed in our company foundry. A wax pattern of the required part must first be made for the lost wax process. This pattern is coated in ceramic material to create a mould. The wax is then removed from the resulting negative mould creating a cavity. Molten metal is then poured into the negative mould. The liquid metal fills the cavity, adopting the exact shape of the original pattern. Once the metal has cooled and solidified, the surrounding ceramic shell is removed. The resulting metal part is cleaned of excess material, post-processed if necessary and polished.
Continue reading to find out more: Creating a wax injection mouldThe pattern mould is manufactured according to customer documentation, which can be a drawing and/or 3D model. To make the mould we use state-of-the-art technologies, such as 5-axis machining centres as well as the latest CAD systems. An optimally designed and manufactured mould is the foundation for quality investment castings. Thanks to in-house tooling, we have complete control over the process from the outset.
Building a wax patternFor investment casting, a wax pattern must first be made of each part. Liquid wax is machine-injected into the corresponding mould. Our expert employees then assemble the wax patterns with a central sprue and runner system to form a pattern cluster or “tree”.
Fabricating a casting shellThe “trees” are dipped into a liquid ceramic mass, known as slurry, and then sprinkled with refractory sand. The ceramic dipping process, including the drying time of each individual layer, is repeated several times. This creates a ceramic shell of approx. 7mm in thickness. Now it is time to remove the wax. The shells are placed in a steam autoclave to melt away the wax. Once empty they are fired at 1000°C. At the end of this procedure, the ceramic shells are ready to be used for investment casting. Investment castingThe customised metal alloy is melted in the induction furnace and then poured into the still glowing ceramic shell at approx. 1650 °C. These precise part-specific temperatures ensure that even thin cross-sections can be achieved in investment casting. An extremely high-grade material and surface quality is also obtained. Extracting and separatingAfter the casting metal has cooled down, the ceramic shell is broken off with compressed air hammers. The cast parts are then separated from the “tree”. In the interests of a responsible and sustainable use of resources, we ensure that steel residues from the sprue and runner system are subsequently recycled and reused in the casting process. FinishingAny residual ceramic is removed by sandblasting and pickling in the finishing stage. Our expert employees then remove any remaining sprue protrusions in a grinding operation. Further processingDepending on the customer’s requirements, the investment castings undergo heat treatment and/or further mechanical processing. We offer a variety of surface treatments, including:
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