Selective laser melting: lessons from medical devices industry and other applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Iván La Fé-Perdomo ◽  
Jorge Andres Ramos-Grez ◽  
Gerardo Beruvides ◽  
Rafael Alberto Mujica
Keyword(s):  
Health Care ◽  
Selective Laser Melting ◽  
Medical Devices ◽  
Process Modeling ◽  
Manufacturing Process ◽  
Research Work ◽  
Laser Melting ◽  
Content Type ◽  
Novel Materials ◽  
Metallic Systems

Purpose The purpose of this paper is to outline some key aspects such as material systems used, phenomenological and statistical process modeling, techniques applied to monitor the process and optimization approaches reported. All these need to be taken into account for the ongoing development of the SLM technique, particularly in health care applications. The outcomes from this review allow not only to summarize the main features of the process but also to collect a considerable amount of investigation effort so far achieved by the researcher community. Design/methodology/approach This paper reviews four significant areas of the selective laser melting (SLM) process of metallic systems within the scope of medical devices as follows: established and novel materials used, process modeling, process tracking and quality evaluation, and finally, the attempts for optimizing some process features such as surface roughness, porosity and mechanical properties. All the consulted literature has been highly detailed and discussed to understand the current and existing research gaps. Findings With this review, there is a prevailing need for further investigation on copper alloys, particularly when conformal cooling, antibacterial and antiviral properties are sought after. Moreover, artificial intelligence techniques for modeling and optimizing the SLM process parameters are still at a poor application level in this field. Furthermore, plenty of research work needs to be done to improve the existent online monitoring techniques. Research limitations/implications This review is limited only to the materials, models, monitoring methods, and optimization approaches reported on the SLM process for metallic systems, particularly those found in the health care arena. Practical implications SLM is a widely used metal additive manufacturing process due to the possibility of elaborating complex and customized tridimensional parts or components. It is corroborated that SLM produces minimal amounts of waste and enables optimal designs that allow considerable environmental advantages and promotes sustainability. Social implications The key perspectives about the applications of novel materials in the field of medicine are proposed. Originality/value The investigations about SLM contain an increasing amount of knowledge, motivated by the growing interest of the scientific community in this relatively young manufacturing process. This study can be seen as a compilation of relevant researches and findings in the field of the metal printing process.

Voice activity detection using optimal window overlapping especially over health-care infrastructure

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Shilpa Sharma ◽  
Punam Rattan ◽  
Anurag Sharma ◽  
Mohammad Shabaz
Keyword(s):  
Health Care ◽  
Health Care Professionals ◽  
Research Work ◽  
Voice Activity Detection ◽  
Support Vector ◽  
Activity Detection ◽  
Content Type ◽  
Health Care Infrastructure ◽  
Voice Activity ◽  
Optimal Window

Purpose This paper aims to introduce recently an unregulated unsupervised algorithm focused on voice activity detection by data clustering maximum margin, i.e. support vector machine. The algorithm for clustering K-mean used to solve speech behaviour detection issues was later applied, the application, therefore, did not permit the identification of voice detection. This is critical in demands for speech recognition. Design/methodology/approach Here, the authors find a voice activity detection detector based on a report provided by a K-mean algorithm that permits sliding window detection of voice and noise. However, first, it needs an initial detection pause. The machine initialized by the algorithm will work on health-care infrastructure and provides a platform for health-care professionals to detect the clear voice of patients. Findings Timely usage discussion on many histories of NOISEX-92 var reveals the average non-speech and the average signal-to-noise ratios hit concentrations which are higher than modern voice activity detection. Originality/value Research work is original.

