K09-變壓器鐵心級(jí)進(jìn)模設(shè)計(jì)

資源目錄里展示的全都有，所見(jiàn)即所得。下載后全都有,請(qǐng)放心下載。原稿可自行編輯修改=【QQ：401339828 或11970985 有疑問(wèn)可加】 Journal of Materials Processing Technology 212 (2012) 2669 2677Contents lists available at SciVerse ScienceDirectJournal of Materials Processing Technologyjou rnal h om epa g e: machining for control of wettability with surface topographyTakashi Matsumuraa, Fumio Iidaa, Takuya Hirosea, Masahiko YoshinobaDepartment of Mechanical Engineering, Tokyo Denki University, 5 Senjyu Asahi-cho, Adachi-ku, Tokyo, 120-8551, JapanbDepartment of Mechanical and Control Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japana r t i c l e i n f oArticle history:Received 23 October 2011Received in revised form 17 April 2012Accepted 25 May 2012Available online 23 June 2012Keywords:Micro machining, FIB, Stamping, Plasticmolding, Functional surface,Hydrophobicity, Contact anglea b s t r a c tA micro fabrication is presented to manufacture hydrophobic surfaces with micro-scale structures.Hydrophobicity is controlled with the shape and the alignment of micro pillars in the structure. Thestructures are manufactured in large areas at high production rates in the following processes: (1) thestructure is fabricated on a tool by focused ion beam sputtering; (2) the reverse structure is formed on ametal plate by incremental stamping using the structured tool; and (3) the structure is transferred ontoplastic plates by molding. A consecutive stamping is also proposed to fabricate several structures on asurface accurately with a structured tool, in which the moving pitch of the structured tool is numericallycontrolled. The effect of the surface topography on hydrophobicity is discussed with measuring contactangles on the structured surfaces in the water droplet tests. Hydrophobicity on the plastic plate is associ-ated with the solid fraction on the structured surface based on the CassieBaxter model. A larger contactangle is observed for a smaller solid fraction of the surface. 2012 Elsevier B.V. All rights reserved.1. IntroductionFunctional surfaces have been increasing with demand ofsophisticated devices for not only industrial but also biomedicaluses. Bruzzone et al. discussed functional properties of surfaces andreviewed many applications of the functional surfaces (Bruzzoneet al., 2008). The surface function is also controlled by not only thematerial properties but also the surface topography. When micro-scale structures are fabricated on surfaces by micro machining withnumerical control, the controllable functional surfaces such as thefunctionally graded surfaces and the functionally integrated sur-faces are manufactured (Yoshino et al., 2006).Wettability is one of the important functions on surfaces tocontrol fluid flow and/or adhesion. Hydrophobic and hydrophilicsurfaces have been associated with surface energies controlledby the surface materials and the surface structures. Many studieshave discussed on wettability with contact angles of liquid dropletssince the pioneering works of Laplace and Young in the surfactantresearch field (Hartland, 2004). As the attempts for control of wet-tability with the surface topography, Wenzel associated wettabilitywith the surface roughness and proposed a model of the wettingbehavior on the solid surface (Wenzel, 1936). Cassie and Baxteralso associated hydrophobicity with the controlled surface topogra-phy and proposed another model for the structured surface (Cassieand Baxter, 1944). Patankar reviewed those models and discussedCorresponding author. Tel.: +81 3 5280 3391; fax: +81 3 5280 3568.E-mail address: tmatsumucck.dendai.ac.jp (T. Matsumura).well from the energy point of view (Patanker, 2003). Onda et al.showed water repellency on fractal surfaces (Onda et al., 1996).Bico et al. designed the hydrophobic surfaces with the micro-scalestructures based on the earlier works and verified their design inthe water droplet tests (Bico et al., 1999). Bizi-Bandoki et al. con-trolled wettability in the surface modification with femtosecondlaser treatment (Bizi-Bandoki et al., 2011). Zhang et al. improvedthe surface properties in micro testing devices (Zhang et al., 2009).Although the surface structures are applied to change wettabil-ity, most of them are machined by etching. However, in etching, thematerial to be machined has been limited by physical and chem-ical properties. Furthermore, flexible controllability of wettabilityhas recently been required for industrial devices. Then, the etchingprocess has some difficulties to control the change in wettabilitywith the surface structure as it is designed. More flexible processesare required to manufacture the surface structures for control ofwettability.Mechanical machining is an effective process to control thesurface structures numerically. Miniaturization in the mechanicalprocess has remarkably progressed with micro tools and high pre-cision motion controls. Then, the micro-scale cutting, forming andinjection molding have recently been applied to the