Research

17 pages, 10606 KiB

Open AccessArticle

Design and Manufacture of a Micro-Ejector and the Testing Stand for Investigation of Micro-Ejector Refrigeration Systems

by Kamil Śmierciew, Dariusz Butrymowicz, Jerzy Gagan, Paweł Jakończuk and Mateusz Pawłowski

Micromachines 2024, 15(4), 429; https://doi.org/10.3390/mi15040429 - 23 Mar 2024

Viewed by 646

Abstract

This paper describes the procedure of design and manufacture of a micro-ejector proposed for miniature ejection refrigeration systems. It describes the procedure of design, fabrication, and experimentation on supersonic micro-ejectors and makes the case for isobutane as a working fluid for such systems. [...] Read more.

This paper describes the procedure of design and manufacture of a micro-ejector proposed for miniature ejection refrigeration systems. It describes the procedure of design, fabrication, and experimentation on supersonic micro-ejectors and makes the case for isobutane as a working fluid for such systems. It was demonstrated that it is possible to design and fabricate a micro-ejector with a cooling capacity of approximately 3 W. The discussed micro-ejector was driven by a heat source with temperature below 60 °C. The evaporation temperature was approximately 15 °C. For these operating parameters, the reported entrainment ratio was approximately 0.20. The difficulties in fabricating the micro-ejector due to its small dimensions are discussed in the paper. Additionally, the potential difficulties and solutions related to ensuring and maintaining stable operation of the testing stand are presented. The performance of the proposed system is demonstrated and discussed, including relations between mass entrainment ratio, compression ratio, cooling capacity, and temperature. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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17 pages, 2968 KiB

Open AccessArticle

Microfabricating Mirror-like Surface Precision Micro-Sized Amorphous Alloy Structures Using Jet-ECM Process

by Lei Han, Pingmei Ming, Shen Niu, Guangbin Yang, Dongdong Li and Kuaile Cheng

Micromachines 2024, 15(3), 375; https://doi.org/10.3390/mi15030375 - 11 Mar 2024

Viewed by 618

Abstract

Amorphous alloy (AA) is a high-performance metal material generally with significantly excellent mechanical and corrosion resistance properties and thus is considered as a desirable material selection for micro-scale articles. However, the microfabrication of AA still faces a variety of technical challenges mainly because [...] Read more.

Amorphous alloy (AA) is a high-performance metal material generally with significantly excellent mechanical and corrosion resistance properties and thus is considered as a desirable material selection for micro-scale articles. However, the microfabrication of AA still faces a variety of technical challenges mainly because the materials are too hard to process and easily lose their original properties, although at moderately high temperatures. In this study, jet-electrolyte electrochemical machining (Jet-ECM) was proposed to microfabricate the Zr-based AA because it is a low-temperature material-removal process based on the anode dissolution mechanism. The electrochemical dissolution characteristics and material removal mechanism of AA were investigated, and then the optimal process parameters were achieved based on the evaluation of the surface morphologies, surface roughness, geometrical profile, and machining accuracy of the machined micro-dimples. Finally, the feasibility was further studied by using Jet-ECM to fabricate arrayed micro-dimples using the optimized parameters. It was found that Jet-ECM can successfully microfabricate mirror-like surface AA arrayed precision micro-dimples with significantly high dimensional accuracy and geometrical consistency. Jet-ECM is a promisingly advantageous microfabrication process for the hard-to-machine AA. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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18 pages, 3623 KiB

Open AccessArticle

Tool Run-Out in Micro-Milling: Development of an Analytical Model Based on Cutting Force Signal Analysis

by Andrea Abeni, Cristian Cappellini, Greta Seneci, Antonio Del Prete and Aldo Attanasio

Micromachines 2024, 15(3), 305; https://doi.org/10.3390/mi15030305 - 23 Feb 2024

Viewed by 575

Abstract

Micro-machining is a widespread finishing process for fabricating accurate parts as biomedical devices. The continuous effort in reducing the gap between the micro- and macro-domains is connected to the transition from conventional to micro-scale machining. This process generates several undesired issues, which complicate [...] Read more.

