Cast Urethane


In this process there are three steps:

  • A hard plastic prototype of the part is made using one of the many different additive manufacturing techniques like SLA or FDM.
  • A two-part, RTV (room-temperature-vulcanizing) silicone is cast around the hard plastic prototype.  Then the silicone block with the hard plastic prototype in the center is carefully cut into two pieces and the hard plastic prototype is removed.  This becomes the mold, sometimes referred to as “soft-tooling”.
  • A castable urethane is then poured into the silicone tool and allowed to cure.  The urethane part is removed from the silicone tool, yielding a flexible, rubbery prototype identical to the original hard plastic prototype.

Cast Urethane Product Prototyping


  • Excellent abrasion and tear resistance
  • Durometer of actual material can be matched very closely
  • Sometimes this can be made translucent which can be good for display purposes


  • Not the actual material that will be used in production; sometimes can't be trialed in the actual application or operating conditions
  • “Soft Tooling” only yields 5-20 pieces before it fails; the range is dependent on the complexity of the geometry of the part