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1 – 10 of 242
Article
Publication date: 19 October 2015

Christina Blümel, Marius Sachs, Tobias Laumer, Bettina Winzer, Jochen Schmidt, Michael Schmidt, Wolfgang Peukert and Karl-Ernst Wirth

The purpose of this paper is to demonstrate the processability of cohesive PE-HD particles in laser beam melting processes (LBM) of polymers. Furthermore, we present a…

Abstract

Purpose

The purpose of this paper is to demonstrate the processability of cohesive PE-HD particles in laser beam melting processes (LBM) of polymers. Furthermore, we present a characterization method for polymer particles, which can predict the quality of the powder deposition via LBM processes.

Design/methodology/approach

This study focuses on the application of dry particle coating processes to increase flowability and bulk density of PE-HD particles. Both has been measured and afterwards validated via powder deposition of PE-HD particles in a LBM machine.

Findings

For efficient coating in a dry particle coating process, the PE-HD particles and the attached nanoparticles need to show similar surface chemistry, i.e. both need to behave either hydrophobic or hydrophilic. It is demonstrated that dry particle coating is appropriate to enhance flowability and bulk density of PE-HD particles and hence considerably improves LBM processes and the resulting product quality.

Originality/value

At present, in LBM processes mainly polyamide (PA), 12 particles are used, which are so far quite expensive in comparison to, for example, PE-HD particles. This work provides a unique and versatile method for nanoparticulate surface modification which may be applied to a wide variety of materials. After the coating, the particles are applicable for the LBM process. Our results provide a correlation between flowability and bulk density and the resulting product quality.

Details

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

Keywords

Article
Publication date: 18 October 2018

Zhi Guo, Zhongde Shan, Dong Du, Mengmeng Zhao and Milan Zhang

This paper aims to determine how the viscosity and curing agent content affect the flowability of moist silica sand granules. In addition, a coating device was designed according…

Abstract

Purpose

This paper aims to determine how the viscosity and curing agent content affect the flowability of moist silica sand granules. In addition, a coating device was designed according to the flow properties of silica sand granules.

Design/methodology/approach

The flowability of silica sand granules premixed with two curing agents of different viscosities is studied using a Jenike shear apparatus. An open-ended device was used in discharge testing of sand granules with a design based on the variable dip angle of the two plates and variable outlet size.

Findings

The test results show that increasing the curing agent content would significantly decrease the flowability of silica sand granules, and a curing agent of higher viscosity has a greater effect on the flowability of silica sand. The presence of a curing agent strengthens the cohesion among sand granules, lubricates them and restrains their deformation. The shape function of the coating device was obtained by theoretical derivation.

Practical implications

The flow properties provide a valuable theoretical guidance for the design of coating device for sand mold printing.

Originality/value

This paper deals with experimental work on flow properties of silica sand granules with different viscosities and curing agent content. The shape function of a wedge-shaped coating device is obtained based on experimental data.

Details

Rapid Prototyping Journal, vol. 24 no. 9
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 7 December 2020

Sean Daniel Dobson and Thomas Louis Starr

Characteristics of the metal powder are a key factor in the success of powder bed fusion (PBF) additive manufacturing. Powders for PBF from different manufacturers may have a…

Abstract

Purpose

Characteristics of the metal powder are a key factor in the success of powder bed fusion (PBF) additive manufacturing. Powders for PBF from different manufacturers may have a different particle size and/or bulk packing and flow behavior. Powder properties change as the powder is reused for multiple builds. This study seeks to measure the variability of commercial 17-4 PH stainless steel powders to determine the effect of powder variability on part density and demonstrate characterization methods that ensure part quality.

Design/methodology/approach

Commercial atomized metal powders from four different vendors were produced with two different atomizing gases (N2 and argon). Powder was characterized in both new and extensively reused conditions. All powders were characterized for flow and packing behavior, particle size and internal porosity. Coupons were manufactured using the laser PBF process with optimized scan strategy and exposure parameters. The quality of fabricated parts was measured using bulk density measurement.

