3D puff works by laying foam on the garment, stitching over it, and letting the needle perforate everything outside the design so the excess tears away. The thread has to cover the foam completely and cut it cleanly at every edge.
If the density is wrong, foam shows through and the piece is scrap. If the edge closure is loose, ragged foam stays attached around the outline and someone ends up picking it off by hand.
Puff is a popular cap upgrade for team and club caps and promotional headwear, but it does not suit every element. Fine lettering, thin serifs and small detail collapse under foam, so part of the job is deciding what gets raised and what stays flat.
A digitizer who puffs everything is not doing you a favor. We tell you when an element is too fine to hold foam and usually suggest a mixed design: bold shapes raised, detail stitched flat.