Prototype castings are once-off or limited run parts manufactured as prototypes of a design concept using various casting techniques. The prototype parts may be cast in a variety of materials, including metals, liquid urethane, and epoxy resins. Commonly employed casting methods include rubber plaster molds, precision sand casting, and investment casting techniques. Depending on the casting process involved and the type of part in question, some post-production machining may be employed to fully finish the prototype part. Although not strictly a rapid prototyping process, prototype casting is often referred to as such due to the short average turnaround times for the finished parts.
Prototype production is a critical part of any design process. Prototypes give the design team essential, tangible proof of concept feedback, allow unexpected idiosyncrasies and faults to show themselves before production and, in later stages of development, give the investor and the public a look at what they'll be getting for their money. There are several ways that designers can produce prototypes including rapid prototyping, computer numeric control (CNC) machining, and casting. Of these, prototype casting is one of the most attractive methods from both timeline and costing perspectives.
Casting is the process of pouring a liquid polymer or molten metal into a mold where it is left to cool or cure to form a finished product with an external surface mirroring the mold interior. This is an ideal process for the manufacture of prototype parts capable of producing a wide range of sizes, surface detail levels, and finishes. Prototype castings are often also produced quicker and cheaper than those manufactured using other processes. In some cases, a design team can have the finished prototype on their floor inside of two days.
There are several methods used to manufacture prototype castings, each being suitable for a specific range of part types. For instance, designs that include thin walls such as heat sinks would benefit from techniques such as rubber plaster mold casting where a silicone rubber master of the part is used to produce precision plaster molds. Parts with complex geometry, on the other hand, would be made using rapid investment casting methods. Large, thick-walled parts featuring superior surface finishes would best be produced using techniques such as precision sand casting. Materials used in these processes include a range of metal alloys, epoxy resins, and liquid urethane.
In many cases, prototype castings will require some secondary, post-production machining. This process is typically only used to clean up the part in preparation for delivery, though. Although prototype castings are often referred to as rapid prototyping products, the rapid prototyping process is an altogether different technology.