Cast Urethane, RTV Molding and Polyurethanes refers to a low volume production method that produces parts from cast urethane plastic material for prototyping purposes.
From product development models and prototypes for short run products and clinical builds, to fit and function test prototypes and even low-volume production runs, this rapid prototyping process allows us to produce parts that accurately mimic the color, texture, feel and physical properties of injection molded parts. One of the greatest benefits of the Cast Urethane process is the ability to over-mold existing parts or hardware with a second material. Cast Urethane works great for pre-production runs, marketing samples, test prototypes and low-volume manufacturing.
The Cast Urethane process begins with a stereolithography (SLA) rapid prototype master pattern. Machined and/or fabricated master patterns can also be used for tighter tolerances. The SLA RP model is inspected for accuracy then the “appearance” surfaces are bead blasted, sanded smooth, and a primer coat is applied to achieve the surface finish required to meet your application requirements. If the parts are to be polished or cast in clear resin then the surface will be polished to a gloss finish in preparation for making the silicone rubber mold.
Next the mold is created. The silicone rubber uses a room temperature vulcanization process typically referred to as RTV. The part is carefully scrutinized by one of our technicians to determine the best molding setup to achieve the highest quality urethane casting reproduction. Parting lines are selected to assure best location thus avoiding flash on appearance surfaces. Rubber mold runners, gates, sprues and vents are located in areas to optimize mold fill, isolate and minimize air bubbles to non-critical areas, and optimize appearance surface quality.
The SLA rapid prototype master is set-up on a parting block to make a two (or many) part mold or suspended in a frame to make a one-part cut mold. Silicone is poured around the SLA master pattern to create the mold. After the silicone is fully cured (approximately one day), the master pattern is removed and the mold is reassembled, whereupon the Cast Urethane material is poured into the mold to create the cast urethane part.