UV activated glue

Do you have any advice about UV activated glues as they apply to FRC? Are they useful to have around? How does their strength compare? Ideal applications?

Dentists seem to use them almost exclusively since they harden in minutes and don’t have bothersome fumes. I assume they are better than superglue at filling voids but that’s just a guess.


Not sure. As a former wearer of braces I can say the stuff sticks pretty good. Would be interesting to try.

Annoying stuff needs a drill to remove. I hate that drill

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No advice, but some commentary:
Useful to have around: Possibly, if you need a decent amount of strength without much flexibility (iirc from braces)
Strength: Probably around super glue. Idk though, I managed to do something to my braces related to loosening the glue which the dentist had never seen before. That was fun.
Ideal applications: I have no idea, but I’d try something that needs to be held in place with a fast acting super glue of some sort.

In Stronghold we had an arm that lifted field pieces. It was not well designed and had too much force on the pivot where the motor mounted to it.

We would tighten it and every match it would come loose. One of the mentors brought a kit that contained a liquid, a powder and a UV pen light.

Once “the kit” was used the arm never loosened again. Two years after the season we tried to salvage parts from that joint. Many tried to separate the parts but nothing could break the bond of the UV “weld”. The parts were finally scrapped.

We have not needed anything like “the kit” since that season. We try to design proper joints and attachments that do not require “the kit”.

We had a good laugh at our last meeting, as we reminisced how bad that robot was and what it took to keep it on the field. It was the teams second season. We have learned so much from our failures.

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I’ve used UV curing glues when I worked in medical device. This was the industrial quality stuff, not what is available online or the local pharmacy super mart. Having said that, I’ve used the cheaper (online) UV glues too around the house. I don’t think it’s technically a glue, but I’m gonna use that word for simplicity.

I don’t know about bonding strength. I guess a lot of that will depend on the application and how the parts mate together. Understand that you must be able to get the UV light onto the glue, as opposed to a cyanoacrylate (super glue) or epoxy that can bond two pieces together where the mating surfaces are not visible after bonding. Think of a broken handle on a tea cup. The cyano can stick the broken surfaces back together and you’d never be able to shine a light onto the glued surface.
Think of the UV glue as a weld. You can create a fillet with it on the external surface.

So, for FRC use, an application might be where you’re trying to position something to glue together but there is no mechanical locator for the two parts. …You want to glue a washer to the middle of a plate. You could use cyano and just hold the washer in place for a minute. Or, you could use UV glue and “tack” it down in a few seconds. The cyano is a one shot deal. You stick it, and it’s stuck. The UV cure allows you to move the part around until you have it just right then hit it with the light. Now it’s stuck.
I’ve seen some uses such as reinforcing strain reliefs on cables… You could probably use it to help retain bearing flanges in your ill fitting bearing holes. Stop e-clips/rings from coming off. Put on motor shafts to keep keyed gears/sprockets from moving easily.

In the machine shop (at the medical device company), I did use the UV glue on a few occasions to tack down thin materials I was machining.

FWIW, I’ve known about UV curing glues for 20 years and haven’t really found an application for it that couldn’t be just as easily solved with a cyano or expoxy. But it’s only been the last few years that the cheap stuff has been available online. I will have to (re)consider possibilities with the readily available stuff.

Also to note that the industrial UV lamps highly recommend wearing the proper color/shade of eye protection. The online stuff doesn’t mention anything about eye protection from the UV light.

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I took a quick look at McMaster-Carr. Without going too deep into the weeds, their UV-set adhesives are about 2400 psi shear strength. A quick-cure superglue (cyanoacrylite, IIRC) is 2900 psi, and cures without the UV in about the same initial time. That said, that’s somewhat dependent on what you’re actually gluing together. (Quick-set epoxies tend to be lower in shear strength and higher in cure time, FWIW. But I have been known to use a high-strength longer-cure epoxy to help beef up some aluminum joints.)

Now, that said… 90% chance that there’s something out there that McMaster doesn’t have, because they don’t appear to have the greatest selection of UV-curing adhesives. And another 90% chance that other stuff is in fact better. But knowing where to look is half the battle with this sort of thing, and most teams aren’t going to be thinking much beyond McMaster/local hardware store.

If it was up to me… I’d just use superglue for an emergency fix, and some combination of more superglue and/or epoxy for an overnight fix, before swapping the part for a stronger one before the next event.

J to the B to the Weld, yo.

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