Digitalization of directed energy deposition process through a multidirectional height monitoring sensor system

Abstract

Industrialization of directed energy deposition (DED) process relies on the development and implementation of a quality assurance system that makes the process reliable and repetitive. One of the geometrical characteristics that needs constant monitoring and control during any DED process is the height of the deposited layer. In this paper, a multidirectional layer height monitoring system relying on the laser triangulation principle that has been developed for real-time direct measurement, in contrast to the majority of the sensor systems that derive layer height based on melt pool temperature, is presented. Existing commercial laser triangulation systems are unidirectional, which hinder the flexibility of the material handling system, like industrial robot, in most of the cases. An additional challenge lies on the integration with the deposition head due to its form, size, and extreme working conditions. Therefore, a novel configuration of laser triangulation sensors that enable multidirectionality and limit shadowing effect has been developed at Fraunhofer IAPT. In this paper, the development of such a sensor with a focus on the mechanical design has been presented. The sensor is designed for operation at high temperature and harsh environmental conditions close to the build zone. The developed sensor has been successfully tested for the powder-based laser metal deposition system. In-process layer height measurement and control are possible with this sensor, thereby enabling digitalization and quality assurance during the build process. 3D point cloud generated using this sensor can be used for the dimensional deviation measurement and also for downstream processes like machining. Such an in-process quality measurement and assurance system negates a postmeasurement step, thereby saving cost and time and ensuring quality.