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.