posts tagged with the keyword ‘hdpe’



I’m still (slowly) working through using the Little CNC Milling Machine. I (mostly) successfully milled a PCB, but before I did that I managed to grab a piece of HDPE and mill something.


I started with a vector file of one of the Milwaukee Makerspace logos, taking just the (“new style”) helmet and I brought that into MakerCAM to create the cutting paths. I created a pocket for the inside part, and used a profile for the cut to remove the part from the material. Since I was just using one bit I exported both jobs into one file so it could run it all at once, since I didn’t need to change tools.


I then used GrblController to connect to the machine and send the G-code needed to cut the part. I’m still not convinced everything is working as it should be, because either I keep doing the math wrong (possible) or the machine seems to step down farther than I expect it to. More experimentation is needed.


I secure the HDPE piece down to a piece of MDF that is attached to the bed of the machine. The bed is a piece of Aluminum and I’d rather dig into the MDF if I go to deep than carve into the Aluminum. I’m still not totally happy with what I’ve got going on with the bed, but I’ll work on that another time.


Let the milling begin! Again, it seems like the machine was going a bit deeper than I estimated. I’ll have to work on getting the speeds & feeds more dialed in, but that’s pretty much a true statement with every CNC machine & material combo, right?


Here’s our final piece. I made the pocket deep enough that you can actually see some light coming through. Nice! There’s one little bad spot around the outside cut. I should have added tabs to hold the piece down, since it shifted a little when it was finally cut all the way through and the bit took a bite out of the material.


In a way, this is an update to my original HDPE milling experiment, which is fitting, because I used a Shapeoko the first time. Now, when the Shapeoko was first presented on Kickstarter it was presented as a CNC mill that would cost around $300. Well, it ended up casting quite a bit more, but six years later we’ve got the (under) $300 CNC milling machine you can have at home. Yes, the work area is a little small, but we’re going to rectify that in the future.


Recycled HDPE Plastic

It’s the return of HDPE! I was recently at IKEA and grabbed a metal baking pan. I gave up on glass after the last episode, and while people suggested Silicone, I never got around to buying a Silicone pan.

Recycled HDPE Plastic

Now, it’s important to remember this is recycled HDPE, and it’s not virgin material. Also, some foreign matter may get mixed in. The HDPE for this batch came from a few sheets I asked John McGeen to plane for me. He swept up the shreds and bagged it and returned it to me to re-melt. (The sweeping from the floor is probably why some foreign matter gets in.)

Recycled HDPE Plastic

The bottom (the part that was touching the metal pan) shows a bit more of a “burny” look to it, being yellow, and such. That may be the difference between glass and metal. I’ll experiment more to find out.

Recycled HDPE Plastic

Like the other pieces I pressed the hot HDPE between some pieces of wood. Removing the plastic from the metal pan was much easier than the glass pan. You could even consider skipping the pressing and just let it cool in the metal pan. It should shrink a little bit and pop right out.


HDPE Sheet

My most recent HDPE adventure did not turn out well. While I got a nice sized sheet, I managed to slice my finger open and wasn’t sure why, until I investigated more closely…

HDPE, now with glass!

If you can see those shiny pieces, those are pieces of glass. But since I’m personally cutting up all the HDPE scraps and putting them in the oven, where did this glass come from?

Glass, damaged...

Oh yeah, I put it in the oven in a glass baking pan. The HDPE actually tore some layers from the bottom of the pan when I was removing it! The HDPE doesn’t exactly fall out of the pan, and requires some coaxing to come out. I typically pry it out with a screwdriver, then pull it out. (I wear gloves the entire time, as that stuff is HOT!)

Obviously the glass baking pan isn’t ideal for this. I’ve gone back to using the smaller glass loaf pan. I’m hoping the smaller surface area will help prevent this from happening again.

Baked to Hell!

The glass pan is pretty beat anyway, and with pieces missing from the bottom, I guess I’ll just scrap it. (Unless someone wants to melt it down!)



After all of my experiments with recycling various HDPE scraps, I finally got around to milling a piece on the Shapeoko at BAMspace.

Milling on the Shapeoko

The piece I used was close to 0.5″ thick. I added a thin piece of MDF beneath the piece so I wouldn’t chew up our nice looking hold-down surface…


The milling took quite a while. The first attempt with a different piece did not work out well, partly due to too high of feed rate, and partly due to a piece getting stuck after being cut out. (I can see the appeal of a vacuum table!)

GRBL Controller

We use GRBL Controller on one of my old Linux laptops to control the Shapeoko.


Did I mention the milling took a long time? It was about 14 passes at 0.04″ per pass to cut through. I used a 1/8″ bit.


The end results were nice. A little rough, but some sanding and a few hits with a blow touch should clean things up just fine.


Shredded HDPE

Our latest experiment in recycling HDPE into sheets uses material that one of the guys in the shop got from Craigslist. It’s a giant bag of shredded HDPE scrap. It’s all white, and very clean. I think it was used for archery targets or something.

Bag of shreds

Here’s a photo of one of the bags with a one gallon jug on top of it. (We’ve got three of these bags!)

Pan of shreds

I thought this would be the perfect material, and it is good, but it takes a while to melt down. With jugs I could cut them up into small flat pieces and fill the baking pan, but with the shreds it’s mostly a matter of trying to stuff as much as I could into the pan, then heating it until it melted flat, and then adding more. It’s not a fast process.

Flattened sheet

Despite the time involved, the results were good. I may have rushed things a bit, as the, plastic did not seem completely pliable when I put it on the board (aka “The Press”) but I decided to go for it anyway.

The results were ok, but it’s definitely not as smooth (or shiny) on the surface as the last attempt. Getting it the right plasticity is important in this process.

Surface of sheet

The size of this (oval shaped) piece is about 8″ x 7.5″, which should yield a square sheet of 6.5″ x 6.5″. I’ll probably go back to using the larger square glass pan next time instead of the loaf pan.

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