Cast polyurethane can be readily turned, sawed, drilled, ground or milled.
These and other secondary operations present many similarities to the
machining of metal, but there are also some important differences. This
following information is intended to provide some general guidelines for
machining urethanes. See our complete guide to machining cast polyurethane here.
It is important to note that the material presented here is a starting point.
The wide variety of urethane compounds and their respective physical
properties and characteristics create a wide range of machining situations.
Harder urethanes – 90 Shore A and up – have a high degree of
machinability. Lathe turning, flycutting, grinding, contouring and milling are
more easily accomplished on conventional metalworking equipment by
machinists who are familiar with procedures for handling plastics.
Some different tools and techniques are required for compounds of 80 Shore
A durometer and lower. These lower modulus compounds are typically
machined by knifing, grinding, and sanding. In some cases, however, they
can be worked like higher modulus materials by “freezing” them in dry ice or
liquid nitrogen environments.
Ultimate dimensions can be affected by temperature and humidity.
Polyurethane will show small changes in dimensions when subjected to high
humidity and/or high temperatures. Machined parts should be stored at
ambient temperatures and 50% relative humidity.