When it comes to prototyping, machining parts out of urethane is the best cost-effective solution. Here are a few tips to help you through the process.
The first factor to put into consideration is the durometer (hardness) of the material. The durometer of the urethane has a significant effect on the machinability of the material. That means, the harder the material, the easier it is to cut. It is also important to note that all elastomers bend and as such move away from the cutting tool.
Another factor is the formulation used. As the formulation of urethane can vary widely, so can its physical properties. When the formulation is created to increase properties such as tensile strength, rebound, and tear strength, the machinability of the urethane is significantly affected. Plan Tech offers unique machining formulations for any form of hardness.
Urethane is an excellent thermal insulator and therefore retains heat as it is machined. If the machining is too aggressive then this can be a problem. To solve this problem you can either use coolant or freeze the part before you begin machining. Grinding is a great option if a smooth finish or close tolerance is what you’re going for. Grinding urethane creates heat on its surface, so the operator is required to allow the part cool before taking measurements.
Holes and countersinks should be molded into the part rather than machined. This is because holes drilled or milled in urethane may leave small cuts and tears which will weaken its tear strength.