ANISOTROPIC CUTTING FORCE CHARACTERISTICS IN MILLING OF MARAGING STEEL PROCESSED THROUGH SELECTIVE LASER MELTING

2021 ◽  
pp. 1-16
Author(s):  
Shoichi Tamura ◽  
Takashi Matsumura ◽  
Atsushi Ezura ◽  
Kazuo Mori
Keyword(s):  
Additive Manufacturing ◽  
Cutting Force ◽  
Maraging Steel ◽  
Selective Laser Melting ◽  
Cutting Forces ◽  
Manufacturing Process ◽  
Laser Scanning ◽  
Force Model ◽  
Laser Melting ◽  
Scanning Direction

Abstract Additive manufacturing process of maraging steel has been studied for high value parts in aerospace and automotive industries. The hybrid additive / subtractive manufacturing is effective to achieve tight tolerances and surface finishes. The additive process induces anisotropic mechanical properties of maraging steel, which depends on the laser scanning direction. Because anisotropy in the workpiece material has an influence on the cutting process, the surface finish and the dimension accuracy change according to the direction of the cutter feed with respect to the laser scanning direction. Therefore, the cutting parameters should be determined to control the cutting force considering material anisotropy. The paper discusses the cutting force in milling of maraging steel stacked with selective laser melting, as an additive manufacturing process. Anisotropic effect on the cutting forces is proved with the changing rate of the cutting force in milling of the workpieces stacked by repeating laser scanning at 0/90 degrees and 45/-45 degrees. The cutting forces, then, are analyzed in the chip flow models with piling up of orthogonal cuttings. The force model associates anisotropy with the shear stress on the shear plane. The changes in the cutting forces with the feed direction are discussed in the cutting tests and analysis.

Deformations and stresses prediction of cantilever structures fabricated by selective laser melting process

2021 ◽  
Vol 27 (3) ◽  
pp. 453-464
Author(s):  
Lan Li ◽  
Tan Pan ◽  
Xinchang Zhang ◽  
Yitao Chen ◽  
Wenyuan Cui ◽  
...  
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Selective Laser Melting ◽  
Thermal Distortion ◽  
Cantilever Beams ◽  
Support Structures ◽  
Laser Melting ◽  
Content Type ◽  
Two Samples ◽  
Validation Experiments

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.

Track evolution and surface characteristics of selective laser melting Ti6Al4V

2018 ◽  
Vol 24 (9) ◽  
pp. 1554-1562 ◽  
Author(s):  
Luo Zhang ◽  
Haihong Zhu ◽  
Jiahe Liu ◽  
Xiaoyan Zeng
Keyword(s):  
Surface Morphology ◽  
Selective Laser Melting ◽  
Surface Characteristics ◽  
Scanning Speed ◽  
Bulk Sample ◽  
Three Dimension ◽  
Single Track ◽  
Heat Accumulation ◽  
Laser Melting ◽  
Content Type

Purpose The purpose of this paper is to investigate the track evolution and surface characteristics of selective laser melting Ti6Al4V. Design/methodology/approach In the present paper, Ti6Al4V single-track, multi-track and bulk sample were formed at different scanning speed by selective laser melting (SLM). Then, the surface morphology, three-dimension profile and surface roughness were evaluated. The width of the single and multi-track was measured and compared. Findings The results showed that the heat accumulation played a great role on the evolution of tracks and surface characteristics from single-track to multi-track and to bulk. The surface morphology of the subsequent tracks became more regular when the single-track was irregular at the same high scanning speed. The width of last track Wn was always larger than that of the first track W1. The Ra of the top of the bulk increased with the increase of the scanning speed, this trend was as same as the Ra of the single-track, but the trend of Ra of the side was opposite. Originality/value The effect of heat accumulation on the track evolution and surface characteristics is obtained. The results can help to derive a smooth surface with a regular and continuous track in SLM.

