Mr. Peter Abels Profile

Peter Abels

Group Leader at Fraunhofer-ILT

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Publications (6)

Proceedings Article | 6 September 2019 Paper

Deep learning-based semantic segmentation for in-process monitoring in laser welding applications

C. Knaak, G. Kolter, F. Schulze, M. Kröger, P. Abels

Proceedings Volume 11139, 1113905 (2019) https://doi.org/10.1117/12.2529160

KEYWORDS: Image processing, Laser welding, Image segmentation, Cameras, Feature extraction, Visual process modeling, Laser processing, Convolutional neural networks, Defect detection, Machine learning

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Proceedings Article | 18 March 2016 Paper

Observation of melting conditions in selective laser melting of metals (SLM)

U. Thombansen, Peter Abels

Proceedings Volume 9741, 97410S (2016) https://doi.org/10.1117/12.2213952

KEYWORDS: Pyrometry, Cameras, Sensors, Image processing, Staring arrays, Particles, Spatial light modulators, Imaging systems, Metals, Laser processing

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Proceedings Article | 9 March 2015 Paper

Process observation in selective laser melting (SLM)

U. Thombansen, P. Abels

Proceedings Volume 9356, 93560R (2015) https://doi.org/10.1117/12.2079475

KEYWORDS: Image processing, Signal processing, Atmospheric particles, Laser processing, Particles, Spatial light modulators, Pyrometry, Feature extraction, Sensors, Visualization

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In additive manufacturing, the quality of products can be traced by observation of process variables track by track and layer by layer. The stacking of layer wise information can be used to consolidate the entire build up history of a product thus leading to a truly three dimensional quality histogram. The first step that is necessary to achieve such a quality histogram is the acquisition of process measurands that are related to product quality. Successful acquisition of measurements for thermal radiation has been reported in several publications. The authors of such papers report the detection of changes in boundary conditions of the process by observing the thermal radiation of the process. It has been reported that for example a change in laser power has an influence on the thermal emission and that different readings are received for processing a thin powder layer on a solid work piece compared to scanning pure powder in the situation of an overhang structure. A correlation to the underlying reason for the increase in thermal radiation however is mostly related to the experimental setup rather than to in process measurements. This report demonstrates an approach of acquiring and combining synchronous measurements of different physical properties of the process. The coaxial observation system used in the experiments enables the synchronous acquisition of measurements of the thermal emission and the acquisition of images that visualize the surface of the powder bed in the vicinity of the interaction zone. The images are used to monitor the motion of powder particles as they are influenced by the melting process. This amount of particle motion is then correlated to areas of different powder thicknesses. The combination of this information with excessive readings in thermal emission classifies the event to be a situation of noncritical deviation of thermal emission. In fact, this combination of extracted features establishes a first key criterion for an unequivocal event mapping.

Proceedings Article | 6 March 2014 Paper

Real-time laser cladding control with variable spot size

J. Arias, M. Montealegre, F. Vidal, J. Rodríguez, S. Mann, P. Abels, F. Motmans

Proceedings Volume 8970, 89700Q (2014) https://doi.org/10.1117/12.2040058

KEYWORDS: Cladding, Control systems, Zoom lenses, Image processing, Beam controllers, Cameras, Coating, Laser processing, Field programmable gate arrays, Lenses

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Proceedings Article | 20 February 2014 Paper

Seam tracking with texture based image processing for laser materials processing

S. Krämer, W. Fiedler, A. Drenker, P. Abels

Proceedings Volume 8963, 89630P (2014) https://doi.org/10.1117/12.2040483

KEYWORDS: Image processing, Laser welding, Laser processing, Video, Image analysis, Detection and tracking algorithms, Head, Cameras, Imaging systems, Process control

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Proceedings Article | 7 February 2000 Paper

Coaxial process control during laser beam welding of tailored blanks

Christian Kratzsch, Peter Abels, Stefan Kaierle, Reinhart Poprawe, Wolfgang Schulz

Proceedings Volume 3888, (2000) https://doi.org/10.1117/12.377055

KEYWORDS: Cameras, Process control, Plasma, Sensors, Control systems, Imaging systems, Image processing, Laser processing, Capillaries, Compound parabolic concentrators

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Production of laser beam welded tailored blanks requires both, high quality processing as well as a quality assurance by reliable monitoring systems for each welded part. Actual quality monitoring systems for tailored blank applications make use of different sensors for seam tracking, seam shape detection and process control. The suitable process diagnostic device is a plasma sensor which detects the optical emission of the weld plasma. Experimental evidence show that the reliability of the seam quality prediction can significantly be improved by using a camera system with a two-dimensional spatial resolution instead of an integrating plasma detector. The improvement is achieved by exploiting the information provided by the spatially distributed intensity of the plasma emission. In particular, by coaxial arrangement of the camera with respect to the laser beam axis, the direction of observation allows to detect significant process characteristics. Based upon these results a coaxial process control system was developed that can be adapted for different laser materials processing applications like welding, cutting and surface treatment. The system consists of a high speed camera mounted directly at the welding head. The optical path of the camera goes coaxial with the laser beam path through the focusing optics. The camera images taken from the process are analyzed using image processing algorithms. The algorithms are chosen depending on the type of application to be monitored. In the case of welding tailored blanks the system can monitor a full penetration of the workpiece, deviations from the desired welding path, seam width, stability of the capillary shape and defects of the seam caused by spatter and ejection of molten material. The camera system offers the ability to perform simultaneously different quality monitoring tasks like determination of seam and capillary shape, seam tracking and process control. Thus the number of sensors required for quality monitoring is reduced to one single system.

Showing 5 of 6 publications

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