Resin + Laser Pointer = Awesome Glue!

In the past, I’ve done a fair amount of 3D printing with ABS. One of the nice things about ABS is that you can use acetone to join parts together very strongly by a technique known as “solvent welding.”

Cured Formlabs resin won’t dissolve in acetone, but you can do the same sort of solvent welds between parts with just a little bit of extra clear resin and a laser pointer (or other UV source, like the Sun). If I have two pieces I want to join together, I take just a small amount of the resin, using a toothpick or the like, and spread it around where I want the join to take place. Then, I push the objects together and expose the resin to UV light to get it to cure. Blue-violet (405 nm) laser pointers are perfect for this and are inexpensive ( The resin cures very quickly, so you have a strong bond in no time.

And you can use the exact same technique to glue other things around the house! Just a small amount of resin can be a surprisingly effective UV-cured glue on lots of surfaces.


Awesome! I had been wondering about this and was going to try this out myself.

I’m curious about safety. I’ve heard the team say that the orange lid is meant to keep UV light out and the laser light in. Does this mean the 405nm laser light is harmful to the naked eye? If so, I might look into getting a pair of safety glasses that block out the harmful stuff.

This is exactly how I was thinking of doing it, good to see I’m not the only one, and that it works!

TJ, it depends on the power of the 405 nm laser pointer. If you purchase a class I or class II (less than 1mW) product, then it should be safe, though you may need a longer exposure for it to cure.

Yes you will want safety glasses, the 405nm light can be quite intense, even at low power. You never want to risk your eyes. I have a 1.5W 405nm laser, and glasses are absolutely mandatory.

If you’re worried about light from the FORM1 you should be fine as the lid is essentially a pair of glasses. It works both ways, it keeps external UV from entering and prematurely hardening the resin, and it keeps the laser light from exiting and harming any onlookers.

Definitely!  Safety first!  Most laser pointers come with some instructions for how to use the laser safely, which you should definitely follow.

And if you don’t want to mess with a laser, taking the object out into the sunshine ought to also work, though you may need to hold it together a bit longer for it to cure.

The laser pointer I have is Class IIIB with an output of <200mW. Would that work for this process?

The light from the printer I’m not worried about, but I’ve noticed that the spot from my laser pointer looks strange when I look at it. The spot looks a lot bigger than it actually is, like it’s messing with my retinas or something. This is why I’m concerned that it’s bad for my eyes. It creates awesome effects on glow-in-the-dark paints and watch dials, though! :smiley:

Funny enough, I actually purchased a green one, but the shipper sent me the 405nm one instead. Imagine my surprise when the light was blue-violet instead of green lol.

Yes your pointer should work… basically the more power, the shorter the cure time.

Definitely get glasses. Even looking at the intense specular spot can cause eye damage over prolonged periods.You’ll probably notice that after looking at the spot, you can still see its ghost when you look away or even close your eyes.

Hmm, I haven’t seen the “ghost” you speak of yet. Maybe I’m just not looking at it long enough (good thing!). I’ll definitely invest in a pair of safety goggles. Thanks for the info, everyone! :slight_smile:

Great tip Martin once again!

That’s a really nice tip !!

Deep blue and especially violet light don’t focus quite correctly in the eye.  The low-light receptors are also more sensitive to blue than the detail receptors in the eye (rods vs cones, forget which is which.)  It’s not necessarily because blue light is more dangerous.

Visible lasers under 1mW are considered safe (though not recommended) even if shined into the eye because of blink reflex.  The spot of a 200mW laser would not have the intensity of a 1mW laser.  Looking at the spot would be similar to looking at about a 500mW blue LED (diffuse light, difference in power is because laser power is measured by measuring the output power, LED power is measured in input power.)

Laser safety glasses are still a necessity when dealing with higher power lasers (above class 2,) because if you accidentally shine the laser at something reflective (rather than scattering… any shiny surface,) you may end up getting a significant portion of that power to the eye.  Even a flat surface on clear resin could reflect enough light into your eye that you’d rather not do it.

As far as other UV curing devices, a blacklight flashlight would probably do a good job as well (don’t look into a powerful one of those either.)

i gotta say, this is one of the best tips of all time. whether to attach two different parts, or repair one that i broke when removing supports (oops), this has been incredibly useful!

Martin = Cool tips super hero

UV LEDs should work as well.  You can get ~1-3W UV LEDs in a variety of wavelengths (360-415nm) that mount on an aluminum star board.  Shorter wavelengths are closer to UV B which carries an exposure risk (just like the ‘bad’ UV in sunlight), but I suspect they’ll cure the resin faster too.  Other sources of UV are UV “Black” lights (they’re usually ‘safer’ UV A wavelengths) and germicidal lamps (UV B).  Handheld commercial UV lamps are used for curing some types of industrial adhesives as well, but for most of us a few bucks for an LED would be way cheaper and easier if you need to do a large area instead of ‘painting’ it with a UV laser of buying a commercial lamp…

Hi guys,

I found a couple of ‘high power’ laser pointers that meet the specs listed on the ‘How to Glue Parts and Repair Small Holes’ page–one is green and the other is violet. Does the color of the laser matter? And if so, which color is preferred and why?

Thanks in advance for any helpful info.



Artist/Partner | Little Green Dog |

The ‘violet’ is the one you want.  The resins are cured by UV light, so since violet laser pointers are usually ~405nm or so (pretty close to true ‘UV’) they’ll work just fine.  You don’t need a ton of power from the laser because the spot size is going to be relatively small.

One of the ~$7, “5mW” 405nm laser pointers on eBay will work fine for most small ‘glue’ type tricks.  I can put a (grain of rice sized) droplet of resin on the end of a toothpick and fully harden it with the 5mW pointer in maybe ~2-3 seconds.  (If the laser was scanning quickly like in the Form1 you’d want a lot more power, but for manually shining it on a spot and holding it still the ‘average’ power in to the resin is probably the same or greater as the Form1’s scanning.)

I tried a ~1W 395nm LED also and it will ‘skin’ resin in 5-10 seconds, so bright UV LEDs left on for some time could also further cure parts.

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Thanks! That makes sense and it’s exactly the info I needed to learn. :slight_smile:


I have a few old DVD players around the garage. I’m thinking that I could build a box with a few of the working lasers diodes (and maybe a diffuser to spread the light more)  inside box to post cure prints. Maybe, those laser diodes are too weak? Thoughts?

DVD’s are ‘red’ (~605nm) and likely won’t work (well) to cure the resin.  HD-DVD or BluRay diodes would work.  Given my early test with the ~395nm LEDs I suspect they’d be the way to go for a solid state post cure setup.  (blacklight tubes would certainly pump out a lot more, but then you’ve got high voltages and hot glass running around…)