manufacture ofthe micro parts (Vollertsen et al., 2004; Qin, 2006). The size effectin micro forming was discussed to study material behavior in FEsimulation (Chen and Tsai, 2006). Because the crystal grain size ofthe material is estimated as large relative to the processing size, themicro forming has been discussed in terms of the material science(Yeh et al., 2008). Some models on the crystal grain and the grainboundary were proposed to simulate the material behavior in FEM0924-0136/$ see front matter 2012 Elsevier B.V. All rights reserved.http:/dx.doi.org/10.1016/j.jmatprotec.2012.05.0212670T. Matsumura et al. / Journal of Materials Processing Technology 212 (2012) 2669 2677(Ku and Kang, 2003). Wang et al. simulated the crystal plasticityin micro forming (Wang et al., 2009). Because the material defor-mation is critical in the micro forming process, heating assistancehas been tried to improve the flow stress during deformation. Penget al. analyzed the laser heating for micro-part stamping (Peng et al.,2004a,b, 2007).Micro injection molding is also a relevant process in micromanufacturing. Sha et al. discussed the effects of the process-ing parameters and the geometric factor on the surface qualityof micro-features in three different polymer materials (Sha et al.,2007). Song et al. made a parametric study in molding of ultra-thin wall plastic parts (Song et al., 2007). Griffiths et al. associatedthe tool surface roughness with the melt flow length and the partquality (Griffiths et al., 2007). Larsson presented a micromouldingof 3D polymer features with arbitrary profiles for MEMS applica-tions (Larsson, 2006). Some of nanoimprint technologies have alsobeen developed and applications have recently been diversifiedwith the progress in MEMS. Schift et al. developed a versatile andfast stamping process incorporated with nanoimprint lithography(Schift et al., 2005).The paper presents a micro manufacturing of the functionalsurface to control wettability with the surface topography. Themicro-scale structures are fabricated in large areas on the surfacesat high production rates in a sequence of micro machining pro-cesses. The processes control the shape and the alignment of thestructure elements as it is designed. According to Cassies model(Cassie and Baxter, 1944), the change in contact angle on thehydrophobic surface is associated with the solid fraction, whichis the ratio of the liquid-solid contact areas on the structure ele-ments to the total area of the surface. Then, the effect of the surfacetopography on hydrophobicity is discussed with manufacturing thestructured surfaces.2. Manufacturing of structured surface2.1. Manufacturing processManufacturing of the functional surface with the surface topog-raphy requires consideration of the production efficiency as well asthe structure quality. The functional requirements of the processesare:(1) The structure elements should be micro-scale size to controlfunctionalities.(2) The structure should be machined in a wide area enough tocontrol the surface function for the practical use.(3) The structured surfaces should be manufactured at high pro-duction rates and low costs.Focused ion beam sputtering is normally effective inmicro/nano-scale machining. However, it takes a long time tomachine the structure in a large area. Then, the manufacturing costincreases with the production time. In this study, a manufacturingsequence shown in Fig. 1 is presented to improve the productionrate. The micro-scale structures are machined in the followingprocesses:(1) The micro-scale structure is fabricated on a tool by the focusedion beam sputtering.(2) Then, the reverse structure is formed a metal plate by incre-mental stamping.(3) Finally, the structure on the plate is transferred onto polymersby plastic molding.Fig. 1. Manufacturing sequence of structured surface: (a) FIB sputtering; (b) incre-mental stamping; (c) plastic molding.Although the structure is machined in a small area less than0.1 mm square in the first process, the second process expands thestructured area in a short time. The third process transfers the samesurface structure as that of the first process onto the plastic plateat a high production rate.2.2. Manufacturing of structured toolThe micro-scale structure is machined on the tool made of tung-sten carbide, which is usually used for the tool insert in turning.The machining area is specified with grinding the tool, as shownin Fig. 2(a). The structure is controlled numerically by the focusedT. Matsumura et al. / Journal of Materials Processing Technology 212 (2012) 2669 26772671Fig. 2. Structured tool: (a) ground tool; (b) structured area; (c) profile of a pillar.ion beam sputtering. Fig. 2(b) shows an example of the struc-tured tools, where 9 cylindrical micro pillars are machined at apitch of 60 ?m in 140 ?m square area. The diameter is 18 ?m andthe height is 18 ?m. A structured tool is machined to reduce themanufacturing time in the roughing and the finishing processes.Ions with a