Plastics processing with moulds: Vacuum and gravity casting

Vacuum casting: What is it for? How does it work? What does it involve? What are its advantages?

Vacuum casting is a low-pressure injection moulding or vacuum duplication manufacturing process that allows the manufacturing of a customised plastic part in small and medium quantities. Vacuum casting is particularly suitable for the manufacture of a prototype or very small quantities. In plastics processing A very small quantity lays between 1 – 30 pieces per year. The medium run starts at about 5 pieces per year and goes up to 2,000, 5,000 or 10,000 pieces per year, depending on the size, shape and complexity of the part. The large series lay normally above a requirement of 10,000 per year.
Definition :
Vacuum or vacuum casting or bagging is a process for shaping parts made of composite materials by moulding. (Wikipedia) These materials are based on thermosets.

How does the vacuum casting process work in plastics processing?

In contrast to mouldless plastics processing, vacuum casting machines require a mould. This mould makes it possible to produce several parts with the same mould. The mould is made from a master model. This is mainly produced by stereolithography (3D printing) or digital cutting (CNC). The master model is the part to be manufactured.

For example: I want to make a custom-made Tool A.

The Tool A is made in stereolithography (3D printing). The quality of the surface of my mould will depend on the quality of the surface of my master model from Tool A. It is mainly resin that is used for this manufacturing process. Therefore, the post-fabrication treatment is essential when my needs for the aesthetic quality of the parts I wish to manufacture demand it.
We take the Tool A (my master model) and put it in a dedicated holder. The silicone is poured around the Tool A. After drying, we cut the silicone block in two to obtain 2 shells by removing the master model.
We can now start the production of the custom-made parts in vacuum casting. The chosen material will be poured into the silicone mould installed in the vacuum casting machine to make your Tool A in small quantities.
When the piece is dry, depending on your needs, you can add finishing or mounting parts such as inserts, hinges etc.

What are the advantages of vacuum casting compared to the no tooling plastics sheet bending technology?

Vacuum casting allows the manufacture of round parts and gives flexibility in the choice of materials. As the master model is manufactured in 3D printing, there is also a gain in responsiveness.

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