CEAD Patents a Nonstop Toolpath Strategy for 3D Printing Hard-to-Control Materials

Why stopping is a problem

Most desktop 3D printers slice a model into horizontal layers, print one layer, stop extrusion, move to the next feature, and start again. That works fine for PLA and PETG. It does not work well for viscous materials like silicone, elastomers, epoxy, or concrete. These materials keep flowing after the motor stops, so travel moves leave strings, blobs, or dragged wisps across the part.

CEAD, the Dutch large-format additive manufacturing company, has filed a patent application that attacks the problem from the slicer side instead of the extruder side. US patent application US20260225319A1, published in early August, describes a method for calculating toolpaths across multiple layers so the nozzle never really has to stop.

How the toolpath changes

The idea is straightforward in concept. When the print head reaches a point where it would normally make an empty travel move, the slicer instead routes it to a nearby feature on an adjacent layer and keeps extruding. The head bounces between two neighboring layers, tracing available geometry and only switching direction when the geometry forces it to.

The patent describes slicing the object into an even number of layers, then grouping them in pairs. Corresponding nodes on adjacent layers are identified so the print head can transition using a short vertical or diagonal move. In practice, the machine prints part of one layer, jumps to the matching layer next to it, prints there, and jumps back later. The result is a continuous string of extrusion with no true start-stop points.

Where it helps most

The technique depends heavily on geometry. Suitable paths must exist on nearby layers, so some shapes will benefit more than others. The patent specifically names elastomers, silicone, glass, epoxy, and concrete as target materials. High-throughput extrusion systems, where pressure lingers in the delivery tube after a commanded stop, stand to gain the most.

CEAD's approach does not require new hardware. It is a slicing strategy that could, in theory, be adopted by existing CAM or slicer software for large-format robot cells. Most slicers today spend their optimization effort on single layers. CEAD is asking what happens when the slicer is allowed to think in three dimensions instead of two.