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Article
Publication date: 7 June 2013

Guy A. Bingham and Richard Hague

The purpose of this paper is to investigate, develop and validate a three‐dimensional modelling strategy for the efficient generation of conformal textile data suitable…

Abstract

Purpose

The purpose of this paper is to investigate, develop and validate a three‐dimensional modelling strategy for the efficient generation of conformal textile data suitable for additive manufacture.

Design/methodology/approach

A series of additive manufactured (AM) textiles samples were modelled using currently available computer‐aided design software to understand the limitations associated with the generation of conformal data. Results of the initial three‐dimensional modelling processes informed the exploration and development of a new dedicated efficient modelling strategy that was tested to understand its capabilities.

Findings

The research demonstrates the dramatically improved capabilities of the developed three‐dimensional modelling strategy, over existing approaches by accurately mapping complex geometries described as STL data to a mapping mesh without distortion and correctly matching the orientation and surface normal.

Originality/value

To date the generation of data for AM textiles has been seen as a manual and time‐consuming process. The research presents a new dedicated methodology for the efficient generation of complex and conformal AM textile data that will underpin further research in this area.

Details

Rapid Prototyping Journal, vol. 19 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 1 October 2005

R. Sharma and O.P. Sha

To focus on grid generation which is an essential part of any analytical tool for effective discretization.

Abstract

Purpose

To focus on grid generation which is an essential part of any analytical tool for effective discretization.

Design/methodology/approach

This paper explores the application of the possibility of unstructured triangular grid generation that deals with derivationally continuous, smooth, and fair triangular elements using piecewise polynomial parametric surfaces which interpolate prescribed R3 scattered data using spaces of parametric splines defined on R2 triangulations in the case of surfaces in engineering sciences. The method is based upon minimizing a physics‐based certain natural energy expression over the parametric surface. The geometry is defined as a set of stitched triangles prior to the grid generation. As for derivational continuities between the two triangular patches C0 and C1 continuity or both, as per the requirements, has been imposed. With the addition of a penalty term, C2 (approximate) continuity can also be achieved. Since, in this work physics‐based approach has been used, the grid is analyzed using intersection curves with three‐dimensional planes, and intrinsic geometric properties (i.e. directional derivatives), for derivational continuity and smoothness.

Findings

The triangular grid generation that deals with derivationally continuous, smooth, and fair triangular elements has been implemented in this paper for surfaces in engineering sciences.

Practical implications

This paper deals with the important problem of grid generation which is an essential part of any analytical tool for effective discretization. And, the examples to demonstrate the theoretical model of this paper have been chosen from different branches of engineering sciences. Hence, the results of this paper are of practical importance for grid generation in engineering sciences.

Originality/value

The paper is theoretical with worked examples chosen from engineering sciences.

Details

Engineering Computations, vol. 22 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 14 October 2020

Christopher Gottlieb Klingaa, Sankhya Mohanty and Jesper Henri Hattel

Conformal cooling channels in additively manufactured molds are superior over conventional channels in terms of cooling control, part warpage and lead time. The heat…

Abstract

Purpose

Conformal cooling channels in additively manufactured molds are superior over conventional channels in terms of cooling control, part warpage and lead time. The heat transfer ability of cooling channels is determined by their geometry and surface roughness. Laser powder bed fusion manufactured channels have an inherent process-induced dross formation that may significantly alter the actual shape of nominal channels. Therefore, it is crucial to be able to predict the expected surface roughness and changes in the geometry of metal additively manufactured conformal cooling channels. The purpose of this paper is to present a new methodology for predicting the realistic design of laser powder bed fusion channels.

Design/methodology/approach

This study proposes a methodology for making nominal channel design more realistic by the implementation of roughness prediction models. The models are used for altering the nominal shape of a channel to its predicted shape by point cloud analysis and manipulation.

Findings

A straight channel is investigated as a simple case study and validated against X-ray computed tomography measurements. The modified channel geometry is reconstructed and meshed, resulting in a predicted, more realistic version of the nominal geometry. The methodology is successfully tested on a torus shape and a simple conformal cooling channel design. Finally, the methodology is validated through a cooling test experiment and comparison with simulations.

Practical implications

Accurate prediction of channel surface roughness and geometry would lead toward more accurate modeling of cooling performance.

Originality/value

A robust start to finish method for realistic geometrical prediction of metal additive manufacturing cooling channels has yet to be proposed. The current study seeks to fill the gap.

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Article
Publication date: 20 March 2017

Zhijia Xu, Qinghui Wang and Jingrong Li

The purpose of this paper is to develop a general mathematic approach to model the microstructures of porous structures produced by additive manufacturing (AM), which will…

Abstract

Purpose

The purpose of this paper is to develop a general mathematic approach to model the microstructures of porous structures produced by additive manufacturing (AM), which will result in fractal surface topography and higher roughness that have greater influence on the performance of porous structures.

