Why does my resin print 3D model failing in sanding?

Resin 3D prints often fail during sanding due to incomplete post-curing, brittle resin, or improper sanding techniques. Incomplete curing leaves resin soft or sticky—sanding gums it up or scratches unevenly instead of smoothing. Brittle standard resins crack or chip under pressure. Too coarse sandpaper or dry sanding (instead of wet) damages the surface. Fix it by extending UV post-curing time (follow your resin’s guidelines), using "tough" resin for sandable parts, and starting with 200–400 grit sandpaper + wet sanding to reduce heat and friction.