▁structure , ▁which ▁can ▁be ▁broken ▁away ▁during ▁finishing . ▁Usually , ▁the ▁software ▁that ▁converts ▁the ▁ 3 D ▁model ▁into ▁a ▁set ▁of ▁flat ▁layers , ▁called ▁s lic er , ▁takes ▁care ▁of ▁the ▁addition ▁of ▁these ▁supports ▁and ▁some ▁other ▁resources ▁to ▁allow ▁the ▁fabric ation ▁of ▁this ▁kind ▁of ▁shapes . ▁ ▁F used ▁de position ▁model ing ▁is ▁also ▁referred ▁to ▁as ▁f used ▁fil ament ▁fabric ation ▁( FF F ) ▁by ▁companies ▁who ▁do ▁not ▁hold ▁the ▁original ▁pat ents ▁like ▁Str at as ys ▁does . ▁ ▁Pow der ▁bed ▁fusion ▁▁ ▁Another ▁ 3 D ▁printing ▁approach ▁is ▁the ▁select ive ▁f using ▁of ▁materials ▁in ▁a ▁gran ular ▁bed . ▁The ▁technique ▁f uses ▁parts ▁of ▁the ▁layer ▁and ▁then ▁moves ▁up ward ▁in ▁the ▁working ▁area , ▁adding ▁another ▁layer ▁of ▁gran ules ▁and ▁repeating ▁the ▁process ▁until ▁the ▁piece ▁has ▁built ▁up . ▁This ▁process ▁uses ▁the ▁unf used ▁media ▁to ▁support ▁over hang s ▁and ▁thin ▁walls ▁in ▁the ▁part ▁being ▁produced , ▁which ▁reduces ▁the ▁need ▁for ▁temporary ▁auxili ary ▁supports ▁for ▁the ▁piece . ▁For ▁example , ▁in ▁select ive ▁heat ▁s inter ing , ▁a ▁thermal ▁print head ▁applies ▁heat ▁to ▁layers ▁of ▁pow der ed ▁therm op last ic ; ▁when ▁a ▁layer ▁is ▁finished , ▁the ▁pow der ▁bed ▁moves ▁down , ▁and ▁an ▁autom ated ▁roll er ▁adds ▁a ▁new ▁layer ▁of ▁material ▁which ▁is ▁s inter ed ▁to ▁form ▁the ▁next ▁cross