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Article
Publication date: 31 May 2019

Mohammadreza Riahi, Fatemeh Karimi and Atefeh Ghaffari

The purpose of this paper is to present three-dimensional (3D) printing of structures with a new method called selective laser baking (SLB) of Poly Dimethyl Siloxane (PDMS).

Abstract

Purpose

The purpose of this paper is to present three-dimensional (3D) printing of structures with a new method called selective laser baking (SLB) of Poly Dimethyl Siloxane (PDMS).

Design/methodology/approach

A 3D model is designed on the computer. PDMS Base is mixed with its hardener and poured into a container. Before it is hardened which normally occures after several hours, a CO2 laser selectively exposes different areas on the surface of the PDMS mixture according to the pattern of a slice of a 3D model designed on the computer. Because of the thermal effect of the CO2 laser, once exposed, PDMS heats up and hardens, producing a cured layer of PDMS which is attached to a base. The base with the cured layer is lowered in the container for a short distance and a layer of new uncured PDMS is spread over the previous layer. The laser exposes new areas again and hardens them. This process is repeated until the whole structure is fabricated.

Findings

The parameters involved in the baking process are investigated and the relation between temperature, mixing portion and laser irradiance on the curing time and layer thickness are investigated.

Originality/value

This fabrication technique is a unique fabrication method that helps to 3D print with two base polymers which their polymerization can be boosted by heat. This 3D printing method has not been presented earlier.

Details

Rapid Prototyping Journal, vol. 25 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 31 July 2009

Elena Bassoli and Eleonora Atzeni

The purpose of this paper is to optimize the mechanical performances of parts produced by the ZCast Direct Metal Casting process varying the thermal treatment parameters. Adopting…

1415

Abstract

Purpose

The purpose of this paper is to optimize the mechanical performances of parts produced by the ZCast Direct Metal Casting process varying the thermal treatment parameters. Adopting the optimized settings, a specific dimensional evaluation is planned to calculate the international tolerance (IT) grade ensured by the process.

Design/methodology/approach

Cylindrical ZCast samples are manufactured and heat treated varying time and temperature. The baked parts underwent compression tests and the rupture surfaces are observed using the scanning electron microscopy. A regression analysis is performed on the results to optimize the baking process. For the dimensional assessment, a specific benchmark is designed, built and treated. It is measured before and after baking using a coordinate measuring machine and the results are processed to obtain the IT grade.

Findings

The results proved that in the heat treatment of ZCast parts time has a negligible effect on the compressive strength, whereas temperature can be optimized for best mechanical response. The IT grade is calculated for green and baked parts; separately in all three directions in space. Tolerance is proved to be fundamentally the same in every direction and independent on the heat treatment. The considered rapid casting process can be classified in IT15 grade.

Originality/value

The paper suggests an original approach to improve knowledge of the ZCast process. The study of the building phenomena is combined with macroscopic measurements to develop a solid understanding of the expected performances, which is fundamental in order to support the industrial application of the technology.

Details

Rapid Prototyping Journal, vol. 15 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 2 November 2012

V.F.C. Lins, L. Madeira, J.M.C. Vilela, M.S. Andrade, V.T.L. Buono, J.P. Guimarães and E.A. Alvarenga

The purpose of this paper is to study the effect of chemical composition on the selective oxidation on the surface of bake hardenable steel, and on the surface of modified bake

Abstract

Purpose

The purpose of this paper is to study the effect of chemical composition on the selective oxidation on the surface of bake hardenable steel, and on the surface of modified bake hardenable steel with titanium addition, annealed at different dew points.

Design/methodology/approach

The subject scope of the paper is the selective oxidation. The methodology used is the annealing of steels at different dew points, and the surface characterization by using atomic force microscopy, X‐ray photo electronic spectroscopy, and glow discharge optical emission spectroscopy.

Findings

The modified bake hardenable steel showed a higher oxidized area than the bake hardenable steel. The optimum condition for annealing of the bake hardenable steel was at 800°C with −30°C dp and −60°C dp as selective oxidation is less voluminous.

