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Article
Publication date: 27 March 2009

Tieshu Huang, Michael S. Mason, Xiyue Zhao, Gregory E. Hilmas and Ming C. Leu

The purpose of this paper is to develop an inexpensive and environmentally friendly solid freeform fabrication technique, called the freeze‐form extrusion fabrication

Abstract

Purpose

The purpose of this paper is to develop an inexpensive and environmentally friendly solid freeform fabrication technique, called the freeze‐form extrusion fabrication (FEF), and use this technique in advanced ceramic fabrication.

Design/methodology/approach

FEF uses a highly loaded aqueous ceramic paste (≥50 vol.% solids loading) with a small quantity (2 vol.%) of organic binder to fabricate a ceramic green part layer by layer with a computer‐controlled 3D gantry machine at a temperature below the freezing point of the paste. Further, a freeze‐drying technique is used for preventing deformation and the formation of cracks during the green part drying process. Following the freeze‐drying, the ceramic green part undergoes binder removal and is sintered to near full density.

Findings

Extrudable, alumina pastes of high solids loading and process parameters for FEF processing of these pastes have been developed. Paste rheological properties and stability, extrusion rate, 3D gantry motion speed and other process parameters strongly affect the quality of the final ceramic parts. The minimum deposition angle, which reflects the maximum amount of extrusion offset to produce components with overhanging features without using support materials, is strongly related to the fabrication (environment) temperature. The lower the fabrication temperature, the lower the minimum deposition angle that could be achieved. Four point bending flexure strengths of the FEF processed Al2O3 test samples were 219 and 198 MPa for longitudinally deposited and transversely deposited samples, respectively. Major defects, which limited the strength of the materials, were due to under‐filling during the extrusion.

Originality/value

Successful development of the FEF technique will introduce a new approach to manufacturing ceramic materials into useful, complex shapes and components. The significant advantages of this technique include the use of environmentally friendly processing medium (water), inexpensive method of medium removal (freeze‐drying), and a much smaller quantity of organic binder to remove by pyrolysis techniques. The products can be sintered to near full density.

Details

Rapid Prototyping Journal, vol. 15 no. 2
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 27 November 2018

Cunfu Yan, Shujuan Li, Leipeng Yang and Longfei He

The purpose of this paper is to investigate the effects of parameters on the liquid phase migration (LPM) during the freeze-form extrusion fabrication (FEF) process.

Abstract

Purpose

The purpose of this paper is to investigate the effects of parameters on the liquid phase migration (LPM) during the freeze-form extrusion fabrication (FEF) process.

Design/methodology/approach

To carry out this study, three factors were systematically investigated using orthogonal design of experiments. These three parameters are the extrusion velocity, the extrusion interval time and the extrusion head length. An orthogonal array with nine test units was selected for the experiments. Range analysis and analysis of variance were used to analyze the data obtained by the orthogonal experiments to identify the order of significant factors on LPM.

Findings

It was found that the LPM decreased with the increase of extrusion velocity and increased with the lengthening of extrusion interval time and the length of the extrusion nozzle. The order of significant factors for the LPM were found to be extrusion velocity > extrusion nozzle length > extrusion interval time.

Practical implications

Using an orthogonal design of experiments and a statistical analysis method, the liquid content of extrudate can be predicted and appropriate process parameter values can be selected. This leads to the minimization of LPM during the FEF process. Also, this analysis method could be used to study the LPM in other paste extrusion processes.

Originality/value

This paper suggests that the factors have significant impact on LPM during FEF process. The following analysis in this paper is useful for FEF users when prediction of LPM is needed. This methodology could be easily applied to different materials and initial conditions for optimization of other FEF-type processes. The research can also help to get better understanding of LPM during the FEF process.

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Article
Publication date: 16 March 2015

Fangyong Niu, Dongjiang Wu, Guangyi Ma, Siyu Zhou and Bi Zhang

The purpose of this paper is to investigate how a second-phase doping may affect Al2O3 ceramic parts deposited by additive manufacturing (AM) with a laser-engineered net…

Abstract

Purpose

The purpose of this paper is to investigate how a second-phase doping may affect Al2O3 ceramic parts deposited by additive manufacturing (AM) with a laser-engineered net shaping system. Direct fabrication of engineering ceramic components by AM is a relatively new method for producing complex mechanical structures.

Design/methodology/approach

In this study, ZrO2 and Y2O3 powders are, respectively, doped into Al2O3 powders at the eutectic ratio as second phases to improve the quality of a deposited part. The deposited Al2O3, Al2O3/ZrO2 and Al2O3/YAG (yttrium aluminum garnet) parts are examined for their micro-structures and micro-hardness, as well as defects.

Findings

The experimental results show that doping of ZrO2 or Y2O3 as a second phase performs a significant role in suppressing cracks and in refining grains of the laser-deposited parts. The micro-hardness investigation reveals that the second-phase doping does not result in much hardness reduction in Al2O3 and the two eutectic ceramics are both harder than 1,500 Hv.