Findings

Despite differences in powder flowability and particle size, fully dense parts (>99 per cent) were produced using all powders, except one. Residual porosity in these parts appeared to result from gas trapped in the powder particles. The powder with extensive reuse (400+ h in machine fabrication environment) exhibited reduced flowability and increased fraction of fine particles, but still produced full density parts.

Originality/value

This study demonstrates that full density parts can be fabricated using powders with a range of flowability and packing behavior. This suggests that a single flowability measurement may be sufficient for quality assurance in a production environment.

Details

Rapid Prototyping Journal, vol. 27 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Abstract

Purpose

The purpose of this study is to analyse the problem of high binder content in sand mould and to solve it. Meanwhile, to increase build speed, especially for heavy casting’s sand mould with a high value in layer height, such as 2 mm in construction instead of the industry standard of 0.3 mm, line forming for three-dimensional (3D) sand mould printing is researched.

Design/methodology/approach

Brief introduction of 3D sand mould printing and key issues are given first. Then, this paper quantitatively analyses binder content in sand mould. Finally, to acquire sand mould with appropriate binder content and high build speed, line forming combining traditional furan no-bake sand manufacture technique is researched, as well as relevant feasible schemes and current progress.

Findings

The study shows that compared with traditional technique, binder content in sand mould produced by available 3D printing technique is too high, bad for sand mould’s properties and quality of castings, while line forming brings guaranteed binder content and improved build speed.

Research limitations/implications

More experiments are needed to demonstrate quantitative analysis of binder content and to obtain flowability of moist sand, detailed structure design of nozzle and practical build speed, as well as methods of circulation of materials considering solidification time.

Practical implications

Line forming with higher build speed and suitable binder content means excellent properties of sand mould and castings as well, bringing obvious implication for moulds industries and manufacturing industry.

Originality/value

This new method could increase build speed and meanwhile guarantee binder content. Thus, its application prospect is promising.

Details

Rapid Prototyping Journal, vol. 25 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 23 May 2018

Jiang Wu, Jingxuan Cai, Miao Jin and Ke Dong

Although interdisciplinary research is an increasing trend in scientific funding projects, they are suffering from a lower probability of being funded. The purpose of this paper…

Abstract

Purpose

Although interdisciplinary research is an increasing trend in scientific funding projects, they are suffering from a lower probability of being funded. The purpose of this paper is to analyze the current situation on successful case of funding application and provides suggestions on how libraries can expand services to help scientific funding application.

Design/methodology/approach

This paper utilizes the co-occurrences of disciplinary application codes to construct an interdisciplinary knowledge flow network. Based on 193517 sponsored projects of the National Natural Science Foundation of China, the authors study the interdisciplinary flow of knowledge and investigate the evolution of network structure using social network analysis.

Findings

Results show that the interdisciplinary knowledge flow network is not only a small-world network but also a scale-free network. Two main knowledge flow paths across scientific departments exist, showing the heterogeneity of knowledge distributions across scientific disciplines. The authors also find that if two disciplines in the same scientific department both have a wide influence to other disciplines, they are more prone to link together and create a knowledge chain.

Originality/value

Funding consultation currently has not occupied an advisory role either in library services or in the research team. This paper conducts a co-occurrences network analysis of interdisciplinary knowledge flow in scientific funding projects. Considering the complexity of funding application and the advantage of traditional library services on information collection, integration, and utilization, the authors conclude the possibility and necessity of embedding funding consultation in traditional library services.

Details

Library Hi Tech, vol. 36 no. 3
Type: Research Article
ISSN: 0737-8831

Keywords

Article
Publication date: 17 August 2020

Juan Sebastian Gomez Bonilla, Maximilian Alexander Dechet, Jochen Schmidt, Wolfgang Peukert and Andreas Bück

The purpose of this paper is to investigate the effect of different heating approaches during thermal rounding of polymer powders on powder bulk properties such as particle size…

Abstract

Purpose

The purpose of this paper is to investigate the effect of different heating approaches during thermal rounding of polymer powders on powder bulk properties such as particle size, shape and flowability, as well as on the yield of process.