Micro-machining is a widespread finishing process for fabricating accurate parts as biomedical devices. The continuous effort in reducing the gap between the micro- and macro-domains is connected to the transition from conventional to micro-scale machining. This process generates several undesired issues, which complicate the process’s optimization, and tool run-out is one of the most difficult phenomena to experimentally investigate. This work focuses on its analytical description; in particular, a new method to calibrate the model parameters based on cutting force signal elaboration is described. Today, run-out prevision requires time-consuming geometrical measurements, and the main aim of our innovative model is to make the analysis completely free from dimensional measurements. The procedure was tested on data extrapolated from the micro-machining of additively manufactured AlSi10Mg specimens. The strategy appears promising because it is built on a strong mathematical basis, and it may be developed in further studies. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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13 pages, 11499 KiB

Open AccessArticle

Jet Electrochemical Micromilling of Ti-6Al-4V Using NaCl–Ethylene Glycol Electrolyte

by Shen Niu, Kaiqiang Huang, Pingmei Ming, Siru Wang, Fei Zhao, Ge Qin and Huan Liu

Micromachines 2024, 15(2), 173; https://doi.org/10.3390/mi15020173 - 24 Jan 2024

Cited by 1 | Viewed by 698

Abstract

Titanium alloys are widely used in aerospace and biomedicine because of their excellent mechanical characteristics, but these properties also make such alloys difficult to cut. Jet electrochemical micromilling (JEMM) is based on the principle of electrochemical anodic dissolution; it has some inherent advantages [...] Read more.

Titanium alloys are widely used in aerospace and biomedicine because of their excellent mechanical characteristics, but these properties also make such alloys difficult to cut. Jet electrochemical micromilling (JEMM) is based on the principle of electrochemical anodic dissolution; it has some inherent advantages for the machining of titanium alloy microstructures. However, titanium oxidizes readily, forming an oxide film that impedes a uniform dissolution during electrochemical machining. Therefore, a high voltage and an aqueous NaCl electrolyte are usually used to break the oxide film, which can lead to severe stray corrosion. To overcome this problem, the present study investigated the JEMM of Ti-6Al-4V using a NaCl–ethylene glycol (NaCl-EG) electrolyte. Electrochemical testing showed that Ti-6Al-4V exhibits a better corrosion resistance in the NaCl-EG electrolyte compared to the aqueous NaCl electrolyte, thereby reducing stray corrosion. The localization and surface quality of the grooves were enhanced significantly when using JEMM with a NaCl-EG electrolyte. A multiple-pass strategy was adopted during JEMM to improve the aspect ratio, and the effects of the feed depth and number of passes on the multiple-pass machining performance were investigated. Ultimately, a square annular microstructure with a high geometric dimensional consistency and a smooth surface was obtained via JEMM with multiple passes using the optimal parameters. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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24 pages, 18976 KiB

Open AccessArticle

Experimental Study on the Roundness of Deep Holes in 7075 Aluminum Alloy Parts by Two-Dimensional Ultrasonic Elliptical Vibration Boring

by Shuaikun Yang, Jinglin Tong, Ziqiang Liu, Yanqiu Ye, Haojie Zhai and Hongqing Tao

Micromachines 2023, 14(12), 2185; https://doi.org/10.3390/mi14122185 - 30 Nov 2023

Viewed by 687

Abstract

The 7075 aluminum alloy deep hole pipe finds extensive applications in the aerospace industry due to its remarkable attributes, such as high strength, exceptional wear resistance, and favorable mechanical properties. However, traditional boring processes for 7075 aluminum alloy deep hole pipes tend to [...] Read more.