fluence of 2.0 1014ions/cm2were used. The sputter-ing is performed at a probe current of 14 nA for 8 h in roughingand then is done at a probe current of 5.2 nA for 8.5 h in fin-ishing. Fig. 2(c) shows the profile of a pillar in a cross sectionon the structured tool, which is measured with a laser confocalmicroscope. The profile signal cannot be obtained around the pil-lar because the depth is deeper than the maximum depth to bemeasured.2.3. Manufacturing of structured plateThe structure on the tool is stamped to form the reverse struc-ture on a metal plate. A machine shown in Fig. 3(a) was developedfor the incremental stamping. The machine controls three axes withthe stepping motors. X- and Y- axis are controlled at a resolutionof 25 nm. The resolution of Z-axis is 2.5 nm. The structured tool ismounted on the upper crossbeam. The structure is stamped withrepeating the vertical motion of the machine table in Z-axis, asshown in Fig. 3(b). Two piezoelectric dynamometers are mountedunder the table to detect the contact of the structured tool withthe workpiece and control the stamping load. The structured areais controlled by motions in X- and Y-axis.2672T. Matsumura et al. / Journal of Materials Processing Technology 212 (2012) 2669 2677Fig. 3. Incremental stamping: (a) stamping machine; (b) stamping process.Fig. 4(a) shows a structure on an aluminum plate, which ismachined in 1.5 mm squares by the structured tools shown in Fig. 2.Kerosene was used to reduce the friction between the tool andthe workpiece in stamping of the structured plate. The stampingoperation was repeated at a load of 12.5 N, which was determinedso as to form the dimples in the same depth as the pillar height onthe structured tool. Although the processing time is no more than45 min on the developed machine, the stamping rate would beincreased on the higher performance machines. Fig. 4(b) comparesthe profile of a formed dimple on the plate with that of a pillaron the structured tool, where the profile of the structured tool isshown upside down. The flat surfaces of the structured tool andthe plate are the reference for comparison. The forming error in thedepth of the dimple is more or less 1 ?m because of elastic recoverythough the material behavior should be analyzed numerically formore accurate stamping. Although tolerance depends on the speci-fications of the structure design, the error is small enough to ignorein control of wettability in the droplet tests as described later.2.4. Plastic moldingThe structure is transferred onto polyethylene plates in plas-tic molding. The molding machine shown in Fig. 5(a), on whichthe samples were usually mounted for the observation with SEM,was used here. Plastic molding was conducted at 180C at apressure of 180 kPa for 40 min. The motion in the mold releaseshould be controlled to prevent deterioration of the shape ofthe structure elements. A device shown in Fig. 5(b) was devel-oped to release the plastic plate from the mold in the straightmovement. The plastic material was molded on the metal plateclamped by the supporting device. Then, the plastic plate wasreleased from the metal plate with the screw motion on therelease device. The inner side of the release device worked as amotion guide. In the operation, the molding time was restrictedby the specification of the molding machine. The production ratecould be improved remarkably on the conventional mold injectionmachines.T. Matsumura et al. / Journal of Materials Processing Technology 212 (2012) 2669 26772673Fig. 4. Structured plate: (a) structured area; (b) profile of a dimple.Fig. 6(a) shows the structured surfaces on the polyethyleneplates molded by the structured metal plate shown in Fig. 4. Fig. 6(b)compares the profile of a pillar on the plastic plate with that of adimple on the metal plate. Although further discussion should bedone for the plastic flow in the micro-scale structure, the profileof the pillar agrees with that of the dimple. Compared with theerror in Fig. 4(b), the error in the plastic molding is smaller thanthe forming error. The forming error in the incremental stampingis the dominant factor in the manufacturing sequence.2.5. Consecutive control of micro-scale structureAs an advantage of the process, the micro-scale structures arecontrolled with changing the moving pitch of a structured tool.Fig. 5. Molding process: (a) molding machine; (b) releasing device.2674T. Matsumura et al. / Journal of Materials Processing Technology 212 (2012) 2669 2677Fig. 6. Structured surface on a plastic plate: (a) structured area; (b) profile of a pillar.Fig. 7 shows examples of incremental stamping processes with themotion control. The different structures are machined on a metalplate using a structured tool. Then, those structures are transferredonto a plastic plate. Fig. 8(a) shows an example of the structuredtool, which consists of 8 ?m square pillars. The micro dimples aremachined on a metal with changing the pitch, as shown in Fig. 8(b).Finally, the micro pillars shown