MPCNC foam-cutter attachment

Simple foam cutter for Ryan "allted" Zellars' Mostly Printed CNC (http://www.thingiverse.com/thing:724999). Cut foam planes and figures from $tree foamboard or 1/4" fanfold foam insulation board. Uses DC motor salvaged from inkjet printer or battery-powered drill/screwdriver, .025" music-wire needle, small ball-bearing with 3mm bore, and sports-ball inflation needle for guide. Vary motor voltage to get good cut action -- 10-15 strokes/perforations per mm cleanly cuts paper and foam. Form needle loop around drill bit shank to be just under bearing OD. Mount bearing with 3x10mm screw in off-center hole, put small washer between inner race and plastic wheel, and lightly groove outer race with Dremel and cutoff wheel to retain wire needle loop. Dress the needle point with a fishhook sharpener to remove burrs and barbs. Needle exposure below end of guide should be material thickness plus 2-3 mm. Works well at feedrate of 1000 mm/min and cutter speed of 10000 rpm (strokes/min).

Originally