Micromachines

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17 pages, 1103 KiB

Open AccessArticle

From Formulation to Application: Effects of Plasticizer on the Printability of Fluoro Elastomer Compounds and Additive Manufacturing of Specialized Seals

by Mookkan Periyasamy, AA Mubasshir, Stiven Kodra, Sangeetham Chandramouli, Ronald Campbell, David O. Kazmer and Joey L. Mead

Micromachines 2024, 15(5), 622; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15050622 - 5 May 2024

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Abstract

This work investigated material extrusion additive manufacturing (MatEx AM) of specialized fluoroelastomer (FKM) compounds for applications in rubber seals and gaskets. The influence of a commercially available perfluoropolyether (PFPE) plasticizer on the printability of a control FKM rubber compound was studied using a [...] Read more.

This work investigated material extrusion additive manufacturing (MatEx AM) of specialized fluoroelastomer (FKM) compounds for applications in rubber seals and gaskets. The influence of a commercially available perfluoropolyether (PFPE) plasticizer on the printability of a control FKM rubber compound was studied using a custom-designed ram material extruder, Additive Ram Material Extruder (ARME), for printing fully compounded thermoset elastomers. The plasticizer’s effectiveness was assessed based on its ability to address challenges such as high compound viscosity and post-print shrinkage, as well as its impact on interlayer adhesion. The addition of the PFPE plasticizer significantly reduced the FKM compound’s viscosity (by 70%) and post-print shrinkage (by 65%). While the addition of the plasticizer decreased the tensile strength of the control compound, specimens printed with the plasticized FKM retained 34% of the tensile strength of compression-molded samples, compared to only 23% for the unplasticized compound. Finally, the feasibility of seals and gaskets manufacturing using both conventional and unconventional additive manufacturing (AM) approaches was explored. A hybrid method combining AM and soft tooling for compression molding emerged as the optimal method for seal and gasket fabrication. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

14 pages, 6895 KiB

Open AccessArticle

Effect of Geometrical Parameters on the Mechanical Performance of Bamboo-Inspired Gradient Hollow-Strut Octet Lattice Structure Fabricated by Additive Manufacturing

by Junxian Ge, Yu Song, Zhenyu Chen, Yuhao Zhuo, Tongzheng Wei, Chen Ge, Yuang Cheng, Ming Liu and Qingbo Jia

Micromachines 2024, 15(5), 583; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15050583 - 28 Apr 2024

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Abstract

Hollow-strut metal lattice structures are currently attracting extensive attention due to their excellent mechanical performance. Inspired by the node structure of bamboo, this study aimed to investigate the mechanical performance of the gradient hollow-strut octet lattice structure fabricated by laser powder bed fusion [...] Read more.

Hollow-strut metal lattice structures are currently attracting extensive attention due to their excellent mechanical performance. Inspired by the node structure of bamboo, this study aimed to investigate the mechanical performance of the gradient hollow-strut octet lattice structure fabricated by laser powder bed fusion (LPBF). The effect of geometrical parameters on the yield strength, Young’s modulus and energy absorption of the designed octet unit cells were studied and optimized by FEA analysis. The hollow-strut geometrical parameters that deliver the best mechanical property combinations were identified, and the corresponding unit cells were then redesigned into the 3 × 3 × 3 type lattice structures for experimental evaluations. Compression tests confirmed that the designed gradient hollow-strut octet lattice structures demonstrated superior mechanical properties and deformation stability than their solid-strut lattice structure counterparts. The underlying deformation mechanism analysis revealed that the remarkably enhanced bending strength of the gradient hollow-strut lattice structure made significant contributions to its mechanical performance improvement. This study is envisaged to shed light on future hollow-strut metal lattice structure design for lightweight applications, with the final aim of enhancing the component’s mechanical properties and/or lowering its density as compared with the solid-strut lattice structures. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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11 pages, 2646 KiB

Open AccessArticle

A Novel Low-Temperature Extrusion Method for the Fused Filament Fabrication of Fluoroelastomer Compounds

by Mookkan Periyasamy, Ronald Campbell, Joey M. Mead, David O. Kazmer, ShibShankar Banerjee, AA Mubasshir, Leeda A. Phaen and Stiven Kodra

Micromachines 2024, 15(5), 582; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15050582 - 27 Apr 2024

Viewed by 443

Abstract

In this work, an additive manufacturing process for extruding fully compounded thermosetting elastomers based on fluorine-containing polymer compositions is reported. Additive manufacturing printers are designed with a dry ice container to precool filaments made from curable fluoroelastomer (FKM) and perfluoroelastomer (FFKM) compounds. A [...] Read more.