in Fig. 8(c) are transferred onto aplastic plate.Although other processes such as chemical etching have beenapplied to the machining of the surface structures, the structuresare determined uniquely by the masks covering on the non-machining areas. The process presented in this paper, meanwhile,controls the structures numerically by the motions of the stagesusing only one structured tool in the incremental stamping. Thedimples are formed accurately at specified positions according tothe resolution of the stages. If the structured tools were manufac-tured for all structures, the more tool cost would be required withthe manufacturing time. The accuracy of the positions and the ori-entations of the structures would be deteriorated by the clampingerrors at the tool changes. The process with a tool shown in Fig. 7 iseffective in the accurate stamping and flexibility for the structuredesign.3. Evaluation of wettability3.1. Hydrophobic surface with surface topographyFig. 9(a) shows a water droplet on a flat surface of a polyethy-lene plate. Wettability is associated with contact angle, the anglebetween vaporliquid and liquidsolid boundaries of a liquiddroplet. The contact angle is larger than 90on hydrophobic sur-face and increases with hydrophobicity. It is well known the contactangle depends on the surface roughness. The contact angle on therough surface is larger than that of the flat surface for hydrophobicmaterial. Wenzel and Cassie presented the models with the sur-face structures (Wenzel, 1936; Cassie and Baxter, 1944). Accordingto Cassies model, the liquid phase is supported by the structure ele-ments and the vapor phase penetrates under the liquid meniscus,Fig. 7. Incremental stamping process with changing pitch: (a) full pitch; (b) half pitch; (c) 1/4 pitch.T. Matsumura et al. / Journal of Materials Processing Technology 212 (2012) 2669 26772675Fig. 8. Consecutive control of structures: (a) structured tool; (b) metal plate; (c) structured surface on a plastic plate.as shown in Fig. 9(b). As a consequence, the contact angle increaseson the structured surface. In Cassies model, the apparent contactangle ?rCis given by:cos ?Cr= ?scos ?e+ ?s 1 (1)where ?eis the contact angle on the flat surface; and ?sis thesolid fraction of the structured surface. The contact angle ?eof thepolyethylene plate is 96, as shown in Fig. 9(a). The solid fraction ?sis the ratio of the liquidsolid contact area on the pillars to the totalarea. The smaller solid fraction is estimated for the smaller pillarsaligned in the larger pitch.3.2. Hydrophobicity on structured surfaceThe contact angles were measured with changing the surfacestructure and were compared with Cassies model. Here, 8 ?msquare pillars were aligned with changing the distance betweenpillars. The height of pillars was designed to be 10 ?m so that thevapor phase exists under the liquid meniscus, which does not con-tact the bottom of the structure. The solid fraction of the squarepillars in the structure is:?s=?ad?2(2)where a is the length of a side of the square pillar and d is the pitchof the pillars.2676T. Matsumura et al. / Journal of Materials Processing Technology 212 (2012) 2669 2677Fig. 9. Water droplet: (a) water droplet on a flat surface; (b) model of water dropleton a structured surface.Fig. 10 shows examples of the surface structures, where thepitch of pillars are 15 ?m and 30 ?m and the solid fractions are0.28 and 0.07, respectively. Fig. 11(a) shows the change in theapparent contact angle ?rCwith the solid fraction ?s, where thevariances of the angles are less than 5% of the average. The solidline shows Cassies model given by Eq. (1), where the contactangle on the flat surface ?eis 96. The apparent contact angle onthe structured surface increases with decreasing the solid frac-tion. The change in the measured contact angle almost agreeswith Cassies model. However, the discrepancies of the measuredcontact angles from Cassies model are observed at high solid frac-tions. Cassies model discusses the change in the contact anglefor isotropic solid contact, which does not depend on the shapeand the alignment of the pillars. Meanwhile, the tested struc-tures consist of rectangular pillars. Therefore, the side and thediagonal lengths of the pillars are different. Then, the distancesbetween the pillars in the side and the diagonal directions areFig. 11. Water droplet on structured surface: (a) change in contact angle with solidfraction; (b) super hydrophobic surface.also different in the orthogonal array of the pillars. The erroris induced by anisotropy of the shape and the alignment of thepillars. When the solid contact increases with the solid fraction,the anisotropy effects on wettability increase. Fig. 11(b) com-pares the water droplets on the structured and the flat areason a surface. The contact angle is more than 150at a solidfraction of 0.07 on the structured surface, where the pillars arealigned at a pitch of 30 ?m. Fig. 11(b) proves that the differ-ent functionalities in wettab