For me, I ended up going with essentially a 29” cube, using (12) 700mm extrusions and (3) 3-way corner pieces. It may seem oversized, but that’s because it is. When I switch laser units out for testing, maintenance, and the like, I want to leave the camera system, cables, power supply, and exhaust system in place. This will also let me put one of my 3D printers inside if/when I decide to try printing in ABS or other materials which need exhaust and temperature stability.
The first thing to do was mock up the bottom of the enclosure so that measurements could be made. The corner pieces slide in the channels of the 2020, and get held there by the built in grub screws. Now that the bottom frame was assembled, I took measurements for all sides to determine how big the piece of cement board needed to be. To account for the channels, an extra 7/16” needed to be added on so that the cement board would sit in the channels without interfering or flapping around much.
Measurements made, it was time to cut the cement board. The scoring on the stuff I got was done in 1” squares, so that it was fairly easy to get into the general size I needed. Had I been working in whole inches, that would have been perfect. But no, fractions were needed. Using a ruler, I added the fractional value to the total length on both sides of the cement board. Then I ran a line between the two marks, using the edge of another board. The “right” way to do this would be a carpenter’s square, yard stick, 3’ or longer level, or a chalk line, but using a reasonably straight board edge worked well enough. That took care of the length. Using the same technique, I did the width. Note, it’s best if you use the board’s corners as your start location, so that you get at least two straight edges no matter what. LOL.
Once marked off, it was time to cut. The maker of these boards, Hardibacker, says that they can be scored (cut into a little ways) with a utility knife, then snapped along the score line. And yes, it does work. But, it’s murder on your blades, not to mention hands. Cement is abrasive, and within one cut, the tip of my blade was rounding off. It didn’t help that I had to go over it some 40 times either. Once well scored, the board did indeed snap along the score lines as advertised, so there’s that. After two sections were cut, I was out of blades, and went to find a better method.
Turns out they make a tool for this, which uses carbide tips to dig into the board without taking much damage. It’s like $10, and available at hardware stores. Then there is the power tool method. As mentioned, dust is a problem with these, you don’t want to breath it in or get it in your eyes if possible. The best power tool for the job is the jigsaw, mated with a blade specially made for cutting these boards. There is some dust, but not as much as using an angle grinder or circular saw. You can wet the surface to help keep the dust down too. As it happens, I have a jig saw, the blade is another $10, and it was available at the hardware store. I stepped out and spent the twenty bucks on both items.
The scoring knife worked great compared to the utility knife. It dug into the cement board without a ton of pressure and while I still needed to do a good number of strokes to get the board scored well enough to snap, it was much easier and faster. Not as fast as the jigsaw though. With the special blade on it, my el cheapo jigsaw went through the cement board like butter. Dust in the air wasn’t too bad, but way more than with either of the knives. Next time, I’ll douse the board with water or bring the vacuum along.
Anyhow, board cut, it was time to fit it into the bottom frame. This is when I discovered that the boards were actually ¼’ thick, which is too thick to fit into the channels. The fix – bevel the edge. To do this, you can break out the utility knife and slice along the edge at an angle to make the edge thinner. Or, you can sand it. Both work, I tried them, but sanding throws up more dust. Trial and error with a spare piece of 2020 let me know when I’d trimmed well enough, the board settled into the channels nicely, and I tightened all the corners.
From here, I went on to do the top assembly, so that when the sides were all done and in place, I could just slip the top assembly on. Once that was done, I took measurements for the side walls and back wall. They aren’t the same as the top and bottom walls, because of how the 3-way corner pieces work. When I said “essentially a cube”, this is why. Anyhow, I also had to contend with one side wall being a two piece affair with an extra 2020 length running front to back. This was intentional, as I am mounting a camera over the center of the closure, about ¾ of the way up.
For the exhaust port, I needed a hole in the side wall capable of handling a 6“ vent hose. If you want to cut a circle, the best method is to trace your circle out, then divide it up like a pie, and then use the scoring knife along all the lines. When well scored, smack the center with a hammer, your palm, or whatever, to snap the pieces free. If you’re into pre-planning, and have the tools, you could use a drill with a sizable bit and the jigsaw with the good blade to cut the circle out. If you opt for a vent cover, like the ones used for laundry and such, you can cheat a little by making a square opening, which is then hidden by the cover. Confession, I made a 5″ square and stuffed the 6″ hose in it. Yes it’s ugly. Maybe I’ll fix that.
When it comes to cable ports, you’re in the same boat, though drilling a hole big enough to fit the fattest end of your cables through is easiest.
This is probably a good place to tell you that you don’t need this enclosure to be airtight. Any opening you have in the enclosure will serve as an air intake port, which is something you need for your exhaust to work. So don’t sweat it.
Now for the doors. Confession, I haven’t made them yet. Instead, I slip some laser safety plastic sheet into the front bottom channel and side channel. The exhaust fan, the port of which sits a bit higher than the laser work area, takes care of the rest. The vacuum it creates sucks in all the smoke and scent. The plan however is to build a set of double doors from more extrusion and use the safety plastic as window inserts. Hinge and handle kits are readily available for less than $20, and these bolt right on.
