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Article
Publication date: 12 October 2018

Xiaopeng Li, Brecht Van Hooreweder, Wout Lauwers, Bavo Follon, Ann Witvrouw, Kurt Geebelen and Jean-Pierre Kruth

The cooling process of polymer components fabricated by selective laser sintering (SLS) plays a vital role in determining the crystallinity, density and the resultant properties…

494

Abstract

Purpose

The cooling process of polymer components fabricated by selective laser sintering (SLS) plays a vital role in determining the crystallinity, density and the resultant properties of the produced parts. However, the control and optimization of the cooling process remains challenging. The purpose of this paper is to therefore investigate the cooling process of the SLS fabricated polyamide 12 (PA12) components through simulations. This work provides necessary fundamental insights into the possibilities for optimization and control of this cooling process for achieving desired properties.

Design/methodology/approach

The thermal properties of the PA12 powder and SLS fabricated PA12 components including density, specific heat and thermal conductivity were first determined experimentally. Then, the finite element method was used to optimize a container (a cuboid aluminum box where PA12 parts are built by the SLS) geometry in which the SLS parts can cool down in a controlled manner. Also, the cooling parameters required for maximum temperature homogeneity and minimum cooling time were determined.

Findings

Two different approximations in the finite element (FE) model were used and compared. It was found that the approximation which considers powder as a solid medium with porous material properties gives better results as compared to the approximation which treats powder as a collection of air and particles with solid material properties. The results also showed that the geometry of the containers has an important influence on the cooling process of the SLS fabricated PA12 components regarding temperature homogeneity and cooling time required. A container with a small width, long length and high height tends to result in a more homogenous temperature distribution during the cooling process.

Originality/value

Thermal constants of PA12 powder and parts were accurately determined as a starting point for numerical simulations. The FE model developed in this work provides useful and necessary information for the optimization and control of the cooling process of the SLS fabricated PA12 components and can thus be used for ensuring high-quality products with desired component properties.

Details

Rapid Prototyping Journal, vol. 24 no. 7
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 18 April 2016

Jan Patrick Deckers, Khuram Shahzad, Ludwig Cardon, Marleen Rombouts, Jozef Vleugels and Jean-Pierre Kruth

The purpose of this paper is to compare different powder metallurgy (PM) processes to produce ceramic parts through additive manufacturing (AM). This creates the potential to…

899

Abstract

Purpose

The purpose of this paper is to compare different powder metallurgy (PM) processes to produce ceramic parts through additive manufacturing (AM). This creates the potential to rapidly shape ceramic parts with an almost unlimited shape freedom. In this paper, alumina (Al2O3) parts are produced, as Al2O3 is currently the most commonly used ceramic material for technical applications.

Design/methodology/approach

Variants of the following PM route, with indirect selective laser sintering (indirect SLS) as the AM shaping step, are explored to produce ceramic parts: powder synthesis, indirect SLS, binder removal and furnace sintering and alternative densification steps.

Findings

Freeform-shaped Al2O3 parts with densities up to approximately 90 per cent are obtained.

Research limitations/implications

The resulting Al2O3 parts contain inter-agglomerate pores. To produce higher-quality ceramic parts through indirect SLS, these pores should be avoided or eliminated.

Originality/value

The research is innovative in many ways. First, composite powders are produced using different powder production methods, such as temperature-induced phase separation and dispersion polymerization. Second, four different binder materials are investigated: polyamide (nylon-12), polystyrene, polypropylene and a carnauba wax – low-density polyethylene combination. Further, to produce ceramic parts with increased density, the following densification techniques are investigated as additional steps of the PM process: laser remelting, isostatic pressing and infiltration.

Details

Rapid Prototyping Journal, vol. 22 no. 3
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 1 December 2003

J.P. Kruth, X. Wang, T. Laoui and L. Froyen

Selective laser sintering (SLS) is one of the most rapidly growing rapid prototyping techniques (RPT). This is mainly due to its suitability to process almost any material…

19115

Abstract

Selective laser sintering (SLS) is one of the most rapidly growing rapid prototyping techniques (RPT). This is mainly due to its suitability to process almost any material: polymers, metals, ceramics (including foundry sand) and many types of composites. The material should be supplied as powder that may occasionally contain a sacrificial polymer binder that has to be removed (debinded) afterwards. The interaction between the laser beam and the powder material used in SLS is one of the dominant phenomena that defines the feasibility and quality of any SLS process. This paper surveys the current state of SLS in terms of materials and lasers. It describes investigations carried out experimentally and by numerical simulation in order to get insight into laser‐material interaction and to control this interaction properly.