Design/methodology/approach

This study focuses on the rounding of commercial high-density polyethylene polymer particles in two different downer reactor designs using heated walls (indirect heating) and preheated carrier gas (direct heating). Powder bulk properties of the product obtained from both designs are characterized and compared.

Findings

Particle rounding with direct heating leads to a considerable increase in process yield and a reduction in powder agglomeration compared to the design with indirect heating. This subsequently leads to higher powder flowability. In terms of shape, indirect heating yields not only particles with higher sphericity but also entails substantial agglomeration of the rounded particles.

Originality/value

Shape modification via thermal rounding is the decisive step for the success of a top-down process chain for selective laser sintering powders with excellent flowability, starting with polymer particles from comminution. This report provides new information on the influence of the heating mode (direct/indirect) on the performance of the rounding process and particle properties.

Details

Rapid Prototyping Journal, vol. 26 no. 9
Type: Research Article
ISSN: 1355-2546

Keywords

Open Access
Article
Publication date: 4 August 2021

Francesco Sillani, Dominik Wagner, Marvin Aaron Spurek, Lukas Haferkamp, Adriaan Bernardus Spierings, Manfred Schmid and Konrad Wegener

Powder bed-based additive manufacturing (AM) is a promising family of technologies for industrial applications. The purpose of this study is to provide a new metrics based on the…

Abstract

Purpose

Powder bed-based additive manufacturing (AM) is a promising family of technologies for industrial applications. The purpose of this study is to provide a new metrics based on the analysis of the compaction behavior for the evaluation of flowability of AM powders.

Design/methodology/approach

In this work, a novel qualification methodology based on a camera mounted onto a commercially available tap density meter allowed to assess the compaction behavior of a selection of AM materials, both polymers and metals. This methodology automatizes the reading of the powder height and obtains more information compared to ASTM B527. A novel property is introduced, the “tapping modulus,” which describes the packing speed of a powdered material and is related to a compression/vibration powder flow.

Findings

The compaction behavior was successfully correlated with the dynamic angle of repose for polymers, but interestingly not for metals, shedding more light to the different flow behavior of these materials.

Research limitations/implications

Because of the chosen materials, the results may lack generalizability. For example, the application of this methodology outside of AM would be interesting.

Originality/value

This paper suggests a new methodology for assessing the flowing behavior of AM materials when subjected to compression. The device is inexpensive and easy to implement in a quality assurance environment, being thus interesting for industrial applications.

Details

Rapid Prototyping Journal, vol. 27 no. 11
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 15 August 2019

Donghua Zhao, Weizhong Guo, Baibing Zhang and Feng Gao

This paper aims to investigate the circulation of moist silica sand to provide appropriate feeding modes and references for designing the coating device when printing sand mold…

Abstract

Purpose

This paper aims to investigate the circulation of moist silica sand to provide appropriate feeding modes and references for designing the coating device when printing sand mold with line-forming.

Design/methodology/approach

First, this paper briefly introduces sand mold printing with line-forming and the circulation problem brought by moist silica sand. The outlet may be choked due to poor flowability and solidification characteristic, resulting in poor dimensional tolerance and even production failure. Then, based on circulation modeling, a series of feeding modes is proposed to guarantee adequate feeding, avoid solidification and ensure successful fabrication. Finally, the GUI of control software is developed, including slicing, path planning and the function of virtual printing.

Findings

Several feeding modes of moist silica sand are put forward to avoid the choke.

Research limitations/implications

The authors will further investigate the flowability of furan no-bake sand based on experiments.

Originality/value

This paper is going to provide references for the novel design of nozzle, prototype and sand mold printing, influencing significantly on mold manufacturing and the casting industry. This research applies equally to equipment having the circulation of high moist particles with solidification features.

