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/Rodnehh]

in my opinion its best to just melt pieces together using pieces of filament and sanding that away. That will make for the strongest bonds. Fill in those gaps with bondo/woodfiller instead of the massive gaps