Influence of building strategies on the accuracy of parts in selective laser sintering

Senthilkumaran, K.; Pandey, Pulak M.; Rao, P. Venkateswara

doi:10.1016/j.matdes.2009.01.009

Cited by 140 publications

(73 citation statements)

References 12 publications

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“…However, many factors may contribute to shrinkage but mainly including materials, process parameters, and the geometries of parts produced [18]. The dimensional variations are caused by inhomogeneous shrinkage which appears during the building and cooling processes which then leads to distortion in the sintered parts caused by stresses.…”

Section: Part Dimensionsmentioning

confidence: 99%

Influence of laser power on tensile properties and material characteristics of laser-sintered UHMWPE

2016

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-Ultra High Molecular Weight Polyethylene (UHMWPE) has excellent properties, such as high mechanical performance, low friction, high wear and chemical resistance but so far there has been limited use in additive manufacturing (AM). Laser sintering of polymers is one of the most promising AM technologies due to its ability to produce complex geometries with accurate dimensions and good mechanical properties. Consequently, this study investigates the influence of laser power on physical and mechanical properties of UHMWPE parts produced by laser sintering. In particular mechanical properties, such as Ultimate Tensile Strength (UTS), Young's Modulus and elongation at break were evaluated alongside relative density, dilation and shrinkage. Finally, the fracture surface of the tensile test specimens was examined by electron microscopy. Results show that within a laser power range of 6-12 W there appears to be an optimum where tensile strength and relative density reach a maximum, dilation is minimised and where elongation increases with laser power. UTS up to 2.42 MPa, modulus up to 72.6 MPa and elongation at break up to 51.4% were observed. Relative density and part dimensions are also influenced by laser power.

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Section: Part Dimensionsmentioning

confidence: 99%

Influence of laser power on tensile properties and material characteristics of laser-sintered UHMWPE

2016

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“…While these recent studies have demonstrated the feasibility of using SLS manufacturing techniques for dynamic prosthetic and orthotic applications, previous reports indicate that dimensional accuracy of SLS-fabricated parts can vary because of several factors, including part shrinkage and SLS build parameters [22][23][24][25]. This drawback is a concern when parts are manufactured that require specific dimensions, such as the size and shape of the force-bearing surface of the cuff and foot outline of a PD-AFO.…”

Section: Introductionmentioning

confidence: 99%

Dimensional accuracy of ankle-foot orthoses constructed by rapid customization and manufacturing framework

Schrank¹,

Stanhope²

2011

JRRD

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Abstract-Passive-dynamic ankle-foot orthoses (PD-AFOs) constitute a class of ankle braces that rely on material properties and physical features to establish functional characteristics such as bending or rotational stiffness. We have developed a novel framework that combines a fully parameterized PD-AFO computer-aided design (CAD) model and free-form fabrication to rapidly manufacture customized PD-AFOs. The threedimensional locations of select anatomic landmarks serve to fit customize the PD-AFO CAD model. A virtual orthopedic alignment process and selection of discrete design parameter values further customize the orthosis, which is fabricated via selective laser sintering. CAD models were customized and fullscale orthoses were manufactured for two nondisabled subjects. The surface of one half-scale CAD model was marked with 3 mm hemispherical dimples, and four orthoses were manufactured in different build orientations and positions. Dimensional accuracy was determined by calculating discrepancies between corresponding CAD and fabricated orthoses interdimple distances. Subjective evaluations of the full-scale PD-AFOs following use in gait were positive. Dimension discrepancies were well under a 2 mm tolerance for the four half-scale orthoses. Mean foot plate, strut, and cuff component discrepancies were 0.31 +/-0.28, 0.34 +/-0.08, 0.52 +/-0.39 mm, respectively, and 0.29 +/-0.23 mm for the overall orthosis. Dimensional accuracy of the rapid customization and manufacturing framework was well within tolerances suggested in the literature.

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“…During the process of sintering, a number of physical processes occur to take the particle distribution and consolidate them with the input of heat energy and melting to form a material cross section [24]. The degree of sintering and properties of the end product are strongly dependant on the SLS machine parameters discussed [25]. It is also necessary to note that the excess powder to be recycled after each process is completed thermally degrades and leads to subsequent lower mechanical properties when it is used again.…”

Section: Nylon-12 Properties and Sintered Micro-structurementioning

confidence: 99%

What triggers a microcrack in printed engineering parts produced by selective laser sintering on the first place?

et al. 2015

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The proximity of un-melted particles within Selective Laser Sintered (SLS) printed engineering parts made of nylon-12 is found as a major triggering effect for cracking and ultimately failure. The numerical investigation, by means of the eXtended Finite Element Method (XFEM), was performed over samples with different arrangements of un-melted particles obtained experimentally . The onset and propagation of microcracks was simulated. This included inherently how the degree of particle melt (DPM) in SLS parts affects and controls both crack initiation and propagation. The results evidenced that a microcrack started invariably between the two closest un-melted particles in all numerical tests performed considering different arrangements of un-melted particles.

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Influence of building strategies on the accuracy of parts in selective laser sintering

Cited by 140 publications

References 12 publications

Influence of laser power on tensile properties and material characteristics of laser-sintered UHMWPE

Influence of laser power on tensile properties and material characteristics of laser-sintered UHMWPE

Dimensional accuracy of ankle-foot orthoses constructed by rapid customization and manufacturing framework

What triggers a microcrack in printed engineering parts produced by selective laser sintering on the first place?

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