In-situ digitising system for geometric improvement of layer contours in additive manufacturing

Abstract Additive manufacturing (AM) has faced challenges in achieving the part accuracy required for industrial adoption. Most research has focused on offline inspection of geometric deviations in test parts. This paper introduces a novel approach to enhance part accuracy and process control in Polymer Extrusion AM (MEX/P) by integrating in-situ digitising and compensation systems. A custom 3D-printing test bench was developed for this purpose, incorporating a laser-stripe sensor for real-time measurement of layer contours during the printing process. The paper details the integration procedure, including sensor installation, calibration, and validation test. To validate the system accuracy, irregular-shaped test parts were scanned using the integrated sensor and compared to ground truth measurements from a Coordinate Measuring Machine. The results demonstrated close agreement between the two measurement methods. The methodology was applied to a case study, wherein digitised layer contours were recognised and their geometric deviations from the nominal contours were measured and compensated for. This process also accounted for the thermal shrinkage experienced by the part during cooling. This resulted in a significant improvement in part quality, with virtually eliminated average layer contour deviations and a reduction in error dispersion by over 50%. The proposed methodology, validated for parts with uniform complex cross-sections, can be extended to the production of serial components with any layer shape including both outer and inner contours.