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@PHDTHESIS{zurJacobsmhlen:760489,
author = {zur Jacobsmühlen, Joschka},
othercontributors = {Merhof, Dorit and Ohm, Jens-Rainer},
title = {{I}mage-based methods for inspection of laser beam melting
processes},
school = {Rheinisch-Westfälische Technische Hochschule Aachen},
type = {Dissertation},
address = {Aachen},
reportid = {RWTH-2019-04231},
pages = {1 Online-Ressource (vi, 187 Seiten) : Illustrationen},
year = {2018},
note = {Veröffentlicht auf dem Publikationsserver der RWTH Aachen
University 2019; Dissertation, Rheinisch-Westfälische
Technische Hochschule Aachen, 2018},
abstract = {Laser beam melting (LBM) is an additive manufacturing (AM)
method which enables the layer-based production of
three-dimensional parts from metal powder. AM enables
complex geometries which are not manufacturable by
conventional, subtractive methods. In recent years, LBM has
matured from a rapid prototyping method to a rapid
manufacturing method which is used for production of
individual parts or small batches, e.g. spare parts or
dental prosthetics. In spite of its advantages, LBM still
has not replaced conventional manufacturing methods for
suitable applications which can be attributed to a lack of
reproducibility, process monitoring and quality assurance.
To enable widespread application of LBM, comprehensive
process documentation of process results and associated
analysis methods are required. By providing data about the
production process, parts from LBM may be utilized in
application areas with strict quality requirements.
Additionally, the analysis results enable process
optimization for parts with challenging geometrical
features, such as thin walls or overhanging structures. This
work describes an imaging setup with optimized lighting for
acquisition of high resolution layer images (20-30 μm/px)
of powder bed and exposure results which can be retrofitted.
Automatic image analysis methods for error detection and
measurement and a process documentation format complete the
inspection system for LBM. Elevated part regions pose a
major risk for build stability which is why process
parameter optimization often focuses on reducing elevated
part region area. Detection methods working on layer images
of the powder bed or melt result are described and
measurements for quantitative evaluation of build job
stability are defined. As the probability of elevated part
region formation depends on both process parameters and
local part geometry, e.g. the angle of overhanging surfaces,
the feasibility of predicting build stability based on
elevation detection results and analysis of part geometry is
examined. Complex part geometries, e.g. internal cooling
channels in tools, which are inaccessible for measuring
tools, complicate post-process quality assurance. Therefore,
in-situ inspection is required to verify the dimensional
accuracy of these structures. To this end, contour
segmentation methods for layer images of the exposure result
are compared to provide automatic in-situ geometry
inspection. The surface topography of produced layers
indicates the quality of the compound and is usually
assessed by microscopy. The high resolution of layer images
enables inspection of surface topography by computing a
feature which rates the prominence of laser scan lines in
layer images. The documentation system and the associated
analysis methods enable process inspection and quality
assurance in LBM thereby helping to establish this
technology for more applications.},
cin = {611710},
ddc = {621.3},
cid = {$I:(DE-82)611710_20140620$},
typ = {PUB:(DE-HGF)11},
doi = {10.18154/RWTH-2019-04231},
url = {https://publications.rwth-aachen.de/record/760489},
}
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