The 7075 aluminum alloy deep hole pipe finds extensive applications in the aerospace industry due to its remarkable attributes, such as high strength, exceptional wear resistance, and favorable mechanical properties. However, traditional boring processes for 7075 aluminum alloy deep hole pipes tend to generate elevated cutting forces, potentially leading to deformation issues in these deep holes. In response to these challenges, this study introduces a novel approach involving the use of a two-dimensional ultrasonic elliptical vibration tool. This tool features a single excitation asymmetric structure and aims to enhance the deep hole machining process in 7075 aluminum alloy. The research methodology involved several key steps. First, theoretical analysis and simulation were performed to study the motion trajectory of the cutting edge of the tool. Second, practical experiments were conducted comparing two-dimensional ultrasonic elliptical vibration boring with conventional boring for 7075 aluminum alloy deep hole pipes. The results demonstrate that, in contrast to conventional boring, two-dimensional ultrasonic vibration boring could achieve a maximum reduction of 54.1% and an average reduction of 50.4% in the roundness value of the deep holes. The impact of machining parameters on deep hole roundness is assessed through experimental analysis, leading to the determination of optimal processing parameters. In summary, this experimental research has a certain reference significance for the application of 7075 aluminum alloy deep hole parts in the aerospace field. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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12 pages, 9065 KiB

Open AccessArticle

Optimization of Machining Parameters to Minimize Cutting Forces and Surface Roughness in Micro-Milling of Mg13Sn Alloy

by Ali Ercetin, Kubilay Aslantaş, Özgür Özgün, Mustafa Perçin and Manjunath Patel Gowdru Chandrashekarappa

Micromachines 2023, 14(8), 1590; https://doi.org/10.3390/mi14081590 - 12 Aug 2023

Cited by 7 | Viewed by 1620

Abstract

This comprehensive study investigates the micro-milling of a Mg13Sn alloy, a material of considerable interest in various high-precision applications, such as biomedical implants. The main objective of the study was to explore the optimizations of variable feed per tooth (fz), cutting speed (Vc), [...] Read more.

This comprehensive study investigates the micro-milling of a Mg13Sn alloy, a material of considerable interest in various high-precision applications, such as biomedical implants. The main objective of the study was to explore the optimizations of variable feed per tooth (fz), cutting speed (Vc), and depth of cut (ap) parameters on the key outcomes of the micro-milling process. A unique experimental setup was employed, employing a spindle capable of achieving up to 60,000 revolutions per minute. Additionally, the study leveraged linear slides backed by micro-step motors to facilitate precise axis movements, thereby maintaining a resolution accuracy of 0.1 μm. Cutting forces were accurately captured by a mini dynamometer and subsequently evaluated based on the peak to valley values for Fx (tangential force) and Fy (feed force). The study results revealed a clear and complex interplay between the varied cutting parameters and their subsequent impacts on the cutting forces and surface roughness. An increase in feed rate and depth of cut significantly increased the cutting forces. However, the cutting forces were found to decrease noticeably with the elevation of cutting speed. Intriguingly, the tangential force (Fx) was consistently higher than the feed force (Fy). Simultaneously, the study determined that the surface roughness, denoted by Sa values, increased in direct proportion to the feed rate. It was also found that the Sa surface roughness values decreased with the increase in cutting speed. This study recommends a parameter combination of fz = 5 µm/tooth feed rate, Vc = 62.8 m/min cutting speed, and ap = 400 µm depth of cut to maintain a Sa surface roughness value of less than 1 µm while ensuring an optimal material removal rate and machining time. The results derived from this study offer vital insights into the micro-milling of Mg13Sn alloys and contribute to the current body of knowledge on the topic. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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21 pages, 14254 KiB

Open AccessArticle

Effect of Drilling Parameters and Tool Geometry on the Thrust Force and Surface Roughness of Aerospace Grade Laminate Composites

by Çağın Bolat, Uçan Karakılınç, Bekir Yalçın, Yahya Öz, Çağlar Yavaş, Berkay Ergene, Ali Ercetin and Fatih Akkoyun

Micromachines 2023, 14(7), 1427; https://doi.org/10.3390/mi14071427 - 15 Jul 2023

Cited by 11 | Viewed by 1876

Abstract

Carbon fiber-reinforced plastics (CFRPs) have been specially developed to enhance the performance of commercial and military aircraft because of their strength, high stiffness-to-density ratios, and superior physical properties. On the other hand, fasteners and joints of CFRP materials may be weak due to [...] Read more.

