Precise calibration for error detection and correction in material extrusion additive manufacturing using digital fringe projection

Abstract This work proposes a novel calibration method to align the coordinate system of a digital fringe projection system and a material extrusion additive manufacturing machine for in-process error detection and correction. A calibration geometry is printed and measured with the DFP system. Three-dimensional and two-dimensional data processing techniques are then implemented to estimate a rigid transformation matrix between the coordinate systems. The proposed calibration method and geometry are designed to run every time before the start of the manufacturing process. This removes inaccuracies caused by processes in additive manufacturing such as homing and auto-leveling, and allows the transformation to have a high accuracy. The proposed calibration method has achieved a sub-millimeter accuracy with an average root mean square error (RMSE) of 0.028 mm. The proposed method was further used for process monitoring to detect and correct sub-layer under-extrusion errors on a layer-by-layer basis. This error correction process improved the average RMSE by a factor of 1.7 for a simple shape error.