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HDPE Shreds

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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HDPE Sheet Cake

HDPE

In our last experiment recycling HDPE into usable form, we created a brownie pan full of plastic. While this looked impressive, it wasn’t the best idea for something that was going to be milled. It ended up being much thicker than needed, and finding a cutting bit with the proper LOC (Length of Cut) proved to be an issue. I was all set to mill a thicker piece, but we blew a fuse on the Shapeoko.

HDPE

I decided that I needed sheet material of a uniform thickness, so I ended up creating a simple press using two pieces of wood, with some spacers. Once I warmed up the HDPE block I got it out of the pan, onto the wood, and stood on it until it was squished flat(ish.) I then put some weights on it until it cooled.

HDPE

It turned out well! It’s a pretty uniform thickness now, and this was just under 1/3rd of a bread loaf pan, so I may need a bigger press if I want to do bigger melts. I can also make different presses with different thicknesses as well.

HDPE

Funky!

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Laser Pointer Switch

Laser Pointer Switch

I modeled a laser pointer switch which you can use with your cheap laser pointer to turn it on and do stupid things like throw it in the air while doing long exposure photography. (Actually, that’s not a bad idea! Or is it?)

Laser Pointer Switch

OK, these are really part of the Laser Maze we’ll be running at Maker Faire Milwaukee this year. The last thing I did for Laser Maze was the mounts, but Vishal is still doing most of the hard work on this project. (Thanks, Vishal!)

Laser Pointer Switch

If you want one, you can grab it from Thingiverse or Youmagine. And remember kids, laser are dangerous, don’t just go pointing those things around!

Laser Pointer Switch

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HDPE Brownies

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.

HDPE Slab

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.

HDPE Slab

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.

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Laser Maze Mounts

My plan for Maker Faire Milwaukee’s 2015 Laser Maze got a little sidetracked, but that’s okay, because Vishal ended up writing some of the code I needed for another project and then I decided to just have him take over the some of the build.

Laser Holder

I did get a few more things done in recent weeks, like making these mounts to hold the lasers in place. Adam provided us with these clamp devices meant to hold a flashlight on your bike, but the lasers are a smaller diameter and tended to shift around, which isn’t great when you need to align lasers…

In our first attempt to make something that would go into the flashlight mounts and adapt to the size of the lasers, we ran down to the basement shop at the museum and used a hole saw in the drill press to cut a piece of plastic, and then we drilled another hole, and cut out a piece using the band saw. This was a neat idea, but did not work.

Laser Holder

The hand-fashioned one just wasn’t quite the right size. We didn’t have the exact hole saw or drill bit sizes needed, and the plastic just didn’t flex enough to allow for tightening. I ended up pulling out the calipers to get exact measurements and re-create what we tried to do with 3D printing.

Laser Holder

The 3D printed version sort of worked, but it was tough to slide the laser into place. I could have just kept trying to get the perfect fit, but instead of trying to emulate the limitations of using a drill and saw, I modified the design to have less surface area where the laser was sliding in, and also allow for more flex, and more strength, due to the way 3D printing works.

Laser Holder

These pieces don’t have a lot of infill, and they don’t need them. The shape of the interior section provides extra strength because of the nature of how it’s structured.

Laser Holder

These mount should work well, and the bike flashlight part saves me the trouble of creating an entire mounting system, or modifying previous mount work.

We’ve got less than 90 days until Maker Faire Milwaukee so hopefully we can get a test set-up running within the next 30 days or so.