Originality/value

The study concludes that the second-phase doping of ZrO2 and Y2O3 is good for improving laser-deposited Al2O3 ceramic parts.

Details

Rapid Prototyping Journal, vol. 21 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 16 March 2015

Krishna C R Kolan, Albin Thomas, Ming C Leu and Greg Hilmas

The purpose of this paper is to utilize the selective laser sintering (SLS) process to fabricate scaffolds with complex pore shapes and investigate the effects of pore…

Abstract

Purpose

The purpose of this paper is to utilize the selective laser sintering (SLS) process to fabricate scaffolds with complex pore shapes and investigate the effects of pore geometry in vitro. The pore geometry of scaffolds intended for use in bone repair is one of the most important parameters used to determine the rate of bone regeneration.

Design/methodology/approach

Scaffolds with five different architectures, having approximately 50 per cent porosity, were fabricated with silicate (13–93) and borate (13–93B3)-based bioactive glasses using the SLS process. An established late-osteoblasts/early-osteocytes cell line was used to perform cell proliferation tests on the scaffolds. The cell-seeded scaffolds were incubated for two, four and six days followed by MTT assay to quantify the metabolically active cells.

Findings

The results indicated that the cells proliferate significantly more on the scaffolds which mimic the trabecular bone architecture compared to traditional lattice structures. The surface roughness of the SLS-fabricated scaffolds drives the initial cell proliferation which is followed by curvature-driven cell proliferation.

Originality/value

There have been very few studies on the effects of pore geometry on tissue growth and the existing reports do not provide clear indications. Instead of using bio-polymer or titanium-based scaffolds, we use bioactive glass scaffolds. The results obtained from this study add to the understanding of the effect of pore geometry on cell proliferation, which is based on the experimental data and analysis of the scaffolds’ surface curvature.

Details

Rapid Prototyping Journal, vol. 21 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 20 March 2017

Özgür Keleş, Caleb Wayne Blevins and Keith J. Bowman

Increasing use of 3D printing techniques to manufacture consumer products and open-source designs raises the question of “What is the mechanical reliability of 3D printed…

Abstract

Purpose

Increasing use of 3D printing techniques to manufacture consumer products and open-source designs raises the question of “What is the mechanical reliability of 3D printed parts?” Therefore, the purpose of this paper is to investigate the impacts of build orientation on the mechanical reliability of acrylonitrile butadiene styrene (ABS) produced using 3D printing.

Design/methodology/approach

Tensile tests on ABS specimens were performed with and without a hole in the center, which were produced by fused deposition modeling (FDM). Seven sets of approximately 30 specimens were printed in XY, XZ and C+45 orientations to obtain reliable fracture statistics. Weibull analysis was performed to quantify the variation in the tensile strength.

Findings

The Weibull analysis showed that the reliability of FDM produced ABS can be as low as advanced ceramics. Weibull moduli of specimens without a hole were between 26 and 69, and specimens with a hole had Weibull moduli between 30 and 41. P-type deviations from the Weibull statistics were observed. The XZ orientation resulted in the highest average fracture strength for specimens with and without a hole, and C+45 orientation resulted in the lowest strength.

Practical implications

As the Weibull distribution relates the applied stress to probability of failure, the Weibull analysis provides a practical design criterion to achieve specific reliability levels for additively manufactured parts.

Originality/value

This study, for the first time, provides Weibull statistics for FDM-produced ABS parts, which can be used to predict mechanical reliability.

Details

Rapid Prototyping Journal, vol. 23 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 18 May 2021

Anabel Renteria, Luisa F. Garcia, Jorge A. Diaz, Luis C. Delfin, Jaime E. Regis, Elizabeth I. Reza, David Espalin, Tzu-Liang Bill Tseng and Yirong Lin

The purpose of this study is to evaluate different 3D structures for humidity sensing that will enable the fabrication of complex geometries with high moisture sensitivity.

Abstract

Purpose

The purpose of this study is to evaluate different 3D structures for humidity sensing that will enable the fabrication of complex geometries with high moisture sensitivity.

Design/methodology/approach

Humidity sensors based on alumina ceramics were fabricated using direct ink write (DIW) technique. Different engineered surface area, polymer binder ratio and post-processing treatment were considered to increase moisture sensitivity.

Findings

It was found that the binder ratio plays an important role in controlling the rheology of the paste during printing and determining the pore size after post-processing treatment. The sensibility of the fabricated humidity sensor was investigated by measuring its capacitance response toward relative humidity (RH) varying from 40% to 90% RH at 25°C. It is shown that using 3D lattice design, printed alumina humidity sensor could improve sensitivity up to 31.6 pF/RH%, over an order of magnitude higher than solid alumina.

Originality/value

Most of the alumina humidity sensors available are films in nature because of manufacturing difficulties, which limited its potential of higher sensitivity, and thus broader applications. In this paper, a novel 3D alumina humidity sensor was fabricated using DIW 3D printing technology.

