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A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (29 February 2020) | Viewed by 44434

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Prof. Dr. Ken-Ichi Manabe

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Professor Emeritus, Department of Mecanical Systems Engineering, Tokyo Metro University, Hino, Tokyo, 191-0065, Japan
Interests: deformation mechanics & process simulation; intelligent forming process; materials processing; micro-forming
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Dear Colleagues,

Micro-forming of metals is an excellent technology as a mass production method with high productivity and good mechanical and functional properties to manufacture very small parts. This technology has attracted much attention in the manufacture of metallic micro parts in electronics, the biomedical industry, the communication industry, and so on.

So far, several metal forming processes have been achieved by scaling down the process configuration, the dies and tools, and the forming machines. There are, however, several technological issues related to the occurrence of size effects due to miniaturization. Major issues include understanding materials properties and the deformation mechanism, micro-formability and -forming limits, material/tool interfacial conditions, process modeling and analysis, process design optimization, etc. Moreover, to achieve high micro-formability and high dimensional accuracy, novel special micro-forming techniques combined with the laser system, ultrasonic vibration, special heating, or ultra-high pressure have been developed.

The aim of this Special Issue is to present the latest achievements in various metal micro-forming processes and the latest research related to the elucidation of size effect. Through this Special Issue, enhancing the understanding of the present status and trend of metal micro-forming technology and further promoting are expected. Thus, all researchers in this field are invited to contribute.

Prof. Emer Dr. Manabe Ken-ichi
Guest Editor

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Keywords

Micro bulk forming
Micro forming of thin sheets and tubes
Micro blanking
Micro rolling
Micro tribology, Surface texturing
Die and tool materials
Microstructure
Materials evaluation testing method
Process simulation model and analysis
Novel micro processing

Published Papers (12 papers)

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Editorial

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3 pages, 154 KiB

Open AccessEditorial

Metal Micro-Forming

by Ken-ichi Manabe

Metals 2020, 10(6), 813; https://doi.org/10.3390/met10060813 - 18 Jun 2020

Cited by 3 | Viewed by 2814

Abstract

Metal micro-forming is the technological field of micro-manufacturing [...] Full article

(This article belongs to the Special Issue Metal Micro-forming)

Research

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12 pages, 6687 KiB

Open AccessFeature PaperArticle

Study of Wire Deformation Characterization and Size Effects during the Micro-Flat-Rolling Process

by Haibo Xie, Ken-ichi Manabe and Zhengyi Jiang

Metals 2020, 10(3), 405; https://doi.org/10.3390/met10030405 - 22 Mar 2020

Cited by 4 | Viewed by 2930

Abstract

A comprehensive research on the flat rolling deformation characterization of microwire has been conducted systematically through finite element simulation and testified by the results from the experimental analysis. The obtained results are compared in terms of lateral spread, geometrical characteristic, contact area width and surface roughness considering the effects of pass reduction and initial wire diameter. The size effect has been identified and surface layer modeling has been set up based on surface grain share and grain size distribution. The numerical method combined with varied flow stress has been verified by experimental value with a maximum difference of 3.7% for the 1.5 mm wire. With the increase of the height reduction, the curvature radius is decreased while the lateral spread and contact area width are increased. Surface roughness evolution in the range of 0.52–0.85 µm for the rolled wire has also been investigated. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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23 pages, 18192 KiB

Open AccessFeature PaperArticle

Material Deformation Behavior in T-Shape Hydroforming of Metal Microtubes

by Hajime Yasui, Shoichiro Yoshihara, Shigeki Mori, Kazuo Tada and Ken-ichi Manabe

