I am building an underwater ROV and have 3D printed thruster shrouds and props in yellow Hatchbox PLA. They did not handle the vibrations and power from the motors very well and split along the junction of the mount and shroud that were 3D printed. To put them together I used 2 part epoxy rated especially for water, but 2 of the 4 have already broken along the glue line and some of the props are also shattering too from the stress (Fully 3D printed with no glue used for the props). Maybe using an epoxy is the wrong glue with the PLA, but I thought this would be the strongest I could get since CA is very prone to cracking with the vibrations.

So is there a better glue to use to fuse PLA together than H20 hold epoxy?

I am also thinking maybe I should use a different filament that would especially handle vibrations and have the strength for the 1 to 2 kg of thrust I am producing on the ROV props (This thrust is just an estimate, I have not measured it). I thought maybe yellow PETG would be a great compromise having the strength of ABS and have the ease ability to print of PLA, but I was not sure if anyone had a great suggestion of what yellow filament to print them in. I figured if I changed the props over they would be stronger and hold up much longer. It is also a little scary to test out a prop with the chance part of the blade might come flying off at you.

In short my two questions… (Sorry sometimes I give too much info)

Which glue to use for fusing PLA in high vibration and stress situations?

Which filament would be best to print a prop and shroud in?

Never to much info. Interesting project!

I think PETG would be a great choice to try as opposed to ABS. The only thing might be it is a bit flexible on thin parts but still strong.

ASA might be worth a look also. Not sure about water but it has great outdoor qualities so might be good. I used it for pole clamps for a weather station and it has been outdoors in the Oklahoma heat and weather for a year with no issues.

I would have though CA glue also. Probably have to do some googling! I did find one post that talked about super glue not doing well with vibration etc.

Look forward to hear about what you find out on these issues.

Here is a post I came across. Has possibilities.

"PLA + heat. Put some PLA filement in a dremel, spin it, and “friction weld” it together. For larger pieces I use a dab of 5 min epoxy (a little goes a long way) in the middle first to set the bond, and then weld the outside. This gets rid of seams while making a bond that is the same material as the print itself. Very strong and looks great, but as with metal welding a bit of finesse is involved or you can mess it up.

Not my invention, by the way. There’s youtube videos of this technique, under “PLA friction welding” or similar. Have a look, it’s worthwhile."

And another glue for PLA. This is what I was looking for. Never tried it but appears to act like acetone on ABS.

the PLA solvent you are looking for is dichloromethane (DCM). as found in:

  • scigrip weld-on 3
  • scigrip weld-on 4
  • scigrip weld-on 16
  • plastruct plastic weld

DCM is a true PLA solvent and will melt PLA, welding it together for a true PLA bond.

weld-on 3 and 4 are thinner than water, about as thin as ether. they can be tricky to apply. easiest to use a syringe.

neither acetone nor MEK can even scratch PLA.

Funny you mention scigrip weld-on acrylic glue. I have a lot of it from an acrylic Open ROV my students built. I will give it a shot. I also have extra syringes we didn’t use on the project. Would you also use it on PETG if I switch over?

I have never heard of ASA. Will give that a look to see how easy it is to print. The shroud has to be pretty rigid since the prop clearance is pretty tight.

A student of mine gave the friction welding a shot and it worked pretty well, but I am thinking it might not hold up to vibration. We will see…

What have you found on glue for PLA? I now find I have a few larger flat surfaces to glue together and was wondering what you found.

I am trying the acrylic glue right now (#3 That is really thin. Had to use a syringe to apply it) It looks like it has “melted” the PLA together, but it will take atleast 24 hours to check. The old H20 epoxy did not even bond with the PLA so I was able to pull the pices apart way too easily…

I tried the acrylic #3 glue and it worked really well so far. It really does melt the PLA. The joint seems really strong and is so much better than H20 epoxy!

I used the acrylic glue #3 on the ROV thruster and it works great. Looks like it will hold up to the vibrations! Hopefully the PLA will hold up to the extreme weathers… if not I will switch over to ASA… Thanks for all the help and suggestions!

Thanks for the update. I got some gel CA to try out that isn’t “instant” bond. My part isn’t going to be subjected to the stresses of yours! This will be round one of testing glues. I’ll look for the #3 also and have some on hand.

Here is the finished product made from 3D printed parts and recycled junk around the house. ?

I tried my gel CA glue and it sure gave me plenty of time to align the parts! Taking forever to dry and I still don’t know how good the joint will be.
I looked at the #3 and see how “watery” it is. I have asked them their advice on what glues would be best but no response so far. I would like on that is maybe a bit thicker - maybe not quite a gel but that can fill a little gap.