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Article

Lindsey Bass, Nicholas Alexander Meisel and Christopher B. Williams

Understanding how material jetting process parameters affect material properties can inform design and print orientation when manufacturing end-use components. This study…

Abstract

Purpose

Understanding how material jetting process parameters affect material properties can inform design and print orientation when manufacturing end-use components. This study aims to explore the robustness of material properties in material jetted components to variations in processing environment and build orientation.

Design/methodology/approach

The authors characterized the properties of six different material gradients produced from preset “digital material” mixes of polypropylene-like (VeroWhitePlus) and elastomer-like (TangoBlackPlus) materials. Tensile stress, modulus of elasticity and elongation at break were analyzed for each material printed at three different build orientations. In a separate ten-week study, the authors investigated the effects of aging in different lighting conditions on material properties.

Findings

Specimens fabricated with their longest dimension along the direction of the print head travel (X-axis) tended to have the largest tensile strength, but trends in elastic modulus and elongation at break varied between the rigid and flexible photopolymers. The aging study showed that the ultimate tensile stress of VeroWhitePlus parts increased and the elongation decreased over time. Material properties were not significantly altered by lighting conditions.

Research limitations/implications

Many tensile specimens failed at the neck region, especially for the more elastomeric parts. It is hypothesized that this is due to the material jetting process approximating curves with a pixelated droplet arrangement, instead of curved contour as seen in other additive manufacturing processes. A new tensile specimen design that performs more consistently with elastomer-like materials should be considered. The aging component of this study is focused solely on polypropylene-like (VeroWhitePlus) material; additional research into the effects of aging on multiple composite materials is needed.

Originality/value

The study provides the first known description of orientation effects on the mechanical behavior of photopolymers containing varied concentrations of elastomeric (TangoBlackPlus) material. The aging study presents the first findings on how time affects parts made via material jetting.

Details

Rapid Prototyping Journal, vol. 22 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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Article

Seijiro Takeshita, Soo Hee Lee, Christopher Williams and Jacqueline Jing You

The authors examine the nature of institutional rigidity and governance problems contributing to crisis and under-performance of large corporations in Japan during a…

Abstract

Purpose

The authors examine the nature of institutional rigidity and governance problems contributing to crisis and under-performance of large corporations in Japan during a period of environmental turbulence for corporate Japan.

Design/methodology/approach

Through explorative case studies of Mitsubishi Motors and Kanebo over a 10-year period from the mid-1990s to the mid-2000s the authors see how informal norms deeply embedded in the Japanese business system prevented the adoption of more liberal forms of governance that may have helped to overcome crisis.

Findings

Despite fundamental differences in formal organization between the two cases, there were similar underlying problems in terms of (1) mechanisms for capital investment that would underpin strategic resilience and rejuvenation and (2) management decision-making and strategic control during crisis.

Research limitations/implications

The cases show how normative institutions rather than formal regulative institutions matter to strategic continuity in national business systems that are put under pressure.

Originality/value

The authors link informal norms of governance intrinsic to a country to the issues of strategic resilience and responses during crisis and warn against the retrenching to traditional governance approaches where there has been criticism of alternative governance approaches.

Details

Continuity & Resilience Review, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2516-7502

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Article

Nicholas Alexander Meisel, David A. Dillard and Christopher B. Williams

Material jetting approximates composite material properties through deposition of base materials in a dithered pattern. This microscale, voxel-based patterning leads to…

Abstract

Purpose

Material jetting approximates composite material properties through deposition of base materials in a dithered pattern. This microscale, voxel-based patterning leads to macroscale property changes, which must be understood to appropriately design for this additive manufacturing (AM) process. This paper aims to identify impacts on these composites’ viscoelastic properties due to changes in base material composition and distribution caused by incomplete dithering in small features.

Design/methodology/approach

Dynamic mechanical analysis (DMA) is used to measure viscoelastic properties of two base PolyJet materials and seven “digital materials”. This establishes the material design space enabled by voxel-by-voxel control. Specimens of decreasing width are tested to explore effects of feature width on dithering’s ability to approximate macroscale material properties; observed changes are correlated to multi-material distribution via an analysis of ingoing layers.

Findings

DMA shows storage and loss moduli of preset composites trending toward the iso-strain boundary as composition changes. An added iso-stress boundary defines the property space achievable with voxel-by-voxel control. Digital materials exhibit statistically significant changes in material properties when specimen width is under 2 mm. A quantified change in same-material droplet groupings in each composite’s voxel pattern shows that dithering requires a certain geometric size to accurately approximate macroscale properties.

Originality/value

This paper offers the first quantification of viscoelastic properties for digital materials with respect to material composition and identification of the composite design space enabled through voxel-by-voxel control. Additionally, it identifies a significant shift in material properties with respect to feature width due to dithering pattern changes. This establishes critical design for AM guidelines for engineers designing with digital materials.

