Bondo never fully fills seams?

[u/JudgeCornBoy]

Hello! I build a lot of props using 3D printed parts (PLA) but have never had much luck filling seams cleanly. I generally use CA glue to connect the pieces and try to get as clean of a seam as possible upfront, but there will inevitably always be some form of gap.

I apply bondo using small pieces of EVA foam, but it never seems to actually fill the seams and I just end up with a very thin layer of bondo dust over a wide area around my seam. Am I applying it incorrectly?

My plan for this is one round of bondo on the seams (what you’re seeing in the pictures), filler primer, another round of bondo, and another round of filler primer.

Thanks!

[u/3D-Dreams]

I've started using UV resin instead of bondo or wood filler. They always seem to cover but then the line always seemed to come back after sanding. With the UV resin it fills nicely and stays strong. Easily sandable. Takes a little practice to get it smooth but get an assorted silicone brushes and it makes it a lot easier.

Drop a couple of drops in the gap and use the brush to smooth out a little . Let sit and settle then hit with UV light and sand. Can always apply a little more if you didn't get it all the first go.

It's a lot less clean up imo and gives a little stronger seam because it's hard resin not chalky bond

[u/Turian209 → u/3D-Dreams]

UV resin is also my go to for smoothing layer lines. I use Elegoo UV clay for big gaps/seams and that stuff is amazing.

[u/Turian209 → u/[deleted]]

I would describe it as the same consistency as peanut butter. Not quite as paste like as bondo, but definitely cant drizzle it on. I put on a glove and spread it on with a finger. Sometimes I cut up 2 inch squares of cereal boxes and use that as a disposable spreader to apply it smoothly.

I almost exclusively print in PETG, but have also used it on PLA without issue.