3D Printer Babbling
InfilI happens once the bottom layer is down, between the inner and outer perimeters that make up the outer skin of the print. You can have any degree of fill from 0% hollow to 100% solid: 15-20% is usually enough to support a structure without much weight - or cost. Filament is cheap, but solid structures suck it up *fast*.
This is a standard rectilinear fill. I'm also quite partial to hexagons. n.n
2.5mm down on the bed now.