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Article
Publication date: 20 June 2016

Wei Zhu, Chunze Yan, Yunsong Shi, Shifeng Wen, Changjun Han, Chao Cai, Jie Liu and Yusheng Shi

Semi-crystalline polymers such as polyamide-12 can be used for selective laser sintering (SLS) to make near-fully dense plastic parts. At present, however, the types of…

Abstract

Purpose

Semi-crystalline polymers such as polyamide-12 can be used for selective laser sintering (SLS) to make near-fully dense plastic parts. At present, however, the types of semi-crystalline polymers suitable for SLS are critically limited. Therefore, the purpose of this paper is to investigate the processibility of a new kind of semi-crystalline polypropylene (PP) with low isotacticity for SLS process.

Design/methodology/approach

The SLS processibility of the PP powder, including particle size and shape, sintering window, degree of crystallinity and degradation temperature, was evaluated. Effects of the applied laser energy density on the surface micromorphology, density, tensile strength and thermal properties of SLS-built PP specimens were studied.

Findings

The results show that the PP powder has a nearly spherical shape, smooth surfaces, an appropriate average particle size of 63.6 μm, a broad sintering window of 21 oC and low crystalline degree of 30.4 per cent comparable to that of polyamide-12, a high degradation temperature of 381.8°C and low part bed temperature of 105°C, indicating a very good SLS processibility. The density and the tensile strength first increase with increasing laser energy density until they reach the maximum values of 0.831 g/cm3 and 19.9 MPa, respectively, at the laser energy density of 0.0458 J/mm2, and then decrease when the applied laser energy density continue to increase owing to the degradation of PP powders. The complex PP components have been manufactured by SLS using the optimum parameters, which are strong enough to be directly used as functional parts.

Originality/value

This paper provides a new knowledge for this field that low-isotacticity PPs exhibit good SLS processibility, therefore increasing material types and broadening the application of SLS technology.

Details

Rapid Prototyping Journal, vol. 22 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 5 November 2020

Nan Zhang, Lichao Zhang, Senlin Wang, Shifeng Wen and Yusheng Shi

In the implementation of large-size additive manufacturing (AM), the large printing area can be established by using the tiled and fixed multiple printing heads or the…

Abstract

Purpose

In the implementation of large-size additive manufacturing (AM), the large printing area can be established by using the tiled and fixed multiple printing heads or the single dynamic printing head moving in the xy plane, which requires a layer decomposition after the mesh slicing to generate segmented infill areas. The data processing flow of these schemes is redundant and inefficient to some extent, especially for the processing of complex stereolithograph (STL) models. It is of great importance in improving the overall efficiency of large-size AM technics software by simplifying the redundant steps. This paper aims to address these issues.

Design/methodology/approach

In this paper, a method of directly generating segmented layered infill areas is proposed for AM. Initially, a vertices–mesh hybrid representation of STL models is constructed based on a divide-and-conquer strategy. Then, a trimming–mapping procedure is performed on sliced contours acquired from partial surfaces. Finally, to link trimmed open contours and inside-signal square corners as segmented infill areas, a region-based open contour closing algorithm is carried out in virtue of the developed data structures.

Findings

In virtue of the proposed approach, the segmented layered infill areas can be directly generated from STL models. Experimental results indicate that the approach brings us the good property of efficiency, especially for complex STL models.

Practical implications

The proposed approach can generate segmented layered infill areas efficiently in some cases.

Originality/value

The region-based layered infill area generation approach discussed here will be a supplement to current data process technologies in large-size AM, which is very suitable for parallel processing and enables us to improve the efficiency of large-size AM technics software.

