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Article
Publication date: 15 June 2010

Cheekur Krishnamurthy Srinivasa, Chinnakurli Suryanarayana Ramesh and S.K. Prabhakar

The purpose of this paper is to study the effect of blending time, SiC content and fill ratio on the homogeneity of iron‐silicon carbide powder mixture, blended in…

1121

Abstract

Purpose

The purpose of this paper is to study the effect of blending time, SiC content and fill ratio on the homogeneity of iron‐silicon carbide powder mixture, blended in double‐cone blender; to evaluate density, microstructure and micro hardness of laser sintered iron and iron‐SiC specimens; and study the feasibility of building a complex iron‐SiC metal matrix composite (MMC) part by direct metal laser sintering (DMLS) process.

Design/methodology/approach

The morphology and particle size of iron and silicon carbide powders were evaluated. Nickel coating was carried out on silicon carbide particles. Blending of iron‐SiC powders were carried out in two phases in a double‐cone blending equipment. In the first phase, three tests were conducted with fill ratios (ratio of volume of conical blender to volume of powder mixture) of 1.68, 3.39, and 6.8 percent while iron‐SiC weight ratio was kept constant at 97:3. In the second phase, four tests were conducted with iron‐SiC weight ratios of 99:1, 98:2, 97:3, and 95:5 while keeping a constant fill ratio of 1.68 percent. In both the phases, blending was carried out for duration of 43 minutes. Homogeneity of the powder mixture was evaluated at different intervals of time by adopting sampling process. Sintering was carried out on iron and iron‐SiC powder mixture using DMLS machine at laser speed of 50, 75, 100, and 125 mm/s. Microstructure, density and micro hardness studies were carried out on the sintered specimens. A 3D model of a part with complex geometry was modeled using Unigraphics CAD/CAM software and prototype part was built by DMLS technology using the blended iron‐2 weight percent SiC powder.

Findings

A reduction in blending time was observed with increase in SiC content and decrease in fill ratio. Microstructure and micro hardness tests conducted on laser sintered iron‐silicon carbide specimens, reveal the homogeneity of blended powder. The density of the iron‐SiC composites sintered at a laser speed of 50 and 75 mm/s, decreased with increase in SiC content. Further, an increase in the micro hardness of iron‐SiC composites was observed with increase in SiC content and decrease in laser speed. Complex functional part was built by DMLS technology with out any supports.

Research limitations/implications

The experiments were conducted with standard blending equipment in which the speed is limited to 48 revolutions per minute only.

Originality/value

Meager information is available on blending of powders for producing MMCs by laser sintering process. The work presented in this paper will be a guideline for researchers to carry out further work in blending of powders for producing MMCs by rapid prototyping process.

Details

Rapid Prototyping Journal, vol. 16 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 18 January 2016

Ana R. Lapcevic, Danimir P Jevremovic, Tatjana M Puskar, Robert J. Williams and Dominic Eggbeer

The purpose of this paper is to analyse structure and measure hardness of Co-Cr dental alloy samples made with two different technologies, conventional casting method (CCM…

Abstract

Purpose

The purpose of this paper is to analyse structure and measure hardness of Co-Cr dental alloy samples made with two different technologies, conventional casting method (CCM samples) and additive direct metal laser sintering technology (DMLS samples), and to compare the results.

Design/methodology/approach

CCM samples were made in a conventional casting machine, using remanium 800+ Co-Cr dental alloy (Dentaurum, Ispringen, Germany). DMLS samples were fabricated out of EOS CC SP2 Co-Cr alloy (EOS, GmbH, Munich, Germany) using DMLS technology. Samples for structural analysis were plate-shaped (10 × 10 × 1.5 mm3) and for the hardness test were prismatic-shaped (55 × 10.2 × 11.2 mm3). Structure was analysed via an inverting microscope and colour metallography method.

Findings

CCM samples have a dense, irregular dendritic mesh, which is typical for the metallic phase of the Co-Cr dental alloy. DMLS alloy has a more homogenous and more compact structure, compared to CCM. Metals, the alloy basis consists of, form semilunar stratified layers, which are characteristic for the additive manufacturing (AM) technique. Hardness values of DMLS (mean value was 439.84 HV10) were found to be higher than those of CCM (mean value was 373.76 HV10).

Originality/value

There are several reports about possible use of AM technologies for manufacturing dental devices, and investigation of mechanical properties and biocompatibility behaviour of AM-produced dental alloys. Microstructure of Co-Cr alloy made with DMLS technology has been introduced for the first time in the present paper.

