Machining metal and plastics are similar some aspects, but each have unique properties where it differs. In Part 1 of our guide to machining cast polyurethane elastomers, we look at 4 machining techniques: sawing, turning, facing, and boring:
Sawing: We’ll most often use a band saw for cutting urethane because the long blades run cooler, and help prevent melting of the plastic. Most projects use a four-tooth per inch blade, but for finer finishes we’ll use a 10-tooth per inch blade. To further prevent burning or melting of the urethane, we spray a mist of water soluble oil on the surface.
Turning: Based on the hardness of the urethane, we adjust the cutting speed (from 330 – 1650 ft/minute), feed (from 0.004 – 0.008 in/sec), tool shape (12, 53, 25), and surface roughness (10 – 50 microinches).
Facing: When cutting thin, facing board parts, we use a very acute blade (~15 degrees included in angle). Cooling is also incorporated to the process due to the friction.
Boring: Normal cutting is done at speeds of 130 – 170 ft/min and slow feeds (0.0004 – 0.0012 in/min) with faster speeds being used for harder material. Holes at depths less than one inch can be made without coolant, and hole diameters will be up to 4% less than drill diameter for materials under 80 Shore A.
We invite you to contact us about your cast polyurethane machining needs to learn more about the processes involved in fabricating your designs.