In this work, an additive manufacturing process for extruding fully compounded thermosetting elastomers based on fluorine-containing polymer compositions is reported. Additive manufacturing printers are designed with a dry ice container to precool filaments made from curable fluoroelastomer (FKM) and perfluoroelastomer (FFKM) compounds. A support tube guides the stiffened filament towards the printer nozzle. This support tube extends near the inlet to a printer nozzle. This approach allows low-modulus, uncured rubber filaments to be printed without buckling, a phenomenon common when 3D printing low-modulus elastomers via the fused deposition modeling (FDM) process. Modeling studies using thermal analyses data from a Dynamic Mechanical Analyzer (DMA) and a Differential Scanning Calorimeter (DSC) are used to calculate the Young’s modulus and buckling force, which helps us to select the appropriate applied pressure and the nozzle size for printing. Using this additive manufacturing (AM) method, the successful printing of FKM and FFKM compounds is demonstrated. This process can be used for the future manufacturing of seals or other parts from fluorine-containing polymers. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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15 pages, 9623 KiB

Open AccessArticle

A Real-Time Monitoring Method for Selective Laser Melting of TA1 Materials Based on Radiation Detection of a Molten Pool

by Tao Zhou, Wei Huang and Congyan Chen

Micromachines 2024, 15(5), 570; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15050570 - 26 Apr 2024

Viewed by 349

Abstract

Selective laser melting (SLM) technology is a promising additive manufacturing technology. However, due to the numerous influencing factors in this complex process, a reliable real-time method is needed to monitor the forming process of SLM. The molten pool is the smallest forming unit [...] Read more.

Selective laser melting (SLM) technology is a promising additive manufacturing technology. However, due to the numerous influencing factors in this complex process, a reliable real-time method is needed to monitor the forming process of SLM. The molten pool is the smallest forming unit in the SLM process, the consistency of which can effectively reflect the quality of the printing process. By using a coaxial optical path structure and a compound amplifier circuit, high-speed acquisition of molten pool radiation can be realized. Next, single factor analysis and orthogonal experimentation were used to investigate the influence levels of key process parameters on the radiation of molten pool. In addition, numerical simulation was carried out with the same parameter setting schemes, the results of which are consistent with those in radiation detection experiments. It is shown that the laser power has the greatest effect on the radiation of the molten pool, while the scanning speed and the hatch spacing have little effect on the radiation. Finally, the positioning experiment involving the small hole structure was carried out, and the experimental results showed that the device could accurately locate the position coordinates of the given hole structure. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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13 pages, 4908 KiB

Open AccessArticle

Effects of Heat Treatment on the Microstructure and Mechanical Properties of a Dual-Phase High-Entropy Alloy Fabricated via Laser Beam Power Bed Fusion

by Xiaojun Tan, Zihong Wang, Haitao Chen, Xuyun Peng, Wei Zhang, Haibing Xiao, Zhongmin Liu, Yu Hu, Liang Guo and Qingmao Zhang

Micromachines 2024, 15(4), 471; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15040471 - 29 Mar 2024

Viewed by 635

Abstract

To enhance the applicability of dual-phase high-entropy alloys (HEAs) like Fe32Cr33Ni29Al3Ti3, fabricated via laser beam power bed fusion (LB-PBF), a focus on improving their mechanical properties is essential. As part of this effort, heat treatment was explored. This study compares the microstructure and [...] Read more.

