Beschreibung
Additive manufacturing of concrete components represents an innovative approach to facing today's challenges in construction. However, the reproducibility of concrete-based additive manufacturing processes leaves much to be desired since the geometry of the printed strand is unpredictably affected by environmental influences, material shrinkage, and process flow characteristics. Especially during the manufacturing of large-scale components, the slightest deviation between as-planned and as-printed layer height stacks up. It leads to substantial discrepancies between the designed and printed component. Divergence is even worse when spraying the material instead of extruding since underestimating the layer height lowers the application level within the spray cone, leading to a widened but even more flattened strand in each layer. An online process control can increase the accuracy of additive manufacturing by compensating for such deviations during printing. This paper aims to implement a process control algorithm to compensate for the above-mentioned deviations by adjusting the material volume flow. A 2D laser scanner runs ahead of the printing nozzle to gain exact information on layer height deviations. The error can be calculated and compensated by comparing the real-time information on the actual layer height and the target height set during path planning. As an alternative additive manufacturing process for concrete components, a sprayable insulation foam test setup reduces the effort required to experiment with concrete. The developed process control algorithm was used to 3D print an object of 1 m height. In addition, the influence of different controller settings on the process was investigated. Results show a significant process stability improvement when printing with the proposed control approach.
