Igor Yadroitsev, Ina Yadroitsava, Philippe Bertrand and Igor Smurov
Properties of the parts manufactured by selective laser melting (SLM) depend strongly on the each single laser‐melted track and each single layer, as well as the strength of the…
Abstract
Purpose
Properties of the parts manufactured by selective laser melting (SLM) depend strongly on the each single laser‐melted track and each single layer, as well as the strength of the connections between them. The purpose of this paper to establish links between the principal SLM parameters (laser power density, scanning speed, layer thickness), properties of the powder and geometrical characteristics of single tracks. This study will provide a theoretical and technical basis for production of parts from metal powders.
Design/methodology/approach
This paper discusses the SLM parameters affecting on geometrical characteristics of the synthesized single tracks. Granulomorphometric characteristics of powders were studied in detail. A Greco‐Latin square design was used to control geometrical characteristics of the tracks. Analysis of variance (ANOVA) permitted to establish a statistically significant influence of the SLM process parameters on geometry of the single laser‐melted track.
Findings
The behavior of individual tracks and their geometric characteristics depend on the process parameters, and physical‐chemical and granulomorphometrical properties of the powder. Each powder shows peculiar behavior in the process of single track formation. For stainless steel grade 904L powders with different particle size it was found that the most influencing parameter is the laser power (the following values were applied: 25, 37.5, 50 W), and then, in order of decreasing importance, are the powder layer thickness (60, 90, 120 μm), the scanning speed (0.05, 0.10, 0.15 m/s), and, finally, the particle size.
Originality/value
The proposed hierarchy of the process parameters is a new systematic study presented by the authors, developed for selective laser melting. Obtained data can be used in surface structuring and micro‐manufacturing characterized by a small number of layers within a part and, thus, sensible to the geometric dimensions and shape of the individual tracks.
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Nikolay K. Tolochko, Sergei E. Mozzharov, Igor A. Yadroitsev, Tahar Laoui, Ludo Froyen, Victor I. Titov and Michail B. Ignatiev
The particularities of the selective laser processing of single‐component metal powder layers were investigated, especially the occurrence of the balling‐processes under different…
Abstract
The particularities of the selective laser processing of single‐component metal powder layers were investigated, especially the occurrence of the balling‐processes under different processing conditions. During laser processing, sintered, semi‐sintered/semi‐melted or completely melted cakes can be formed. Size and shape of the laser processed parts can change depending on the energy and time parameters of the laser irradiation and on the properties of initial powder layers.
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Nikolay K. Tolochko, Sergei E. Mozzharov, Igor A. Yadroitsev, Tahar Laoui, Ludo Froyen, Victor I. Titov and Michail B. Ignatiev
A comparison of selective laser sintering (SLS) and selective laser cladding (SLC) methods is presented. Loose single‐component, Ni‐alloy powder was used in this study. The powder…
Abstract
A comparison of selective laser sintering (SLS) and selective laser cladding (SLC) methods is presented. Loose single‐component, Ni‐alloy powder was used in this study. The powder feeding system formed the flow of powder particles directed into the zone of laser spot. The particles were deposited directly onto a substrate or onto the top of a pedestal. The powders were treated with a CW‐ Nd:YAG laser (λ=1.06 μm). The beam was motionless relative to the powder bed. As a result, the samples of sintered or remelted powders were built up as the vertical rods. The geometrical characteristics, structure and mechanical properties of samples were investigated.
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Maria Doubenskaia, Sergey Grigoriev, Ivan Zhirnov and Igor Smurov
This paper aims to propose methods for on-line monitoring and process quality assurance of Selective Laser Melting (SLM) technology as a competitive advantage to enhance its…
Abstract
Purpose
This paper aims to propose methods for on-line monitoring and process quality assurance of Selective Laser Melting (SLM) technology as a competitive advantage to enhance its implementation into modern manufacturing industry.
Design/methodology/approach
Monitoring of thermal emission from the laser impact zone was carried out by an originally developed pyrometer and a charge-coupled device (CCD) camera which were integrated with the optical system of the PHENIX PM-100 machine. Experiments are performed with variation of the basic process parameters such as powder layer thickness (0-120 μm), hatch distance (60-1,000 μm) and fabrication strategy (the so-called “one-zone” and “two-zone”).
Findings
The pyrometer signal from the laser impact zone and the 2D temperature mapping from HAZ are rather sensible to variation of high-temperature phenomena during powder consolidation imposed by variation of the operational parameters.