Article
Publication date: 10 July 2017

Saroj Kumar Giri, Shukadev Mangaraj, Lalan Kumar Sinha and Manoj Kumar Tripathi

Soy beverage is becoming more and more popular because it is touted as a healthy food containing useful phytochemicals and is free from lactose and cholesterol. The purpose of…

Abstract

Purpose

Soy beverage is becoming more and more popular because it is touted as a healthy food containing useful phytochemicals and is free from lactose and cholesterol. The purpose of this paper is to optimize the spray drying process parameters for obtaining soy beverage powder with good reconstitution and handling properties.

Design/methodology/approach

Pre-concentrated soy beverage was dried in a laboratory model spray dryer, and the effects of inlet air temperature (180-220°C), feed rate (20-40 ml/min) and feed solid content (15-25 per cent) on some physical parameters and reconstitution properties (wettability and dispersibility) of spray-dried soy beverage powders were investigated. Second order polynomial response surface model was selected for the analysis of data and optimization of the process.

Findings

Spray drying of soy beverage at different processing conditions resulted in powders with particle size (volume mean diameter) in the range of 86 to 156 µm. Dispersibility and wetting time of the spray-dried soy beverage powders was found to be in the range of 56 to 78 per cent and 30 to 90 s respectively, under various drying conditions. Inlet air temperature was found to be the main factor affecting most of the quality parameters, followed by solid content of the feed. Temperature significantly affected the wettability, dispersibility, colour parameters, particle size and flowability of the powder at p ≤ 0.01. Lower temperature and higher feed solid content produced bigger-sized powder particles with better handling properties in terms of flowability and cohesiveness. A moderate inlet air temperature (196°C), higher feed solid content (24 per cent) and lower feed rate (27 ml/min) were found suitable for drying of soy beverage.

Practical implications

The study implied the possibility of producing powder from soy beverage using the spray-drying method and optimized drying conditions for obtaining soy beverage powder with good reconstitution properties.

Originality/value

The finding of this study demonstrated for the first time how the inlet air temperature, feed solid content and feed rate during spray-drying influenced different quality parameters of soy beverage powder. Further, an optimized drying condition has been identified.

Details

Nutrition & Food Science, vol. 47 no. 4
Type: Research Article
ISSN: 0034-6659

Keywords

Article
Publication date: 20 December 2023

İdris Tuğrul Gülenç, Mingwen Bai, Ria L. Mitchell, Iain Todd and Beverley J. Inkson

Current methods for the preparation of composite powder feedstock for selective laser melting (SLM) rely on costly nanoparticles or yield inconsistent powder morphology. This…

Abstract

Purpose

Current methods for the preparation of composite powder feedstock for selective laser melting (SLM) rely on costly nanoparticles or yield inconsistent powder morphology. This study aims to develop a cost-effective Ti6Al4V-carbon feedstock, which preserves the parent Ti6Al4V particle’s flowability, and produces in situ TiC-reinforced Ti6Al4V composites with superior traits.

Design/methodology/approach

Ti6Al4V particles were directly mixed with graphite flakes in a planetary ball mill. This composite powder feedstock was used to manufacture in situ TiC-Ti6Al4V composites using various energy densities. Relative porosity, microstructure and hardness of the composites were evaluated for different SLM processing parameters.

Findings

Homogeneously carbon-coated Ti6Al4V particles were produced by direct mixing. After SLM processing, in situ grown 100–500 nm size TiC nanoparticles were distributed within the α-martensite Ti6Al4V matrix. The formation of TiC particles refines the Ti6Al4V β grain size. Relative density varied between 96.4% and 99.5% depending on the processing parameters. Hatch distance, exposure time and point distance were all effective on relative porosity change, whereas only exposure time and point distance were effective on hardness change.

Originality/value

This work introduces a novel, cost-effective powder feedstock preparation method for SLM manufacture of Ti6Al4V-TiC composites. The in situ SLM composites achieved in this study have high relative density values, well-dispersed TiC nanoparticles and increased hardness. In addition, the feedstock preparation method can be readily adapted for various matrix and reinforcement materials in future studies.

Details

Rapid Prototyping Journal, vol. 30 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

1 – 10 of 242