Research limitations/implications

One suggestion for future works is the use of transmission electron microscopy for the evaluation of selective oxidation on the steel surfaces.

Practical implications

One practical implication is the determination of the optimum condition for annealing of the bake hardenable steel in the steel plant, decreasing the selective oxidation and increasing the quality of galvanized steels. Another implication is the discard by the steel industry of the development of the modified bake hardenable steel.

Originality/value

The originality of the present work is to use advanced surface analysis techniques to quantify the selective oxidation on the surface of commercial steels. The selective oxidation on the surface of steels must be minimized in order to increase the wet ability of zinc layer on the steel surface.

Details

Anti-Corrosion Methods and Materials, vol. 59 no. 6
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 February 2013

Hao Rong, Baoming Wang, Wei‐Qing Lin, Lichao Sun, Jin‐Cheng Zheng and Miao Lu

The purpose of this paper is to report a simple, room temperature approach to assemble dense, vertically aligned single‐walled carbon nanotubes (SWNTs) between a chip and its…

Abstract

Purpose

The purpose of this paper is to report a simple, room temperature approach to assemble dense, vertically aligned single‐walled carbon nanotubes (SWNTs) between a chip and its substrate acting as a kind of thermal interface material by virtue of better mechanical and thermal properties.

Design/methodology/approach

Two silicon chips, with shallow trenches about 2 μm deep on the surface, were pressed together face to face with the trench direction perpendicular to each other. SWNT aqueous solution was driven into the gap between the two chips by capillary force. Later, the sample was baked to remove the moisture completely.

Findings

SWNTs beams were found to be assembled in the gap and have their two ends bonding with the interface of the two chips, respectively. The shear strength of the two chips was measured, and the thermal conductivity of the stacked chip‐SWNTs‐chip was tested using a laser flash method. In result, shear strength up to about 100 kPa, and an average thermal conductivity of 19.3 W·m−1·K−1 were demonstrated.

Originality/value

The paper proposes an approach to grown dense SWNT array bridging a chip and its substrate, and these SWNTs have potential capability to provide mechanical strength and higher thermal conductance instead of commercial thermal interface materials.

Details

Soldering & Surface Mount Technology, vol. 25 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 August 2005

M.A. Alghoul, M.Y. Sulaiman, B.Z. Azmi and M.Abd. Wahab

To cover the main contributions and developments in solar thermal collectors through focusing on materials, heat transfer characteristics and manufacturing challenges.

4598

Abstract

Purpose

To cover the main contributions and developments in solar thermal collectors through focusing on materials, heat transfer characteristics and manufacturing challenges.

Design/methodology/approach

A range of published papers and internet research including research work on various solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube) were used. Evaluation of solar collectors performance is critiqued to aid solar technologies make the transition into a specific dominant solar collector. The sources are sorted into sections: finding an academic job, general advice, teaching, research and publishing, tenure and organizations.

Findings

Provides information about types of solar thermal collectors, indicating what can be added by using evacuated tube collectors instead of flat plate collectors and what can be added by using heat pipe collectors instead of evacuated tubes.

Research limitations/implications

Focusing only on three types of solar thermal collectors (flat plate, evacuated tubes, and heat pipe tube).

Practical implications

Useful source of information for consultancy and impartial advice for graduate students planning to do research in solar thermal technologies.

Originality/value

This paper fulfils identified information about materials and heat transfer properties of materials and manufacturing challenges of these three solar thermal collectors.

Details

Anti-Corrosion Methods and Materials, vol. 52 no. 4
Type: Research Article
ISSN: 0003-5599

Keywords

Article
Publication date: 1 January 1989

M.W. Gray

The possible causes of inner layer junction cracks on multilayer PCBs are discussed and the problems that cracks can cause under rework conditions. The procedure to identify the…

Abstract

The possible causes of inner layer junction cracks on multilayer PCBs are discussed and the problems that cracks can cause under rework conditions. The procedure to identify the cracks and their exact location within and around the electroless copper junction is shown, along with guidelines on the possible ways to eliminate the cracking problem and on testing procedures to ensure a reliable product.

