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Article
Publication date: 2 October 2007

O.B. Godbold, R.C. Soar and R.A. Buswell

Limitations in traditional manufacturing methods currently employed in the production of acoustic devices, restricts the development of design led performance…

Abstract

Purpose

Limitations in traditional manufacturing methods currently employed in the production of acoustic devices, restricts the development of design led performance improvements. These devices are used to control sound energy and are commonly employed for tailoring room acoustics. solid freeform fabrication allows the production of acoustic structures more complex than traditionally manufactured devices. This paper aims to focus on a novel absorber based on destructive interference, considering performance, design and manufacture.

Design/methodology/approach

Selective laser sintering has been used in the investigation of the performance and manufacturing possibilities and limitations of a novel destructive interference absorber. Validation of the absorber performance is benchmarked against a conventional resonant absorber and compared to published results. The implications for acoustic devise design, the advances and limitations in manufacture using solid freeform fabrication techniques and potential applications are discussed.

Findings

An original absorber design has been shown to exhibit comparable acoustic absorption to that of a traditional solution. The nature of the geometry of the novel absorber demonstrates that the design flexibility afforded by solid freeform fabrication processes holds potential for applications incorporating new types of acoustic absorber. The use of solid freeform fabrication has demonstrated its potential to the application of acoustics, and has highlighted limitations due to post‐processing, material strength and the precision of the selectivity process.

Practical implications

Solid freeform fabrication techniques enable a new family of specifically engineered acoustic absorbers capable of incorporating performance benefits over conventional absorbers.

Originality/value

This paper focuses on room acoustic applications, the creation of high performance, conformal absorbers, applicable to a wide range of applications within the aerospace, automotive and construction industries, where space, weight and performance are key criteria.

Details

Rapid Prototyping Journal, vol. 13 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 30 May 2008

Evan Malone, Megan Berry and Hod Lipson

The paper's aim is to show the development of materials and methods which allow freeform fabrication of macroscopic Zn‐air electrochemical batteries. Freedom of geometric…

Abstract

Purpose

The paper's aim is to show the development of materials and methods which allow freeform fabrication of macroscopic Zn‐air electrochemical batteries. Freedom of geometric design may allow for new possibilities in performance optimization.

Design/methodology/approach

The authors have formulated battery materials which are compatible with solid freeform fabrication (SFF) while retaining electrochemical functionality. Using SFF processes, they have fabricated six Zn‐air cylindrical batteries and quantitatively characterized them and comparable commercial batteries. They analyze their performance in light of models from the literature and they also present SFF of a flexible two‐cell battery of unusual geometry.

Findings

Under continuous discharge to 0.25 V/cell with a 100 Ω load, the cylindrical cells have a specific energy and power density in the range of 40‐70 J/g and 0.4‐1 mW/cm2, respectively, with a mass range of 8‐18 g. The commercial Zn‐air button cells tested produce 30‐750 J/g and 7‐9 mW/cm2 under the same conditions, and have a mass range of 0.2‐2 g. The two‐cell, flexible Zn‐air battery produces a nominal 2.8 V, open‐circuit.

Research limitations/implications

The freeform‐fabricated batteries have ∼10 percent of the normalized performance of the commercial batteries. High‐internal contact resistance, loss of electrolyte through evaporation, and inferior catalyst reagent quality are possible causes of inferior performance. Complicated material preparation and battery fabrication processes have limited the number of batteries fabricated and characterized, limiting the statistical significance of the results.

Practical implications

Performance enhancement will be necessary before the packaging efficiency and design freedom provided by freeform‐fabricated batteries will be of practical value.

Originality/value

The paper demonstrates a multi‐material SFF system, material formulations, and fabrication methods which together allow the fabrication of complete functional Zn‐air batteries. It provides the first quantitative characterization of completely freeform‐fabricated Zn‐air batteries and comparison to objective standards, and shows that highly unusual, functional battery designs incorporating flexibility, multiple cells, and unusual geometry may be freeform fabricated.

Details

Rapid Prototyping Journal, vol. 14 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 30 September 2013

Charlie C.L. Wang and Yong Chen

Given an intersection-free mesh surface S, the paper introduces a method to thicken S into a solid H located at one side of S. By such a surface-to-solid conversion…

Abstract

Purpose

Given an intersection-free mesh surface S, the paper introduces a method to thicken S into a solid H located at one side of S. By such a surface-to-solid conversion operation, industrial users are able to fabricate a designed (or reconstructed) surface by rapid prototyping.

Design/methodology/approach

The paper first investigates an implicit representation of the thickened solid H according to an extension of signed distance function. After that, a partial surface reconstruction algorithm is proposed to generate the boundary surface of H, which retains the given surface S on the resultant surface.

Findings

Experimental tests show that the thickening results generated by the method give nearly uniform thickness and meanwhile do not present shape approximation error at the region of input surface S. These two good properties are important to the industrial applications of solid fabrication.

