Separation force analysis and prediction based on cohesive element model for constrained-surface Stereolithography processes

Liravi, Farzad; Das, Sonjoy; Zhou, Chi

doi:10.1016/j.cad.2015.05.002

Cited by 76 publications

(42 citation statements)

References 34 publications

(49 reference statements)

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“…Process parameter (Variable) [12] Strain Temperature [13] Part shrinkage Thermal compensation, amorphous/crystalline polymer, mould material, cooling conditions [14] Deformation compensation [15] Dimensional Accuracy Layer thickness, part position on the platform, shrinkage compensation, retraction, hatch spacing, alternate hatching, blade gap, stagger weave [16] Cure depth Penetration depth of UV radiation, scattering coefficient [17][18][19] Etching, deposition, lithography mechanics Surface type, material, shape [20] Tool strength, ejection forces, decision about the quality of a tool according to the previous two [21] Separation force Pulling-up speed, others [22] Strength of parts Layer thickness, orientation, hatch spacing [22] Tensile, flexural and impact strength Layer thickness, orientation, hatch spacing [23] Part strength (tensile, impact, flexural) Layer thickness, post-curing time and orientation [24] Tensile strength, crystallographic orientationdensity analysis…”

Section: Kpimentioning

confidence: 99%

“…More specifically, the modelling works of VP focus on the topology and dimensional accuracy ( [12][13][14] numerical) and mainly on the mechanical properties ( [16] analyticalempirical, [17][18][19][20][21] numerical and [21][22][23][24] empirical) and finally in [25] an analytical-empirical approach models heat transfer related issues.…”

Section: Vat Photopolymerization Processesmentioning

confidence: 99%

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Modelling of additive manufacturing processes: a review and classification

Stavropoulos

Foteinopoulos

2018

Manufacturing Rev.

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Abstract. Additive manufacturing (AM) is a very promising technology; however, there are a number of open issues related to the different AM processes. The literature on modelling the existing AM processes is reviewed and classified. A categorization of the different AM processes in process groups, according to the process mechanism, has been conducted and the most important issues are stated. Suggestions are made as to which approach is more appropriate according to the key performance indicator desired to be modelled and a discussion is included as to the way that future modelling work can better contribute to improving today's AM process understanding.

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Section: Kpimentioning

confidence: 99%

Section: Vat Photopolymerization Processesmentioning

confidence: 99%

Modelling of additive manufacturing processes: a review and classification

Stavropoulos

Foteinopoulos

2018

Manufacturing Rev.

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“…Furthermore, the sloped "pages" of the open book are freely extending in space and are fabricated without supports, partly aided by the bottom-up build approach. Conventional AM approaches either lack chemical cohesion between layers or impart a mechanical strain on the part in the separation step, thus preventing the fabrication of large overhangs without additional aids in the form of supports (37,38). The continuity of fabrication enabled by CLIP allows for the reduction of the staircasing effect without affecting build time and results in a part with the mechanical integrity to support large overhangs.…”

Section: Discussionmentioning

confidence: 99%

Layerless fabrication with continuous liquid interface production

Janusziewicz

Tumbleston

Quintanilla

et al. 2016

Proc. Natl. Acad. Sci. U.S.A.