To enhance the applicability of dual-phase high-entropy alloys (HEAs) like Fe32Cr33Ni29Al3Ti3, fabricated via laser beam power bed fusion (LB-PBF), a focus on improving their mechanical properties is essential. As part of this effort, heat treatment was explored. This study compares the microstructure and mechanical properties of the as-printed sample with those cooled in water after undergoing heat treatment at temperatures ranging from 1000 to 1200 °C for 1 h. Both pre- and post-treatment samples reveal a dual-phase microstructure comprising FCC and BCC phases. Although heat treatment led to a reduction in tensile and yield strength, it significantly increased ductility compared to the as-printed sample. This strength-ductility trade-off is related to changes in grain sizes with ultrafine grains enhancing strength and micron grains optimizing ductility, also influencing the content of FCC/BCC phases and dislocation density. In particular, the sample heat-treated at 1000 °C for 1 h and then water-cooled exhibited a better combination of strength and ductility, a yield strength of 790 MPa, and an elongation of 13%. This research offers innovative perspectives on crafting dual-phase HEA of Fe32Cr33Ni29Al3Ti3, allowing for tailorable microstructure and mechanical properties through a synergistic approach involving LB-PBF and heat treatment. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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15 pages, 10199 KiB

Open AccessArticle

Study on Laser-Electrochemical Hybrid Polishing of Selective Laser Melted 316L Stainless Steel

by Jun Liu, Chunbo Li, Huan Yang, Jiani Liu, Jiayan Wang, Leimin Deng, Licun Fang and Can Yang

Micromachines 2024, 15(3), 374; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15030374 - 11 Mar 2024

Viewed by 810

Abstract

The process of forming metal components through selective laser melting (SLM) results in inherent spherical effects, powder adhesion, and step effects, which collectively lead to surface roughness in stainless steel, limiting its potential for high-end applications. This study utilizes a laser-electrochemical hybrid process [...] Read more.

The process of forming metal components through selective laser melting (SLM) results in inherent spherical effects, powder adhesion, and step effects, which collectively lead to surface roughness in stainless steel, limiting its potential for high-end applications. This study utilizes a laser-electrochemical hybrid process to polish SLM-formed 316L stainless steel (SS) and examines the influence of process parameters such as laser power and scanning speed on surface roughness and micro-morphology. A comparative analysis of the surface roughness, microstructure, and wear resistance of SLM-formed 316L SS polished using laser, electrochemical, and laser-electrochemical hybrid processes is presented. The findings demonstrate that, compared to laser and electrochemical polishing alone, the laser-electrochemical hybrid polishing exhibits the most significant improvement in surface roughness and the highest material wear resistance. Additionally, the hybrid process results in a surface free of cracks and only a small number of tiny corrosion holes, making it more suitable for polishing the surface of 316L SS parts manufactured via SLM. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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28 pages, 22560 KiB

Open AccessArticle

Surface Roughness of Interior Fine Flow Channels in Selective Laser Melted Ti-6Al-4V Alloy Components

by Shamoon Al Islam, Liang Hao, Zunaira Javaid, Wei Xiong, Yan Li, Yasir Jamil, Qiaoyu Chen and Guangchao Han

Micromachines 2024, 15(3), 348; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15030348 - 29 Feb 2024

Viewed by 942

Abstract

A challenge remains in achieving adequate surface roughness of SLM fabricated interior channels, which is crucial for fuel delivery in the space industry. This study investigated the surface roughness of interior fine flow channels (1 mm diameter) embedded in SLM fabricated TC4 alloy [...] Read more.

A challenge remains in achieving adequate surface roughness of SLM fabricated interior channels, which is crucial for fuel delivery in the space industry. This study investigated the surface roughness of interior fine flow channels (1 mm diameter) embedded in SLM fabricated TC4 alloy space components. A machine learning approach identified layer thickness as a significant factor affecting interior channel surface roughness, with an importance score of 1.184, followed by scan speed and laser power with scores of 0.758 and 0.512, respectively. The roughness resulted from thin layer thickness of 20 µm, predominantly formed through powder adherence, while from thicker layer of 50 µm, the roughness was mainly due to the stair step effect. Slow scan speeds increased melt pools solidification time at roof overhangs, causing molten metal to sag under gravity. Higher laser power increased melt pools temperature and led to dross formation at roof overhangs. Smaller hatch spaces increased roughness due to overlapping of melt tracks, while larger hatch spaces reduced surface roughness but led to decreased part density. The surface roughness was recorded at 34 µm for roof areas and 26.15 µm for floor areas. These findings contribute to potential adoption of TC4 alloy components in the space industry. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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15 pages, 8662 KiB

