Warpage Analysis and Control of Thin-Walled Structures Manufactured by Laser Powder Bed Fusion

Lu, Xufei; Chiumenti, Michele; Cervera, Miguel; Tan, Hua; Lin, Xin; Wang, Song

doi:10.3390/met11050686

Cited by 29 publications

(14 citation statements)

References 39 publications

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“…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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“…Bugatti et al [13] studied the effect of overhanging surfaces on the formation of internal defects in the laser powder bed fusion-type process. Lu et al [14] assessed the warping for thin-walled structures that are widely used for aeronautical applications. They found that different geometrical characteristics, i.e., the wall thickness, the build height, the wall curvature, and the presence of an open or closed structure, play a key role in the warping occurrence.…”

Section: Introductionmentioning

confidence: 99%

A new control parameter to predict micro-warping-induced job failure in LPBF of TI6AL4V titanium alloy

Buffa

Costa

Palmeri

et al. 2023

Int J Adv Manuf Technol

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Laser powder bed fusion (LPBF) includes a few printing techniques widely used, in recent years, concerning the additive manufacturing of Ti6Al4V alloys. These produced parts, typically utilized in sectors such as aerospace and biomedical, are characterized by very high added value. It is therefore fundamental to identify the influence of process parameters typical of LPBF technology on the occurrence of warping leading to process failure. This study deals with the characterization of single-track and “micro-scale” level warping phenomena which may lead to protrusion of material over the powder bed and process failure before normal termination. This phenomenon was investigated as a function of process parameters, referring also to the strength and ductility characteristics of the manufactured samples. With this purpose, several samples were printed using variable process parameters both in terms of line energy density (LED) values and in terms of laser power and speed combinations such as to guarantee constant LED values. For the samples that did not show significant micro-warping phenomena, in addition to the transversal and longitudinal geometric characterization of the single track, tensile tests were performed to determine both the resistance of the material and the ductility characteristics. The single tracks, for given process parameters, were printed on a homogeneous material substrate. For every single track, a microstructural and morphological transverse and longitudinal characterization has been carried out and the measured geometrical features were correlated to the process parameters. The obtained results allowed the identification of a new threshold parameter, indicating the limit operating conditions beyond which significant warping phenomena and process failure occur.

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“…However, AM is a complicated multi-physics and multi-scale process characterized by several thermal cycles with large temperature gradients as well as melting and solidification phase changes. As a consequence, AM-built products typically show non-uniform microstructure distribution, large residual stresses, thermal distortions, cracks and unsatisfactory mechanical properties [4][5][6][7][8][9][10]. Such drawbacks significantly prevent the extensive application of AM technologies in high-end manufacturing industry.…”

Section: Introductionmentioning

confidence: 99%

Mitigation of residual stresses and microstructure homogenization in directed energy deposition processes

Chiumenti

Cervera

et al. 2022

Engineering with Computers

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In additive manufacturing (AM), residual stresses and microstructural inhomogeneity are detrimental to the mechanical properties of as-built AM components. In previous studies the reduction of the residual stresses and the optimization of the microstructure have been treated separately. Nevertheless, the ability to control both them at the same time is mandatory for improving the final quality of AM parts. This is the main goal of this paper. Thus, a thermo-mechanical finite element model is firstly calibrated by simulating a multi-track 40-layer Ti-6Al-4V block fabricated by Directed Energy Deposition (DED). Next, the numerical tool is used to study the effect of the baseplate dimensions and the energy density on both residual stresses and microstructure evolution. On the one hand, the results indicate that the large baseplate causes higher residual stresses but produces more uniform microstructures, and contrariwise for the smaller baseplate. On the other hand, increasing the energy density favors stress relief, but its effect fails to prevent the stress concentration at the built basement. Based on these results, two approaches are proposed to control both the stress accumulation and the metallurgical evolution during the DED processes: (i) the use of a forced cooling suitable for small baseplates and, (ii) the adoption of grooves when large baseplates are used.The numerical predictions demonstrated the effectiveness of the proposed manufacturing strategies.

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Warpage Analysis and Control of Thin-Walled Structures Manufactured by Laser Powder Bed Fusion

Cited by 29 publications

References 39 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

A new control parameter to predict micro-warping-induced job failure in LPBF of TI6AL4V titanium alloy

Mitigation of residual stresses and microstructure homogenization in directed energy deposition processes

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