Details

Circuit World, vol. 15 no. 2
Type: Research Article
ISSN: 0305-6120

Article
Publication date: 1 January 1993

Dhan Bhandari

Reviews the factors affecting bread‐making quality in UK wheat:condition; milling quality (endosperm quality, high flour yield and goodflour colour); water absorption; baking

Abstract

Reviews the factors affecting bread‐making quality in UK wheat: condition; milling quality (endosperm quality, high flour yield and good flour colour); water absorption; baking quality; protein quantity and quality; α‐amylase activity.

Details

Nutrition & Food Science, vol. 93 no. 1
Type: Research Article
ISSN: 0034-6659

Keywords

Article
Publication date: 1 March 2002

Michael Huff

Describes the key attributes of MEMS technology and existing and future business opportunities. Discusses the various stages in the fabrication of MEMS devices and offers guidance…

3897

Abstract

Describes the key attributes of MEMS technology and existing and future business opportunities. Discusses the various stages in the fabrication of MEMS devices and offers guidance regarding the selection of processing methods for deposition, lithography and etching. Also describes the MEMS‐Exchange program and associated network of fabrication centres.

Details

Sensor Review, vol. 22 no. 1
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 1 June 2000

B. Engel and D.L. Bourell

Selective laser sintering (SLS) is a solid freeform fabrication process whereby a part is built layerwise by scanning a powder bed. The processability of metal powder varies…

2134

Abstract

Selective laser sintering (SLS) is a solid freeform fabrication process whereby a part is built layerwise by scanning a powder bed. The processability of metal powder varies depending on the state of the powder prior to SLS. A powder thermal pre‐treatment was developed which involved degassing the powder at an elevated temperature in a vacuum. Without powder thermal pre‐treatment, the powder may flow poorly and may “ball” or form molten clumps during the laser exposure rather than wetting into the present and previous layer. These effects result in SLS parts with poor surface finish, mechanical properties and density. The purpose of this study was to identify for titanium alloy powder the mechanisms responsible for the improvements obtained after powder thermal pre‐treatment and to optimize the thermal excursion.

Details

Rapid Prototyping Journal, vol. 6 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 15 February 2021

Lan Li, Tan Pan, Xinchang Zhang, Yitao Chen, Wenyuan Cui, Lei Yan and Frank Liou

During the powder bed fusion process, thermal distortion is one big problem owing to the thermal stress caused by the high cooling rate and temperature gradient. For the purpose…

Abstract

Purpose

During the powder bed fusion process, thermal distortion is one big problem owing to the thermal stress caused by the high cooling rate and temperature gradient. For the purpose of avoiding distortion caused by internal residual stresses, support structures are used in most selective laser melting (SLM) process especially for cantilever beams because they can assist the heat dissipation. Support structures can also help to hold the work piece in its place and reduce volume of the printing materials. The mitigation of high thermal gradients during the manufacturing process helps to reduce thermal distortion and thus alleviate cracking, curling, delamination and shrinkage. Therefore, this paper aims to study the displacement and residual stress evolution of SLMed parts.

Design/methodology/approach

The objective of this study was to examine and compare the distortion and residual stress properties of two cantilever structures, using both numerical and experimental methods. The part-scale finite element analysis modeling technique was applied to numerically analyze the overhang distortions, using the layer-by-layer model for predicting a part scale model. The validation experiments of these two samples were built in a SLM platform. Then average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model.

Findings

The validation experiments results of average displacement of the four tip corners and residual stress on top surface of cantilever beams were tested to validate the model. It was found that they matched well with each other. From displacement and residual stress standpoint, by introducing two different support structure, two samples with the same cantilever beam can be successfully printed. In terms of reducing wasted support materials, print time and high surface quality, sample with less support will need less post-processing and waste energy.

Originality/value

Numerical modeling in this work can be a very useful tool to parametrically study the feasibility of support structures of SLM parts in terms of residual stresses and deformations. It has the capability for fast prediction in the SLMed parts.

Details

Rapid Prototyping Journal, vol. 27 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

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