Carbon fiber-reinforced plastics (CFRPs) have been specially developed to enhance the performance of commercial and military aircraft because of their strength, high stiffness-to-density ratios, and superior physical properties. On the other hand, fasteners and joints of CFRP materials may be weak due to occurring surface roughness and delamination problems during drilling operations. This study’s aim is to investigate the drilling characterization of CFRPs with different drilling parameters and cutting tools. Drilling tests were performed with the Taguchi orthogonal array design (L18: 2^1 3^3). Tests were conducted with three levels of cutting speed (15, 30, 45 m/min), three levels of feed rate (0.05, 0.1, 0.2 mm/rev), two levels of drill diameter (3 and 5 mm), and three different types of drills (two twist drills with a point angle of 138° and 120° and one brad drill). Thrust forces were recorded during drilling tests, and afterwards surface roughness and hole delamination were measured. Obtained results were analyzed with Taguchi and two-way ANOVA. The general tendency was that low cutting speed, high feed rate, and small diameter drill caused an increase in thrust force. Surface roughness decreases with increasing tool diameter, decreasing feed, and cutting speed. Delamination factors of the samples dropped depending on decreasing thrust force levels. Remarkably, it is possible to control the delamination factor values via better surface quality. The brad drill and larger point angle have a negative effect on the drilling quality of CFRPs. According to all results, the cutting speed of 45 m/min and feed rate of 0.05 mm/rev using a type II drill having a 120° point angle and 5 mm diameter (12th trial) and the cutting speed of 30 m/min and feed rate of 0.05 mm/rev using a type II drill having a 120° point angle and 3 mm diameter (2nd trial) were determined as optimum drilling conditions. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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17 pages, 9358 KiB

Open AccessArticle

A Non-Sacrificial 3D Printing Process for Fabricating Integrated Micro/Mesoscale Molds

by Amirreza Ghaznavi, Jie Xu and Seth A. Hara

Micromachines 2023, 14(7), 1363; https://doi.org/10.3390/mi14071363 - 30 Jun 2023

Viewed by 1374

Abstract

Three-dimensional printing technology has been implemented in microfluidic mold fabrication due to its freedom of design, speed, and low-cost fabrication. To facilitate mold fabrication processes and avoid the complexities of the soft lithography technique, we offer a non-sacrificial approach to fabricate microscale features [...] Read more.

Three-dimensional printing technology has been implemented in microfluidic mold fabrication due to its freedom of design, speed, and low-cost fabrication. To facilitate mold fabrication processes and avoid the complexities of the soft lithography technique, we offer a non-sacrificial approach to fabricate microscale features along with mesoscale features using Stereolithography (SLA) printers to assemble a modular microfluidic mold. This helps with addressing an existing limitation with fabricating complex and time-consuming micro/mesoscale devices. The process flow, optimization of print time and feature resolution, alignments of modular devices, and the advantages and limitations with the offered technique are discussed in this paper. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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12 pages, 6439 KiB

Open AccessArticle

Ultrafast-Laser-Induced Tailoring of Crystal-in-Glass Waveguides by Precision Partial Remelting

by Alexey S. Lipatiev, Sergey V. Lotarev, Tatiana O. Lipateva, Sergey S. Fedotov, Elena V. Lopatina and Vladimir N. Sigaev

Micromachines 2023, 14(4), 801; https://doi.org/10.3390/mi14040801 - 31 Mar 2023

Cited by 1 | Viewed by 1249

Abstract

Space-selective laser-induced crystallization of glass enables direct femtosecond laser writing of crystal-in-glass channel waveguides having nearly single-crystal structure and consisting of functional phases with favorable nonlinear optical or electrooptical properties. They are regarded as promising components for novel integrated optical circuits. However, femtosecond-laser-written [...] Read more.