Details

Rapid Prototyping Journal, vol. 24 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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Article

Nicholas A. Meisel, Christopher B. Williams, Kimberly P. Ellis and Don Taylor

Additive manufacturing (AM) can reduce the process supply chain and encourage manufacturing innovation in remote or austere environments by producing an array of…

Abstract

Purpose

Additive manufacturing (AM) can reduce the process supply chain and encourage manufacturing innovation in remote or austere environments by producing an array of replacement/spare parts from a single raw material source. The wide variety of AM technologies, materials, and potential use cases necessitates decision support that addresses the diverse considerations of deployable manufacturing. The paper aims to discuss these issues.

Design/methodology/approach

Semi-structured interviews with potential users are conducted in order to establish a general deployable AM framework. This framework then forms the basis for a decision support tool to help users determine appropriate machines and materials for their desired deployable context.

Findings

User constraints are separated into process, machine, part, material, environmental, and logistical categories to form a deployable AM framework. These inform a “tiered funnel” selection tool, where each stage requires increased user knowledge of AM and the deployable context. The tool can help users narrow a database of candidate machines and materials to those appropriate for their deployable context.

Research limitations/implications

Future work will focus on expanding the environments covered by the decision support tool and expanding the user needs pool to incorporate private sector users and users less familiar with AM processes.

Practical implications

The framework in this paper can influence the growth of existing deployable manufacturing endeavors (e.g. Rapid Equipping Force Expeditionary Lab – Mobile, Army’s Mobile Parts Hospital, etc.) and considerations for future deployable AM systems.

Originality/value

This work represents novel research to develop both a framework for deployable AM and a user-driven decision support tool to select a process and material for the deployable context.

Details

Journal of Manufacturing Technology Management, vol. 27 no. 7
Type: Research Article
ISSN: 1741-038X

Keywords

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Article

Mohammad I. Albakri, Logan D. Sturm, Christopher B. Williams and Pablo A. Tarazaga

This work proposes the utilization of electromechanical impedance measurements as a means of non-destructive evaluation (NDE) for additive manufacturing (AM). The…

Abstract

Purpose

This work proposes the utilization of electromechanical impedance measurements as a means of non-destructive evaluation (NDE) for additive manufacturing (AM). The effectiveness and sensitivity of the technique for a variety of defect types commonly encountered in AM are investigated.

Design/methodology/approach

To evaluate the feasibility of impedance-based NDE for AM, the authors first designed and fabricated a suite of test specimens with build errors typical of AM processes, including dimensional inaccuracies, positional inaccuracies and internal porosity. Two polymer AM processes were investigated in this work: material jetting and extrusion. An impedance-based analysis was then conducted on all parts and utilized, in a supervised learning context, for identifying defective parts.

Findings

The newly proposed impedance-based NDE technique has been proven to be an effective solution for detecting several types of print defects. Specifically, it was shown that the technique is capable of detecting print defects resulting in mass change (as small as 1 per cent) and in feature displacement (as small as 1 mm) in both extruded nylon parts and jetted VeroWhitePlus parts. Internal porosity defects were also found to be detectable; however, the impact of this defect type on the measured impedance was not as profound as that of dimensional and positional inaccuracies.

Originality/value

Compared to currently available NDE techniques, the newly proposed impedance-based NDE is a functional-based technique with the advantages of being cost-effective, sensitive and suitable for inspecting AM parts of complex geometry and deeply embedded flaws. This technique has the potential to bridge the existing gaps in current NDE practices, hence paving the road for a wider adoption of AM to produce mission-critical parts.

Details

Rapid Prototyping Journal, vol. 23 no. 3
Type: Research Article
ISSN: 1355-2546

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Article

Joseph R. Kubalak, Alfred L. Wicks and Christopher B. Williams

Material extrusion (ME) suffers from anisotropic mechanical properties that stem from the three degree of freedom (DoF) toolpaths used for deposition. The formation of…

Abstract

Purpose

Material extrusion (ME) suffers from anisotropic mechanical properties that stem from the three degree of freedom (DoF) toolpaths used for deposition. The formation of each layer is restricted to the XY-plane, which produces poorly bonded layer interfaces along the build direction. Multi-axis ME affords the opportunity to change the layering and deposition directions locally throughout a part, which could improve a part’s overall mechanical performance. The purpose of this paper is to evaluate the effects of changing the layering and deposition directions on the tensile mechanical properties of parts printed via multi-axis ME.

Design/methodology/approach

A multi-axis toolpath generation algorithm is presented and implemented on a 6-DoF robotic arm ME system to fabricate tensile specimens at different global orientations. Specifically, acrylonitrile butadiene styrene (ABS) tensile specimens are printed at various inclination angles using the multi-axis technique; the resulting tensile strengths of the multi-axis specimens are compared to similarly oriented specimens printed using a traditional 3-DoF method.