Details

Assembly Automation, vol. 23 no. 4
Type: Research Article
ISSN: 0144-5154

Keywords

Available. Content available
Article
Publication date: 19 January 2015

Ian Campbell

293

Abstract

Details

Rapid Prototyping Journal, vol. 21 no. 1
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 18 January 2008

Maarten van Elsen, Farid Al‐Bender and Jean‐Pierre Kruth

This paper aims to present a possible complete set of dimensionless parameters to describe the process of selective laser melting (SLM). This makes it possible to compare the…

4509

Abstract

Purpose

This paper aims to present a possible complete set of dimensionless parameters to describe the process of selective laser melting (SLM). This makes it possible to compare the similarity between different experiments, a sine‐qua‐non for a correct comparison of the results.

Design/methodology/approach

The paper describes the application of dimensional analysis to SLM.

Findings

Although the idea of dimensionless numbers is far from new, it has apparently never been applied rigorously to rapid prototyping and rapid manufacturing technologies. The technique is important, since it reduces the number of factors and makes it possible to compare results of different research groups. Furthermore, some more fundamental insights about the process can be gained.

Originality/value

This work is a first step towards a manageable system to control very difficult processes.

Details

Rapid Prototyping Journal, vol. 14 no. 1
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 7 August 2007

Ben Vandenbroucke and Jean‐Pierre Kruth

This paper seeks to investigate the possibility of producing medical or dental parts by selective laser melting (SLM). Rapid Manufacturing could be very suitable for these…

15516

Abstract

Purpose

This paper seeks to investigate the possibility of producing medical or dental parts by selective laser melting (SLM). Rapid Manufacturing could be very suitable for these applications due to their complex geometry, low volume and strong individualization.

Design/methodology/approach

The SLM‐process has been optimized and fully characterized for two biocompatible metal alloys: Ti‐6Al‐4V and Co‐Cr‐Mo. Mechanical and chemical properties were tested and geometrical feasibility, including process accuracy and surface roughness, was discussed by benchmark studies. By developing a procedure to fabricate frameworks for complex dental prostheses, the potential of SLM as a medical manufacturing technique has been proved.

Findings

Optimized SLM parameters lead to part densities up to 99.98 percent for titanium. Strength and stiffness, corrosion behavior, and process accuracy fulfil requirements for medical or dental parts. Surface roughness analyses show some limitations of the SLM process. Dental frameworks can be produced efficiently and with high precision.

Originality/value

This study presents the state‐of‐the‐art in SLM of biocompatible metals by thoroughly testing material and part properties. It shows opportunities for using SLM for medical or dental applications.

Details

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

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Article
Publication date: 1 October 2006

Peter Mercelis and Jean‐Pierre Kruth

This paper presents an investigation into residual stresses in selective laser sintering (SLS) and selective laser melting (SLM), aiming at a better understanding of this…

27928

Abstract

Purpose

This paper presents an investigation into residual stresses in selective laser sintering (SLS) and selective laser melting (SLM), aiming at a better understanding of this phenomenon.

Design/methodology/approach

First, the origin of residual stresses is explored and a simple theoretical model is developed to predict residual stress distributions. Next, experimental methods are used to measure the residual stress profiles in a set of test samples produced with different process parameters.

Findings

Residual stresses are found to be very large in SLM parts. In general, the residual stress profile consists of two zones of large tensile stresses at the top and bottom of the part, and a large zone of intermediate compressive stress in between. The most important parameters determining the magnitude and shape of the residual stress profiles are the material properties, the sample and substrate height, the laser scanning strategy and the heating conditions.

Research limitations/implications

All experiments were conducted on parts produced from stainless steel powder (316L) and quantitative results cannot be simply extrapolated to other materials. However, most qualitative results can still be generalized.

Originality/value

This paper can serve as an aid in understanding the importance of residual stresses in SLS/SLM and other additive manufacturing processes involving a localized heat input. Some of the conclusions can be used to avoid problems associated with residual stresses.

Details

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

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Article
Publication date: 2 August 2011

Evren Yasa, Jan Deckers and Jean‐Pierre Kruth

Selective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the process, a…

7085

Abstract

Purpose

Selective laser melting (SLM) is a powder metallurgical (PM) additive manufacturing process whereby a three‐dimensional part is built in a layer‐wise manner. During the process, a high intensity laser beam selectively scans a powder bed according to the computer‐aided design data of the part to be produced and the powder metal particles are completely molten. The process is capable of producing near full density (∼98‐99 per cent relative density) and functional metallic parts with a high geometrical freedom. However, insufficient surface quality of produced parts is one of the important limitations of the process. The purpose of this study is to apply laser re‐melting using a continuous wave laser during SLM production of 316L stainless steel and Ti6Al4V parts to overcome this limitation.

