Good tip.
And good point about CA and heat - I’ve used a heat gun before to “unglue” something. Didn’t know that about water though.
/K
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Here’s another tip:
If you’re fixing tiles, and they’re glued down with the older-style brown mastic, soak it in acetone. The mastic will fizz like it’s been dipped in acid and eventually soften and either come off on its own, or can be easily scraped off.
Just be careful, acetone is highly flammable and this should be done outdoors if at all possible.
I have the same “problem” because some adhesives work better on certain things than others. Though 90% of the repair projects can be done with what I specified before, I have others too, like windshield mirror adhesive for gluing to glass, some conductive lacquer for fixing and gluing down rear-window traces, etc.
The big problem is that adhesives have a relatively short shelf-life - and many are not trivially cheap so it can be expensive to keep a good array of glues in stock.
One other thing:
Scotch double-sided tape is a phenomenal general-purpose adhesive if you need to glue two flat things together. I use it to replace the E-ink screen in my wife’s book when she breaks it, and things like the SSD drive on Charlie’s back are stuck down with double-sided tape. It makes a great bond, but can be, (carefully!), removed if necessary.
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Update July 15th, 2021:
Total failure of the repaired joint with the epoxy coming off in chunks leaving no residue or trace of adhesion.
Viz.:
As you can see, there is virtually no trace of the adhesive on the plastic.
The “chunks” were removed by use of a razor knife and any remaining residue was removed using a fingernail.
I do not know why the adhesive failed.
Thought:
Possible moisture incursion into the joint? It’s been hot and humid, but a good bond shouldn’t have that kind of a problem.
I am going to try to re-repair with a different epoxy after re-cleaning the joint with acetone and pure alcohol.
We’ll see what happens.
@KeithW,
I guess this didn’t work. . . . 
@cleoqc,
What techniques do you folks use to repair acrylic body parts?
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Well that’s a bummer.
I found this about working with acrylic
There is a solvent glue that seems to be specifically for acrylic. It’s available on Amazon:
https://www.amazon.com/Weld-Acrylic-Adhesive-Applicator-Bottle/dp/B0096TWKCW
But I suspect delivery to Russia wouldn’t be possible (even if it weren’t cost-prohibitive).
/K
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We don’t. We just replace. And we hate it. It’s very wasteful 
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AFAICT, (As Far As I Can Tell), the correct verb is “was”, not “is”, as it appears to be out of stock everywhere with no estimate when it will be back in stock.
Weld-on’s Russian offices claim to have never heard of it.
I found a liter bottle of a solvent used to “finish and smooth” the surfaces of virtually every kind of hard plastic known to man. Expensive as hell. Bought a can. Tried it on the broken pieces and it did nothing.
I’m still searching.
Do you know what kind of plastic this is? Polycarbonate? Something else?
That’s weird - it shows in stock for me. Maybe it’s a location issue? Not from Amazon per se - it’s sold and shipped by a third party. That can always be a little dicey.
Good luck in finding a solution (or more correctly - in finding the right solvent to make a solution 
)
/K
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I discovered that after I posted the update.
Apparently, (for Russia at least), nobody has any stock. Off of a VPN, it’s a horse of a different hue.
I found a alledged supplier. Apparently you order from them and they order from some guy on eBay in West Nyack NY.
Also, and this is important, there is no indication of the age of the can of adhesive. If the can is too old, you can end up with a can of Jello instead of solvent.
Neither the home site or any subsidiary site mention it.
Any search for “solvent for acrylic”, whether on Yandex, (Russia’s “Google”, invented by the same guy), or any US search engine brings me back to Weld-On 4 (or 3).
If I buy it, it will end up costing me something like 2x or more because of overseas shipping.
@cleoqc,
Is there any chance you (M.R.) can buy a can and try it on the laser-cut acrylic parts you have broken, if you didn’t toss them? I’d really rather not pay almost $100 for yet another solvent that doesn’t work.
I don’t even know if it ships internationally.
P.S.
This being stuck overseas B.S. is beginning to REALLY VACUUM ROYALLY and I don’t need it as there is a neighbor who raises a cow, and some goats, and there’s enough B.S., (actually C.S./G.S.), for anyone who wants it.
(My next door neighbor has about an acre under cultivation and makes regular wheelbarrow trips for it. Great for when you have friends over for a BBQ!)
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Doesn’t that get you about 10 GoPiGo3 Spare Chassis Kits (knock off one or two for shipping)?
