Ever tried to machine UHMW? It’s no easy task given the material’s instability. In fact, UHMW has 12x the expansion rate of steel. Controlling heat with the right coolant and tools is critical. Let’s review some techniques:
Ultra High Molecular Weight (UHMW) polyethylene is a semi-crystalline polymer that offers good abrasion and impact resistance plus a low coefficient of friction. It’s flexible enough to excel in both wet and dry environments with good wear and service life. These are the pluses.
But one of the negatives that we often hear about is that the material is incredibly hard to machine; particularly for those shops who are new to plastics. Yet machining is a must, since the material is impossible to mold. Like all polyethylenes, UHMW has a low melting point (270°) and a high COF (120 x10” IN/IN/ÜF), which all contribute to the challenge.
Limit heat!
For best results, it’s critical to reduce heat buildup, since the very act of machining generates friction, and thus, heat. An accumulation of heat presents dimensional challenges where your cutting tool can instead become a “melting tool.” To avoid this challenge, consider these techniques:
Drilling:
Milling and Cutting:
Sawing:
Speeds and feeds:
Coolants:
Without the right heat levels, you risk an uneven surface finish and an accumulation of plastic debris (burrs). For more UHMW machining techniques, get the Guide to Machining and Custom Fabrication!