Robust calibration marker detection in powder bed images from laser beam melting processes

Jacobsmühlen, Joschka zur; Achterhold, Jan; Kleszczynski, Stefan; Witt, Gerd; Merhof, Dorit

doi:10.1109/icit.2016.7474873

Cited by 5 publications

(3 citation statements)

References 7 publications

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“…After 2-D image acquisition, the correction of lens and perspective distortions are crucial steps for the subsequent image processing. Besides, illumination adaption and filter concepts are also essential for a high image quality (Zur Jacobsmühlen et al, 2016). These influences of image pre-processing are basic for the following extraction of the relevant image information by contour detection.…”

Section: Process-accompanying Quality Control By Optical Measurement Techniquesmentioning

confidence: 99%

Methods and procedure of referenced in situ control of lateral contour displacements in additive manufacturing

Lerchen¹,

Hornung²,

Zou³

et al. 2021

J. Sens. Sens. Syst.

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Abstract. Additive manufacturing technologies are further developing from prototype to serial production. This trend requires rising challenges to the process-accompanying quality assurance. Optical in situ quality control approaches show great potential to generate accurate measurement data, which are essential for feedback control. If a reliable referencing concept for the layer-by-layer measured data is guaranteed, contour information can be used during the manufacturing to correct occurring geometrical deviations. Within this scientific study, two methods of optical, referenced in situ control of lateral displacements of additive manufactured contours are presented. In the first approach the 2-D contour of the melting pool is analysed in relation to a position-stable reference system implemented in the powder bed. The second approach uses the translucent contour of deeper layers covered with powder as a reference. Within the image evaluation several pre-processing steps like calibration, undistortion, rectification, illumination correction and low-pass filtering are essential for reliable and correct geometric measurements. The following adapted contour detection and position determination of the referenced melting pool contours are based on an extended edge detection algorithm according to Canny (1986). With the evaluation of further manufacturing layers of already lowered powder bed levels, it is possible to specify the influence of powder application on geometrical displacements separately. This is done by a comparison of the position of the detected powder-covered melting pool contours with the previously applied melted region. Consequently a better understanding of lateral contour displacements within the additive manufacturing process is the goal, which is important for a process-accompanying correction of geometrical deviations.

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Section: Process-accompanying Quality Control By Optical Measurement Techniquesmentioning

confidence: 99%

Methods and procedure of referenced in situ control of lateral contour displacements in additive manufacturing

Lerchen¹,

Hornung²,

Zou³

et al. 2021

J. Sens. Sens. Syst.

View full text Add to dashboard Cite

show abstract

“…This step is important for a subsequent alignment of the measuring systems and the deformation correction within image processing. A stable, reliable referencing is further essential for meaningful geometric analysis (Zur Jacobsmühlen et al, 2016).…”

Section: Process-accompanying Quality Control By Optical Measurement Techniquesmentioning

confidence: 99%

“…6b is performed to compensate the perspective image deformation. As a result of the rectification, the edges of the image are bevelled, but the centre of the image is reproduced realistically as if the viewing angle is perpendicular to it (Zur Jacobsmühlen et al, 2016). The last step of image preprocessing includes an area restriction to a smaller measuring field, which is shown in Fig.…”

Section: Rectification and Undistortionmentioning

confidence: 99%

Referencing of powder bed for in situ detection of lateral layer displacements in additive manufacturing

Lerchen¹,

Schinn²,

Hausotte³

2021

J. Sens. Sens. Syst.

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Abstract. An increasing number of additive manufacturing (AM) applications leads to rising challenges for the process-accompanying quality assurance. Beside post-processing measurement systems, in situ monitoring systems in particular are currently requested to ensure feedback controlling during AM processes. For data acquisition and subsequent evaluation, a high data quality is of importance. It depends on a high resolution and accuracy of measurement systems, adapted measurement conditions and a reference to the powder bed or component for geometric measurements. Within this scientific study, a new reference system has been implemented into the powder bed to reduce measurement deviations by an abbreviated metrological loop. After data acquisition and image processing layer by layer, the position stability of the reference system has been analysed in relation to the optical measuring system. Based on a contour detection of the reference markers, the evaluation of geometrical process deviations is presented as an essential basis for a closed-loop controlling system. Thermally induced and mechanical drifts within the manufacturing process can be verified by the reference system in the powder bed. As an outlook, two methods are suggested for a process-accompanying referenced detection of the melting pool and resulting contour displacements during additive manufacturing.

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In situ measurement of part geometries in layer images from laser beam melting processes

et al. 2018

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Robust calibration marker detection in powder bed images from laser beam melting processes

Cited by 5 publications

References 7 publications

Methods and procedure of referenced in situ control of lateral contour displacements in additive manufacturing

Methods and procedure of referenced in situ control of lateral contour displacements in additive manufacturing

Referencing of powder bed for in situ detection of lateral layer displacements in additive manufacturing

In situ measurement of part geometries in layer images from laser beam melting processes

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