Development of control systems for laser powder bed fusion

Abstract

Abstract This article aims to highlight the development of an intermittent controller designed to compensate and rectify the lack of fusion (LoF) zones that induce during the LPBF process. The initial step involved the utilization of the Self-Organizing Map (SOM) algorithm to identify the location of LoF defects. Subsequently, the identified defects undergo clustering through the K-means algorithm to form a matrix of cells on the build plate. The center of each cell that encompasses the defective area is then selected as the optimal position for increasing laser power during the subsequence printed layer. To identify the optimum laser power value, various artificial voids, mimicking actual defects, are embedded in the coupons. The capping layer (a layer that covers the artificial void) is then manufactured with different laser powers to heal the underlying defects. Based on the optimum laser power and defect size, several controlling rules are defined to change the laser power in-situ in the targeted cells located within the capping layer of defects. The change in laser power is transferred as a Laser Correction File (LCF) to the actuator via the Message Queuing Telemetry Transport (MQTT) broker. Finally, the performance of the controller is evaluated by designing and fabricating two new sets of experiments, including artificial and randomized defects. The results are validated by performing a micro CT scan, in which the density of defects is analyzed on parts produced with and without the controller. The results suggest that the use of the controller increased the density of the sample with randomized defects by up to 1%.