Thermographic process monitoring in powderbed based additive manufacturing

Journal Article · Tue Mar 31 00:00:00 EDT 2015 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.4914608· OSTI ID:22391233

Krauss, Harald; Zaeh, Michael F. ^[1]; Zeugner, Thomas ^[2]

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1. AMLab, iwb Application Center Augsburg, Technische Universität München (Germany)
2. Augsburg University (Germany)

Selective Laser Melting is utilized to build metallic parts directly from CAD-Data by solidification of thin powder layers through application of a fast scanning laser beam. In this study layerwise monitoring of the temperature distribution is used to gather information about the process stability and the resulting part quality. The heat distribution varies with different kinds of parameters including scan vector length, laser power, layer thickness and inter-part distance in the job layout which in turn influence the resulting part quality. By integration of an off-axis mounted uncooled thermal detector the solidification as well as the layer deposition are monitored and evaluated. Errors in the generation of new powder layers usually result in a locally varying layer thickness that may cause poor part quality. For effect quantification, the locally applied layer thickness is determined by evaluating the heat-up of the newly deposited powder. During the solidification process space and time-resolved data is used to characterize the zone of elevated temperatures and to derive locally varying heat dissipation properties. Potential quality indicators are evaluated and correlated to the resulting part quality: Thermal diffusivity is derived from a simplified heat dissipation model and evaluated for every pixel and cool-down phase of a layer. This allows the quantification of expected material homogeneity properties. Maximum temperature and time above certain temperatures are measured in order to detect hot spots or delamination issues that may cause a process breakdown. Furthermore, a method for quantification of sputter activity is presented. Since high sputter activity indicates unstable melt dynamics this can be used to identify parameter drifts, improper atmospheric conditions or material binding errors. The resulting surface structure after solidification complicates temperature determination on the one hand but enables the detection of potential surface defects on the other hand. These issues and proper key figures for thermographic monitoring of the Selective Laser Melting process are discussed in the paper. Even though microbolometric temperature measurement is limited to repetition rates in the Hz-regime and sub megapixel resolution, current results show the feasibility of process surveillance by thermography for a limited section of the building platform in a commercial system.

• OSTI ID: 22391233
• Journal Information: AIP Conference Proceedings, Vol. 1650, Issue 1; Conference: 41. Annual Review of Progress in Quantitative Nondestructive Evaluation, Boise, ID (United States), 20-25 Jul 2014; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
DETECTION
ENERGY LOSSES
HEAT
HEAT TRANSFER
HOT SPOTS
LASER RADIATION
LAYERS
MELTING
POWDERS
SOLIDIFICATION
TEMPERATURE DISTRIBUTION
TEMPERATURE MEASUREMENT
TEMPERATURE MONITORING
THERMAL DIFFUSIVITY
THERMAL EFFLUENTS
THERMOGRAPHY
TIME RESOLUTION