Experimental investigation of surface roughness and microstructure characterization of the SLM printed parts

The selective laser melting (SLM) technology, a 3D printing method, has been gaining more attraction recently due to its ability to fabricate highly complex and intricate featured medical, aerospace, automotive components. The extensive use of SLM in recent years has been augmented by readily available processing materials and distinct product features such as enhanced surface properties and improved mechanical strength of the printed products. This paper investigated the effects of support structures, building direction and post-processing on mechanical properties, surface roughness and microscopic analysis of parts printed by SLM. Support structures are required during the SLM printing process. It is desired to optimize the support structures, as this increases printing time and material consumption and reduces surface finish. Finite element analysis has been carried out prior to metal printing to optimize the support structure. It was found that the spider-cone line support shows efficient structure for this study. The mechanical properties of the fabricated specimen were studied, and experimental results were validated and compared with conventionally machined specimen. It was observed that the SLM printed parts have 20% increment in tensile strength as compared with conventionally cast specimen. However, the percent of elongation is low for SLM specimen due to large number of pores and un-melted powder presented in the printed part. In this study, the SLM specimens were subjected to heat treatment at the temperature of 550 °C for 2 h in order to achieve increment or optimal mechanical properties. The heat treatment demonstrated a 2-fold increment in elongation, as compared with the SLM as printed specimen. The present study is also aimed at evaluating the surface roughness of SLM printed specimen. It was observed that the surface roughness of SLM specimen ranged between ~ 0.3 and 3 μm. This demonstrated that SLM process is capable of providing the good surface quality component and considered an alternative process to conventional manufacturing process. The morphological studies have been carried out to support the results derived from the evaluation of mechanical properties and surface roughness. The morphological behaviour clearly shows the large pores and un-melted particles in fractured specimen. The results revealed that the support structure, build direction, orientation, surface finish and post-processing are important parameters to build a part using SLM effectively and efficiently.

PurposeThe purpose of this paper is to study the influence of changing printing parameters (powder layer thickness and binder saturation) in a three dimensional printing machine (3DP) on the transformation of 3DP printed plaster of paris to hydroxyapatite by low temperature phosphorization.Design/methodology/approachPlaster of paris‐based powder mixture was used to print specimens using different powder layer thickness (0.080, 0.10 and 0.20 mm) and saturation ratio (1 and 2). Subsequently, density, microstructure, mechanical properties, transformation rate and phase composition were analyzed to compare the influence of such printing parameters on properties.FindingsIt was found that printing parameters strongly affect the transformation efficiency and properties of the samples. The sample printed at layer thickness of 0.10 mm and saturation ratio of 1 yielded the highest transformation rate, density and greatest flexural modulus and strength after conversion. This was related to the sufficiently low density structure with good mechanical properties of the as‐fabricated 3DP sample which was suitable for the low temperature phosphorization process. Hydroxyapatite and monetite were found to be the main phases after conversion and the content of each phase depended on the conversion time and on also the printing parameters.Research limitations/implicationsThe optimal printing parameters were true for the materials used in this study. In the case of using other materials formulation, the optimal printing parameters might be different from these values.Practical implicationsThe results presented here can be used as a guideline for selecting printing parameters in 3DP machine for achieving properties as desired for specific applications or post‐processing techniques.Originality/valueThe paper demonstrates the printing parameters that were needed to be considered for efficient phase transformation and high mechanical properties.

Laser powder bed fusion (LPBF) is a promising technology that requires further work to improve productivity to be adopted more widely. One possible approach is to increase the laser power and scan speed. A customized high-speed and high-power LPBF system has been developed for this purpose. The current study investigated the surface roughness and near-surface porosity as a result of unsupported overhangs at varying inclination angles and orientations during the manufacturing of Ti6Al4V parts with this custom high-speed and high-power LPBF system. It is known that surface roughness and porosity are among the main drawbacks for parts manufactured by LPBF, and that supports are required for overhang regions with low inclination angles relative to the powder bed, typically in commercial LPBF systems requiring supports for regions with inclination angles less than 45°. However, the appropriate inclination angles for this custom system with high power and speed requires investigation. In this article, a simple benchmark test artefact with different inclination angles was manufactured in different orientations on the build platform and characterized by X-ray tomography, touch probe roughness meter, optical microscopy, and scanning electron microscopy. The analysis of surface roughness and near-surface porosity at upskin and downskin regions was performed as a function of inclination angle. The results indicate that the high-speed LPBF process produces relatively high roughness in all cases, with different porosity distributions at upskin and downskin areas. Both roughness and porosity vary as a function of inclination angle. Significant warping was observed, depending on build orientation relative to laser scanning direction. These are the first reported results of the detailed surface roughness and porosity characterization of part quality from such a high-speed, high-power LPBF process.