Research limitations/implications

The input polygonal model is assumed to be intersection-free, where models containing self-intersection will lead to invalid thickening results.

Originality/value

A novel robust operation is to convert a freeform open surface into a solid by introducing no shape approximation error. A new implicit function gives a compact mathematical representation, which can easily handle the topological change on the thickened solids. A new polygonization algorithm generates faces for the boundary of thickened solid meanwhile retaining faces on the input open mesh.

Details

Rapid Prototyping Journal, vol. 19 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 1 October 2006

Evan Malone and Hod Lipson

To seek to produce low‐voltage, soft mechanical actuators entirely via freeform fabrication as part of a larger effort to freeform fabricate complete electromechanical…

Abstract

Purpose

To seek to produce low‐voltage, soft mechanical actuators entirely via freeform fabrication as part of a larger effort to freeform fabricate complete electromechanical devices with lifelike and/or biocompatible geometry and function.

Design/methodology/approach

The authors selected ionomeric polymer‐metal composite (IPMC) actuators from the literature and the authors' own preliminary experiments as most promising for freeform fabrication. The authors performed material formulation and manual device fabrication experiments to arrive at materials which are amenable to robotic deposition and developed an SFF process which allows the production of complete IPMC actuators and their fabrication substrate integrated within other freeform fabricated devices. The authors freeform fabricated simple IPMC's, explored some materials/performance interactions, and preliminarily characterized these devices in comparison to devices produced by non‐SFF methods.

Findings

Freeform fabricated IPMC actuators operate continuously in air for more than 4 h and 3,000 bidirectional actuation cycles. The output stress scaled to input power is one to two orders of magnitude inferior to that of non‐SFF devices. Much of this difference may be associated with process‐sensitive microstructure of materials. Future work will investigate this performance gap.

Research limitations/implications

Device performance is sufficient to continue exploration of SFF of complete electromechanical devices, but will need improvement for broader application. The feasibility of the approach for producing devices with complex, non‐planar geometry has not been demonstrated.

Practical implications

This work demonstrates the feasibility of freeform fabricating IPMC devices, and lays groundwork for further development of the materials and methods.

Originality/value

This work constitutes the first demonstration of complete, functional, IPMC actuators produced entirely by freeform fabrication.

Details

Rapid Prototyping Journal, vol. 12 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 1 December 2004

Wei Sun, Tao Jiang and Feng Lin

A processing algorithm for freeform fabrication of heterogeneous structures is presented. The algorithm was developed based on the heterogeneous fabrication structural…

Abstract

A processing algorithm for freeform fabrication of heterogeneous structures is presented. The algorithm was developed based on the heterogeneous fabrication structural model, which was constructed from the STL based multi‐material volume regions and with material identifications. The reasoning Boolean operation based modelling approach was used to construct the heterogeneous CAD assembly and to output the needed STL format. Procedures for generating the database hierarchy and the storage of the heterogeneous structural model, and derivation for developing the processing algorithm for layered fabrication of heterogeneous structure are presented. The developed algorithm was applied to a heterogeneous structure consisting of two discrete material volumes, and the detailed processing path is described.

Details

Rapid Prototyping Journal, vol. 10 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 16 January 2009

Xuesong Lu, Yoonjae Lee, Shoufeng Yang, Yang Hao, Julian Evans and Clive Parini

The aim of this paper is to provide an easy method of extrusion freeforming to fabricate microwave electromagnetic bandgap (EBG) crystals. EBG crystals are periodic…

Abstract

Purpose

The aim of this paper is to provide an easy method of extrusion freeforming to fabricate microwave electromagnetic bandgap (EBG) crystals. EBG crystals are periodic dielectric structures that can block wave propagation and generate a bandgap. These crystals can be used in high capability antennae, electromagnetic wave semiconductors, microresonators, high‐reflectivity mirrors and polarizing beam splitters.

Design/methodology/approach

The effects of extrusion process parameters and paste characteristics were investigated. Finally, one‐period and two‐period woodpile EBG crystals with bandgaps in the frequency region of 90‐110 GHz were fabricated and the bandgap was measured.

Findings

The filament diameter is influenced by whether extrusion is carried out with or without a substrate and by the free fall‐distance from the nozzle. The quality of lattice structures is dependent on paste flow and properties. A ceramic paste with 60 vol. % (the fraction of ceramic powder based on solvent‐free polymer) was well suited to fabrication. The solvent content also influenced the fabrication. The experimental results show that under ∼12 per cent solvent mass fraction in the paste and relatively high extrusion ram velocity (more than 0.014 mm/s) at a pressure of 14 MPa, samples with high quality were fabricated.

Originality/value

This paper demonstrates that the rapid prototyping method of extrusion freeforming can be applied for the fabrication of EBG crystals from ceramic powders and the important factors which influence the product quality are identified.

