I use
HPDE for some of my parts. It is a great material, but it is difficult to find at a good price. I have found that a good source for it is plastic cutting boards from stores like Walmart or Target. The problem is the quality and consistency. The thickness can very from store to store. I like at least 3/8" thick, but often settle for thinner.
Some of the translucent white ones tend to be a little stringy when cutting and spirals can get caught on the router bit. This can ruin parts if it rubs and melts. The more opaque white is my favorite, but it is harder to find. It make chips rather than spirals. After not finding any of the white this week, I started searching on line.
I ended up at
cuttingboardcompany.com. They sell commercial sized board 18"x24" for about $25 at 1/2" thick. Also, there is no trough at the edge which is normally just wasted material for me. They sell them in a variety of colors. This helps restaurants segregate food types. I bought 4 sheets of the blue (cooked foods), but was tempted by the red (beef) and yellow (poultry) for the cautionary look for the tube brackets.
I test cut some parts and it cuts like a dream. Pure chips, no spirals. I cut it with a 1/8" 2 flute bit, a cutting speed of 50 inches/minute, plunge of 20 ipm and a depth per pass of 0.13.
Note: The stringy material tended to have most of it's trouble on the plunges. Ramping down into the material helped a little.