Details

Rapid Prototyping Journal, vol. 22 no. 1
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 1 August 2006

Vijay Kumar Meena and Nagahanumaiah

The purpose of this paper is to optimise the electro‐discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as…

1475

Abstract

Purpose

The purpose of this paper is to optimise the electro‐discharge machining (EDM) parameters and investigate feasibility of using direct metal laser sintering (DMLS) parts as EDM electrodes.

Design/methodology/approach

In this paper the effects of discharge current, pulse‐on‐time, flushing pressure are optimized for minimum tool wear rate (TWR), maximum metal removal rate (MRR) and minimum surface roughness (Ra). Taguchi‐based L9 orthogonal array has been used for performing experiments on EDM machining of EN 24 steel using DMLS electrodes. The grey relational analysis combined with ANOVA techniques have been employed to determine the optimal level as well as their significance.

Findings

Experimental results have shown that the performance characteristics of the EDM process (TWR, MRR and surface roughness) using DMLS electrode can be quantified and controlled effectively by grey relational approach presented in the study. Current is found to be the most affective parameter in EDM machining using DMLS electrode. Excessive DMLS tool (electrode) wear was also reported, which limits the use of DMLS tool for EDM machining and it has been found out that porosity (which was about 20 per cent) was one of the primary cause.

Research limitations/implications

This paper was focused on understanding the effects of important EDM parameters on three performance characteristics (TWR, MRR and surface roughness). While this study identifies that DMLS electrode wear rate is high and porosity could be one of the main cause, presently it does not cover the investigations on reducing the porosity level and its implications.

Practical implications

The DMLS material had shown huge potential to be used as EDM electrode. The current investigation established a structured experimental approach to understand the effects of EDM parameters on multi response characteristics. The results derived from this study helps to focus future research on two aspects including enriching the copper content and reducing the porosity level, thereby the benefits of lead time reduction in EDM electrode making could be realized.

Originality/value

The previous research attempts were not focussed on optimising the EDM machining process using rapid tooling electrodes. With the best of author's knowledge none of the researchers have reported these aspects especially for DMLS electrodes. Application of grey relational analysis for performance evaluation of rapid tooling‐based EDM electrodes (DMLS electrodes) appear to be completely new.

Details

Rapid Prototyping Journal, vol. 12 no. 4
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 12 March 2018

Hamza Hassn Alsalla, Christopher Smith and Liang Hao

The purpose of this paper is to study new process parameters which were selected to achieve the full density of Ti-6Al-4V samples in different building orientations and…

Abstract

Purpose

The purpose of this paper is to study new process parameters which were selected to achieve the full density of Ti-6Al-4V samples in different building orientations and investigate fracture toughness property and its relation to the microstructure, an area which has not previously been reported in full detail and which may offer information to a designer. Direct metal laser sintering (DMLS) is an additive manufacturing technique that directly manufactures three-dimensional parts, layer-by-layer, to scan and melt metal powders for aerospace applications.

Design/methodology/approach

Hardness and tensile tests were carried out to evaluate the effect of consolidation on the mechanical performance of specimens made at three different building directions. Optical and electron microscopy were used to characterise the microstructure of the DMLS specimens and their effects on the fractures and mechanical properties.

Findings

It was found that the built samples have an excellent density at 4.5 g/cm, and the sample surfaces parallel to the building direction are rougher than the perpendicular surfaces. The fracture toughness result was higher than that of the cast material for the same alloy and higher than the Ti-6Al-4V parts fabricated by electron beam melting. This results in the superior mechanical properties of DMLS, while slightly lower in the zy direction owing to cracks, porosity and surface finish.

Research limitations/implications

The tensile strength was found to be higher than the wrought material, and the samples exhibited brittle fractures owing to the martensitic phase, which is caused by a high temperature gradient, and the mechanical properties change with the change in the microstructures at different building directions.

Originality/value

This paper contains original research.

Details

Rapid Prototyping Journal, vol. 24 no. 2
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 20 October 2014

Manickavasagam Krishnan, Eleonora Atzeni, Riccardo Canali, Flaviana Calignano, Diego Manfredi, Elisa Paola Ambrosio and Luca Iuliano

The aim of this research is to reach a deep understanding on the effect of the process parameters of Direct Metal Laser Sintering process (DMLS) on macroscopic properties…

2140

Abstract

Purpose

The aim of this research is to reach a deep understanding on the effect of the process parameters of Direct Metal Laser Sintering process (DMLS) on macroscopic properties (hardness and density) of AlSi10Mg parts and resulting microstructure.

