Monitoring and control of metal-based additive manufacturing technologies

Abstract

This work shows the development of monitoring and control strategies for additive manufacturing (AM) processes. An arc-length control system and a PID temperature control system were developed for Wire-arc AM processes. An Oxygen monitoring/control system with a shielding gas crossflow was developed for Powder based fusion (PBF) processes. The arc-length control system delivered a constant transfer mode and allowed for consistent temperature measurements whilst drastically improving process stability and part appearance. Small improvements where observed with the use of the PID temperature control system. Maximum temperatures were reduced by approximately 200°C. The results indicate a successful temperature control system requires the use of an independent arc-length control system. For PBF, a controlled environment capable of maintaining oxygen levels of 1ppm during the entire build process was designed. A simple monitoring/control system was developed to ensure the machine did not operate over a user selected oxygen concentration threshold. A laminar cross-flow device was developed to remove unwanted by-products generated by the PBF process. High speed imaging experiments were used to test the validity of the crossflow. The results show, that the use of a laminar crossflow device leads to a drastic improvement in process stability.