The purpose of this paper is to evaluate the influence of 3D printing parameters (i.e. print speed, infill density, infill patterns) on the elastic and mechanical properties (i.e. Young modulus, yield limit, ultimate tensile strength). These properties have been determined experimentally on different specimens subjected to tensile loading using a universal testing machine INSTRON 8872. For these experimental investigations, the test specimens were manufactured in accordance to ASTM standards, modifying the following printing parameters: print speed, infill density, infill patterns. The influence of printing parameters on elastic and mechanical properties is necessary for a better understanding of the material behavior necessary in modelling and design of some type of structures manufactured using 3D printing method.

Additive manufacturing has got wide applications in different industries. Fused Deposition Modelling (FDM) is one of the most widely used additive manufacturing processes in which the part is manufactured by depositing the material layer-by-layer. Poly-ether-ether-ketone (PEEK) is a biocompatible thermoplastic with excellent mechanical properties and it can potentially replace the metal or ceramic parts being used in biomedical and aerospace industries. FDM with its ability to form parts with complex structures offers advantages for manufacturing PEEK parts compared to other processing techniques. However, the higher melting temperature of PEEK makes its processing difficult through FDM. In the present work, FDM is utilised to perform the printing of PEEK. The quality of the printed parts in form of surface finish and mechanical properties mainly depends on the temperature and the viscosity of the molten material. Hence, the melting behaviour of polymer in terms of the temperature, viscosity, and pressure distribution in the nozzle is simulated through finite element analysis (FEA). Also, experimental investigations have been carried out to analyse the effect of various printing parameters such as printing temperature, printing speed, and printing layer thickness, on surface quality and mechanical properties of printed PEEK parts.

Laser Powder Bed Fusion (LPBF) is a metal additive manufacturing technology (AM) that uses high power laser to melt powder layer by layer to create mechanical parts. LPBF several advantages, including short manufacturing time, freedom to design complex geometries and user-friendly customization. It is widely used in the manufacture of high-value parts in aerospace, automotive and biomedical industries. Due to the nature of the layer-by-layer process, partially melted powder is attached to the as-built part surface during LPBF, resulting in a significant increase in surface roughness. Furthermore, initial surface roughness of final part is different with locations since quantity of powder adhesion varies depending on building angle. Increase of surface roughness due to attached metal powder can cause out of dimensional tolerance that designed. Such dimensional inaccuracy can lead to failure or breakage of the mechanical parts. Therefore, surface post-treatment is essential to reduce surface roughness with minimizing dimensional change. Conventional mechanical and chemical treatments for surface finishing have limitations such as limited tooling range and surface damage due to the use of strong acids and long-time of processing. Electropolishing, based on electrochemical reactions, is suitable for improving the roughness of LPBF manufactured parts with complex geometries. Thickness reduction can be predicted by controlling the applied voltage and processing time. Also, surfaces in contact with the electrolyte is polished without geometric restrictions. Studies have been reported that analyze the change in surface roughness after electropolishing to improve the roughness of alloys manufactured with LPBF. However, for application to real parts, it is necessary to conduct basic research to optimize the electropolishing conditions to obtain satisfactory surface roughness with minimal thickness reduction by considering the effect of dimensional changes during electropolishing. In this study, we electropolished Hastelloy X fabricated by LPBF. Four types of electrolytes were selected for electropolishing. We measured surface roughness and thickness reduction with respect to applied voltage and processing time. With such results, optimized condition to reduce the surface roughness with minimal thickness changes are discussed. Then, these conditions were applied to LPBF specimen with different building angles. Surface roughness and weight changes were measured to compare polishing efficiency to each electrolyte.