Design/methodology/approach

The overall shapes of pores were modeled by triply periodic minimal surface (TPMS), and the micro-roughness details attached to the overall pore shapes were represented by Weierstrass–Mandelbrot (W-M) fractal representation, which was integrated with TPMS along its normal vectors. An index roughly reflecting the irregularity of fractal TPMS was proposed, based on which the influence of the fractal parameters on the fractal TPMS was qualitatively analyzed. Two complex samples of real porous structures were given to demonstrate the feasibility of the model.

Findings

The fractal surface topography should not be neglected at a micro-scale level. In addition, a decrease in the fractal dimension Ds may exponentially make the topography rougher; an increase in the height-scaling parameter G may linearly increase the roughness; and the number of the superposed ridges has no distinct influence on the topography. Furthermore, the synthesis method is general for all implicit surfaces.

Practical implications

The method provides an alternative way to shift the posteriori design paradigm of porous media to priori design mode through numeric simulation. Therefore, the optimization of AM process parameters, as well as the porous structure, can be potentially realized according to specific functional requirement.

Originality/value

The synthesis of TPMS and W-M fractal geometry was accomplished efficiently and was general for all implicit freeform surfaces, and the influence of the fractal parameters on the fractal TPMS was analyzed more systematically.

Details

Rapid Prototyping Journal, vol. 23 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 11 March 2014

Mohammad Hayasi and Bahram Asiabanpour

The main aim of this study is to generate curved-form cut on the edge of an adaptive layer. The resulting surface would have much less geometry deviation error and closely…

Abstract

Purpose

The main aim of this study is to generate curved-form cut on the edge of an adaptive layer. The resulting surface would have much less geometry deviation error and closely fit its computer aided design (CAD) model boundary.

Design/methodology/approach

This method is inspired by the manual peeling of an apple in which a knife's orientation and movement are continuously changed and adjusted to cut each slice with minimum waste. In this method, topology and geometry information are extracted from the previously generated adaptive layers. Then, the thickness of an adaptive layer and the bottom and top contours of the adjacent layers are fed into the proposed algorithm in the form of the contour and normal vector to create curved-form sloping surfaces. Following curved-form adaptive slicing, a customized machine path compatible with a five-axis abrasive waterjet (AWJ) machine will be generated for any user-defined sheet thicknesses.

Findings

The implemented system yields curved-form adaptive slices for a variety of models with diverse types of surfaces (e.g. flat, convex, and concave), different slicing direction, and different number of sheets with different thicknesses. The decrease in layer thickness and increase of the number of the sloped cuts can make the prototype as close as needed to the CAD model.

Research limitations/implications

The algorithm is designed for use with five-axis AWJ cutting of any kind of geometrical complex surfaces. Future research would deal with the nesting problem of the layers being spread on the predefined sheet as the input to the five-axis AWJ cutter machine to minimize the cutting waste.

Practical implications

The algorithm generates adaptive layers with concave or convex curved-form surfaces that conform closely to the surface of original CAD model. This will pave the way for the accurate fabrication of metallic functional parts and tooling that are made by the attachment of one layer to another. Validation of the output has been tested only as the simulation model. The next step is the customization of the output for the physical tests on a variety of five-axis machines.

Originality/value

This paper proposes a new close to CAD design sloped-edge adaptive slicing algorithm applicable to a variety of five-axis processes that allow variable thickness layering and slicing in different orientations (e.g. AWJ, laser, or plasma cutting). Slices can later be bonded to build fully solid prototypes.

Details

Rapid Prototyping Journal, vol. 20 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 9 March 2010

Xiaoming Luo and Matthew C. Frank

The purpose of this paper is to present an algorithm for an additive/subtractive rapid pattern manufacturing (RPM) process where thick slabs of material are sequentially…

Abstract

Purpose

The purpose of this paper is to present an algorithm for an additive/subtractive rapid pattern manufacturing (RPM) process where thick slabs of material are sequentially stacked and then cut to 3D shapes. Unlike traditional rapid prototyping processes where layer thickness is typically uniform, this process is able to vary the layer thickness in order to most effectively generate feature shapes.

Design/methodology/approach

This paper discusses the factors affecting layer thickness decisions and then presents an algorithm to determine layer thicknesses for a given part model. The system is designed to import a computer‐aided design file and use the algorithm to automatically generate the set of layers based on the slab height, material and bonding properties and the process parameters used in the system.

Findings

The layer thickness algorithm is implemented and tested using an additive/subtractive manufacturing system developed in the laboratory. The algorithm has proved effective in determining appropriate layer heights for thick slab machining, taking into account a variety of geometries. Several sand casting patterns have been successfully created using the proposed system, which could significantly improve traditional sand casting pattern manufacturing.

Originality/value

The proposed RPM process is a new process presented by the authors, developed for rapid sand castings. The layer thickness algorithm is an original contribution that enables automatic process planning for this new process.

Details

Rapid Prototyping Journal, vol. 16 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 1 September 2005

Seungryeol Yoo and Daniel Walczyk

To provide an advanced cutting trajectory algorithm for the profiled edge laminae (PEL) rapid tooling (RT) process, which is ideally suited for large‐scale dies and molds…

Abstract

Purpose

To provide an advanced cutting trajectory algorithm for the profiled edge laminae (PEL) rapid tooling (RT) process, which is ideally suited for large‐scale dies and molds. The process involves assembling an array of laminae whose top edges are simultaneously profiled and beveled using a line‐of‐sight cutting method based on a CAD model of the intended tool surface.