Space-selective laser-induced crystallization of glass enables direct femtosecond laser writing of crystal-in-glass channel waveguides having nearly single-crystal structure and consisting of functional phases with favorable nonlinear optical or electrooptical properties. They are regarded as promising components for novel integrated optical circuits. However, femtosecond-laser-written continuous crystalline tracks typically have an asymmetric and strongly elongated cross-section, which causes a multimode character of light guiding and substantial coupling losses. Here, we investigated the conditions of partial remelting of laser-written LaBGeO₅ crystalline tracks in lanthanum borogermanate glass by the same femtosecond laser beam which had been used for their writing. Exposure to femtosecond laser pulses at 200 kHz repetition rate provided cumulative heating of the sample in the vicinity of the beam waist sufficient to provide space-selective melting of crystalline LaBGeO₅. To form a smoother temperature field, the beam waist was moved along the helical or flat sinusoidal path along the track. The sinusoidal path was shown to be favorable for tailoring the improved cross-section of the crystalline lines by partial remelting. At optimized laser processing parameters, most of the track was vitrified, and the residual part of the crystalline cross-section had an aspect ratio of about 1:1. Thermal-induced stress emerging during the tailoring procedure was efficiently eliminated by fine post-annealing. The proposed technique suggests a new way to control the morphology of laser-written crystal-in-glass waveguides by tailoring their cross-section, which is expected to improve the mode structure of the guided light. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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20 pages, 9228 KiB

Open AccessArticle

Theoretical and Experimental Study of Friction Characteristics of Textured Journal Bearing

by Hongtao Wang, Wenbo Bie, Shaolin Zhang and Tengfei Liu

Micromachines 2023, 14(3), 577; https://doi.org/10.3390/mi14030577 - 28 Feb 2023

Cited by 1 | Viewed by 1467

Abstract

The proposed lubrication theory of textured journal bearing is a major innovation in the study of the tribological properties of surface morphology. When it comes to the study of surface topography, it is essential to consider the effect of surface roughness when analyzing [...] Read more.

The proposed lubrication theory of textured journal bearing is a major innovation in the study of the tribological properties of surface morphology. When it comes to the study of surface topography, it is essential to consider the effect of surface roughness when analyzing the characteristics of journal bearing. In this paper, a Reynolds equation containing longitudinal roughness is established for journal bearing and solved by the finite difference principle to obtain the bearing load and friction characteristics. Subsequently, a combination of laser etching and ultrasonic vibration milling processes was used to prepare 5 µm, 20 µm, and 40 µm bearing friction subsets with square micro-texture surfaces. The analysis of the results shows that the surface roughness distributed in the non-texture region can substantially increase the oil film pressure. When the roughness profile and the surface weave work together, the presence of a surface texture with an optimum depth of 5 µm within a roughness range of less than 1.6 µm can improve the load-bearing characteristics by a maximum of 43%. In the study of the preparation of textured bearing friction substrate, it was found that laser etching can ablate the surface of the friction substrate to a depth greater than 20 µm with the ideal effect, while the surface texturing to a depth of 5 µm is more suitable using an ultrasonic vibration processing process. In the simplified journal bearing operating condition, the frictional wear test shows that if the effect of roughness is considered, the frictional force of the depth of 20 µm and 40 µm is significantly reduced and changes less with increasing load, while the frictional force of the textured frictional pair with a depth of 5 µm is improved but significantly affected by the load carrying capacity. Therefore, when the difference between the roughness profile and the depth of the texture is of a small order of magnitude, it indicates that the effect caused by the roughness factor is not negligible. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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13 pages, 9269 KiB

Open AccessArticle

Research on the Cutting Force and Serrated Chips in Ultra-Precision Micro-Grooving of SLM Ti6Al4V Alloy

by Zhongpeng Zheng, Jiajing Guo, Ruilin Gao and Xin Jin

Micromachines 2023, 14(3), 533; https://doi.org/10.3390/mi14030533 - 24 Feb 2023

Cited by 1 | Viewed by 1145

Abstract

Selective laser melting (SLM) has significant advantages in the near net shape manufacturing of metal parts with complex geometries. However, SLM parts usually have problems such as poor surface quality and low dimensional accuracy, which require post-processing. This paper focuses on the research [...] Read more.