Details

Rapid Prototyping Journal, vol. 27 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

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Article
Publication date: 21 August 2020

Andrej Simeunović and David John Hoelzle

The purpose of this study is to develop nonlinear and linearized models of DW printing dynamics that capture the complexity of DW while remaining integrable into control…

Abstract

Purpose

The purpose of this study is to develop nonlinear and linearized models of DW printing dynamics that capture the complexity of DW while remaining integrable into control schemes. Control of material metering in extrusion-based additive manufacturing modalities, such as positive displacement direct-write (DW), is critical for manufacturing accuracy. However, in DW, transient flows are poorly controlled due to capacitive pressure dynamics – pressure is stored and slowly released over time from the build material and other compliant system elements, adversely impacting flow rate start-ups and stops. Thus far, modeling of these dynamics has ranged from simplistic, potentially omitting key contributors to the observed phenomena, to highly complex, making usage in control schemes difficult.

Design/methodology/approach

The authors present nonlinear and linearized models that seek to both capture the capacitive and nonlinear resistive fluid elements of DW systems and to pose them as ordinary differential equations for integration into control schemes. The authors validate the theoretical study with experimental flow rate and material measurements across a range of extrusion nozzle sizes and materials. The authors explore the contribution of the system and build material bulk modulus to these dynamics.

Findings

The authors show that all tested models accurately describe the measured dynamics, facilitating ease of integration into future control systems. Additionally, the authors show that system bulk modulus may be substantially reduced through appropriate system design. However, the remaining build material bulk modulus is sufficient to require feedback control for accurate material delivery.

Originality/value

This study presents new nonlinear and linear models for DW printing dynamics. The authors show that linear models are sufficient to describe the dynamics, with small errors between nonlinear and linear models. The authors demonstrate control is necessary for accurate material delivery in DW.

Details

Rapid Prototyping Journal, vol. 26 no. 10
Type: Research Article
ISSN: 1355-2546

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Article
Publication date: 16 October 2018

Özgür Keleş, Eric H. Anderson and Jimmy Huynh

Mechanical reliability (variations in mechanical properties) of fused deposition modeled (FDMed) short-fiber-reinforced composites are unknown, which limits wider and…

Abstract

Purpose

Mechanical reliability (variations in mechanical properties) of fused deposition modeled (FDMed) short-fiber-reinforced composites are unknown, which limits wider and safer use of these composites. Accordingly, this paper aims to investigate the mechanical reliability of FDMed model material short-carbon-fiber-reinforced acrylonitrile butadiene styrene (SCFR-ABS). A new vibration-assisted FDM (VA-FDM) process was used to reduce porosity.

Design/methodology/approach

Tensile tests were performed on FDMed SCFR-ABS produced with and without vibrations. Weibull analysis was performed to quantify the variation in fracture strength, tensile strength, strain at break and strain at tensile strength.

Findings

Introduction of vibrations to the extrusion head during FDM decreased the inter-bead porosity in SCFR-ABS and thus improved elastic modulus, toughness, fracture strength, tensile strength and strain at break. Weibull modulus of fracture strength increased from 25 to 57 with vibrations.

Practical implications

The reported Weibull analysis offers a practical design guideline to predict failure rates at specific service stresses.

Originality/value

A detailed Weibull analysis of the variations in the mechanical properties of FDMed SCFR-ABS was performed for the first time. A new vibration-assisted FDM process was reported to reduce inter-bead porosity in FDMed composites.

Details

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

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Article
Publication date: 19 June 2019

Christopher-Denny Matte, Michael Pearson, Felix Trottier-Cournoyer, Andrew Dafoe and Tsz Ho Kwok

The purpose of this paper is to introduce a novel technique for printing with multiple materials using the DLP method. Digital-light-processing (DLP) printing uses a…

Abstract

Purpose

The purpose of this paper is to introduce a novel technique for printing with multiple materials using the DLP method. Digital-light-processing (DLP) printing uses a digital projector to selectively cure a full layer of resin using a mask image. One of the challenges with DLP printing is the difficulty of incorporating multiple materials within the same part. As the part is cured within a liquid basin, resin switching introduces issues of cross-contamination and significantly increased print time.

Design/methodology/approach

The material handling challenges are investigated and addressed by taking inspiration from automated storage and retrieval systems and using an active cleaning solution. The material tower is a compact design to facilitate the storage and retrieval of different materials during the printing process. A spray mechanism is used for actively cleaning excess resin from the part between material changes.

Findings

Challenges encountered within the multi-material DLP technology are addressed and the experimental prototype validates the proposed solution. The system has a cleaning effectiveness of over 90 per cent in 15 s with the build area of 72 inches, in contrast to the previous work of 50 per cent cleaning effectiveness in 2 min with only 6 inches build area. The method can also hold more materials than the previous work.

Originality/value

The techniques from automated storage and retrieval system is applied to develop a storage system so that the time complexity of swapping is reduced from linear to constant. The whole system is sustainable and scalable by using a spraying mechanism. The design of the printer is modular and highly customizable, and the material waste for build materials and cleaning solution is minimized.

Details

Rapid Prototyping Journal, vol. 25 no. 5
Type: Research Article
ISSN: 1355-2546

Keywords

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