Development of an automatic tool-offset calibration system for a multi-material 3D printer

Currently we are working on the development of  a multi-material 3D printing process, for the fabrication of 3D printed sensors. This process is build around a multi-material 3D printer from Diabase Engineering called H-Series Hybrid, which has multiple printheads mounted on a rotary stage. These tools need to be accurately aligned relative to each other to achieve repeatable results. However the alignment of these tools currently is done using test structures, which is time consuming and has limited results. Your assignment consists of the selection of suitable sensors and the implementation of an algorithm to calibrate the toolhead offsets in x, y and z.