Formation of integral fins function-surface by extrusion-ploughing process

Available online at www.sciencedirect.comsCIENCE (@oIRECT.Transactions of.Nonferrous MetalsSociety of ChinaScienceTrans. Nonferrous Met. Soc. China 16(2006) 1029-1034PressFormation of integral fins function-surface by extrusion-ploughing processCHEN Ping(陈平), TANG Yong(汤勇), LIU Xiao-kang(刘小康), LIU Xiao-qing(刘晓晴)Collge of Mechanical Engineering, South China University of Technology, Guangzhou 510640, ChinaReceived 9 November 2005; accepted 10 May 2006A bstract: An extrusion-ploughing process was presented to fabricate the integral fin function- surface. Cutting edge inclination angleand rake angle can be calculated from the tool's geometry relationship. The description of fins' geometry characters was standardized.The experiments show that, when the middle cutting edge's inclination angle η is less than 35", continuous fin will come out; when ηis between 35° and 55;, the fins will be saw-tooth ones, and the fins will be torn when this angle is above 55"; when the extrusionangle θ is between 60° and 150", the fins will appear, or else, the fins will be torm into chips from the base. Forming angle andclearance angle have lttle effect on fin's formation. For continuous fin, its height is close to cutting depth when it is small, but it willbecome approximately constant as cutting depth grows; for saw-tooth fins, the width, the height, as well as the clearance willincrease with the increase of cutting depth, but the increment of clearance is small; neither for continuous fin, nor for saw-tooth ones,cutting velocity has little influence on their structure parameters.Key words: fins; integral fins; extrusion- ploughing formation; heat function surfaceexternal convection pattern, even needs to employ1 Introductionsurface meta-structure and micro-structure to strengthenthe heat transmission. But which SHFS to use and how toThe ever-increasing integrity of electronic chipsmachine remain unclear; the description， design,results in high heat flow density, which makes themachining and the application of SHFS lack necessarycooling become the ever more serious[1 - -5]. Thetheories, so it can't realize the design and machining oftraditional single-scale and simple figure surfaceSHFS effectively, according to the active requirement,heat-function macro-structure can not meet the coolingyet nor can realize the digital design and fabrication.requirement,which slows the development ofIn this work, an extrusion-ploughing technologyhigh- integrity chips.with no chip is presented to generate fin SHFS，and theAt present, the research of surface heat functionmachining theory of SHFS can be richened and perfectedstructure(SHFS) mainly focuses on the analysis andby studying the forming mechanism and relevantdesign of heat transmission in macro-scale. For example,influencing factors, which provides the optimum methodGeogria Institute of Technology[6] has done somefor high heat flow density.researches on the surface macro-structure andmeta-structure. With the worsening of cooling, the study2 Experimentalof SHFS is turming to meta/micro field, such as thedevelopment of micro heat transfer[7- 12]. Themachining of meta-structure and micro-structure of the2.1 Experimentmacro structure surface[13-15], as well as the ke;The experiment was carried out on the universalplaner B6050B. The tool was made of high speed steeltechnology, has been studied at home.Solving the present high heat flow density needs toW18Cr4V, and the workpiece was made of red copper T2.design heat function surface macro structure, based onThe fitness of the workpiece and the tool is shown inthe special radiating environment requirement andFig.1.中国煤化工Foundation item: Projects(50436010; 50375055) supprted by the National Natural Science Fou: supported by theNatural Science Foundation of Guangdong Province, China; Project(2005B10201:YHC N M H Gnnological Projcetof Guangdong Province, ChinaCorresponding author: GHEN Ping; Tel: +86-20-87114634; Fax: +86-20-87604634; E-mail: cp629@163 com.1030CHEN Ping, et al/Trans. Nonferrous Met. Soc. China 16(2006)2.3 Tool's anglesFrom Fig.2, differing from the common planer tool,the extrusion-ploughing formed tool has 3 characters.The first is that the rake angle y is minus, and the secondis that the cutting edge inclination angle h is not zero,and the last is that the tool has multi cutting edges, so thecutting pattern corresponds to the multi-edge cutting withinclination angle. Supposing the cutting velocity is alongZ minus axis, that is perpendicular to the base level Prand pointing to the tool. From tool's geometryrelationship, 7 and h can be calculated as follows:θcos- cosa cosηsinλ =(1Fig.1 Experimental device of extrusion-ploughing process/sin2二sin2 (a +η)+cos2二cos2 η2.2 Formed toolContrary to the common cutting process which cutsout the redundant metal to get the part, the extrusion-cosY=√R+B +Cploughing process makes the chips remain on the base,thus the radiating area is enlarged; not only the material'sutilization is bettered, but also the problem of practicalcossin a cosηcontact thermal resistance in heat control is solved. Thedesign of formed tool should fully reflect the non-chipn2 :sin2(a +7)+cos2 sin2 a cos2 ηtechniques. As shown in Fig.2， the tool's movingdirection is parallel to the formed plane.