Využití neplanárního tisku ve stavebních konstrukcích

prof. Dr. Henri Hubertus Achten, Ing. arch. Lukáš Kurilla, Ph.D., Ing. arch. Jiří Vele

The traditional method of data preparation for 3D printing, known as planar slicing, involves slicing the 3D model into horizontal layers and printing them gradually. This is the simplest option with the main parameter being layer height. However, this method has several limitations, including poor surface finish with stair-stepping contours of layers at steep angles and a necessity to print additional support structure for overhangs. Nonplanar slicing is a newer method that involves slicing the 3D model into non-horizontal layers with varying layer heights. This technique is mostly explored in plastics, with observed improvements in buildability, surface finish and reduction of cracking alongside the layers. In construction scale, non-planar printing is used primarily for achieving unique surface finish, or for printing on an uneven base. Its potential for improving buildability is still yet to be properly tested. This paper examines how non-planar layers can be derived with a help of force flow lines and how it affects the buildability. While printing overhangs, shear force can ultimately break the interlayer bond and layers can start deforming and sliding on top of each other, resulting in buckling, or even collapse. By guiding these forces into the bulk of layers instead of interlayer bonds, printing capabilities can be improved. Goal of this paper is to present how buildability of overhangs can be improved using non-planar slicing. Non-planar layers are derived from force flow line simulations done in Karamba3D. For printing we use clay, as a fast and simple prototyping method with the aim to later utilise our findings into concrete printing.

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prof. Dr. Henri Hubertus Achten, Ing. arch. Jiří Vele

While the CAD model is being prepared for 3D printing, it is sliced into layers. Contrary to planar slicing, where an object is cut by horizontal planes and then a curve for the toolpath is generated from these intersections, non-planar slicing uses twisted planes for object cutting. It brings freedom to toolpath creation and each object can be printed in adjusted layers that reflect its geometry. Benefits of such printing are being explored in plastics and involve enhanced surface finish, cracking reduction and ability to print cantilevers. This paper examines printability of overhangs using clay non-planar printing. Basic potter's clay, from an art supplies shop was mixed with additional water and let in room temperature for one day. Desktop FDM delta printer was retrofitted with a clay printhead, its extruder motor was geared into a 19:1 ratio and connected to the ram. This ram pushes clay from a tank and nylon tube through a 4mm thick nozzle. Set of vase-like objects was designed, each with a different overhang. Starting at 10 degrees and ending at 70 degrees, in increments of 5 degrees. Objects were modelled in Rhinoceros software and G-code for both planar and non-planar print was generated in Grasshopper. Each of those objects were printed twice, once planarly and once non-planarly. During the printing buckling and collapsing of printed objects was monitored. Non-planar printing improves buildability and reduces deformation of overhangs. Right after the print and after they got dry, objects were measured for their deformation. Shrinkage during the drying was measured to be 12,5%. Ideal toolpath for non-planar printing seems to be the one having layers perpendicular to the overhang. Model evaluation and non-planar printing data preparation is being discussed in the paper. If used on a large scale, non-planar printing may allow printing walls with holes for plumbing, or even printing vaults or bridges.

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