Composite Extrusion Modeling (CEM) is an advanced material extrusion additive manufacturing technique for low-cost rapid production of complex parts. In this work, a conventional Metal Injection Moulding (MIM) feedstock is used for 3D printing of low alloy-steel AISI 8740 via CEM. This steel is widely used in aircraft, aerospace, and MIM industries. However, it has, so far, not been processed using CEM-based 3D printing. The influence of four printing parameters, extrusion multiplier, extrusion temperature, nozzle velocity, and layer thickness on green density and surface roughness was explored following the feedstock's investigation. Full-factorial and face-centered response designs were utilized to study the influence of printing parameters and their optimization to achieve maximum green density and minimum surface roughness. The optimized parameters were found to be an extrusion multiplier of 107.6 %, extrusion temperature of 180 °C, nozzle velocity of 20 mm/s and layer thickness of 0.050 mm through a multiple response optimization process. The dense green part with relative densities of ≥ 98 % was achieved with minimum surface roughness of Ra = (2.3 ± 0.1) μm and Rz = (16.1 ± 1.1) μm. Moreover, a scanning electron microscope was utilized to study the surfaces of green parts. The parts printed with optimized printing parameters showed the best quality with minimized printing voids and smooth extrusion.

Influence of tensile edge design and printing parameters on the flexural strength of ZrO2 and ATZ bars prepared by UV-LCM-DLP

As one of the light materials with superior biocompatible properties, magnesium has drawn more attention in recent years. More industries, such as the automotive, aerospace, and medical, are adopting new strategies to employ this material. Mg-based batteries with potential advantages over Li-based batteries are also predicted to be used in electric vehicles shortly. However, significant problems in the production of Mg, such as its low ductility at ambient temperature and high oxidation and flammability at high operating temperatures, have limited its application. Therefore, selecting an appropriate manufacturing method can lessen or resolve Mg's drawbacks. Castings, different traditional forming and Severe Plastic Deformation (SPD) methods, and alloying of Mg with other elements are among the most popular fabrication and processing techniques to improve Mg properties and expand its application. However, as an innovative Additive Manufacturing (AM) method, the Selective Laser Melting (SLM) is considered a more reliable way of producing Mg-based products, especially for applications with complex geometry design, the least amount of waste, and no need for molds and accessories. Of course, SLM also has its challenges, such as the strong dependence of the properties on printing parameters and the raw material; however, apparent horizons can be imagined for SLM of Mg according to recent developments and research. This paper summarizes the SLM of Mg by introducing the SLM parameters, properties, defects, and applications of SLMed Mg alloys and discussing the challenges and solutions of this method. The impact of the SLM parameters and initial Mg powder characteristics as the primary inputs of this method on the resultant properties of the SLMed Mg components and the potential defects are thoroughly discussed. The thermal zones produced in the SLM process of Mg are divided into four categories, which are strongly influenced by the printing parameters and, on the other hand, affect the quality of the final product so that a high relative density of 99% and the much better mechanical and microstructural properties than those produced via other conventional methods, such as casting are achieved by adjusting the printing parameters. The characterization of the primary powder is divided into two categories: morphology and particle size, along with chemical composition. Morphology and chemical composition play an essential role in the final part by affecting the alloy's flowability, oxidation, and ignition. Characterization of properties is also reviewed in three general densifications, mechanical properties, and microstructure of SLMed samples and their dependence on parameters and input materials. Finally, the defects and challenges are briefly discussed, and the applications of Mg alloys in two widely used areas, including automotive and medicine, are presented.

Laser powder bed fusion (PBF-LB) technique can currently offer the lowest surface roughness among all available techniques for metal additive manufacturing. Still the measured values for Ra can easily be over 10 μm depending on the used layer thickness and printing parameters. The current work focuses on improving the surface roughness by utilizing dry electropolishing machine. While suitable for many materials, the material selected for this study is one of the most used in PBF-LB manufacturing, stainless steel 316L. In addition, multistep pre-grinding with the grade of the final finish varied was used to investigate what is the most efficient way to distribute manual preparation work and automated polishing to reach the desired surface roughness. Furthermore, severe shot peening was used before the polishing to study the effect on residual stresses and fatigue life of the material. Laser optical microscopy was used to investigate the surface properties and it was found that dry electropolishing with pre-grinding could be succesfully used to obtain average roughness levels as low as 0.13 μm. The highest reductions in surface roughness were reached with the rougher initial surfaces where it could be reduced by 80% at best. Residual stresses measured after the severe shot peening were preserved after the polishing but did not result in increased fatigue strength.

