If you’d like to cut the jig from acrylic, just slice out one corner so the jig doesn’t come near the joint, like so.
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Gluing acrylic, or “welding” it, as it’s called, is very cool! You basically melt the two pieces into one (the word “weld” is very appropriate). I’ve only used one acrylic welding solvent myself, but just picture ordinary water and you’ve basically got the idea. One thing that you want when welding acrylic is nice, square, polished edges - exactly what I figure the Glowforge will produce! 
I’m sure there’re a ton of videos on YouTube, but here’s one that gives a good overview…
I’ve only made a single acrylic box, so take my advice with a grain of salt… You’ll probably want to employ a flat surface and a second block when you’re setting up the pieces that you’re preparing to weld. The block will keep the two pieces at 90º from each other, but it won’t keep the edges parallel (shown on the left of the image). Using the table and a second block you can set up a better weldment (like the right side of the image).
The solvent is likely to seep through the seem and reach the table. Some wax paper or parchment paper is probably enough to protect the table. (I hope an expert chimes in!)
Another thing to consider: the solvent will accumulate on the table (or whatever) and mar the finish of the acrylic. Perhaps “tacking” a couple spots, just enough to make the connection ridged enough to handle, would be a good idea. Just like when welding metal. Once the tacks are cured you could lift both pieces off the table entirely and finish the welds with less risk of mars.
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I spent some time on an Epilog laser, cutting acrylic to join at 90 deg, as you describe here. I found that the cut edge was not really square. There was a slight taper through the depth, so the vertical piece ended up being a little slanted when the edge was flush to the base. I researched the issue and found that a much longer focal length lens was suggested to get square cuts in acrylic, on the order of 5" or more. I was using a 2" focal length lens, same as the one on the Forge.
Another source suggested defocusing the beam to help get a square cut. I didn’t have time to try that.
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Oh no. I wonder how far off it could be. Do you have a guess by chance?
Just a heads up for everybody: acetone is quite flammable and has a low flash point, so be sure to use in good ventilation and away from spark sources.
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I pulled out some samples I cut and a protractor. Holding the cut edge of the vertical sheet flush against a base sheet, I measure between two and four degrees of slant from true vertical. The sheets were 1/8" thick and the protractor had a 3" radius of measurement.
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Gah! Really good to know. This could cause serious complications. @dan, @fan-of-glowforge said,
“I spent some time on an Epilog laser, cutting acrylic to join at 90 deg, as you describe here. I found that the cut edge was not really square. There was a slight taper through the depth, so the vertical piece ended up being a little slanted when the edge was flush to the base. I researched the issue and found that a much longer focal length lens was suggested to get square cuts in acrylic, on the order of 5” or more. I was using a 2" focal length lens, same as the one on the Forge.
Another source suggested defocusing the beam to help get a square cut. I didn’t have time to try that."
Assuming he’s correct, having a setting to compensate for that would be great!
You could use a 1-2-3 block as your edge to square against. The advantage they have is they are super square and heavy enough to hold normal pieces of acrylic (and since they are stainless steel they won’t weld to the acrylic). I got some super cheap Chinese made ones at Amazon. Only problem was getting them clean (they come packed in heavy cutting oil and wax paper (seriously?). Took a lot of dawn and q-tips to get it clean…
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While it’s possible to align sheets of acrylic so that they meet at right angles, if the edge of the sheet is not square, there will be a small gap between the pieces on one side. That may affect the glue joint strength.
1-2-3 blocks are great, and if you stick a strong magnet on the opposite side they make a very nice jig.
They are not (usually) stainless steel though, and that is a good thing since many grades of SS are not magnetic. The wax paper and greasy stuff is for rust prevention in shipping, and a much easier way of cleaning them is to soak them in some of the “purple” degreaser (lots of brands make this stuff).
One of the benefits of using a thicker (or thickened) solvent glue is that as the solvents evaporate you get some gap filling acrylic left behind. So even if the angle is slightly off as long as you hold the pieces square you can still get good results. It may not be quite as strong as if you have a really square edge though.
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I love this whole thread as I am very interested in working with some acrylic when I get my Glowforge. I have added this info. to my growling list of information and tips. Thank you all.
That’s good to learn!
Solvents for acrylic come in different grades. Thicker slow setting up to water thin very fast.
A benefit of the thicker as @jkopel said, is that it allows more working time. The longer the joint is wet, the more melting happens (Ability to fill gaps).
The thin very fast setting is akin to super glue with little working time.
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If you use an acrylic solvent like Weld-On… I might just take a second and look at the MSDS, I remember that stuff being really bad for you. I would use a chemical respirator if I used it and probably do that outside as well.
Yes, sorry meant hardened steel (was literally holding a stainless project in my hand when writing that). The problem wasn’t getting the oil off, it was the wax paper. Wax paper + cutting oil = pasty gross glop that sticks really, really well to the threads… Citrus based solvent works great for the oil part, but needed the q-tips to pick out the adhered wax-paper. Silicone based parchment paper would be a way better choice I imagine…
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Seriously reconsider buying acrylic solvents.
Get Acetone. Disolve your scrap acrylic (you will have tons), and then you get the same thing, but you have control over exactly how thick of a final product you wind up with.
You can use lots of acrylic and barely any acetone, and wind up with a gooey paste, apply it just like caulking. Or you can use barely any acrylic and lots of acetone, and wind up with basically water, apply it with a syringe.
This lets you always have the right paste for the job at hand, without storing more than a single bottle of acrylic and a scrap bin.
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So, when you mean a little of X and a lot of Y, or vice versa, what would be some amounts, like, a cubic inch of acrylic to how many ounces of acetal for a thick or thin batch (even at an approximation)? And what would be a safe container for it? When applying it, is a natural OR a synthetic brush fine? What material should the syringe be made of? Is it water soluble(can be washed with water)
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I store it in glass jars. Cleaning them out is AWESOME, since I usually swirl the contents around, then dump into a large storage container, or just dilute/re-concentrate for a new mix type. But there is always a thin film of acrylic left over, which (once pried loose) is grocery bag thin and fun to play with.
Any plastic which is not dissolved by acetone can work as well for storage. My syringe bottle is a plastic of some sort. No recycle code on the bottle so no idea what precisely.
And for the rough amounts, I tend to think more in terms of ratios. I get a watery mix with about 1 part acrylic to 10 parts acetone. I have not yet made a putty mix, but I would expect then I would be going about 3 part acrylic to 1 part acetone.
Start with a small batch, that way you can add more of one or the other to get the desired result. Or just aim for too much acetone and leave it exposed to air until it is how thick you want (and away from flame sources during that time of course).
Application by syringe, or by a non-dissolving brush which you immediately clean (with large quantities of acetone I guess). If doing something really thick and caulk-like, then put on neoprene gloves and spread by hand.
Not sure if acetone is water soluble, it evaporates, and any damage it does to your clothes is from it taking things out, not putting things in. So you cannot wash away the damage. The acrylic itself is certainly not water soluble, but can be scraped off most things.
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Acetone is miscible (infinitely soluble) with water. For a check of compatibility with various plastics Cole-Parmer’s chemical compatibility database.
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May I safely assume that somewhere can be bought a larger size of acetone than just buying a bottle of nail polish remover (without added ‘flavors’)? I’m planning on trying some things with acrylic and this would be helpful to me. Thanks.