259

139

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Despite the increasing popularity of 3D printing, also known as additive manufacturing (AM), the technique has not developed beyond the realm of rapid prototyping. This confinement of the field can be attributed to the inherent flaws of layer-by-layer printing and, in particular, anisotropic mechanical properties that depend on print direction, visible by the staircasing surface finish effect. Continuous liquid interface production (CLIP) is an alternative approach to AM that capitalizes on the fundamental principle of oxygen-inhibited photopolymerization to generate a continual liquid interface of uncured resin between the growing part and the exposure window. This interface eliminates the necessity of an iterative layer-by-layer process, allowing for continuous production. Herein we report the advantages of continuous production, specifically the fabrication of layerless parts. These advantages enable the fabrication of large overhangs without the use of supports, reduction of the staircasing effect without compromising fabrication time, and isotropic mechanical properties. Combined, these advantages result in multiple indicators of layerless and monolithic fabrication using CLIP technology.stereolithogaphy | continuous liquid interface production | 3D printing | additive manufacturing | isotropic properties Additive manufacturing (AM), or 3D printing, is a growing field that employs the selective layering of material to build a part, which has distinct advantages compared with subtractive manufacturing (1). The benefits of additive over subtractive manufacturing are numerous and include unlimited design space, freedom of complex geometries, and reduction of waste by-products (2). Significant advancements were made to AM in the 1980s with the development of the stereolithography (SL) apparatus, a platform that uses the exposure of a rastering UV laser to selectively solidify a resin through a photopolymerization process in a top-down manner (3). The method has since been modified to solidify in a bottom-up process through the use of a digital light projection (DLP) chip that eliminates the rastering laser. The process of bottomup SL begins with a computer-aided design (CAD) file that is then converted into a series of 2D renderings using a method called "slicing" (Fig. 1A). The original object is then reconstructed in a layer-by-layer manner by reproducing these 2D renderings, one slice at a time. This process is done iteratively whereby a photoactive resin is selectively exposed to UV light through a transparent substrate, allowing for selective photopolymerization corresponding to a specific slice shape (4). Once the slice has been exposed, a series of mechanical steps of separation, recoating, and repositioning follow (Fig. 1B) to allow for subsequent exposure.The polymeric materials used in the SL process are known to have intrinsic properties that are a function of the chemical structure, molecular weight, and topology (3). Printed part properties differ from intrinsic polymeric properties because they a...

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“…The ultraviolet (UV) light penetrates the transparent constrained surface and cures the liquid polymer. Currently, the two most widely used classes of constrained surfaces are: (1) glass or acrylic plate coated with polydimethylsiloxane (PDMS) [8,[12][13][14][15][16][17][18] and (2) air permeable film that is clamped and tensioned, due to the relatively low cost, ease of fabrication, good oxygen permeability, and excellent optical transparency. The oxygen permeability of constrained surface is critical to the reliability and robustness of the system, and the printable geometries [19].…”

Section: Introductionmentioning

confidence: 99%

Air-Diffusion-Channel Constrained Surface Based Stereolithography for Three-Dimensional Printing of Objects With Wide Solid Cross Sections

Pan

Feinerman

et al. 2018

Journal of Manufacturing Science and Engineering

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Oxygen inhibition has been proved capable of reducing the separation force and enabling successful prints in constrained surface vat photopolymerization (CSVP) based three-dimensional (3D) printing processes. It has also been demonstrated as a key factor that determines the feasibility of the newly developed CSVP-based continuous 3D printing systems, such as the continuous liquid interface production. Despite its well-known importance, it is still largely unknown regarding how to control and enhance the oxygen inhibition in CSVP. To close this knowledge gap, this paper investigates the constrained surface design, which allows for continuous and sufficient air permeation to enhance the oxygen inhibition in CSVP systems. In this paper, a novel constrained surface with air-diffusion-channel is proposed. The influences of the air-diffusion-channel design parameters on the robustness of the constrained surface, the light transmission rate, and light intensity uniformity are studied. The thickness of the oxygen inhibition layer associated with the proposed constrained surface is studied analytically and experimentally. Experimental results show that the proposed air-diffusion-channel design is effective in maintaining and enhancing the oxygen-inhibition effect, and thus can increase the solid cross section size of printable parts.

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Separation force analysis and prediction based on cohesive element model for constrained-surface Stereolithography processes

Cited by 76 publications

References 34 publications

Modelling of additive manufacturing processes: a review and classification

Modelling of additive manufacturing processes: a review and classification

Layerless fabrication with continuous liquid interface production

Air-Diffusion-Channel Constrained Surface Based Stereolithography for Three-Dimensional Printing of Objects With Wide Solid Cross Sections

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