The 3D printing technology is increasingly used in manufacturing, medicine, education, and various other fields. This technology allows for the creation of parts with complex shapes, which would be difficult or even impossible to manufacture using traditional machining methods. However, the quality of the printed products is still a barrier to the widespread use of the 3D printing technology in industrial applications. The former includes the accuracy of the shape, size, and mechanical properties of the printed products. Research to improve the efficiency of the printing process and the printed product quality is essential for application fields. This study, through experiments, determines the relationship between the shape deviation of the printed products and the set of printing parameters. The latter includes the laser power, printing speed, and printing layer thickness. Experimental studies were conducted on the FF-M180D printer using the Selective Laser Melting (SLM) printing method. Ti6Al4V powder is utilized as printing material for this study. Based on the regression model showing the relationship between the printing parameters and shape deviation, the optimal set of parameters to minimize the shape deviation was determined.

Super alloys are widely used in many applications such as aerospace, automotive, biomedical, marine, mining and oil industries. In high-speed micro end milling (HSMEM) of super alloys, the proper selection of cutting tool is necessary to achieve good surface quality without burrs. Surface roughness characterisation is crucial on the work materials to achieve the desired production rate in limited time and at low cost. In this research work, surface roughness characterisation was investigated in order to opt for the better possible tool for machining Near Alpha Titanium Alloy Grade-12 under feasible conditions. The influence of machining parameters i.e. cutting speed, feed and depth of cut on surface roughness was investigated in the present work. Experiments were conducted under dry cutting conditions using Uncoated, PVD Coated TiAlN & AlTiN tungsten carbide tools. It was observed that machining with uncoated tungsten carbide tools generates less surface roughness on near alpha titanium alloy.

Effects of printing parameters of fused deposition modeling on mechanical properties, surface quality, and microstructure of PEEK

Cellular structures are a class of materials that offer greater stiffness, strength-to-weight ratio, good energy absorption capacity, and high heat transfer capability compared to solid parts. Metallic lattice structures have been applied in different industry sectors, such as in biomedical implants, lightweight components, energy absorbers, and catalytic reactors. With the development of advanced manufacturing techniques, especially additive manufacturing (AM), lattice structures with complicated designs can be produced. Lattice structure-based heat exchangers produced by AM techniques have recently gained significant attention due to their promising performance. Interconnected cavities in lattice structures provide flow of fluid and effective thermal conductivity, which is desirable in heat exchangers. AM methods provide the possibility to promote tortuosity and intricate flow patterns leading to improved performance of heat exchangers. Between different AM techniques, laser powder bed fusion (LPBF) proved to be a suitable method for the manufacture of heat exchangers. Using LPBF methods, the distribution and geometry of cavities in the structure can be controlled with an accuracy that is typically better than for other AM methods. Although LPBF-produced heat exchanger showed enhanced thermal conductance, there are limitations associated with LPBF fabrication, such as surface roughness and need for post processing. In order to bridge this gap, the effects of different process parameters and levels of structural complexity in LPBF processes need to be evaluated. In this context, the present contribution constitutes a position paper that contrasts the opportunities that LPBF may provide for the fabrication of heat exchangers with the challenges that need to be overcome to realize design solutions that meet industry demands.

Fused deposition modeling (FDM) in 3D printing is a very promising technology and one of the focuses of scientific research. The main reason is that it has the advantages of simple structure, relatively low price and convenient operation, which has made its development more and more rapid in recent years. However, due to the fact that the FDM products are susceptible to the operating environment, the printing quality is not stable enough and the development is restricted. In addition, this research uses Taguchi method to explore FDM to optimize a long and thin desired volume of the workpiece under different printing parameters (printing temperature, printing speed ratio, and printing layer thickness). From the experimental results, the size of the factors that affect the FDM’s expected volume of the workpiece is, in order, the printing temperature is the most important, the printing speed ratio is the second, and the printing layer thickness is the smallest. The optimal parameter combination for the desired workpiece volume is A1B1C1, that is, the printing temperature is 190°C, the printing speed ratio is 0.286 (20 mm/s on the outer side, 70 mm/s on the inner side), and the printing layer thickness is 0.1 mm. Finally confirmed the experimental results and found that the volume error of the finished product using the best printing parameters is less than 0.3 %, which proves that the optimized printing parameters obtained by Taguchi method are indeed effective and feasible.