Inserting inhibitor to create part boundary isolation during 3D printing

A 3D printing system for printing a desired 3D object comprising:

• a fusible powder that fuses when subjected to a fusing condition;
• a deposition system that deposits portions of the fusible powder on a substrate;
• a fusing system that applies the fusing condition to the deposited fusible powder;
• inhibitor material that does not fuse when subjected to the fusing condition;
• and
• an insertion system that inserts a portion of the inhibitor material between portions of the deposited fusible powder after having been deposited by the deposition system but before being fused by the fusing system so as to form a boundary that defines at least a portion of a surface of the desired 3D object, wherein:
• the insertion system includes a nozzle that has an interior passageway through which the inhibitor material travels;
• the nozzle has a lower end that includes:
• a leading edge in the shape of a plow that can plow a trough between portions of the fusible powder when the lower end of the nozzle traverses such portions;
• and
• a rearward-facing opening though which inhibitor material can be ejected from the nozzle and into the trough immediately after the trough is plowed by the leading edge, thereby filling the trough as the trough is plowed;
• and
• the insertion system causes:
• the leading edge to plow through portions of the unfused fusible powder;
• and
• the opening to elect inhibitor material from the nozzle immediately after the trough is plowed by the leading edge, thereby filling the trough as the trough is plowed.