Design/methodology/approach

A full factorial design of experiment (DOE) was applied to determine the most significant process parameter influencing macroscopic properties of AlSi10Mg parts manufactured by DMLS process. The analysis aims to define the optimum process parameters and deduce the process window that provides better macroscopic properties of AlSi10Mg parts. Optical microscopy observations are carried out to link the microstructure to macroscopic properties.

Findings

Macroscopic properties of DMLS parts are influenced by the change in process parameters. There is a close correlation between the geometry of scan tracks and macroscopic properties of AlSi10Mg parts manufactured by DMLS process.

Originality/value

The knowledge of utilizing optimized process parameters is important to fabricate DMLS parts with better mechanical properties. The present research based on applying experimental design is the first analysis for AlSi10Mg parts produced in DMLS process.

Details

Rapid Prototyping Journal, vol. 20 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 27 April 2022

Hayri Sezer, Joseph Tang, AMM Nazmul Ahsan and Sudhir Kaul

The purpose of this study is to develop a novel comprehensive three-dimensional computational model to predict the transient thermal behavior and residual stresses…

Abstract

Purpose

The purpose of this study is to develop a novel comprehensive three-dimensional computational model to predict the transient thermal behavior and residual stresses resulting from the layer-by-layer deposition in the direct metal laser sintering process.

Design/methodology/approach

In the proposed model, time integration is performed with an implicit scheme. The equations for heat transfer are discretized by a finite volume method with thermophysical properties of the metal powder and an updated convection coefficient at each time step. The model includes convective and radiative boundary conditions for the exposed surfaces of the part and constant temperatures for the bottom surface on the build plate. The laser source is modeled as a moving radiative heat flux along the scanning pattern, while the thermal gradients are used to calculate directional and von Mises residual thermal stresses by using a quasi-steady state assumption.

Findings

In this study, four different scanning patterns are analyzed, and the transient temperature and residual thermal stress fields are evaluated from these patterns. It is found that the highest stresses occur where the laser last leaves off on its scanning pattern for each layer.

Originality/value

The proposed model is designed to capture the layer-by-layer deposition for a three-dimensional geometry while considering the effect of the instantaneous melting of the powder, melt pool, dynamic calculation of thermophysical properties, ease of parametrization of various process parameters and the vectorization of the code for computational efficiency. This versatile model can be used for process parameter optimization of other laser powder bed fusion additive manufacturing techniques. Furthermore, the proposed approach can be used for analyzing different scanning patterns.

Details

Rapid Prototyping Journal, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 17 May 2022

Cemal İrfan Çalışkan and Ümit Arpacıoğlu

The purpose of this article is on the functional usability of metal additive manufacturing (AM) direct metal laser sintering (DMLS) production technology process…

Abstract

Purpose

The purpose of this article is on the functional usability of metal additive manufacturing (AM) direct metal laser sintering (DMLS) production technology process parameters in the construction industry. In the study, the advantages of thermal optimization and weight reduction in the case of the use of foam metals obtained by changing the hatch distance the production process parameter, in the production of facade panels in the architectural field are revealed.

Design/methodology/approach

The methods in the study; production of the small scaled facade panels with nine different hatch distance parameters, determination of the thermal change with the infrared thermography method, microstructure examination, weight measurement.

Findings

The paper lays the groundwork for the manufacturability of lighter and lower thermal conductivity facade panels by changing the hatch distance parameters. Within the scope of the study, the definition of semi-open-cell foam aluminum and the product screening strategy offers innovation. Within the scope of the study, this scope is shared as an algorithmic summary. In addition, the study offers a new perspective within the scope of multiple optimizable panel production in facade panels with AM technology.

Originality/value

Hatch distance parameter change was first discussed in this study in the architectural field, and a semi-open cell foam aluminum panel was obtained with the scanning strategy determined within the scope of the study. This panel geometry, which is defined as semi-open cell foam aluminum, can be used as a design element by painting or coating the outer surface, it can be stated that it will also provide thermal and weight optimization.

Details

Rapid Prototyping Journal, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 17 October 2017

Joshua Gale and Ajit Achuhan

Additive manufacturing (AM) processes involve a layer-by-layer sintering of metallic powders to produce fully functional three-dimensional parts. This layer-by-layer…

Abstract

Purpose

Additive manufacturing (AM) processes involve a layer-by-layer sintering of metallic powders to produce fully functional three-dimensional parts. This layer-by-layer building process provides a unique opportunity to enhance mechanical properties by applying treatments that previously were possible only on the surface in traditional manufacturing techniques. The purpose of the study is to examine the effect of ultrasonic peening (UP) applied during a layer-by-layer direct metal laser sintering (DMLS) fabrication of 316L stainless steel on its mechanical properties and microstructure.