√A2+B2 +C2sin G sin(x +η)RoPn(2)θ./sin2。sin2(a +η)+ cos2O sin2 acos'η2Forming PAfacewhereTool frankMiddleA= cos一sin a cosη sin sinη(3)cutting edge27XsCfABRake faceB= sin2 _sisin(a + n)sinη(4)Main cutting edgea)C = sin2二sin(o + n)cosn + cos二sinocos' η(5)3 Extrusion-ploughing forming process3.1 Critical depth in double edge cuttingIn Fig.2, when ap equals Y value of intersection ofline FC and plane P, both main cutting edge and sidecutting edge cut the workpiece simultaneously, thecutting depth is named as the critical depth her.From Fig.3, the critical depth can be solved asher =hp +k(hc-hp)_6)(b)中国煤化工M tan axYHCNMH G .Fig.2 Extrusion-ploughing formed tool: (a) Tool's geometryk=-(7)LMtan a- LKtan xtan β-LN+ KBparameters; (b) Tool.CHEN Ping, et a/Trans. Nonferrous Met. Soc. China 16(2006)1031hp=LtanηLtanηtanβ+B(8)The cutting sequence between the main cutting edgeand the side cutting edge relies on her. When ap s≤hcr, thetan β- tan°main cutting edge cuts at first, and the side cutting edge2goes first on the contrary conditions.KB tanahc =M tancx -K tano tanβ-N(9)As the tool goes forward, either the main or the sidecutting edge cuts the metal. This process is similar to themulti-edge cutting with large cutting edge inclinationos二cosηangle and oblique angle, and there is angle φ betweenK =-θ(10)the flow chip direction and the cutting edge's normal.√|1-(cos 2 sinη)2Since the formed tool is symmetric, so some interferenceappears in the edge of the two chips; the breakage of theadjacent metals can eliminate this interference. Thesin一cosηexistence of middle edge and the sharp edge create theM=big shearing stress in the chips’ edge, so the shear√|1-(Coss sinn)2; sinconcentration is easy to come out, thus the chips break.The rake angle is minus, and the chip clings to the rake.θface. The stress resulted from the rake face's extrusion一sin二sinηV=-(12)makes the metal in the front of the chip go upwards, thegeometry and the height of the raised metal decide the√1- (cos 2 sinn)2fin's figure and height; the fin will be higher andnarrower when it is near the fake face. The extrusionheight gradually goes higher from the middle edge to theside edge.All the chips are extruded to one side of the formedBoface when they pass along the side cutting edge, and theyjoin the base to form the fins whose height and widthBvary with the change of tool s displacement.2|Eventually continuous fins or saw-tooth fins areformed as seen as Fig.4, and some micro dentateconfigurations could be produced on continuous fins' tip(Fig.5). The workpiece can form integral SHFS whichincludes ploughed channels and fins.(a)(aNC7|Fig.4 Fin structure: (a) Saw-tooth fins; (b) Continuous finsb)4 Results and discussionFig.3 Standard view: (a) Front view; (b) Left view3.2 Extrusion-ploughing process4.1 Description of fin's structureIn the beginning of extrusion-ploughing process,As shown in Fig.6, for the continuous fins, thebefore the main and the side cutting edges contact theparameters for description are the macro fin's height hworkpiece,the wedge block that consists of middleand extrusion中国煤化工ooth fins, thecutting edge and the two rake faces directly cuts theparameters:YHCNMHGdsaw-toothworkpeice，and the extrusion plastic deformationclearance d.appears.For the continuous fins, the fin's height varies with.1032CHEN Ping, et al/Trans. Nonferrous Met. Soc. China 16(2006)The experiments show that, when η is less than 35 , the .continuous fins are easy to come out, and with theincrease of n, the macro saw-tooth fin structure can begenerated either with different cutting velocities or withdifferent cutting depths; when η reaches 55"，the saw-tooth fins are inclined to be torn into small chips. So, wecan conclude that, η is one of the main factors that decidefin's pattern.4.2.2 Extrusion angle θSince the cutting edge inclination angle is not null,the cutting velocity is not vertical to tool's cutting edge,and the cutting velocity has component along the cuttingFig.5 Meta-structure/micro-structureedge's direction. Fromqn.