Optimization of support structures for selective laser melting.

Zeng, Kai

doi:10.18297/etd/2221

Cited by 24 publications

(27 citation statements)

References 95 publications

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“…Most of the studies typically discussed in literature searches discuss rule-of-thumb ways to physically prevent the stresses from destroying the parts during printing and are little concerned with trying to understand the mechanics of the stresses and how they directly affect the overhanging features. There was considerable discussion of this problem in the studies by Hussein et al [21,22], Matsumoto et al [18], Calingnano [23], Mohanty and Hattel [24], Zeng [25], Li et al [26] and Gan and Wong [27], but these addressed application-specific issues and did not discuss the problem at the level of feature and part design. Some of the opinions commonly heard from practitioners are that the overhanging features are most severely affected by the stresses because they are not physically welded to the build plate during the printing and are thinner and less resistant to thermal shock.…”

Section: The Slm/dmls Residual Stresses Problemmentioning

confidence: 99%

Overhanging Features and the SLM/DMLS Residual Stresses Problem: Review and Future Research Need

2017

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Abstract:A useful and increasingly common additive manufacturing (AM) process is the selective laser melting (SLM) or direct metal laser sintering (DMLS) process. SLM/DMLS can produce full-density metal parts from difficult materials, but it tends to suffer from severe residual stresses introduced during processing. This limits the usefulness and applicability of the process, particularly in the fabrication of parts with delicate overhanging and protruding features. The purpose of this study was to examine the current insight and progress made toward understanding and eliminating the problem in overhanging and protruding structures. To accomplish this, a survey of the literature was undertaken, focusing on process modeling (general, heat transfer, stress and distortion and material models), direct process control (input and environmental control, hardware-in-the-loop monitoring, parameter optimization and post-processing), experiment development (methods for evaluation, optical and mechanical process monitoring, imaging and design-of-experiments), support structure optimization and overhang feature design; approximately 143 published works were examined. The major findings of this study were that a small minority of the literature on SLM/DMLS deals explicitly with the overhanging stress problem, but some fundamental work has been done on the problem. Implications, needs and potential future research directions are discussed in-depth in light of the present review.

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Section: The Slm/dmls Residual Stresses Problemmentioning

confidence: 99%

Overhanging Features and the SLM/DMLS Residual Stresses Problem: Review and Future Research Need

2017

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“…Of the limited studies that address overhanging features [40,62] most suggest partspecific design guidelines; however, these are only applicable to geometries similar to those in the study. While these rules-of-thumb provide insight into the residual stress issue, they do not provide a detailed understanding of residual stresses development in overhanging features [40].…”

Section: The Origin Of Residual Stressmentioning

confidence: 99%

“…The cost and time savings makes the SLM process appealing to the aerospace, medical, and automotive industries. Unfortunately, the wide-spread adoption of this technology is severely limited by residual stresses introduced during the SLM process [24,25,38,40,58,62]. These residual stresses, which are produced by the expansion and contraction of the previously solidified layers can lead to localized deformation and in-process failure [24,25,26,40,58].…”

mentioning

confidence: 99%

“…To prevent in-process failure in overhanging features where deformation is most severe [6,38,40], support structures are used to anchor the overhang to the build plate and to conduct heat away from the part [24,62]. Currently, the design of support structures is based on various rules-of-thumb gained from application specific experiences and not based on general support structure design theory [40,62]. When a support structure designed using these rules-of-thumb fails to prevent fractures in a part, a practitioner is forced to use a trial and error manufacturing process which wastes both time and material [57,62].…”

mentioning

confidence: 99%

“…Currently, the design of support structures is based on various rules-of-thumb gained from application specific experiences and not based on general support structure design theory [40,62]. When a support structure designed using these rules-of-thumb fails to prevent fractures in a part, a practitioner is forced to use a trial and error manufacturing process which wastes both time and material [57,62].…”

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confidence: 99%

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Effects of Support Structure Geometry on SLM Induced Residual Stresses in Overhanging Features

Baskett¹

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Selective laser melting (SLM) is a new and rapidly developing manufacturing method for producing full-density, geometrically complex metal parts. The SLM process is time and cost effective for small-scale production; however, wide-spread adoption of this technique is severely limited by residual stresses that can cause large deformations and in-process build failures. The issues associated with residual stress accumulation are most apparent in parts with overhanging features. Due to the complexity of the SLM process, the accumulation of residual stresses is difficult to assess a priori. The deformations and in-process failures caused by residual stress accumulation often lead to an expensive and time consuming iterative manufacturing process.To aid in the development of general SLM design guidelines for overhanging features, the effect of varying two support structure design parameters on residual stress accumulation were investigated. A part-scale thermo-mechanical finite element model was implemented using Diablo, a multi-physics finite element code developed by Lawrence Livermore National Laboratory (LLNL), and trends observed in the model were validated experimentally.By comparing the distribution and magnitude of residual stresses, it was determined that reducing cooling rate gradients in overhanging features reduces the resulting residual stresses. Additionally, it was shown that volume effective material properties can be used to reduce computational costs in computational models of the SLM process. iv ACKNOWLEDGMENTS I would first like to thank my thesis advisor, Dr. Shollenberger, for her continued support on this project. From the initial problem definition through to interpreting the final results, Dr. Shollenberger provided invaluable insight and kept me on track.

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Design Guidelines zur Auswahl geeigneter Supporttypen für verschiedene Anwendungsfälle im Bereich Laserstrahlschmelzen – Auf dem Weg zur automatisierten Supportgenerierung

Gralow,

Blunk,

Imgrund

et al. 2018

Rapid.Tech + FabCon 3.D – International Trade Show &Amp; Conference for Additive Manufacturing

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Optimization of support structures for selective laser melting.

Cited by 24 publications

References 95 publications

Overhanging Features and the SLM/DMLS Residual Stresses Problem: Review and Future Research Need

Overhanging Features and the SLM/DMLS Residual Stresses Problem: Review and Future Research Need

Effects of Support Structure Geometry on SLM Induced Residual Stresses in Overhanging Features

Design Guidelines zur Auswahl geeigneter Supporttypen für verschiedene Anwendungsfälle im Bereich Laserstrahlschmelzen – Auf dem Weg zur automatisierten Supportgenerierung

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