Metals 2020, 10(2), 199; https://doi.org/10.3390/met10020199 - 30 Jan 2020

Cited by 6 | Viewed by 3130

Abstract

In this study, the material behavior in the T-shape microtube hydroforming (MTHF) of pure copper and stainless-steel SUS304 microtubes with an outer diameter of 500 µm and wall thickness of 100 µm was examined experimentally and numerically. This paper elucidates the basic deformation characteristics, the forming defects, and the forming limit as well as the effects of lubrication/friction and tube length. The hydroformability (bulge height) of the SUS304 microtube was shown to be higher than that of the copper microtube because of the high buckling resistance of SUS304. Good lubrication experimentally led to the high hydroformability of T-shape forming. The length of the microtube significantly affects its hydroformability. Friction resistance increases with increasing tube length and restricts the flow of the microtube material into the die cavity. By comparing the T-shape and cross-shape MHTF characteristics, we verified the hydroformability of the T-shape microtube to be superior to that of the cross-shape microtube theoretically and experimentally. In addition, the process window for T-shape MTHF had a narrower “success” area and wider buckling and folding regions than that for cross-shape MTHF. Furthermore, conventional finite element (FE) modeling without consideration of the grains was valid for MTHF processes owing to the many grains in the thickness direction. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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17 pages, 7333 KiB

Open AccessArticle

Lubrication Analysis of Micro-Dimple Textured Die Surface by Direct Observation of Contact Interface in Sheet Metal Forming

by Tetsuhide Shimizu, Hiroyuki Kobayashi, Jochen Vorholt and Ming Yang

Metals 2019, 9(9), 917; https://doi.org/10.3390/met9090917 - 22 Aug 2019

Cited by 12 | Viewed by 4870

Abstract

To investigate the underlying mechanism of the effects of surface texturing on lubricated sliding friction in the metal forming operation, an in-situ observation system using transparent silica glass dies and a high speed recording camera was newly developed. To correlate the dimensional parameters of micro-dimple textured structures and tribological properties in the metal forming operation, the in-situ observation was performed during bending with the ironing process of the stainless steel sheet with a thickness of 0.1 mm. The lubrication behavior were compared between the different lubricant viscosities and the micro-dimple textures with different diameters of 10 µm, 50 µm, 100 µm fabricated by using femto-/pico-second laser processing. As a result, the textured die with dimple diameters of 10 µm and 50 µm showed the lubricant flow transferred from one to the other dimples owing to the lubricant reservoir effect, while that of 100 µm indicated the less supply of the lubricant. However, the textured die with a dimple diameter of 10 µm demonstrated higher ironing force than that of 50 µm, due to the severe adhesion of work materials inside the dimple structures. Based on these experimental findings, the dimple size dependencies on lubricant reservoirs effects and the generation of the hydrodynamic pressure were discussed by correlating with the in-situ observation results, a fluid-flow analysis and a laminar two-phase flow analysis using the finite element method. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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13 pages, 4701 KiB

Open AccessArticle

Formability Analysis and Oxidation Layer Effects in Dieless Drawing of Stainless Steel Wires

by Yeong-Maw Hwang and Han-Hsuan Liu

Metals 2019, 9(8), 828; https://doi.org/10.3390/met9080828 - 25 Jul 2019

Cited by 4 | Viewed by 2804

Abstract

In this study, dieless drawing experiments of stainless steel SUS304 wires of 1 mm in diameter were carried out using a self-developed dieless drawing machine. In order to prevent oxidation, argon gas was applied to a self-designed chamber during dieless drawing processes. The effects of the forming temperature and the oxide layer on the mechanical properties of the drawn SUS304 stainless wires obtained by tensile tests are discussed in this paper. A finite element model considering the high frequency induction heating mode in the finite element software DEFORM2D was developed to conduct the heat transfer analysis and the formability analysis of the drawn products in dieless drawing of stainless steel wires. The effects of the drawing speed and forming temperature on the maximal reachable area reductions are discussed. Through the comparisons of the maximal reachable area reduction between the finite element simulations and experiments, the finite element modelling for dieless drawing processes was validated. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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13 pages, 14876 KiB

Open AccessArticle

Material Flow in Ultrasonic Orbital Microforming

by Wojciech Presz

Metals 2019, 9(4), 475; https://doi.org/10.3390/met9040475 - 24 Apr 2019

Cited by 3 | Viewed by 2674

Abstract

Ultrasonic orbital microforming—UOM—uses the broadly understood idea of orbital forging but uses very different laws of physics. The only shaping force in this process is the inertia force resulting from the acceleration in the rotary motion of the workpiece. Micro specimen blanked from cold rolled aluminum sheet metal was used in the applied UOM process. Only the upper and lower part of the sample is deformed that gives about 70% of volume. The rest—the middle part—remains undeformed. The final shape of the product is influenced by the shape of the inside of the die in which the UMO process is carried out. However, this effect is not a direct one. The product shape does not repeat the shape of the interior of the die. The preliminary experiments with modular micro-die have been performed on the way of controlling the shape of deformed micro-objects. The microstructure analysis has been done as well as micro-hardness distribution. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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10 pages, 10882 KiB

