Selective laser melting of Ti-6Al-4V: Comparing μCT with in-situ process monitoring data

Egan, Darragh S.; Jones, K. M.; Dowling, Denis P.

doi:10.1016/j.cirpj.2020.10.004

Cited by 9 publications

(4 citation statements)

References 17 publications

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“…In the overhanging section of the part, heat is accumulated due to the poor thermal conductivity of the underlying powder. As a result, melt pool size, cooling, and solidification rates increase [33,34], which ultimately affects the microstructure of the part. Due to the higher energy density of laser and slow cooling rates residual stress is generated and results in defects such as warping [35] and loss of corner [10].…”

Section: Disturbance Modelmentioning

confidence: 99%

Feedback Control of Melt Pool Area in Selective Laser Melting Additive Manufacturing Process

et al. 2021

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Selective laser melting (SLM), a metal powder fusion additive manufacturing process, has the potential to manufacture complex components for aerospace and biomedical implants. Large-scale adaptation of these technologies is hampered due to the presence of defects such as porosity and part distortion. Nonuniform melt pool size is a major cause of these defects. The melt pool size changes due to heat from the previous powder bed tracks. In this work, the effect of heat sourced from neighbouring tracks was modelled and feedback control was designed. The objective of control is to regulate the melt pool cross-sectional area rejecting the effect of heat from neighbouring tracks within a layer of the powder bed. The SLM process’s thermal model was developed using the energy balance of lumped melt pool volume. The disturbing heat from neighbouring tracks was modelled as the initial temperature of the melt pool. Combining the thermal model with disturbance model resulted in a nonlinear model describing melt pool evolution. The PID, a classical feedback control approach, was used to minimize the effect of intertrack disturbance on the melt pool area. The controller was tuned for the desired melt pool area in a known environment. Simulation results revealed that the proposed controller regulated the desired melt pool area during the scan of multiple tracks of a powder layer within 16 milliseconds and within a length of 0.04 mm reducing laser power by 10% approximately in five tracks. This reduced the chance of pore formation. Hence, it enhances the quality of components manufactured using the SLM process, reducing defects.

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Section: Disturbance Modelmentioning

confidence: 99%

Feedback Control of Melt Pool Area in Selective Laser Melting Additive Manufacturing Process

et al. 2021

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“…Another factor that can in uence the porosity and morphology of L-PBF printed parts is the heat transfer from the meltpool during part manufacturing [9][10][11][12][13]. Examples of geometric features that affect heat transfer in L-PBF parts include lattice structures [14], support structures [10], and unsupported overhangs [12].…”

Section: Introductionmentioning

confidence: 99%

“…Amongst the in-process monitoring techniques used to monitor L-PBF printing are optical emission spectroscopy and thermal monitoring [4,10,11,[23][24][25].…”

Section: Introductionmentioning

confidence: 99%

“…When the powder layer thickness in the build was decreased, a direct response in the photodiode signal could be seen. Egan et al [11] compare the accuracy of part dimensional data obtained using in-situ optical emission spectroscopy during L-PBF printing (Renishaw RenAM 500M), with post-build µCT scans of the same parts. It was demonstrated that for 600 µm diameter cavities, the in-process and post-print cavity measurements were within 1.7% of each other.…”

Section: Introductionmentioning

confidence: 99%

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Application of in-situ process monitoring to optimize laser parameters during laser powder bed fusion printing of Ti-6Al-4V parts with overhang structures

Power,

Humphreys,

Hartnett

et al. 2023

Preprint

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Geometrically complex features, such as overhang structures, can be a challenge in laser powder bed fusion (L-PBF), as they can be associated with print defects, such as porosity. In this study, Ti-6Al-4V alloy overhang structures were fabricated using an L-PBF system. Differences were observed in the microstructure in the region around the overhang structures, compared with that observed for the bulk alloy. These included larger grain sizes and a less homogenous microstructure in the print layers closest to overhang structures. It is hypothesized that these microstructural changes are associated with the excess heat generated in the overhang region due to the decreased thermal conductivity of the powder immediately below the print layers, compared with solid alloy. Also observed was an increased level of porosity (up to 0.08%) in the overhang print alloy, compared with the corresponding <0.02% in the alloy bulk. During printing, in-situ process monitoring of the meltpool emissions was obtained in the near-infrared range and correlated with the properties of the printed parts. This in-process data assisted in selecting optimal laser processing conditions in the first fifteen layers above the overhang to prevent meltpool overheating. By systematically controlling the laser energy during the printing of L-PBF overhang structures, the level of porosity was reduced to match that of the bulk alloy. There was also an associated reduction in the roughness of the overhang itself, with its Ra decreasing from 62.4 ± 7.3 µm to 7.5 ± 1.9 µm.

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Application of in situ process monitoring to optimise laser parameters during laser powder bed fusion printing of Ti-6Al-4V parts with overhang structures

Power,

Humphreys,

Hartnett

et al. 2023

Int J Adv Manuf Technol

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Selective laser melting of Ti-6Al-4V: Comparing μCT with in-situ process monitoring data

Cited by 9 publications

References 17 publications

Feedback Control of Melt Pool Area in Selective Laser Melting Additive Manufacturing Process

Feedback Control of Melt Pool Area in Selective Laser Melting Additive Manufacturing Process

Application of in-situ process monitoring to optimize laser parameters during laser powder bed fusion printing of Ti-6Al-4V parts with overhang structures

Application of in situ process monitoring to optimise laser parameters during laser powder bed fusion printing of Ti-6Al-4V parts with overhang structures

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