Design/methodology/approach

After each layer is fully molten, the same slice data are used to re‐expose the layer for laser re‐melting. In this manner, laser re‐melting does not only improve the surface quality on the top surfaces, but also has the potential to change the microstructure and to improve the obtained density. The influence of laser re‐melting on the surface quality, density and microstructure is studied varying the operating parameters for re‐melting such as scan speed, laser power and scan spacing.

Findings

It is concluded that laser re‐melting is a promising method to enhance the density and surface quality of SLM parts at a cost of longer production times. Laser re‐melting improves the density to almost 100 per cent whereas 90 per cent enhancement is achieved in the surface quality of SLM parts after laser re‐melting. The microhardness is improved in the laser re‐molten zone if sufficiently high‐energy densities are provided, probably due to a fine‐cell size encountered in the microstructure.

Originality/value

There has been extensive research in the field of laser surface modification techniques, e.g. laser polishing, laser hardening and laser surface melting, applied to bulk materials produced by conventional manufacturing processes. However, those studies only relate to laser enhancement of surface or sub‐surface properties of parts produced using bulk material. They do not aim at enhancement of core material properties, nor surface enhancement of (rough) surfaces produced in a PM way by SLM. This study is carried out to cover the gap and analyze the advantages of laser re‐melting in the field of additive manufacturing.

Details

Rapid Prototyping Journal, vol. 17 no. 5
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 20 October 2014

Karel Kellens, Renaldi Renaldi, Wim Dewulf, Jean-pierre Kruth and Joost R. Duflou

This paper aims to present parametric models to estimate the environmental footprint of the selective laser sintering (SLS)’ production phase, covering energy and resource…

2102

Abstract

Purpose

This paper aims to present parametric models to estimate the environmental footprint of the selective laser sintering (SLS)’ production phase, covering energy and resource consumption as well as process emissions. Additive manufacturing processes such as (SLS) are often considered to be more sustainable then conventional manufacturing methods. However, quantitative analyses of the environmental impact of these processes are still limited and mainly focus on energy consumption.

Design/methodology/approach

The required Life Cycle Inventory data are collected using the CO2PE! – Methodology, including time, power, consumables and emission studies. Multiple linear regression analyses have been applied to investigate the interrelationships between product design features on the one hand and production time (energy and resource consumption) on the other hand.

Findings

The proposed parametric process models provide accurate estimations of the environmental footprint of SLS processes based on two design features, build height and volume, and help to identify and quantify measures for significant impact reduction of both involved products and the supporting machine tools.

Practical implications

The gained environmental insight can be used as input for ecodesign activities, as well as environmental comparison of alternative manufacturing process plans.

Originality/value

This article aims to overcome the current lack of environmental impact models, covering energy and resource consumption as well as process emissions for SLS processes.

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Article
Publication date: 26 July 2021

Rajae Jemghili, Abdelmajid Ait Taleb and Mansouri Khalifa

Although many researchers have widely studied additive manufacturing (AM) as one of the most important industrial revolutions, few have presented a bibliometric analysis of the…

619

Abstract

Purpose

Although many researchers have widely studied additive manufacturing (AM) as one of the most important industrial revolutions, few have presented a bibliometric analysis of the published studies in this area. This paper aims to evaluate AM research trends based on 4607 publications most cited from year 2010 to 2020.

Design/methodology/approach

The research methodology is bibliometric indicators and network analysis, including analysis based on keywords, citation analysis, productive journal, related published papers and authors indicators. Two free available software were employed VOSviewer and Bibexcel.

Findings

Keywords analysis results indicate that among the AM processes, Selective Laser Melting and Fused Deposition Modeling techniques, are the two processes ranked on top of the techniques employed and studied with 35.76% and 20.09% respectively. The citation analysis by VOSviewer software, reveals that the medical applications field and the fabrication of metal parts are the areas that interest researchers greatly. Different new research niches, as pharmaceutical industry, digital construction and food fabrication are growing topics in AM scientific works. This study reveals that journals “Materials & design”, “Advanced materials”, “Acs applied materials & interfaces”, “Additive manufacturing”, “Advanced functional materials” and “Biofabrication” are the most productive and influential in AM scientific research.

Originality/value

The results and conclusions of this work can be used as indicators of trends in AM research and/or as prospects for future studies in this area.

Details

Rapid Prototyping Journal, vol. 27 no. 7
Type: Research Article
ISSN: 1355-2546

Keywords

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