Details

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

Keywords

Article
Publication date: 5 June 2020

Kesheng Lin, Jie Liu, Jia-Min Wu, Yunlong Sun, Feng Li, Yan Zhou and Yusheng Shi

The main cause of aseptic inflammation after an in vivo implantation is that Poly(L-lactide) (PLLA) and Poly(D-lactide) have a slower degradation and absorption rate…

Abstract

Purpose

The main cause of aseptic inflammation after an in vivo implantation is that Poly(L-lactide) (PLLA) and Poly(D-lactide) have a slower degradation and absorption rate, while Poly(D, L-lactide) (PDLLA) has a much faster degradation rate than PLLA because of its amorphous structure. Also, the hydrolyzate of Hydroxyapatite (HA) is alkaline, which can neutralize local tissue peracid caused by hydrolysis of Polylactic acid.

Design/methodology/approach

In this study, the selective laser sintering (SLS) technique was chosen to prepare bone scaffolds using nano-HA/PDLLA composite microspheres, which were prepared by the solid-in-oil-in-water (S/O/W) method. First, the SLS parameters range of bulk was determined by the result of a single-layer experiment and the optimized parameters were then obtained by the orthogonal experiment. The tensile property, hydrophobicity, biocompatibility, biological toxicity and in vitro degradation of the samples with optimized SLS parameters were characterized.

Findings

As a result, the samples showed a lower tensile strength because of the many holes in their interior, which was conducive to better cell adhesion and nutrient transport. In addition, the samples retained their inherent properties after SLS and the hydrophobicity was improved after adding nano-HA because of the OH group. Furthermore, the samples showed good biocompatibility with the large number of cells adhering to the material through pseudopods and there was no significant difference between the pure PDLLA and 10% HA/PDLLA in terms of biological toxicity. Finally, the degradation rate of the composites could be tailored by the amount of nano-HA.

Originality/value

This study combined the S/O/W and SLS technique and provides a theoretical future basis for the preparation of drug-loaded microsphere scaffolds through SLS using HA/PDLLA composites.

Details

Rapid Prototyping Journal, vol. 26 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 7 January 2019

Hai Jiang, YiYing Lu, Liwen Ding, Wenzhong Lu, Guifen Fan and Yusheng Shi

Aluminum nitride (AlN) ceramics are suitable substrate and package materials for high-power integrated circuits.

Abstract

Purpose

Aluminum nitride (AlN) ceramics are suitable substrate and package materials for high-power integrated circuits.

Design/methodology/approach

Dense AlN ceramics with Y2O3 and LaF3 as sintering additives are prepared. The effects of these additives on the density, phase composition, microstructure and thermal conductivity of AlN ceramics are investigated.

Findings

Results show that 2 Wt.% Y2O3-doped additive is insufficient for the samples to achieve the full densification sintered at 1,700°C. When LaF3 is added with Y2O3, the samples are perfectly densified at the same sintering condition. The relative density and thermal conductivity of the samples are 97.8-99.07 per cent and 169.104-200.010 W·m-1·K-1, respectively. The density of the samples and their microstructure, especially the content and distribution of secondary phases, is necessary to control the thermal conductivity of AlN ceramics.

Originality/value

Y2O3 and LaF3 additives can effectively promote densification and enhance the thermal conductivity of AlN ceramics in a low sintering temperature, and the AlN ceramics added with Y2O3-LaF3 might have potential applications in package materials for high-power integrated circuits.

Details

Microelectronics International, vol. 36 no. 1
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 16 January 2017

Changjun Han, Chunze Yan, Shifeng Wen, Tian Xu, Shuai Li, Jie Liu, Qingsong Wei and Yusheng Shi

Selective laser melting (SLM) is an additive manufacturing process suitable for fabricating metal porous scaffolds. The unit cell topology is a significant factor that…

Abstract

Purpose

Selective laser melting (SLM) is an additive manufacturing process suitable for fabricating metal porous scaffolds. The unit cell topology is a significant factor that determines the mechanical property of porous scaffolds. Therefore, the purpose of this paper is to evaluate the effects of unit cell topology on the compression properties of porous Cobalt–chromium (Co-Cr) scaffolds fabricated by SLM using finite element (FE) and experimental measurement methods.

