Speed of part production, easy design modifications, economical low volume manufacture and the ability to incorporate metal inserts were all factors that led design company, PDG to use vacuum casting as the method of choice for producing prototypes and final parts for an aerospace industry project. PDG’s brief was to design a lightweight but robust enclosure for a new portable ultrasonic scanning system used for non destructive testing. A hand held remote was also required to enable operation in small spaces.

The initial challenge was to produce a high quality working prototype in just six weeks to enable the client to demonstrate the unit at an international aerospace exhibition. The anticipated ongoing production volume was around 10 units per year rising to 50. PDG developed a "laptop" style user interface terminal with a special keyboard and employed a bureau to produce the SLA master models for this and the remote unit.

A variety of vacuum casting resins were then used to achieve the various individual component requirements. MCP’s 2160, which is a semi-rigid material with high impact resistance, was used for the main body of the enclosure. MCP 2111, a resin that replicates the appearance and properties of rubber, was used to cast the corner mouldings and the feet, which needed to grip smooth surfaces such as aircraft wings. The key array for the on-screen menu controls was made using MCP 8040, a resin that replicates polypropylene.

Vacuum casting also delivered additional benefits to the project. PDG needed to incorporate around 30 threaded brass inserts into each unit and vacuum casting is the only prototyping method that could achieve this. Furthermore, the castings could be modified easily and inexpensively to incorporate minor design enhancements as the components were developed.

Because PDG made the decision to vacuum cast from the outset of the project, the company was able to design in certain features, which would have been prohibitively expensive to injection mould, for example the large undercut on the top of the remote unit. Injection moulding this part would have required expensive side cores and complicated split lines. A silicone vacuum casting tool can be simply flexed to allow the part to be de-moulded.

At the exhibition, PDG’s client was able to present a working system, which did not look like a prototype and secured orders from several new customers. The unit is now being manufactured commercially using vacuum casting, with each silicone tool expected to produce around 25 identical system components.