Design/methodology/approach

The cutting profiles for an individual tool lamina are based on intersection curves obtained directly from the CAD model, and generated with exact geometrical accuracy. Two adjacent slice profiles, which define a lamination's top edge and are represented as polylines, are stitched together using an adaptive surface reconstruction algorithm. A cutting trajectory algorithm then develops a series of suitable cutting vectors (i.e. position and cutting direction) that minimize abrasive waterjet (AWJ) cutting errors due to non‐uniform motion and variations in kerf geometry resulting from process parameter variations. The proposed cutting trajectory generation process is demonstrated virtually for an actual production tool.

Findings

The proposed algorithm yields well‐behaved AWJ cutting trajectories for individual lamina used in a PEL tool that are better than those obtained using any other algorithm found in the literature.

Research limitations/implications

The algorithm is intended for use with AWJ cutting of PEL tool surfaces. Suggested future research includes assessment of the algorithm for other lamina cutting methods including laser cutting and wire‐type electro‐discharge machining, extending the algorithm to handle conformal cooling/heating channels and internal cavities, and application of the algorithm to several industrial tool case studies.

Practical implications

The algorithm generates cutting trajectories directly from CAD geometry that are ideal for AWJ cutting of profiled edge lamina. It will simply make industrial implementation of the PEL RT process easier.

Originality/value

This paper provides a new cutting trajectory algorithm for the PEL RT process that is a significant improvement over comparable algorithms proposed in the literature.

Details

Rapid Prototyping Journal, vol. 11 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 27 May 2014

Eugeniusz Zieniuk and Krzysztof Szerszen

The purpose of this paper is to apply rectangular Bézier surface patches directly into the mathematical formula used to solve boundary value problems modeled by Laplace's…

Abstract

Purpose

The purpose of this paper is to apply rectangular Bézier surface patches directly into the mathematical formula used to solve boundary value problems modeled by Laplace's equation. The mathematical formula, called the parametric integral equation systems (PIES), will be obtained through the analytical modification of the conventional boundary integral equations (BIE), with the boundary mathematically described by rectangular Bézier patches.

Design/methodology/approach

The paper presents the methodology of the analytic connection of the rectangular patches with BIE. This methodology is a generalization of the one previously used for 2D problems.

Findings

In PIES the paper separates the necessity of performing simultaneous approximation of both boundary shape and the boundary functions, as the boundary geometry has been included in its mathematical formalism. The separation of the boundary geometry from the boundary functions enables to achieve an independent and more effective improvement of the accuracy of both approximations. Boundary functions are approximated by the Chebyshev series, whereas the boundary is approximated by Bézier patches.

Originality\value

The originality of the proposed approach lies in its ability to automatic adapt the PIES formula for modified shape of the boundary modeled by the Bézier patches. This modification does not require any dividing the patch into elements and creates the possibility for effective declaration of boundary geometry in continuous way directly in PIES.

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Article
Publication date: 1 September 2003

J.P. Hernandez, T.A. Osswald and D.A. Weiss

In this paper, a novel boundary element formulation for the deformation of a viscous 2D‐planar cylindrical geometry, immersed in a different viscous fluid and moving…

Abstract

In this paper, a novel boundary element formulation for the deformation of a viscous 2D‐planar cylindrical geometry, immersed in a different viscous fluid and moving towards a rigid wall, is proposed for moderate Reynolds number, considering surface tension effects. The boundary integral formulation for Stokes flow inside and outside the geometry is represented in terms of a combined distribution of a single‐layer and a double‐layer potential of Green functions over the geometry surface. Additionally, non‐linear terms describing effects absent in pure Stokes flow, such as the time derivative of the velocity and inertia, are included. These effects lead to the appearance of domain integrals. Traditional dual reciprocity is applied in order to approximate these domain integrals by a series of particular solutions which are then transformed into boundary integrals. Augmented thin‐plate splines, i.e. r2log(r), plus three additional linear terms from a Pascal triangle expansion were chosen for the dual reciprocity approximation. In order to avoid the discretization of the rigid wall, and using the fact that the velocity on the wall must vanish due to the no‐slip condition, the fundamental solution was modified with a combination of image singularities including an image Stokeslet, a potential dipole and a Stokes‐doublet.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 13 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article
Publication date: 1 March 2000

Haeseong Jee and Emanuel Sachs

Rapid prototyping technologies can create a physical part directly from a digital model by accumulating layers of a given material. Providing tremendous flexibility in the…

Abstract

Rapid prototyping technologies can create a physical part directly from a digital model by accumulating layers of a given material. Providing tremendous flexibility in the part geometry that they can fabricate, these technologies present an opportunity for the creation of new product attributes that cannot be made with existing technologies. For this to be possible, however, various design environments including different fabrication processes need to be considered at the time of design. This paper proposes an extended design automation paradigm for design and fabrication of a new product attribute, surface macro‐texture.

Details

Rapid Prototyping Journal, vol. 6 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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