Open AccessArticle

A Framework to Simulate Friction Stir Additive Manufacturing (FSAM) Using the Finite Element Method

by Bahman Meyghani and Reza Teimouri

Micromachines 2024, 15(3), 303; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15030303 - 23 Feb 2024

Viewed by 847

Abstract

Defining an accurate friction model without having the mesh distortion in an optimized computational time has always been a significant challenge for modelling solid-state natural processes. The presented paper proposes an Eulerian frictional-based solid static model for the accurate modeling of sliding and [...] Read more.

Defining an accurate friction model without having the mesh distortion in an optimized computational time has always been a significant challenge for modelling solid-state natural processes. The presented paper proposes an Eulerian frictional-based solid static model for the accurate modeling of sliding and sticking conditions for the friction stir additive manufacturing process (FSAM). For the frictional behavior, a modified friction model is proposed to investigate the sliding and sticking conditions during the process. The magnesium alloy is selected as the workpiece material and AZ31B-F is employed as the filler material. Two different subroutines, Dflux and Sfilm, are used in order to simulate the heat flux during the process. The convection and emission during the process are determined using the Goldak double ellipsoidal model. DC3D8 and C3D8R elements are employed as the thermal and mechanical models, respectively. The results indicated that the temperature sharply increased up to 870 °C in the first and the second layers. After that, the increasing rate becomes slower with a maxim temperature of 1310 °C. A linear cooling behavior is obtained at the cooling step. The stress results indicated that the tool and the filler material pressure play a significant role in increasing the stress at the center of the workpiece. On the sides of the workpiece, a peak stress is also obtained due to the clamping force. At the cooling phase for the center of the workpiece, the longitudinal residual stress of 5 MP and transverse residual stress of 7 MPa (compression) are achieved. The distortion of the workpiece is also investigated and a maximum value of 0.13 mm is obtained. To wrap up, it should be noted that by implementing an accurate sliding/sticking condition in a frictional based model, a more comprehensive investigation about frictional interactions and their influence on thermal and mechanical behavior can be carried out. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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12 pages, 3531 KiB

Open AccessArticle

Laser Rescanning for Enhancing Mechanical Properties of Laser-Directed Energy-Deposited High-Manganese Steels

by Young Keun Park, Hyun Ji Nam, Yong Ho Park and Wookjin Lee

Micromachines 2024, 15(2), 176; https://0-doi-org.brum.beds.ac.uk/10.3390/mi15020176 - 24 Jan 2024

Viewed by 843

Abstract

This study investigates the effects of laser deposition and laser rescanning (LR) on the microstructure and mechanical properties of high-manganese steel (HMnS) deposited by laser-directed energy deposition (L-DED) comprising 24 wt.% Mn. Four types of laser deposition and LR strategies were investigated: unidirectional [...] Read more.

This study investigates the effects of laser deposition and laser rescanning (LR) on the microstructure and mechanical properties of high-manganese steel (HMnS) deposited by laser-directed energy deposition (L-DED) comprising 24 wt.% Mn. Four types of laser deposition and LR strategies were investigated: unidirectional L-DED scanning without laser rescanning, L-DED scanning with 90° alterations in the laser scanning path on each layer without laser rescanning, unidirectional L-DED with laser rescanning in the same direction, and L-DED with laser rescanning with 90° alterations in the laser scanning path. The L-DED-processed HMnS had only a few small pores and exhibited a microstructure without any serious defects such as cracks. Additionally, a strong fibrous texture along the <101>/building direction of the fully austenite phase was found. The mechanical properties (microhardness and tensile strength) of HMnS were improved by the LR with a grain refinement effect and fine solidification cell size due to the significantly faster solidification rate in LR than that in L-DED. Full article

(This article belongs to the Special Issue Advanced Additive Manufacturing Techniques: From Fundamental Research to Applications)

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