Prototype casting with rubber plaster molding

If you're looking for durability and die cast-like results without the expense of hard tooling, prototype casting via rubber plaster molding may be the answer. Alloys of aluminum and zinc can be used with this prototype casting method to a prototype for form, fit and functional testing.

The rubber plaster molding process generally begins with an RP pattern from which a silicone rubber negative mold is made. Urethane is cast into this mold to create a positive part. This urethane part becomes the master from which the final plaster or ceramic mold is made which will be used for metal casting. This extra step to produce a urethane positive of the part is done because the urethane part is more durable for multiple plaster or ceramic castings.

Once the part is removed from the mold, it's ground and buffed to a smooth finish. Secondary operations are also quite common to achieve even finer detail for features such as holes and other critical areas. Complex parting lines typically are not a problem. Using the rubber plaster molding process, we can create metal cast parts seven to ten days.

For best results…

• Part should fit within a 18" x 18" x 6" build envelope, but larger parts can be produced.
• Add shrink to SLA model production to improve the tolerance of cast parts.
• Tolerances are +/- .007" for the first inch and +/- .003" for each subsequent inch.
• Wall thicknesses are typically between .050" to .500".
• Finer or thicker walls can also be achieved.