Open AccessArticle

A New Compression Test for Determining Free Surface Roughness Evolution in Thin Sheet Metals

by Tsuyoshi Furushima, Kohei Aoto and Sergei Alexandrov

Metals 2019, 9(4), 451; https://doi.org/10.3390/met9040451 - 17 Apr 2019

Cited by 3 | Viewed by 2919

Abstract

In sheet microforming processes, in-surface principal strain rates may be compressive such that the thickness of the sheet increases in the process of deformation. In general, the evolution of free surface roughness depends on the sense of the principal strain normal to the free surface. Therefore, in order to predict the evolution of free surface roughness in processes in which this normal principal strain is positive by means of empirical equations, it is necessary to carry out experiments in which the thickness of the sheet increases. Conventional experiments, such as the Marciniak test, do not provide such strain paths. In general, it is rather difficult to induce a sufficiently uniform state of strain in thin sheets of increasing thickness throughout the process of deformation because instability occurs at the very beginning of the process. The present paper proposes a compression test for thin sheets. Teflon sheets are placed between support jigs and the metallic sheet tested to prevent the occurrence of instability and significantly reduce the effect of the support jigs on the evolution of surface roughness. The test is used to determine the evolution of surface roughness in thin sheets made of C1220-O under three strain paths. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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11 pages, 6230 KiB

Open AccessArticle

Development of a Novel Resistance Heating System for Microforming Using Surface-Modified Dies and Evaluation of Its Heating Property

by Ming Yang and Tetsuhide Shimizu

Metals 2019, 9(4), 440; https://doi.org/10.3390/met9040440 - 15 Apr 2019

Cited by 2 | Viewed by 3026

Abstract

For this study, a novel resistance heating system for microforming was developed using surfaces of forming dies as heating resources. The electrical resistance of the die surfaces was designed and the hard-coating material AlCrSiN was selected to coat the die surfaces for heating. To clarify the effects of the thickness and modified surfaces on heating efficiency, the temperature and stress reduction were evaluated in a micro-compression test using dies coated with 0.5 and 1 μm AlCrSiN films. Furthermore, the formability was also demonstrated using 1 μm thick AlCrSiN-coated tools in a microforging test. By applying surface-modified dies to the forming processes, we found that not only was the heating efficiency improved, but also the dependence of heating on the product’s shape and the material’s electrical properties was reduced. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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11 pages, 4751 KiB

Open AccessArticle

Plasma Printing of an AISI316 Micro-Meshing Punch Array for Micro-Embossing onto Copper Plates

by Tomomi Shiratori, Tatsuhiko Aizawa, Yasuo Saito and Kenji Wasa

Metals 2019, 9(4), 396; https://doi.org/10.3390/met9040396 - 30 Mar 2019

Cited by 8 | Viewed by 3134

Abstract

Packaging using thermoplastic molding for hollowed GaN chips were requested for a leak-proof micro-joining between plastic molds and copper-based substrates. The design and engineering of micro-textures is a key technology for putting leak-proof packaging into practice. In the present paper, a micro-meshing punch array was prepared using plasma-nitriding-assisted printing. Two-dimensional original patterns were screen-printed onto an AISI316 die substrate and plasma nitrided at 673 K for 14.4 ks (or 4 h). The unprinted surfaces were selectively nitrogen super-saturated to have more nitrogen content than 5 mass% and a higher hardness than 1200 HV. The printed surfaces were selectively sand blasted to fabricate the micro-meshing punch array for micro-embossing. A computer numerically controlled stamping system was utilized to describe the micro-embossing behavior onto copper substrates and to investigate how the micro-textures on the array was transcribed onto the copper. Reduction of takt time as well as flexibility in the micro-grooving were discussed with reference to the picosecond laser machining and mechanical milling processes. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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16 pages, 5820 KiB

