Urethane casting fills the awkward gap between a handful of printed parts and a steel tool. A master pattern is used to make a silicone mould, and urethane resin is cast into it under vacuum to pull out the air. The result looks and behaves close enough to a moulded part for testing, marketing and small production, at a fraction of the tooling commitment.
How the process works
A master is printed or machined and finished to the surface you want the parts to have, because the silicone copies it exactly. Silicone is poured around the master and cured, then cut open and the master removed. Urethane is mixed, degassed, poured or drawn into the cavity under vacuum, and cured, often with heat. Each cast is a manual operation, which is why price falls slowly with quantity.
What a silicone tool gives you
Typically a few dozen casts before the surface degrades and the dimensions drift, fewer with abrasive fills or aggressive resins. That number, not the price, is usually what decides whether the process fits. For a hundred parts you are buying two or three tools, and that changes the comparison against a cheap aluminium injection tool considerably.
Materials and what they imitate
Urethane systems are formulated to approximate common thermoplastics in stiffness, impact and appearance, and elastomeric grades cover soft parts across a wide hardness range. Optically clear systems exist for lenses and light pipes. What they do not reproduce is long term thermal and chemical performance, so a cast part is a good stand in for testing fit and appearance and a poor one for a lifetime test.
Where it beats the alternatives
When you need tens to low hundreds of parts that look moulded, in a range of colours or hardnesses, faster than a tool can be cut. When overmoulded soft grips or clear parts are needed for a launch. And when the design is still moving, because a new master and a new silicone tool cost far less than modifying steel.
Questions people ask about urethane casting service
How many parts can one silicone mould make?
Commonly a few dozen before the cavity degrades, and fewer with filled or aggressive resins. Plan tools per hundred parts rather than assuming one tool covers the run.
How accurate are cast urethane parts?
Good, because the silicone copies the master faithfully, but shrinkage and tool wear both move dimensions over a run. Treat them as close to moulded rather than as certified.
Can cast parts be overmoulded?
Yes. Two shot casting with a rigid substrate and an elastomeric overlay is routine, and it is one of the strongest reasons to choose the process for a launch run.
How does it compare with a cheap injection tool?
For a few dozen parts casting wins easily. For a few hundred it is close, and above that an aluminium injection tool almost always wins because each cast is manual labour.