Findings

The multi-axis specimens had similar performances regardless of orientation and were equivalent to the 3-DoF specimens printed in the XYZ orientation (i.e. flat on the bed with roads aligned to the loading condition). This similarity is attributed to those sets of specimens having the same degree of road alignment.

Practical implications

Parts with out-of-plane loads currently require design compromises (e.g. additional material in critical areas). Multi-axis deposition strategies could enable local changes in layering and deposition directions to more optimally orient roads in critical areas of the part.

Originality/value

Though multi-axis ME systems have been demonstrated in literature, no prior work has been done to determine the effects of the deposition angle on the resulting mechanical properties. This work demonstrates that identical mechanical properties can be obtained irrespective of the build direction through multi-axis deposition. For ABS, the yield tensile strength of vertically oriented tensile bars was improved by 153 per cent using multi-axis deposition as compared to geometrically similar samples fabricated via 3-DoF deposition.

Details

Rapid Prototyping Journal, vol. 25 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

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Article

Jane Evans and Christopher Williams

Using data from a survey of social services departments, this paper looks at how local authorities are addressing the needs of people with learning disabilities for…

Abstract

Using data from a survey of social services departments, this paper looks at how local authorities are addressing the needs of people with learning disabilities for protection from crime and abuse within the context of adult protection developments. Previous research indicated that victimisation of this group was less likely to be treated seriously by key agencies. Here, the situation is reassessed.

Details

The Journal of Adult Protection, vol. 3 no. 1
Type: Research Article
ISSN: 1466-8203

Keywords

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Book part

Christopher Williams and Wendelien van Eerde

Prior research into multinational enterprises’ (MNEs) entrepreneurial initiatives has drawn from various theoretical bases, including entrepreneurial cognition…

Abstract

Prior research into multinational enterprises’ (MNEs) entrepreneurial initiatives has drawn from various theoretical bases, including entrepreneurial cognition, knowledge-based view, and management control theory. Empirical studies and cases have consistently pointed to the temporal dimension, highlighting the dynamic elements of learning, capability development and evolution, and consequences of conflict. By incorporating theory on time use into the analysis, we develop a new theoretical insight regarding the temporal dimension of MNE entrepreneurial initiatives. Our analysis offers a basis for a more explicit focus on time use in studies of entrepreneurial initiatives in MNEs than has been offered to date. Implications for research and practice are discussed.

Details

Global Opportunities for Entrepreneurial Growth: Coopetition and Knowledge Dynamics within and across Firms
Type: Book
ISBN: 978-1-78714-502-3

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Article

Thomas A. Karel

For the past twenty‐five years or so, the writings of George Orwell — especially his final novel 1984 — have been a popular topic for student research. From junior high…

Abstract

For the past twenty‐five years or so, the writings of George Orwell — especially his final novel 1984 — have been a popular topic for student research. From junior high through graduate school, interest in Orwell has been consistent. Book reports, term papers, and even seminars on Orwell are common‐place in the national curriculum. Now, as the year 1984 arrives, librarians at all levels — public, school, academic — must brace themselves for a year‐long onslaught of requests for biographical and critical material on Orwell.

Details

Reference Services Review, vol. 12 no. 1
Type: Research Article
ISSN: 0090-7324

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Article

Jacob P. Moore and Christopher B. Williams

– This paper aims to seek to fill a gap in the literature by characterizing the fatigue life and microstructure of a printed elastomer material, the TangoBlackPlus material.

Abstract

Purpose

This paper aims to seek to fill a gap in the literature by characterizing the fatigue life and microstructure of a printed elastomer material, the TangoBlackPlus material.

Design/methodology/approach

Because the TangoBlackPlus material is marketed as “rubber-like”, the printed elastomer specimens were tested according to the ASTM D4482-11 “Test Method for Rubber Property Extension Cycling Fatigue”. The microstructure of the printed material and multi-material interface was examined by slicing specimens and examining them under an optical microscope.

Findings

Findings are developed to show the relationship between elongation and expected fatigue life. Findings also indicate that the smoother, non-support encased “glossy” surface finish option for PolyJet parts improve the fatigue life of components and that there are a number of microscopic voids in the TangoBlackPlus material that seem to be concentrated at layer and print head boundaries.

Research limitations/implications

This paper provides a glimpse into the fatigue properties and microstructure of printed elastomeric parts, a previously unstudied area. This work is limited in that it only looks at specimens created in a single orientation, on a single machine, with a single material. More work is needed to understand the general fatigue properties of printed elastomers and the factors that influence fatigue life in these materials.

Practical implications

The authors provide several design guidelines based on the findings and previous work that can be used to increase the fatigue life of printed elastomer components.

Originality/value

As additive manufacturing (AM) technology moves from a prototyping tool to a tool used to create end use products, it is important to examine the expected lifespan of AM components. This work adds to the understanding of the expected product lifecycle of printed elastomer components that will likely be expected to withstand large repeated loading conditions.

Details

Rapid Prototyping Journal, vol. 21 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

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