(1), we can see that, thedjcutting edge inclination angle decreases with the increaseof θ if other angles are fixed; that is to say, the decreaseof velocity's component weakens the metal's flow alongthe cutting edge's direction, the shearing slip direction ofthe cutting layer changes and chip's flowing angleBre.diminishes. The fins can be generated when θ is between60° and 150*, and when θ is beyond this range, the fincan be easily torn into small chips.Fig.6 Parameters description of fin's structure features4.2.3 Formed angle βThe angle β has ltte influence on fin's structure; itthe change of tool's displacement. Supposing the macrogenerally controls the figure of ploughed channels.fin's height is the mean value of fins at different points,4.2.4 Clearance angle athen, we can getThe angle a also has lttle influence on fin'sstructure; it is mainly used to reduce frictional resistanceh=Zh/n(13)in the extrusion ploughing process.where n is the number of the selected points, and h; is4.3 Influence of processing parameters on fin's for-the corresponding height of fin.mationFor the saw-tooth fins,4.3.1 Influence of processing parameters on formation ofcontinuous finsdj= Cdj;/nThe tool's parameters selected to machine the=ncontinuous fins are listed in Table 1.h;= Zhn;/n(15)Table 1 Tool's geometry parameters for continuous finsParameterValued=2ds/n(16)n/()3(Bo/mm5a()8B/mm0.0/()9L/mmwhere n is the fins’ total number; dji, hi and diB/()20represent the width, height and saw-tooth clearance,respectively.1) Influence of cutting depthAs shown in Fig.7, the fin's height is close to the4.2 Influence of tool's geometry parameters on fin'scutting depth when the cutting depth is small; the heightformationEither the continuous fins or the saw-tooth fins aredoesn't increase very much as the cutting depth increases,it stays at a certain value.created in the extrusion-ploughing process, th2) Influence of cutting velocityconsequence is dominated by tool's geometry paraAs shown in Fig.8. the fin's height fluctuates verymeterslttle with the c中国煤化工o the cutting4.2.1 Inclination angle η of middle cutting edgevelocity affects|YHCNMHGChanging η while supposing other conditions4.3.2 Influence ot processing parameters on formation ofremain the same, we can get fins with different structures.saw-tooth fins.CHEN Ping, et a/Trans. Nonferrous Met. Soc. China 16(2006)1033velocity，the width, the height and the saw-toothclearance of saw-tooth fin change very lttle, their valuestend to be stable. So, the cutting velocity has lttle effect量0.8-on the structure parameters of saw-tooth fins.2.0g 0.6-1- Width1.6 :二HeightClearance0.4e 1.2”。三0.80.40.8.2.6Cutting depth/mmFig.7 Relationship between cutting depth and fin's height (V=177 mm/s)0.2 0.4 0.6 0.8 1.0 1.2 1.41.Fig.9 Relatioonship between cutting depth and parameters ofsaw-tooth fin (V=177 mm/s)g 0.8.6.1.6-高0.4-至0.其0.8-~5010015000250 300Height▲一ClearanceCutting velocity/(mm.s-1)毛0.4-Fig.8 Relationship between cutting velocity and fin's height(ap=1.44 mm)50 100 150 200 250 300 35The tool's parameters selected to machine thesaw-tooth fins are listed in Table 2.Fig.10 Relationship between cutting velocity and parameters ofsaw-tooth fin (ap =0.6 mm)Table 2 Tool's geometry parameters for saw-tooth finsParameterValue5 Conclusionsn/(°)45B/mm5a/()0.2The extrusion-ploughing process is a cutting0/())0L/mmprocess with no chip, and its theory involves metallicB(O)20cutting and plastic extrusion. Different from the ordinarycutting process which cuts out the redundant metal to get1) Influence of cutting depththe part, this process makes the chips remain on the base,As shown in Fig.9, the width, the height and theand thus different SHFS can be got.saw-tooth clearance of saw-tooth fin augment as cuttingdepth increases. The increment of the width is obvious,calculation expressions of cutting edge inclination anglend rake angle are gained, the descriptions of fin'sbut the increment of the saw-tooth clearance is not. So,structure characteristic parameters (such as h, by, d, h;the fin's saw-tooth clearance tends to be stable as cuttingd) are put forward. The formation of integral findepth increases; the number in unit length lessens slowly,structure SHE中国煤化工process isand the saw-tooth fin grows bigger.analyzed. .CNMHG2) Influence of cutting velocity2) When the nude cuge s luo angle n isAs seen in Fig.10, with the increase of cuttingless than 35, the continuous fins will come out; when η.1034CHEN Ping, et al/Trans. Nonferrous Met. Soc. China 16(2006)is between 35° and 55*, the fins will be saw-tooth ones,computers. [A]. 2002 Inter Society Conference on ThermalPhenomena [C] San Diego， CA: Instute of Electrical andand the fins will be torn when this angle is above 55* .When the extrusion angle θ is between 60° and 150*, the2] ZHANG HY, PINJALA D, NAVASOK, CHANPK, LIUXp,fins will appear, or else, the fins will be torn into chipsHAYASHI H, HANJ B. Development of thermal solutions for highfrom the base. The forming angle and clearance angleperformance laptop computers [A]. 2002 Inter Society Conference onThermal Phenomena [C]. 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