The strongest way to glue PLA

If you are trying to print a large model on a small printer, you will come to a point that you need to attache the pieces to each other. Plastic epoxy and super glue are usually the first two that you would go to for this. Unfortunately, both of these options leave much to be desired when it comes to bonding strength. In all cases, even with special care to prep and sanding, the bond broke at the joint.

Because the end result is going into a new printer, it had to be stronger than what could be achieved with epoxy or glue. I have found the strongest way to bond PLA is with a solvent glue. This dissolves part of the print, which then hardens when the solvent evaporates fully. The resulting bond is so strong that the layers separate before the joint breaks. This is as strong as you can get, and hopefully the result will be strong enough to withstand the forces during printing. The solvent that I used is Weld-On #4.

The resulting bond. You can see that the layers separated above the joint itself.

Weld on #4.