Structural optimization design for antenna bracket manufactured by selective laser melting

2018 ◽  
Vol 24 (3) ◽  
pp. 539-547 ◽  
Author(s):  
Zefeng Xiao ◽  
Yongqiang Yang ◽  
Di Wang ◽  
Changhui Song ◽  
Yuchao Bai
Keyword(s):  
Structural Optimization ◽  
Modal Analysis ◽  
Selective Laser Melting ◽  
Optimization Model ◽  
Optimization Design ◽  
Analysis Data ◽  
Laser Melting ◽  
Design Rules ◽  
Content Type ◽  
Process Characteristics

Purpose This paper aims to summarize design rules based on the process characteristics of selective laser melting (SLM) and structural optimization and apply the design rules in the lightweight design of an aluminum alloy antenna bracket. The design goal is to reduce 30 per cent of the weight while maintaining the stress levels in the original part. Design/methodology/approach To reduce weight as much as possible, the titanium alloy with higher specific strength was selected during the process of optimization. The material distribution of the bracket was improved by the topology optimization design. The redesign for SLM was used to obtain an optimization model, which was more suitable for SLM. The component performance was improved by shape optimization. The modal analysis data of the structural optimization model were compared with those of the stochastic lightweight model to verify the structural optimization model. The scanning data were compared with those of the original model to verify whether the model was suitable for SLM. Findings Structural optimization design for antenna bracket realized the mass decrease of 30.43 per cent and the fundamental frequency increase of 50.18 per cent. The modal analysis data of the stochastic lightweight model and the structural optimization model indicated that the optimization performance of structural optimization method was better than that of the stochastic lightweight method. The comparison results between the scanning data of the forming part and the original data confirmed that the structural optimization design for SLM lightweight component could achieve the desired forming accuracy. Originality/value This paper summarizes geometric constraints in SLM and derives design rules of structural optimization based on the process characteristics of SLM. SLM design rules make structural optimization design more reasonable. The combination of structural optimization design and SLM can improve the performance of lightweight antenna bracket significantly.

Anisotropic Cutting Force Characteristics in Milling of Maraging Steel Processed Through Selective Laser Melting

2021 ◽  
Author(s):  
Shoichi Tamura ◽  
Takashi Matsumura ◽  
Atsushi Ezura ◽  
Kazuo Mori
Keyword(s):  
Additive Manufacturing ◽  
Cutting Force ◽  
Maraging Steel ◽  
Selective Laser Melting ◽  
Cutting Forces ◽  
Manufacturing Process ◽  
Laser Scanning ◽  
Force Model ◽  
Laser Melting ◽  
Scanning Direction

Abstract Additive manufacturing process of maraging steel has been studied for high value parts in aerospace and automotive industries. The hybrid additive / subtractive manufacturing is effective to achieve tight tolerances and surface finishes. The additive process induces anisotropic mechanical properties of maraging steel, which depends on the laser scanning direction. Because anisotropy in the workpiece material has an influence on the cutting process, the surface finish and the dimension accuracy change according to the direction of the cutter feed with respect to the laser scanning direction. Therefore, the cutting parameters should be determined to control the cutting force considering material anisotropy. The paper discusses the cutting force in milling of maraging steel stacked with selective laser melting, as an additive manufacturing process. Anisotropic effect on the cutting forces is proved with the changing rate of the cutting force in milling of the workpieces stacked by repeating laser scanning at 0/90 degrees and 45/−45 degrees. The cutting forces, then, are analyzed in the chip flow models with piling up of orthogonal cuttings. The force model associates anisotropy with the shear stress on the shear plane. The changes in the cutting forces with the feed direction are discussed in the cutting tests and analysis.

Selective laser melting of magnesium AZ31B alloy powder

2019 ◽  
Vol 26 (2) ◽  
pp. 249-258 ◽  
Author(s):  
Andrzej Pawlak ◽  
Patrycja E. Szymczyk ◽  
Tomasz Kurzynowski ◽  
Edward Chlebus
Keyword(s):  
Mechanical Properties ◽  
Selective Laser Melting ◽  
Alloy Powder ◽  
Az31 Alloy ◽  
Optimum Process ◽  
Laser Melting ◽  
Content Type ◽  
Fine Grained ◽  
Az31b Alloy ◽  
Hot Rolled

