Vacuum casting metal: the process & its benefits

Release time:2018-09-03
The process

Vacuum casting metal is a flexible and reliable casting process commonly used to generate prototypes and industrial parts. The process requires a high quality master model - this can be the finished industrial part itself, or a model created using stereolithography (generally the case for prototyping applications). Either way, it’s essential that the master model is of perfect quality in terms of both looks and dimensions, so that no flaws are transferred to the prototype/industrial part at the end of the process.

The master model is encapsulated in a two-part silicone rubber mould and cured at a high temperature. Once cured, the mould is cut open, leaving a hollow area at its center which perfectly matches the dimensions of the master model. The mould is now placed in a vacuum chamber and its hollow center is filled with a designated material. For prototyping applications, the material used to fill the mould is usually a polyurethane resin chosen to replicate the specific characteristics of an industrial material, including: high density polyethylene, polycarbonate and glass filled nylon. This resin is often mixed with a metallic powder or colouring pigment in order to achieve certain functional or aesthetic properties.

Once the mould has been filled with resin, it is sealed within the vacuum chamber to prevent any air bubbles from occurring and ruining the final product. Finally, the resin is cured in an oven and the silicone mould is carefully detached so that it can be reused to create additional prototypes/parts from the master model. Once removed, the prototype/part can be painted and decorated as per requirement.

Depending on the requirements of your application, generating parts and prototypes using vacuum casting can have numerous benefits. For aesthetic purposes, vacuum casting offers a very high level of reproduction accuracy and finishing options. The process allows for colouring pigments to be added to the vacuum chamber along with the resin components so that your final part will be an exact colour match with your company’s branding. Certain powders can also be mixed with the resin to give a range of different finishes to your part or prototype, including: gold, bronze, aluminium or even marble. Additional finishes such as these are not as expensive as one would imagine because they are only mixed in to appear on the product’s surface layer.

For functional purposes, resins can be chosen to imbue the part or prototype with certain properties, such as: fire retardation, shock resistance and electrical resistance. Product turnaround is very fast with vacuum casting, which would make it suitable when company objectives require a part or prototype urgently to move forward and not create a bottleneck in the business stream. Vacuum casting would also be a preferable process for creating parts with unusual shapes and small wall thicknesses - other methodologies may struggle to deal with these issues. For short run batches or one-off prototypes, vacuum casting is an economical option, particularly when compared to processes such as plastic injection moulding which incur extensive costs due to tooling.
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