Details

Rapid Prototyping Journal, vol. 15 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 1 February 2004

Evan Malone, Kian Rasa, Daniel Cohen, Todd Isaacson, Hilary Lashley and Hod Lipson

This paper reports on a fabrication platform and extensions to deposition‐based processes that permit freeform fabrication of three‐dimensional functional assemblies with…

Abstract

This paper reports on a fabrication platform and extensions to deposition‐based processes that permit freeform fabrication of three‐dimensional functional assemblies with embedded conductive wiring and power sources. Structure and joints are produced by fused deposition of thermoplastics and deposition of elastomers. Conductive wiring is achieved by deposition of various low‐melting‐point alloys and conductive pastes. Batteries based on zinc‐air chemistry are produced by the deposition of zinc, electrolyte, and catalysts, with separator media and electrodes. Details of the deposition processes are provided and several printed assemblies are demonstrated.

Details

Rapid Prototyping Journal, vol. 10 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 1 March 2003

Suman Das, Scott J. Hollister, Colleen Flanagan, Adebisi Adewunmi, Karlin Bark, Cindy Chen, Krishnan Ramaswamy, Daniel Rose and Erwin Widjaja

The aim of this research is to develop, demonstrate and characterize techniques for fabricating such scaffolds by combining solid freeform fabrication and computational…

Abstract

The aim of this research is to develop, demonstrate and characterize techniques for fabricating such scaffolds by combining solid freeform fabrication and computational design methods. When fully developed, such techniques are expected to enable the fabrication of tissue engineering scaffolds endowed with functionally graded material composition and porosity exhibiting sharp or smooth gradients. Results of bio‐compatibility and in vivo implantation are presented.

Details

Rapid Prototyping Journal, vol. 9 no. 1
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 7 August 2007

Uma Maheshwaraa, David Bourell and Carolyn Conner Seepersad

Frontier environments – such as battlefields, hostile territories, remote locations, or outer space – drive the need for lightweight, deployable structures that can be…

Abstract

Purpose

Frontier environments – such as battlefields, hostile territories, remote locations, or outer space – drive the need for lightweight, deployable structures that can be stored in a compact configuration and deployed quickly and easily in the field. This paper seeks to introduce the concept of lattice skins is introduced to enable the design, solid freeform fabrication (SFF), and deployment of customizable structures with nearly arbitrary surface profile and lightweight multi‐functionality.

Design/methodology/approach

Using Duraform® FLEX material in a selective laser sintering machine, large deployable structures are fabricated in a nominal build chamber by decomposing them into smaller parts. Before fabrication, lattice sub‐skins are added strategically beneath the surface of the part. The lattices provide elastic energy for folding and deploying the structure or constrain expansion upon application of internal air pressure. Nearly, arbitrary surface profiles are achievable and internal space is preserved for subsequent usage.

Findings

A set of virtual and physical prototypes are presented, along with the computational modeling approach used to design them. The prototypes provide proof of concept for lattice skins as a deployment mechanism in SFF and demonstrate the effect of lattice structures on deployed shape.

Research limitations/implications

The research findings demonstrate not only the feasibility of a new deployment mechanism‐based on lattice skins – for deploying freeform structures, but also the potential utility of SFF techniques for fabricating customized deployable structures.

Originality/value

A new lattice skin mechanism is introduced for deploying structures with nearly arbitrary surface profiles and open, usable, internal space. Virtual and physical prototypes are introduced for proof of concept, along with an optimization approach for automated design of these structures.

Details

Rapid Prototyping Journal, vol. 13 no. 4
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 18 January 2011

Uma Maheshwaraa Namasivayam and Carolyn Conner Seepersad

Solid freeform fabrication is particularly suitable for fabricating customized parts, but it has not been used for fabricating deployable structures that can be stored in…

Abstract

Purpose

Solid freeform fabrication is particularly suitable for fabricating customized parts, but it has not been used for fabricating deployable structures that can be stored in a compact configuration and deployed quickly and easily in the field. The purpose of this paper is to present a methodology for deploying flexible, freeform structure with lattice skins as the deploying mechanism.

Design/methodology/approach

A ground structure‐based topology optimization procedure is utilized, with a penalization scheme that encourages convergence to sets of thick lattice elements that are manufacturable and extremely thin lattice elements that are removed from the final structure.

Findings

A deployable wing is designed for a miniature unmanned aerial vehicle. A physical prototype of the optimal configuration is fabricated with selective laser sintering and compared with the virtual prototype. The proposed methodology results in a 78 percent improvement in deviations from the intended surface profile of the deployed part.

Originality/value

The results presented in the paper provide proof‐of‐concept for the use of lattice skins as a deployment mechanism. A topology optimization framework is also provided for designing these lattice skins. Potential applications include portable, camouflaged shelters and deployable aerial vehicles.

Details

Rapid Prototyping Journal, vol. 17 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

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