Print path continuity

Print path continuity is the property of a toolpath in which each layer is deposited as a single uninterrupted movement, avoiding the stops, restarts and travel moves that introduce defects into a printed element. Because a cementitious mortar cannot be retracted the way a thermoplastic can, an interruption leaves a blob where flow stops and a thin or hollow start where it resumes.

In practice

Continuity is a design constraint as much as a machine setting. A floor plan with separate, disconnected wall segments forces the nozzle to lift and travel between them on every layer, so plans intended for printing are often drawn so that each level can be traced in one closed loop. Where an interruption is unavoidable, the start and stop points are staggered between layers so that the resulting weak points do not stack up into a vertical seam. Long pauses are more serious still, because the exposed layer stiffens and the next bead bonds to a surface that has already begun to set.

Related terms

• Toolpath — the full set of movements the nozzle follows.
• Cold joint — what forms when an interruption lasts long enough for the previous layer to set.