Selective laser melting (SLM) has significant advantages in the near net shape manufacturing of metal parts with complex geometries. However, SLM parts usually have problems such as poor surface quality and low dimensional accuracy, which require post-processing. This paper focuses on the research around the influence of ultra-precision micro-grooving the SLM Ti6Al4V alloy on the cutting force and serrated chips. The influence of the processing parameters on the cutting force and surface processing quality was analyzed in detail, and the cutting simulation model of the SLM Ti6Al4V alloy was established. The formation process of the serrated chip was successfully simulated, and the experiments verified the reliability of the established model. The research results show that the dynamic cutting force and surface processing quality are mainly related to the depth of cut, and the two trends are consistent. It is also shown that the serrated chip begins on the free surface of the workpiece and propagates deeply in the shear zone, forming a shear band, and its serrated nodules move upward and forward to form periodic serrated chips. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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11 pages, 9304 KiB

Open AccessArticle

Influences of Material Selection, Infill Ratio, and Layer Height in the 3D Printing Cavity Process on the Surface Roughness of Printed Patterns and Casted Products in Investment Casting

by Thanh Tan Nguyen, Van Tron Tran, Thi Hong Nga Pham, Van-Thuc Nguyen, Nguyen Chi Thanh, Hong Minh Nguyen Thi, Nguyen Vu Anh Duy, Duy Nguyen Thanh and Van Thanh Tien Nguyen

Micromachines 2023, 14(2), 395; https://doi.org/10.3390/mi14020395 - 05 Feb 2023

Cited by 17 | Viewed by 2157

Abstract

As 3D-printed (3DP) patterns are solid and durable, they can be used to create thin wall castings, which is complicated with wax patterns because of the wax’s fragility and high shrinkage ratio. According to this study’s experiment results, polylactic acid (PLA), polyvinyl butyral [...] Read more.

As 3D-printed (3DP) patterns are solid and durable, they can be used to create thin wall castings, which is complicated with wax patterns because of the wax’s fragility and high shrinkage ratio. According to this study’s experiment results, polylactic acid (PLA), polyvinyl butyral (PVB), and castable wax (CW) are suitable materials for preparing investment casting (IC) cavities. The results indicate that the casting product with the highest-quality surface is obtained using a cavity prepared using a CW-printed pattern. PLA- and PVB-printed patterns provide a good surface finish for casted products. In addition, the roughness of both the printed and casted surfaces increases as the printing layer height increases. The roughness of the casted surface varies from 2.25 μm to 29.17 μm. This investigation also considers the correlation between the infill ratio and mechanical properties of PLA-printed patterns. An increase in the infill ratios from 0% to 100% leads to a significant increase in the tensile properties of the PLA-printed pattern. The obtained results can be practically used. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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16 pages, 31652 KiB

Open AccessArticle

Comparative Study about Dimensional Accuracy and Surface Finish of Constant-Breadth Cams Manufactured by FFF and CNC Milling

by Enrique E. Zayas-Figueras and Irene Buj-Corral

Micromachines 2023, 14(2), 377; https://doi.org/10.3390/mi14020377 - 02 Feb 2023

Cited by 2 | Viewed by 1490

Abstract

In this work, the design, manufacture and measurement process of constant-breadth cams is presented. The motion law of the cam was designed by means of Bézier curves and the corresponding design desmodromic constraints. The cams were manufactured in two different materials employing two [...] Read more.

In this work, the design, manufacture and measurement process of constant-breadth cams is presented. The motion law of the cam was designed by means of Bézier curves and the corresponding design desmodromic constraints. The cams were manufactured in two different materials employing two different processes: PLA cams with fused filament fabrication (FFF) and aluminium cams with computer numerical control (CNC) milling. The main aim of this work is to compare both types of cams regarding dimensional accuracy and surface finish, in order to evaluate if it would be possible to temporally replace a metallic cam with a plastic one during the repair of the first one. Dimensions were measured with micrometres and surface roughness with a contact roughness meter. The results show that, in diametral dimensions, similar dimensional error values were obtained for both the 3D-printed and the machined cams. However, in longitudinal dimensions, whose direction is perpendicular to the 3D-printed layers, the 3D-printed cams showed higher dimensional error than the machined ones. The average roughness R_a in the 3D-printed cams was 20 times higher than in the milled cams. According to the results, it would be recommended to temporally replace metallic cams with plastic ones in applications of low-power transmission. Given that in the literature little information is available about the measurement of 3D-printed desmodromic cams, this work will contribute to the study and analysis of this kind of 3D printed mechanism. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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16 pages, 4281 KiB

Open AccessArticle

Evaluation of Thin Wall Milling Ability Using Disc Cutters

by Adelina Hrițuc, Andrei Marius Mihalache, Oana Dodun, Laurențiu Slătineanu and Gheorghe Nagîț

Micromachines 2023, 14(2), 341; https://doi.org/10.3390/mi14020341 - 28 Jan 2023

Cited by 1 | Viewed by 1036

Abstract

In some cases, industrial practice requires the production of walls or parts with a thickness of less than one millimeter from a metal workpiece. Such parts or walls can be made by milling using disc cutters. This machining method can lead to the [...] Read more.

