Additive manufacturing systems can generate highly complex components, which could not be produced with conventional machine tools or only with great effort. Nevertheless, such industrial 3D printers are far from being standard equipment in factories. This is not just due to the purchase costs, but also to many other challenges. The Fraunhofer Institute for Material and Beam Technology IWS Dresden has developed particular solutions and presented them at the recent“Formnext” trade fair in Frankfurt Germany including the “LIsec” analysis device for controlling the powder flow in additive manufacturing processes.
While in conventionally manufacturing processes such as milling, the calibration of the tools corresponds to the state of the art, in laser powder build-up welding it is still a great challenge. The “LIsec” measuring device developed at IWS solves this challenge and move the limits to technical feasibility. The abbreviation stands for “Light Section” and reveals the principle: A measuring laser scans the powder flow after leaving the nozzle. A right-angle camera is mounted, which records light sections through the powder and forwards them to analysis software. “The three-dimensional distribution of the powder stream can be calculated with high precision,” explains IWS engineer Rico Hemschik. “This allows significantly simplified quality control and provides conclusions about the wear degree of the powder nozzle.”
The laser light section method divides the powder jet into a definable number of measuring planes. The precise knowledge of its position allows a three-dimensional image of the powder jet to be created. Analysis algorithms developed at IWS, in conjunction with the corresponding software, calculate all relevant nozzle parameters, such as the exact position and expansion of the powder focus. LIsec enables fast and easy quantitative analysis of all relevant measurement parameters by aligning the captured image information with mathematical functions. This results in optimum comparability of different measurements.
Based on the acquired image data, an analysis algorithm reliably detects the position of the powder focus, the spot of the highest powder density within the powder jet. The comparison of the real with the theoretical focus position allows a direct statement about the further usability of the nozzle. The analysis of the shape and characteristics of the powder jet at several relevant measuring points also allows a quantitative assessment of the nozzle quality. Not only the wear of the nozzle can be observed, but also the service life increases significantly. Transferring the focus position as TCP to the machine control reduces tool change time and significantly increases the process reproducibility. In addition, LIsec ensures a better process understanding and less effort for parameter
studies: In this way, the various influences of the feed parameters on the powder cone characteristics can be investigated.
As an example, the system can be used to repair damaged or worn turbine blades on aircraft in a higher quality and more reliably than before. “In this respect, our measuring device can contribute to greater safety and lower maintenance costs in aviation,” says the IWS engineer. The Dresden Institute is already working on the industrial implementation of the technology with several well-known international companies and research institutes.
For more information: www.iws.fraunhofer.de