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Let’s be sure to be totally accurate when talking about the neighbors.
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“Truth is an absolute defense against slander”.
All of it 1000% true and totally non-judgemental.
The one neighbor up the street keeps livestock and the other polices the pasture areas for fertilizer. Sometimes he borrows our BIG wheelbarrow and doesn’t return it empty - which helps our garden too.
And like the song, we’re “stuck in the middle”.
And there is no scent like cow manure to bring back childhood memories of farming. And it is an all-permeating smell, seconded only by duck farming and skunks. (Skunks being the Gold Standard for 100 megaton stink-bombs!)
For those “lily-livered city slickers” who never lived near a farm, cow manure can be a bit “overwhelming”.
All 100% true as Gospel.
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I’m sure a few of us could test some adhesives with the acrylic pieces at ModBot HQ. I’ll shoot a message over to QC to see if they would be interested.
I’m not too sure about this Industrial-strength adhesive on Amazon though (take a look at the product description). We would need something that can be used in an educational setting.
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Never experienced duck farm. I was going to nominate the chicken operation of the family’s farm I had the “pleasure “ of vacationing on as a child
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The Weld-On adhesives are notable for their very low VOC fumes.
Any kind of repair to acrylic, (AFAIK), is not something to be casually handed off to the unsuspecting student. Properly supervised and properly instructed this is no more dangerous than putting gasoline in your car, perhaps even less so due to the difference in vapor pressure.
If the students are going to try to construct things out of plastic subassemblies, the subject of plastic welding is absolutely proper and necessary to prevent injury.
Therefore I respectfully disagree.
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This can be generalized into poultry farming in general. Since I have had the inestimable honor and privilege of being subjected to a duck farm, I am using it as the “class prototype”.
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I did, and I’m not getting in the same room with that stuff.
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Wimps. . .
I bet you don’t want to put a few grams of elemental sodium in your back pocket either.
Jeez! No sense of adventure.
Sheesh, what’s this world coming to anyway - a deadly pandemic that seems to be mutating every other day - and people turn into wimps!
=============
Seriously, I don’t expect to see this in class, per se, but the ability to repair a difficult to obtain piece quickly if necessary sounds like a good thing.
Or at least give them the knowledge how, and let people gage relative benefit/risk themselves.
You obviously don’t realize how difficult it was to ship three batteries to Moscow from the US. Not trivial.
Say I ordered even TWO spare-parts kits and had them shipped - not only would it take mortal weeks, extending into months, but you can’t ship stuff like that to individuals, you need a “company address”.
The cost of shipping the two kits would pay for several more.
Also!
I have a “spare parts kit”. This is why I was able to repair Charlie so quickly. However, I would like to be able to put the old chassis plate “back into stock” so I can use it if necessary.
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My wife grew up on a dairy farm in Ireland (which her oldest brother still runs), so I’m quite familiar with the aroma (in large quantities). While largely a city-slicker, I have helped on many occasions muck out the barn (which also helps me appreciate the design of Wellington boots, AKA “wellies”).
My grandparents retired to my Grandmother’s home town in NW Arkansas (Tyson territory). Their neighbor grew chickens. When the wind blew from that direction - ugh. Between the two I think I’d take the cows. And no experience with ducks. Fortunately no direct experience with skunk either - only driving/walking past a spot where an event had obviously transpired.
/K
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I agree. The unfortunate thing is that the teachers themselves probably have no experience in repairs like this, and probably no experience in fixing-things in general. That’s one of the reasons I like to see the “Maker” movement spreading to some degree. It encourages people to try things and experiment. For the people on this forum that’s just second nature, and we probably don’t give it a thought. But for someone who’s never done that, it can be daunting. Just giving them even a little experience in making something or trying to fix something can open up a world of possibilities.
/K
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The Gold Standard for plastic repair is plastic welding, either using a solvent or heat and back-filling with additional plastic.
I did the second yesterday on the gas tank from my weed-trimmer which is HDPE, (recycling number 2) which has the solubility constant of Teflon and is virtually impervious to everything.
According to the Internet, the only REAL fix is to melt the defect area with a soldering iron and fill in with a piece of HDPE cut from a bottle.
I did that and after several hours of use it still didn’t leak. (fingers are crossed).
The iron is a soldering gun with a terrible tip, (for soldering), and the fuel tank was emptied and then carefully cleaned and dried before the repair.
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