In some cases, industrial practice requires the production of walls or parts with a thickness of less than one millimeter from a metal workpiece. Such parts or walls can be made by milling using disc cutters. This machining method can lead to the generation of residual stresses that determine the appearance of a form deviation characterized by bending the part or the thin wall. To evaluate the suitability of a metallic material for the manufacturing of thin walls by milling with disc cutters, different factors capable of exerting influence on the deviation generated by the residual deformation of the walls were taken into account. A test sample and an experimental research program were designed for the purpose of obtaining an empirical mathematical model. The empirical mathematical model highlights the magnitude of the influence exerted by different input factors on the disc cutter milling process regarding the size of the deviation from the form, and the correct position of the wall or thin part, in the case of a test sample workpiece made of an aluminum alloy. Input factors considered were cutting speed, feed rate, cutter thickness, wall or part thickness, thin wall length, and height. To rank the input factors whose increase leads to an increase in shape deviation, the values of the exponents attached to the factors in question in the empirical mathematical model of the power-type function were taken into account. It was found that the values of the exponents are in the order 0.782 > 0.319 > 0.169 for wall height, feed rate, and wall width, respectively. It was thus established that the strongest influence on the residual deformation of the thin wall is exerted by its height. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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17 pages, 10562 KiB

Open AccessArticle

Structural Design of a Special Machine Tool for Internal Cylindrical Ultrasonic-Assisted Electrochemical Grinding

by Xiaosan Ma, Feng Jiao, Wenbo Bie, Ying Niu, Shuaizhen Chu, Zhanzhan Hu and Xiaohong Yang

Micromachines 2023, 14(1), 222; https://doi.org/10.3390/mi14010222 - 15 Jan 2023

Cited by 1 | Viewed by 2177

Abstract

During the process of internal cylindrical ultrasonic-assisted electrochemical grinding (ICUAECG), both the workpiece and the conductive grinding wheel are rotating, the machining space is closed and narrow, the electrolyte is difficult to spray into the machining area, and the insulation between the workpiece [...] Read more.

During the process of internal cylindrical ultrasonic-assisted electrochemical grinding (ICUAECG), both the workpiece and the conductive grinding wheel are rotating, the machining space is closed and narrow, the electrolyte is difficult to spray into the machining area, and the insulation between the workpiece and the machine bed is challenging. According to the machining characteristics of ICUAECG, the structure of a special machine tool was designed to mitigate these problems. In particular, the rotation, electrolyte supply, electric connection, and insulation modes of the workpiece clamping parts were studied, yielding a novel workpiece clamping- and rotating-device design. This structure can fully use the internal space of the hollow spindle of the machine tool, effectively reduce the external moving parts, and achieve the appropriate liquid injection angle of the electrolyte. The ultrasonic vibration system and its installation mechanism, the dressing device of the conductive grinding wheel, and the electric grinding spindle-mounting and -fixing device were analyzed in detail. Then, a special machine tool for ICUAECG was designed, the operability and feasibility of which were verified by experiments involving conductive grinding wheel dressing and ICUAECG. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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18 pages, 18683 KiB

Open AccessArticle

On the Behavior of Honeycomb, Grid and Triangular PLA Structures under Symmetric and Asymmetric Bending

by Vasile Cojocaru, Doina Frunzaverde and Calin-Octavian Miclosina

Micromachines 2023, 14(1), 120; https://doi.org/10.3390/mi14010120 - 31 Dec 2022

Cited by 1 | Viewed by 1965

Abstract

Additive manufacturing technologies enable the production of components with lightweight cores, by means of infills with various patterns and densities. Together with reduced mass and material consumption, infill geometries must ensure that strength and stiffness conditions are fulfilled. For the proper correlation of [...] Read more.

