Tag Archives: Tetris

107: Thick Acrylic

A few months ago, my friend Arty got in touch with me and said he had “some thick acrylic” left over from a recent storefront revamp at a mobile phone store. Not really knowing what I was getting into, I said “hey any scrap material that I can laser is good with me!”

This stuff is so clear it's almost hard to see.
This stuff is so clear it’s almost hard to see.

Much more recently, I went to pick up the acrylic that he’d been graciously holding onto for me. As it turned out, the acrylic wasn’t just thick. It was far thicker than I could process with the laser, with 7/8″ as the thinnest edge. But there were several chunks of uniformly cut acrylic, and every surface was smooth enough that you could see clear through to the other side. This was material worth experimenting on!

The first engraving test confirmed that it was cast acrylic.
The first engraving test confirmed that it was cast acrylic.

I first determined whether it was cast or extruded acrylic by doing a surface engraving featuring some art deco frame stock. The surface engraving was powdery and white, which was perfect—cast acrylic engraves in a much more visible manner than extruded acrylic.

The second design didn't really convey the "frosted ice" look I was going for.
The second design didn’t really convey the “frosted ice” look I was going for.

The second design I tried was based on a “frosted ice” theme I developed while working with a client a couple of years ago. While it looked great on the snowflake shapes I used originally, the effect was lost on the square chunk of acrylic, and the “FROSTY” text I added didn’t really come out clearly.

Two different sizes of blocks "comprised" of tetriminos.
Two different sizes of blocks “comprised” of tetriminos.

I revisited some tetrimino patterns from a very early 52LASERS post. Using three different engraving techniques, I created a pattern that highlighted certain shapes with fills and deeper cuts. The result not only looks awesome from straight on, it created some really stunning effects when looking through the unengraved side of the acrylic.

Looking through the clean edge shows off each "deep cut" tetrimino.
Looking through the clean edge shows off each “deep cut” tetrimino.
Any fan of Tetris will recognize these shapes!
Any fan of Tetris will recognize these shapes!

I still have plenty of stock of these blocks left, so if you can think of any more creative ways to jazz up the acrylic’s surface, let me know in the comments!

Quite a supply of material too thick to cut through!
Quite a supply of material too thick to cut through!

14: Box Joints

I’ve done box joints before, just once, for a 3D picture frame celebrating a newborn baby. It was a harrowing experience back then because I didn’t really understand how the width of the laser beam affects the ability of two pieces to fit together and because I was using a thick wood that just didn’t want to play nicely. The piece did turn out fine, but the procedure was such a mess that I haven’t really considered box joints since.

Three tetriminos with etched surfaces.
Three tetriminos with etched surfaces.

That changed this week, because Tetris was still on my mind. At some point while laying out hundreds of tiny tetriminos for the NES etching project I realized that it shouldn’t be too hard to recreate those popular shapes in 3D if I could just get over my box joint demons. Wood was out; I selected varying colors of 1/8″ thick acrylic for my material this time.

The darker shapes were the tricky ones.
The Blue J / Orange L. The darker shapes were the tricky ones.

Figuring out the shapes initially took no time at all.  I settled on 1″ squares to form the basic tetrimino shapes and made sure that the box joints (the teeth shown above) were the same thickness as the material, 1/8″. When I began on the Cyan I, there were no inside corners and the design went incredibly smoothly. Because Yellow O, unpictured, is just a fatter version of the same shape, adjusting the cut was trivial.

When I got around to Blue J and Orange L, I had to get through a few bad test cuts before figuring out how to adjust two shapes to account for the inner corner. Once I discovered how it should be shaped, the same inner corner treatment could be applied to Red Z (shown here) and Green S, as well as the unpictured Purple T.

The trickiest part of layout was the inside seam shown here at center.
The trickiest part of layout was the inside seam shown here at center.

With that design puzzle solved, more test cuts were spent discovering the best kerf setting for this material. After cutting a few box-jointed pieces that wouldn’t fit together and a few that fit together so loosely they’d require glue, I discovered that the laser’s width burned away 0.0064″ of material on each line, which could be solved with an offset path setting of 0.0032″. The resulting graveyard of pieces shows many cracked edges, but the final pieces fit together so perfectly that they’ll never fall apart by accident.

The graveyard: Paper unpeeled, incorrect shapes and cracked joints.
The graveyard: Paper unpeeled, incorrect shapes and cracked joints.
The difference between Orange L and Blue J here is paper: lots and lots of tiny paper tetriminos.
The difference between Orange L and Blue J here is paper: lots and lots of tiny paper tetriminos.

Speaking of accidents and graveyards, don’t soak transfer paper in Goo Gone. One of the fun little extra steps I took during this weekly project was to vector etch a pattern of tiny tetriminos over top of these big 3D pieces. Well, when you vector etch a sheet of acrylic that is covered with transfer paper to prevent burn issues, you end up with hundreds of tiny little paper shapes you then have to remove by hand; you can see them here in the comparison between Orange L and Blue JI thought I’d save time by liberally applying Goo Gone to the paper surfaces and then leaving the pieces overnight. I figured I should be able to just wipe away the paper, its adhesive dissolved.

This gelatinous goop is an incredible pain to remove.
This gelatinous goop is an incredible pain to remove.

The end result was horrific: the Goo Gone did make the paper very easy to remove, but it left the adhesive on the acrylic, which had become a horrible, gummy mess. Way too much time was spent using more Goo Gone, some isopropyl alcohol, and some plain liquid soap to slowly remove the residue from the etched pieces. What a mess.

The Cyan I, everyone's favorite tetrimino.
The Cyan I, everyone’s favorite tetrimino.

Most of my tetriminos were cut out of transparent colored acrylic, though some pieces (shown in the graveyard pictures) were opaque. The Cyan I was the most fun to look at, thanks to the “Ice Blue” acrylic used. It didn’t have much visible color looking at the surface of the material, but the cyan color really shines through the etches and cut edges. It appears to glow, even when placed next to the other transparent tetriminos.

 

 

Plenty of tetriminos stacked in ways they shouldn't be stacked.
Plenty of tetriminos stacked in ways they shouldn’t be stacked.