Design/methodology/approach

Uniaxial tensile tests were performed at 1.27 mm/s to determine the effect of UP treatment on the average global behavior of a 316L part, whereas hardness measurements using nanoindentation were performed to determine the modification of local mechanical properties. Compressive buckling tests at a loading rate of 3 mm/min were performed on sample coupons with a large aspect ratio to evaluate the effect of UP on any potential delamination of DMLS layers. Techniques such as optical and scanning electron microscopy (SEM) imaging were utilized to determine the effect of UP on the microstructure.

Findings

Overall, significant modification in mechanical properties such as hardness and yield strength, along with microstructure, was observed. Large increases in both the average global and local mechanical properties, as well as a disruption in the columnar grain microstructure, was observed in DMLS parts treated with UP treatment.

Originality/value

Results indicate an opportunity for UP to be used as an in-situ process during AM processes for dynamically altering the mechanical behavior, microstructure, and distortion due to residual stress formation, in a tunable fashion.

Details

Rapid Prototyping Journal, vol. 23 no. 6
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 15 January 2020

Travis Edward Shelton, Dylan Joseph Stelzer, Carl R. Hartsfield, Gregory Richard Cobb, Ryan P. O'Hara and Christopher D. Tommila

For many applications, including space applications, the usability and performance of a component is dependent on the surface topology of the additively manufactured part…

Abstract

Purpose

For many applications, including space applications, the usability and performance of a component is dependent on the surface topology of the additively manufactured part. The purpose of this paper is to present an investigation into minimizing the residual surface roughness of direct metal laser sintering (DMLS) samples by manipulating the input process parameters.

Design/methodology/approach

First, the ability to manipulate surface roughness by modifying processing parameters was explored. Next, the surface topography was characterized to quantify roughness. Finally, microthruster nozzles were created both additively and conventionally for flow testing and comparison.

Findings

Surface roughness of DMLS samples was found to be highly dependent on the laser power and scan speed. Because of unintended partially sintered particles adhering to the surface, a localized laser fluence mechanism was explored. Experimental results show that surface roughness is influenced by the varied parameters but is not a completely fluence driven process; therefore, a relationship between laser fluence and surface roughness can be incorporated but not completely assumed.

Originality/value

This paper serves as an aid in understanding the importance of surface roughness and the mechanisms associated with DMLS. Rather than exploring a more common global energy density, a localized laser fluence was initiated. Moreover, the methodology and conclusions can be used when optimizing parts via metal additive manufacturing.

Details

Rapid Prototyping Journal, vol. 26 no. 3
Type: Research Article
ISSN: 1355-2546

Keywords

Article
Publication date: 3 May 2016

Pawel Rokicki, Bogdan Kozik, Grzegorz Budzik, Tomasz Dziubek, Jacek Bernaczek, Lukasz Przeszlowski, Olimpia Markowska, Bartlomiej Sobolewski and Arkadiusz Rzucidlo

The purpose of this paper is to present the methodology for manufacturing of aircraft transmission gears using incremental method of rapid prototyping (RP) – direct metal

Abstract

Purpose

The purpose of this paper is to present the methodology for manufacturing of aircraft transmission gears using incremental method of rapid prototyping (RP) – direct metal laser sintering (DMLS). The production of prototypes from metallic powders using described system allows the execution of final elements of complex structures with additional economic impacts.

Design/methodology/approach

The paper describes the use of selective laser sintering method (DMLS) by EOS Company. Whole chain of production of prototype is presented with the addition of geometric accuracy measurements by blue light laser device.

Findings

Presented in the research analysis of SLS/SLM technologies as rapid manufacturing systems shows that they can be applied in the production of prototypes used in the manufacturing process of gears for propulsion systems in aviation industry. Also, very important is the geometrical accuracy of gear prototypes produced by incremental methods. It determines subsequent treatment steps for aircraft propulsion system gears.

Practical Implications

The use of RP techniques as an alternative for conventionally used manufacturing method has mainly an economic impact related to the cost of time-consuming process and amount of defected elements appearing in serial production.

Originality/value

This paper presents possibility to use RP – DMLS system – for propulsion elements of aircraft structure. This research is original because of the complex description of the whole chain of manufacturing process. Additionally, geometrical accuracy measurement methodology by blue light presented with the RP method of manufacturing gives the research a unique characteristic.

Details

Aircraft Engineering and Aerospace Technology: An International Journal, vol. 88 no. 3
Type: Research Article
ISSN: 1748-8842

Keywords

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