Additive manufacturing technologies enable the production of components with lightweight cores, by means of infills with various patterns and densities. Together with reduced mass and material consumption, infill geometries must ensure that strength and stiffness conditions are fulfilled. For the proper correlation of the infill type with the loading case of the part, the mechanical behavior of the infill along all three principal axes of inertia has to be known. In this paper, the behavior in symmetric and asymmetric bending of three infill geometries, commonly used in 3D printing processes (honeycomb, grid and triangles) is analyzed. The variations of deflections as a function of force orientation are presented, showing that honeycomb and triangular structures exhibit similar behaviors along the Y and Z principal axes of inertia. Furthermore, the displacements obtained for the three types of structures are compared, in relation to the consumed volume of material. The larger displacements of the grid structure compared to the honeycomb and triangular structures are highlighted. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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10 pages, 5163 KiB

Open AccessArticle

Study on the Fatigue Strength of Welding Line in Injection Molding Products under Different Tensile Conditions

by Pham Son Minh, Van-Thuc Nguyen, Vinh Tien Nguyen, Tran Minh The Uyen, Thanh Trung Do and Van Thanh Tien Nguyen

Micromachines 2022, 13(11), 1890; https://doi.org/10.3390/mi13111890 - 02 Nov 2022

Cited by 17 | Viewed by 1695

Abstract

The fatigue performance of polypropylene (PP) at various amplitudes and frequencies on fatigue cycles under tensile test conditions is investigated in this study. The results show that increasing the frequency leads to a decrease in fatigue cycles due to increased cycle time. The [...] Read more.

The fatigue performance of polypropylene (PP) at various amplitudes and frequencies on fatigue cycles under tensile test conditions is investigated in this study. The results show that increasing the frequency leads to a decrease in fatigue cycles due to increased cycle time. The decline rate can be divided into two stages, between 1 and 5 Hz. The first stage rapidly decreases fatigue performance as the frequency increases from 1 Hz to 2 Hz or 3 Hz. The second stage has a lower reduction rate, which occurs between 2 Hz or 3 Hz and 5 Hz due to the strengthening effect of increasing frequency. Furthermore, increasing the amplitude from 0.1 mm to 0.4 mm reduces the fatigue cycle due to the higher deformation rate. In summary, expanding both amplitude and frequency reduces the fatigue performance of the PP material. Moreover, according to the scanning electron microscope microstructure, increasing the frequency results in more microcracks in the polymer matrix. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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18 pages, 2893 KiB

Open AccessArticle

WEDM-Generated Slot Width Variation Modeling

by Oana Dodun, Laurențiu Slătineanu, Gheorghe Nagîț, Adelina Hrițuc, Andrei Marius Mihalache and Irina Beșliu-Băncescu

Micromachines 2022, 13(8), 1231; https://doi.org/10.3390/mi13081231 - 31 Jul 2022

Cited by 4 | Viewed by 1097

Abstract

Wire electrical discharge machining (WEDM) is a process that is used when it is necessary to manufacture small-width slots with a micrometer accuracy or to precisely detach parts with complex contours from metal workpieces in the form of sheets or plates. The fact [...] Read more.

Wire electrical discharge machining (WEDM) is a process that is used when it is necessary to manufacture small-width slots with a micrometer accuracy or to precisely detach parts with complex contours from metal workpieces in the form of sheets or plates. The fact that the wire electrode rests only in the working zone in two of its guides allows it to achieve micrometric oscillations, leading to the generation of an error from the flat shape of the slot surfaces that gradually develops into the workpiece. The slot widths are influenced by several factors, such as the workpiece thickness, pulse-on time, pulse-off time, the wire tension force, the current, and the wire movement speed along its axis. Some theoretical assumptions about the behavior of the wire electrode were first considered. An experimental research plan was then designed to obtain additional information on the influence of the mentioned factors on the slot width in different positions of the cross-section through the slot. The statistical processing of the experimental results led to the elaboration of empirical mathematical models that highlight the order of influence and the intensity of the influence exerted by the factors mentioned above. Full article

(This article belongs to the Special Issue Manufacturing Methods or Processing Methods in Micromachines)

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