Design/methodology/approach

The Co-Cr alloy porous scaffolds constructed in four different topologies, i.e. cubic close packed (CCP), face-centered cubic (FCC), body-centered cubic (BCC) and spherical hollow cubic (SHC), were designed and fabricated via SLM process. FE simulations and compression tests were performed to evaluate the effects of unit cell topology on the compression properties of SLM-processed porous scaffolds.

Findings

The Mises stress predicted by FE simulations showed that different unit cell topologies resulted in distinct stress distributions on the bearing struts of scaffolds, whereas the unit cell size directly determined the stress value. Comparisons on the stress results for four topologies showed that the FCC unit cell has the minimum stress concentration due to its inclined bearing struts and horizontal arms. Simulations and experiments both indicated that the compression modulus and strengths of FCC, BCC, SHC, CCP scaffolds with the same cell size presented in a descending order. These distinct compression behaviors were correlated with the corresponding mechanics response on bearing struts. Two failure mechanisms, cracking and collapse, were found through the results of compression tests, and the influence of topological designs on the failure was analyzed and discussed. Finally, the cell initial response of the SLM-processed Co-Cr scaffold was tested through the in vitro cell culture experiment.

Originality/value

A focus and concern on the compression properties of SLM-processed porous scaffolds was presented from a new perspective of unit cell topology. It provides some new knowledge to the structure optimization of porous scaffolds for load-bearing bone implants.

Details

Rapid Prototyping Journal, vol. 23 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 4 October 2011

Qian Bo, Zhang Lichao, Shi Yusheng and Liu Guocheng

In stereolithgraphy rapid prototyping, the support can constrain the model deformation and avoid a lot of problems such as collapse, shift, and imbalance of the model. The…

Abstract

Purpose

In stereolithgraphy rapid prototyping, the support can constrain the model deformation and avoid a lot of problems such as collapse, shift, and imbalance of the model. The support automatic generation algorithm has become the key research of rapid prototyping technics software; however, presently the efficiency of support automatic generation algorithm is low, and its algorithm is complex. Thus, it is of great importance in improving the overall efficiency of rapid prototyping technics software through enhancing the support generation efficiency. This paper aims to address these issues.

Design/methodology/approach

Based on this, this paper proposes a discrete‐marking support algorithm for treatment of processing on manufactured part model of all triangle‐based discrete‐marking on the support plane, which realizes the three‐dimensional computation of intersection for each line associated with the triangle automatically, and avoid invalid computation between all the support lines and other triangles.

Findings

The algorithm efficiency has reached O(n). Meanwhile, the technics support generation speed has been improved. Furthermore, the new mesh discrete‐marking and automatic support generation algorithm has been successfully applied to the sterolithography apparatus and selective laser melting of HRPS series.

Practical implications

Practical application indicates that the new support generation algorithm based on discrete‐marking considerably improves the support technics efficiency and stereolithgraphy rapid prototyping efficiency of the technics software.

Originality/value

The research presents a Noval support fast generation algorithm based on discrete‐marking in stereolithgraphy rapid prototyping.

Details

Rapid Prototyping Journal, vol. 17 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 9 March 2010

Jie Liu, Biao Zhang, Chunze Yan and Yusheng Shi

The purpose of this paper is to report a study about the rapid prototyping method of dental glass‐ceramic restoration.

2005

Abstract

Purpose

The purpose of this paper is to report a study about the rapid prototyping method of dental glass‐ceramic restoration.

Design/methodology/approach

Dental glass‐ceramic restoration materials have excellent physical and chemical, mechanical, aesthetic and biocompatibility characteristics. However, casting methods adopted at present have complicated procedures and high costs; the forming qualities are especially difficult to control. These problems greatly restrict their clinical application and promotion. Therefore, a new forming process based on selective laser sintering (SLS) technology is proposed. First, dental glass‐ceramic is processed into fine powder through a special heat treatment process. Then, the dental restoration parts are manufactured using SLS without any moulds. In this paper, the effects of processing parameters including laser power, scan speed, scan spacing and preheating temperature on the relative density and mechanical properties of the sintered parts are studied.