Open AccessArticle

Feedstocks of Aluminum and 316L Stainless Steel Powders for Micro Hot Embossing

by Omid Emadinia, Maria Teresa Vieira and Manuel Fernando Vieira

Metals 2018, 8(12), 999; https://doi.org/10.3390/met8120999 - 28 Nov 2018

Cited by 6 | Viewed by 3193

Abstract

In metal powder, shaping the preparation and characterization of the feedstock is an aspect commonly recognized as fundamental. An optimized composition is required to ensure the successful shaping of the feedstock. In this study, a commercial binder system, pure aluminum and 316L austenitic stainless-steel powders were used for micro hot embossing. The optimization process revealed that powder characteristics such as shape and the stability of the torque mixing, were important parameters. Manipulating the feedstock composition by adding multi-walled carbon nanotubes or stearic acid or using a higher powder concentration considerably influenced the torque mixing values. The steady state of torque mixing was achieved for all feedstocks. This torque behavior indicates a homogeneous feedstock, which was also confirmed by microscopic observations. Nevertheless, an extruding process was required for greater homogeneity of the aluminum feedstocks. The presence of the carbon nanotubes increased the homogeneity of green parts and reduced microcrack formation. The roughness was essentially dependent on the feedstock composition and on the plastic deformation of the elastomer die. Shaping the prepared feedstocks (with or without carbon nanotube) was achieved by the optimized powder concentrations and it did not increase by the stearic acid addition. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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33 pages, 19203 KiB

Open AccessArticle

Experimental and Numerical Investigations of a Novel Laser Impact Liquid Flexible Microforming Process

by Fei Liu, Huixia Liu, Chenkun Jiang, Youjuan Ma and Xiao Wang

Metals 2018, 8(8), 599; https://doi.org/10.3390/met8080599 - 31 Jul 2018

Cited by 8 | Viewed by 3157

Abstract

A novel high strain rate microforming technique, laser impact liquid flexible embossing (LILFE), which uses laser induced shock waves as an energy source, and liquid as a force transmission medium, is proposed by this paper in order to emboss three-dimensional large area micro arrays on metallic foils and to overcome some of the defects of laser direct shock microembossing technology. The influences of laser energy and workpiece thickness on the deformation characteristics of the pure copper foils with the LILFE process were investigated through experiments and numerical simulation. A finite element model was built to further understand the typical stages of deformation, and the results of the numerical simulation are consistent with those achieved from the experiments. The experimental and simulation results show that the forming accuracy and depth of the embossed parts increases with the increase in laser energy and decrease in workpiece thickness. The thickness thinning rate of the embossed parts increases with the decrease of the workpiece thickness, and the severest thickness thinning occurs at the bar corner region. The experimental results also show that the LILFE process can protect the workpiece surface from being ablated and damaged, and can ensure the surface quality of the formed parts. Besides, the numerical simulation studies reveal the plastic strain distribution of embossed microfeatures under different laser energy. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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Review

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26 pages, 5471 KiB

Open AccessReview

Review on Advances in Metal Micro-Tube Forming

by Christoph Hartl

Metals 2019, 9(5), 542; https://doi.org/10.3390/met9050542 - 10 May 2019

Cited by 21 | Viewed by 8035

Abstract

Metallic tubular micro-components play an important role in a broad range of products, from industrial microsystem technology, such as medical engineering, electronics and optoelectronics, to sensor technology or microfluidics. The demand for such components is increasing, and forming processes can present a number of advantages for industrial manufacturing. These include, for example, a high productivity, enhanced shaping possibilities, applicability of a wide spectrum of materials and the possibility to produce parts with a high stiffness and strength. However, certain difficulties arise as a result of scaling down conventional tube forming processes to the microscale. These include not only the influence of the known size effects on material and friction behavior, but also constraints in the feasible miniaturization of forming tools. Extensive research work has been conducted over the past few years on micro-tube forming techniques, which deal with the development of novel and optimized processes, to counteract these restrictions. This paper reviews the relevant advances in micro-tube fabrication and shaping. A particular focus is enhancement in forming possibilities, accuracy and obtained component characteristics, presented in the reviewed research work. Furthermore, achievements in severe plastic deformation for micro-tube generation and in micro-tube testing methods are discussed. Full article

(This article belongs to the Special Issue Metal Micro-forming)

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