Inductive XY calibration method for multi-material fused filament fabrication 3D printers

In this work an optical and inductive calibration procedures for calibrating multi-material fused filament fabrication 3D printers in the x and y directions is presented. The inductive calibration is based on the principle that the inductance of a detection coil placed on the print bed changes when the (metallic) extrusion nozzle passes it. This calibration method shows a repeatability of up to 2µm. To determine the accuracy of this calibration method, another calibration method is proposed that directly measures the position of the deposited material. During this alternative process, a calibration structure is printed on an A4-format sheet of paper using every tool. The paper is subsequently scanned using a digital scanner, and the resulting image is analyzed using an image-processing script. Using this method as a reference, it was determined that the inductive method has an accuracy of approximately 45µm. For applications where this accuracy is sufficient, the inductive method provides a fast solution that requires little to no user interaction. For more demanding applications, the optical calibration might be the better choice, since it is more time-consuming but yields a more accurate solution. It is expected that the accurate calibration of tool offsets will reduce both the chance of poor adhesion between materials and the mixing of filaments due to local over- and under-extrusion at material interfaces.