Optimization of trajectory processing algorithms to print 3D circuit boards using piezo ink jet and 6-axis robots

Abstract

Direct printing of conductive inks at the surface of generic 3D objects using 6 axis robots is attracting an ever-increasing interest, however the high precision positioning and the generation of smooth printing trajectories still represent a bottleneck for the manufacturing of 3D electronic circuits. This work presents a new approach for the rapid prototyping of 3D electronics onto generic objects using a 6 axis robot equipped with a piezo jetting printhead and a high speed laser profiler and a six steps protocol composed by the: i) 3D scan of the substrate and mesh smoothing, ii) 2D circuit projection on the planarized mesh and generation of the 3D trajectory, iii) normals alignment of points lying in the 3D trajectory, iv) retrieve of the effective toolhead TCP translation speed along the 3D trajectory with a blank run, v) synchronization of the ink jetting frequency with the effective toolhead speed, vi) generation of the robot code and print.The effect of mesh and normals smoothing and of circuit design on the effective toolhead translation speed was systematically investigated in order to minimize speed fluctuations/heterogeneous ink deposition during printing, the computational load and shape deviation from the pristine 3D substrate.Conductive tracks printed on an ABS dome displayed geometry and line resistance in line with those predicted by a semi-empirical model using the robot nominal speed and silver ink conductivity, thus showing that the robot operated under stable and well controlled conditions during the printing process.The developed process displayed an average duty cycle of ca. 30 min from the 3D scan to the printing of the 3D circuit, thus showing that it could be suitable for the rapid prototyping/benchmarking of 3D electronics on generic objects.