1. Urethane Casting And Its Application
Urethane casting, also known as polyurethane casting, is a resin casting production process used
for casting components made from polyurethane materials. The process uses temporary polymer
molds that are produced from a master pattern or part. This type of casting is a popular process
used for the rapid prototyping of components, especially in cases where the production material
is not suitable for rapid prototyping.
Urethane is chosen for this process mainly because it is a cost effective option and offers
material choice for matching the production materials’ mechanical properties. In addition, by
using urethane castings, manufacturers are also able to duplicate their production parts with great
precision. Drift angles and under cuts are easily reproduced due to the flexible nature of the
mold. The molds that are used for the production of the castings are usually made from RTV
(room-temperature vulcanization) silicone.
This prototyping process creates urethane parts with size, form, as well as properties similar to
the production parts. Using this method, manufacturers can economically produce multiple
urethane prototypes of their components, which can be used for various purposes, including sales
and marketing, focus groups, and as early part samples for customers. Apart from these
applications, urethane castings can also be used for testing prototypes. It should be noted that
urethane cast parts are not ideal substitutes for tests where the production materials play a
significant role, such as failure mode testing and life testing of components. However, in many
cases urethane materials those have properties similar to the production material; can be used for
these tests.
The urethane casting process begins with the production of a master pattern or part, from which
the molds and eventually the castings are produced. A number of methods, including
conventional machining, can be used to produce this master pattern. However, the most common
method of producing the master pattern is by stereo lithography (SLA) - an additive production
process that involves using a UV-curable photopolymer resin in combination with a UV laser, to
produce 3D components
Once the master pattern is created to exact specifications, it is suspended in a box or frame with a
gate assembly, and RTV silicone is poured around it so that the pattern is completely encased by
silicone. Colors as well as textures can be precisely replicated on the urethane part. While the
former is facilitated by either adding the dye to the urethane material prior to pouring into the
mold or painting the final part the latter is achieved by including the texturing in the master

2. pattern. An advantage of using dye rather than painting the final urethane casting is that the
colors do not get chipped off easily, as in painted components.
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