HDPE Brownies

I’m calling these “HDPE Brownies” because I find it slightly amusing. Here’s what’s going on: I’m taking HDPE scrap and putting it in an 8″x8″ glass baking pan (a brownie pan) and popping it in the toaster over at about 270° F for a bit, them smashing it down and repeating the process.

So why am I doing this? Well, at the museum we sometimes mill sheets of HDPE for exhibits, and it creates a lot of chips/sawdust, and I gathered it up remembering that I’ve seem some people heat up HDPE and press it into a mold. Oh, and check out this video for lots more info on melting HDPE.

Once I got a full pan I took it out and cut off the sloped sides on the band saw to create a (mostly) squared-off slab. There are some air bubbles and what not, but for a first attempt, it’s pretty good. And what am I going to do with this stuff? I’d like to mill it using a CNC machine, probably a Shapeoko2 to start with. The HDPE cuts well, and shapes well, similar to working with wood. You can sand it, and whittle it too.

The white you see is from milk jugs and cat litter jugs, and the yellow and blue are from laundry soap jugs. All the black and pinkish-red are the sawdust bits from the milling of HDPE slabs we purchased. I think the sawdust bits caused more air bubbles than the cut up jugs, but more experimentation is needed.

Besides milling this piece, my plan is to keep collecting HDPE by gathering old jugs and cutting them up and making more blocks. Just making more of these should help me refine the process and work out the bugs, or the bubbles, as it were.