HDPE stands for high-density polyethylene. It’s an inexpensive, lightweight, chemical-resistant, food-safe plastic that has a high strength-to-density ratio, which makes it well suited for a vast number of applications. It can be blow molded, injection molded, and extruded. You may recognize it as “#2 plastic” by its recycling symbol.
HDPE is used everywhere in our daily lives: milk jugs, plastic bottles and containers, bottle caps, food-storage containers, plastic bags, the inner lining of TV cables, sewer pipes, swimming pool liners, fuel tanks, toys, landfill liners, 3D printer filament, and even the frame of our milling machine. Many of our community members employ HDPE to make custom fixtures. When you want to make the same thing multiple times, a custom fixture can increase accuracy and significantly reduce the time it takes to attach your material to the bed.
We sell precut pieces of HDPE in our store. They’re the perfect size for many projects and fit nicely on the T-slot bed. You can also order it from various plastic suppliers.
In general, larger tools like ¼”, 1/8", and 1/16" flat end mills are better because they cut through material the fastest and are least likely to break. If you’re making a custom fixture, a 1/4" flat end mill is your best friend. For 3D shapes, a ¼”, 1/8", or 1/16" ball endmill produces the smoothest contours. For best results, keep a set of end mills specifically for HDPE and other plastics, and never use them to cut meta. This will allow for increased milling speeds and a better finish.