Findings

The experimental results have shown that for the composite powder of epoxy resin binder E‐12 and K2O‐Al2O3‐SiO2 series of dental glass‐ceramics, when preheating temperature, layer thickness, laser power, scan speed and scan spacing are, respectively, 30∼35°C, 0.08 mm, 21 W, 1,800 mm/s and 0.10 mm/s, the relative densities of dental glass‐ceramic parts are relatively high; the mechanical properties and forming effect are excellent. The relative density and bending strength of SLS parts under the optimized processing parameters are 37.40 per cent and 2.08 MPa, respectively.

Research limitations/implications

This study only concerns the preparation and SLS of the dental glass‐ceramic powders. Further investigations are planned to be conducted on post processing, such as binder decomposition, isostatic press and high temperature sintering.

Originality/value

This study will provide a theoretical and technical basis for dental glass‐ceramic restorations of SLS.

Details

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

Keywords

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…

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

Keywords

Article
Publication date: 27 April 2022

Qixin Zhu, Yusheng Jin and Yonghong Zhu

The purpose of this paper is to propose a new acceleration/deceleration (acc/dec) algorithm for motion profiles. The motion efficiency, flexibility of the motion profiles…

Abstract

Purpose

The purpose of this paper is to propose a new acceleration/deceleration (acc/dec) algorithm for motion profiles. The motion efficiency, flexibility of the motion profiles and the residual vibration of the movement are discussed in this paper.

Design/methodology/approach

A dynamics model is developed to assess the residual vibration of these two kinds of motion profile. And a Simulink model is created to assess the motion efficiency and flexibility of the motion profiles with the proposed acc/dec algorithm.

Findings

Considering the flexibility of trigonometric motion profiles and the higher motion efficiency of S-curve motion profiles, the authors add the polynomial parts into the jerk profile of the cosine function acc/dec algorithm to hold the jerk when it reaches the maximum so that the motion efficiency can increase and decrease residual vibration at the same time. And the cyclical parameter k shows the decisive factor for the flexibility of trigonometric motion profiles.

Originality/value

Comparing with the traditional motion profiles, the proposed motion profiles have higher motion efficiency and excite less residual vibration. The acc/dec algorithm proposed in this paper is useful for the present motion control and servo system.

Details

Assembly Automation, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0144-5154

Keywords

Article
Publication date: 22 February 2022

Ayman Wael AL-Khatib

The purpose of this study is to identify the impact of intellectual capital on the innovation performance of the Jordanian banking sector and identify the moderating role…

Abstract

Purpose

The purpose of this study is to identify the impact of intellectual capital on the innovation performance of the Jordanian banking sector and identify the moderating role of big data analytics.

Design/methodology/approach

For this study's purposes, 333 questionnaires were analysed. Convergent validity, discriminant validity and reliability tests were performed through structural equation modelling (SEM) in the Smart-PLS program. A bootstrapping technique was used to analyse the data.

Findings

Empirical results showed that each of the components of intellectual capital and big data analytics explains 63.5% of the variance in innovation performance and that all components of intellectual capital have a statistically significant impact on innovation performance. The results also revealed that the relationship between structural capital and innovation performance is moderated through big data analytics.

Research limitations/implications

This cross-sectional study provides a snapshot at a given moment in time, a methodological limitation that affects the generalisation of its results, and the results are limited to one country.

Practical implications

This study promotes the idea of focusing on components of intellectual capital to enhance innovation performance in the Jordanian banking sector and knowing the effect of big data analytics in this relationship.

Social implications

This study makes recommendations for financial policymakers to improve the effectiveness of intellectual capital practices and innovation performance in the context of big data analytics.

Originality/value

This study has important implications for leaders in the Jordanian banking sector, in general, as the study highlights the importance of intellectual capital to enhance the innovation performance, especially in light of the big data analytics in this sector, and thus increase the innovative capabilities of this banks, which leads to an increase in the level of innovation.

Details

EuroMed Journal of Business, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1450-2194

Keywords

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