Purpose This paper aims to discuss the results of material tests conducted on specimens manufactured from AZ31 alloy powder by selective laser melting (SLM) technology. The manufactured specimens were then subjected to porosity assessment, microstructure analysis as well as to mechanical and corrosion tests. Design/methodology/approach SLM process was optimized using the design of experiments tools. Experiments aimed at selecting optimum process parameters were carried out in accordance with a five-level rotatable central composite design. Findings The porosity results showed very low values of <1 per cent, whereas mechanical properties were close to the values reported for the reference wrought AZ31 alloy in hot-rolled state. A fine-grained microstructure was observed with a large range of grain size, which enhanced the material’s mechanical properties. Corrosion characteristics of the SLM-manufactured material exceed those determined for the wrought material. Originality/value The results presented in this paper drive interest in magnesium alloys used in additive manufacturing processes. Low porosity, good mechanical properties, form of the microstructure and, most importantly, improved corrosion characteristics suggest that SLM provides great potential for the manufacture of ultralight structures, including resorbable metallic implants.

Porosity content control of CoCrMo and titanium parts by Taguchi method applied to selective laser melting process parameter

2016 ◽  
Vol 22 (1) ◽  
pp. 20-30 ◽  
Author(s):  
David Joguet ◽  
Sophie Costil ◽  
Hanlin Liao ◽  
Yoann Danlos
Keyword(s):  
Selective Laser Melting ◽  
Design Methodology ◽  
Melting Process ◽  
Research Approach ◽  
Analysis Method ◽  
Laser Melting ◽  
Huge Number ◽  
Energy Estimation ◽  
Content Type ◽  
Potential Applications

Purpose – The purpose of this paper consists in the optimization and understanding of the Selective Laser Melting (SLM) manufacturing process of biomaterials, such as T40 and CoCrMo, as scaffolds. Moreover, process optimization is also challenging, with regards to the huge number of parameters and their influence on the finished product. Design/methodology/approach – The paper opted for an exploratory study using Taguchi analysis method to precisely identify the most relevant parameters and justify the energy estimation. Findings – The study showed that SLM fits perfectly with the T40 and CoCrMo part manufacturing. This method allowed to have a complete overview of all the potential applications of SLM for implant manufacturing. Originality/value – With this research approach, the results may be generalized to other material and showed a good theoretical approach.

Metallographic evaluation of duplex stainless steel powders processed by selective laser melting

2017 ◽  
Vol 23 (6) ◽  
pp. 1146-1163 ◽  
Author(s):  
Karl P. Davidson ◽  
Sarat B. Singamneni
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Selective Laser Melting ◽  
A Priori ◽  
Fine Tuning ◽  
Structure Property ◽  
Laser Melting ◽  
Content Type ◽  
Test Pieces ◽  
Process Structure

Purpose This paper aims to establish the microstructures and the process-structure relationships in duplex stainless steel powders consolidated by selective laser melting (SLM). Design/methodology/approach A priori data on energy density levels most appropriate to consolidation of duplex stainless steel powders through SLM served as the basis to converge on the laser settings. Experimental designs with varying laser power and scan speeds and test pieces generated allowed metallographic evaluations based on optical and scanning electron microscopy and electro backscatter diffraction analyses. Findings Duplex stainless steel powders are established for processing by SLM. However, the dynamic point heat source and associated transient thermal fields affect the microstructures to be predominantly ferritic, with grains elongated in the build direction. Austenite precipitated either at the grain boundaries or as Widmanstätten laths, whereas the crystallographic orientations and the grain growth are affected around the cavities. Considerable CrN precipitation is also evidenced. Originality/value Duplex stainless steels are relatively new candidates to be brought into the additive manufacturing realm. Considering the poor machinability and other difficulties, the overarching result indicating suitability of duplex powders by SLM is of considerable value to the industry. More significantly, the metallographic evaluation and results of the current research allowed further understanding of the material consolidation aspects and pave ways for fine tuning and establishment of the process-structure-property relationships for this important process-material combination.

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