Research limitations/implications
Pyrometer measurements are in arbitrary units. This limitation is due to the difficulty to integrate diagnostic tools into the optical system of a commercial SLM machine.
Practical implications
Enhancement of SLM process stability and efficiency through comprehensive optical diagnostics and on-line control.
Originality/value
High-temperature phenomena in SLM were monitored coaxially with the laser beam for variation of several operational parameters.
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Tomaz Brajlih, Urska Kostevsek and Igor Drstvensek
One of the main problems of selective laser sintering (SLS) manufacturing process is the dimensional accuracy of products. Main causes of dimensional deviations are material…
Abstract
Purpose
One of the main problems of selective laser sintering (SLS) manufacturing process is the dimensional accuracy of products. Main causes of dimensional deviations are material shrinkage and size of laser heat affected zone (LHAZ). This paper aims to present a new method of adapting SLS manufacturing shrinkage and LHAZ compensation parameters to the geometrical characteristics of processed parts to improve their accuracy.
Design/methodology/approach
The first part of this work presents a hypothesis asserting that the shrinkage and the LHAZ size depend on geometrical properties of products. A method that defines geometrical properties by numerical influence factors is described in the continuation. A multi-factorial experiment with adaptable test part is set up. Then, test builds are manufactured on an SLS machine and measured with a three-dimensional optical scanner. Afterwards, the results are analysed in relation to the presumed hypothesis.
Findings
The analysis of variance of multi-factorial experiment proves the hypothesis and the influence of the geometrical properties on the accuracy of the SLS manufacturing process. Afterwards, a part is manufactured with adapted values of compensation parameters and the archived accuracy is discussed.
Research limitations/implications
Presented research is limited on a single SLS material. Also, some numerical factors are directly linked to the build volume dimensions of the SLS machine that was used in the experiment. However, results can be generalised and some guidelines for shrinkage and LHAZ compensation method are presented. Also, some guidelines for future research are proposed.
Practical implications
Based on the presented results, it can be determined that using constant shrinkage and LHAZ values on an SLS machine will not yield the same results in terms of accuracy if the geometrical properties of parts change significantly.
Social implications
By correctly adapting compensation values, the overall achievable accuracy of the SLS process can be achieved, enabling a more reliable production of mass-customised end-user parts such as customised medical accessories and devices for example.
Originality/value
A similar method of numerically describing geometrical properties of part in regard to SLS and directly adapting shrinkage and LHAZ compensation values to them for every individual build has not yet been proposed.
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Hoejin Kim, Yirong Lin and Tzu-Liang Bill Tseng
The usage of additive manufacturing (AM) technology in industries has reached up to 50 per cent as prototype or end-product. However, for AM products to be directly used as final…
Abstract
Purpose
The usage of additive manufacturing (AM) technology in industries has reached up to 50 per cent as prototype or end-product. However, for AM products to be directly used as final products, AM product should be produced through advanced quality control process, which has a capability to be able to prove and reach their desire repeatability, reproducibility, reliability and preciseness. Therefore, there is a need to review quality-related research in terms of AM technology and guide AM industry in the future direction of AM development.
Design/methodology/approach
This paper overviews research progress regarding the QC in AM technology. The focus of the study is on manufacturing quality issues and needs that are to be developed and optimized, and further suggests ideas and directions toward the quality improvement for future AM technology. This paper is organized as follows. Section 2 starts by conducting a comprehensive review of the literature studies on progress of quality control, issues and challenges regarding quality improvement in seven different AM techniques. Next, Section 3 provides classification of the research findings, and lastly, Section 4 discusses the challenges and future trends.
Findings
This paper presents a review on quality control in seven different techniques in AM technology and provides detailed discussions in each quality process stage. Most of the AM techniques have a trend using in-situ sensors and cameras to acquire process data for real-time monitoring and quality analysis. Procedures such as extrusion-based processes (EBP) have further advanced in data analytics and predictive algorithms-based research regarding mechanical properties and optimal printing parameters. Moreover, compared to others, the material jetting progresses technique has advanced in a system integrated with closed-feedback loop, machine vision and image processing to minimize quality issues during printing process.
Research limitations/implications
This paper is limited to reviewing of only seven techniques of AM technology, which includes photopolymer vat processes, material jetting processes, binder jetting processes, extrusion-based processes, powder bed fusion processes, directed energy deposition processes and sheet lamination processes. This paper would impact on the improvement of quality control in AM industries such as industrial, automotive, medical, aerospace and military production.
Originality/value
Additive manufacturing technology, in terms of quality control has yet to be reviewed.