Influences of process conditions on stability of sensor controlled robot-based laser metal deposition

Buhr, Malte; Weber, Julian; Wenzl, Jan-Philip; Möller, Mauritz Leander Birger; Emmelmann, Claus

doi:10.1016/j.procir.2018.08.067

Cited by 16 publications

(12 citation statements)

References 5 publications

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“…Due to the large number of available powder materials, the process can be used quite flexibly [ 7 ]. In order to achieve consistent quality during manufacturing, numerous process monitoring and control methods have been developed [ 8 , 9 , 10 , 11 , 12 , 13 , 14 ].…”

Section: Introductionmentioning

confidence: 99%

In-Line Observation of Laser Cladding Processes via Atomic Emission Spectroscopy

Schmidt

Huke

Gerhard³

et al. 2021

Materials

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Direct metal deposition (DMD) can be used for the cladding of surfaces as well as repairing and additive manufacturing of parts and features. Process monitoring and control methods ensure a consistent quality during manufacturing. Monitoring by optical emission spectroscopy of the process radiation can provide information on process conditions and the deposition layer. The object of this work is to measure optical emissions from the process using a spectrometer and identify element lines within the spectra. Single spectra have been recorded from the process. Single tracks of Co-based powder (MetcoClad21) were clad on an S235 base material. The influence of varying process parameters on the incidence and intensity of element lines has been investigated. Moreover, the interactions between the laser beam, powder jet, and substrate with regard to spectral emissions have been examined individually. The results showed that element lines do not occur regularly. Therefore, single spectra are sorted into spectra including element lines (type A) and those not including element lines (type B). Furthermore, only non-ionised elements could be detected, with chromium appearing frequently. It was shown that increasing the laser power increases the incidence of type A spectra and the intensity of specific Cr I lines. Moreover, element lines only occurred frequently during the interaction of the laser beam with the melt pool of the deposition layer.

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Section: Introductionmentioning

confidence: 99%

In-Line Observation of Laser Cladding Processes via Atomic Emission Spectroscopy

Schmidt

Huke

Gerhard³

et al. 2021

Materials

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“…Datapoints are numbered sequentially according to the parameter list in Table 1. Datapoints for samples 1,4,7,10,13,16,19,22,25 show no dilution (dilution = 0) as well as no peak intensity ratio R I 19 =I 16 ¼ 0. This is caused by the absence of a detectable peak height for peak 19 (Fe).…”

Section: Cross-sectional Dimensions and Spectroscopic Analysismentioning

confidence: 99%

Investigation of Direct Metal Deposition Processes Using High-Resolution In-line Atomic Emission Spectroscopy

et al. 2022

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Process monitoring and control methods during direct metal deposition (DMD) ensure consistent manufacturing quality of the product. Naturally occurring optical process emissions provide selective and specific element lines, which can be investigated by optical spectrometers. However, DMD processes are mainly characterized by thermal conduction. Hence, the resulting optical emission lines have low intensities. The aim of this work is to investigate the spectral lines and determine the required resolution of the spectrometer. Two spectrometers coupled by a bifurcated optical fiber were used simultaneously (resolution = approx. 47 pm FWHM at 522 nm and 55 pm FWHM at 407.5 nm and resolution = 0.73 nm FWHM). A parameter study with varying process parameters using Co-Cr-based (MetcoClad21) powder on low-alloyed tool steel C45W (1.1730) substrate material was conducted. Peaks occurring in spectral data were assigned to specific element emission lines by using data from the NIST atomic spectra database. All identified element lines were non-ionized elements. Cr I, Fe I and Mn I lines in particular were frequently observed. The occurrence of element emission lines as well as the peak intensity ratios for specific elements was compared with the cross-sectional dimensions including height, weld depth and dilution. It has been shown that the occurrence and intensity of emission lines correlate with the process parameters, especially the laser power. Furthermore, the dilution of a deposition track correlates with the occurrence and intensity of an identified Fe I emission line, represented by a Fe-Cr peak intensity ratio.

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“…However, due to the directional dependency and the process emissions, online measurement is challenging, which is why measurements are usually performed after a layer has been applied. Thus, various layer-to-layer control systems have been developed employing such sensors [37][38][39]. Moreover, several authors have used laterally arranged CCD, CMOS, or IR cameras to detect the height of the bead or the part, respectively [40][41][42].…”

Section: A Novel Concept For Multivariable Process Controlmentioning

confidence: 99%

Laser Metal Deposition with Coaxial Wire Feeding for the Automated and Reliable Build-Up of Solid Metal Parts

Bernauer

Merk

Zapata

et al. 2022

KEM

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Due to their outstanding characteristics, additive manufacturing processes are attracting increasing industrial interest. Among these processes, laser metal deposition (LMD) is an innovative technology for the production of metal components. In order to create three-dimensional parts, wire or powder is deposited layer-wise onto a substrate. When wire is used as feedstock, major drawbacks of the powder-based process, such as the low material usage, contamination of the process cell with metal powder, and health or safety issues, can be overcome or even avoided. In addition, recent developments in laser optics allow for a coaxial wire feeding in the center of an annular laser beam. This eliminates the strong directional dependence of the process when feeding the wire laterally. However, wire-based LMD is highly sensitive to process disturbances, which impedes its broader industrial application. Since it is necessary to completely melt the fed wire to achieve a stable process, self-regulating effects such as overspray in powder-based LMD are not present. In contrast to the widely investigated thin walls, the build-up of multi-track solid structures poses a particular challenge. Therefore, process strategies for producing such solid structures are presented in this paper. The experiments were carried out using a laser processing head that enables coaxial wire feeding (CoaxPrinter, Precitec). By systematically varying the lateral overlap between adjacent weld beads, it was shown that an optimum exists at which minimum surface waviness is achieved. Based on this, defect-free multi-layer solid components could be generated in a reproducible manner. During the process, the melt pool temperature was evaluated using a pyrometer. Furthermore, a microscopic examination of the resulting parts was conducted. The results obtained show the need for process monitoring and control, for which a novel and holistic approach has been developed.

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Influences of process conditions on stability of sensor controlled robot-based laser metal deposition

Cited by 16 publications

References 5 publications

In-Line Observation of Laser Cladding Processes via Atomic Emission Spectroscopy

In-Line Observation of Laser Cladding Processes via Atomic Emission Spectroscopy

Investigation of Direct Metal Deposition Processes Using High-Resolution In-line Atomic Emission Spectroscopy

Laser Metal Deposition with Coaxial Wire Feeding for the Automated and Reliable Build-Up of Solid Metal Parts

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