精密加工中切削方向毛刺生成机理的研究(英文).pdf

CUTTING-D IRECTI ON BURR FORMATI ON IN ORTHOGONAL PRECISI ON CUTTING W ang Guicheng Zhang Chunye School ofM achinery Engineering, Jiangsu U niversity of Science and Technology, 212013 Zhenjiang, P. R. China ABSTRACT The cutting burr is one of the common phenomena occurring in metal cutting.In this paper,the form ing processes, main effect factors and change law of the cutting2direction burr in orthogonal cutting have been studied and related theories are analyzed based on the cutting experi ments .The result show s that:(1) the form ing processes of cutting2direction burr consist of normal cutting,flexure deformation of end surface of workpiece, plastic effect, continuous cutting and shear2 breakseparatingin orthogonal cutting; ( 2 )anew phenomenon is found that cutting2direction burr is formed w ith the shear2break separation of the chip andworkpiece machined surfaces;(3)the size of cutting2direction burr varies w ith workpiece materials, cutting parameters and geometric parameters of the cutting tool . Key words: metal cutting; cutting2direction burr; shear2 break separating; cutting edges of the tool; orthogonal precision machining CLC number: TG501. 1 Document code:A Article I D: 100521120(2001)0220194206 INTRODUCTI ON The controlling and deburring technology of machining burrs is one of the key technologies of the precision or superprecision and automatic processing,w hicharetwo maindeveloping directions of the mechanicalmanufacturing.The study on the principles of burr formation in metal cutting is a basic work to positively control and decrease burrs in machining operation,having i mportant scienctific significance and practical value to promote theoreitical development of the precision surface finishing and metal cutting. N ewtechnologies, processings and methods of the controlling burrs developed in this paper can be w idely used to precision or superprecision cutting, flexible manufacturing system and other automatic working.For this reason,scholars andengineersofmachinemanufacture engineering in developed countries have recently begun to study burr formation in metal cutting anddeburringtechnology,andmanynew positive results have been achieved 13. But so far, there have been few academ ic papers on the form ing principle and controlling technology of cutting2direction burrs .Therefore,this project on the basis of metal cutting experi ments,the form ing and changing of cutting2direction burr are systematically studied in order to sucessfully control and decrease machining burrs . Dec. 2001 T ransactions of N anjing U niversity of A eronautics revision received 15 Sep. 2001 1995-2005 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. 1 MA IN FACTORS INFLUENC- INGCUTTING-D IRECTI ON BURRS Invariousmachiningoperations,the cutting burrs are often formed onthe side, corner and end of a workpiece.They seriously affecttheaccuracyofthe workpiece,and especially deburring jobs become usually one of factors, w hich reduces productivity ofmachining system ,andincreases cuttingcostofa workpiece in precision and automatic machining operations .There are 3 kinds of the burrs in machining according to the classification system of the burrs on the basis of cutting motion and tool cutting edges 4. In orthogonal cutting, the two side2direction burr and the cutting2direction burr are formed(Fig. 1).Hexpresses burr height, w hich directly influences accuracy of the workpiece to be cut.Bexpresses burr root thickness, w hich mainly affects the deburring amount and the deburring efficiency. Fig. 1 Burrs in orthogonal cutting In the general case, main factors influencing burrs in orthogonal cutting include workpiece materials,cuttingparameters, cuttingtool geometries, endmorphology of aworkpiece, and so on.In order to clear formation and change law of the cutting2direction burr in orthogonal cutting,theexperi mental studyandthe theoretical analysis are made. 2 EXPERI M ENTAL COND I- TI ONS AND M EASURING M EANS Inthe experi ment,the i mproved m illing machine is used, and H62 brass plate (80 60 3 mm)is selected as workpiece materials in order to avoid effect of the built2up edge formed in machining. Before the test, the end surface of workpiece is machined again and again w ith a w ide single tool rake angle 30, undeformed chip thicknesshD 0. 05mm , making cutting surface get as less hardness alteration as possibility. H igh2speed steelW 18Cr4V is selected as cutting toolmaterial .Thecuttingconditionsin experi ment are show n in Table 1. Table 1 Experi mental conditions ConditionsParameters Cutting speed v?(mm in- 1) 10 10 U ndeformed chip thickness hD?mm 0. 050. 3 0. 1 Tool orthogonal rake 0?() 030 10 Tool orthogonal clearance 0?() 8 8 Rounded cutting edge radius rn ? m 10 30 50 10 Workpiece materialsH62 20# 45# H62 Note:“-”is standard cutting parameter. The heightHof cutting2direction burr in experi ment ismeasured by a dial gauge(measure accuracy is 0. 01 mm)and burr root thicknessB is measured by atool m icroscope(measure accuracy is also 0. 01mm). The rounded cutting edgeradiusrnisdeterm indedbyalight 591No. 2W ang Guicheng, et al . Cutting2D irection Burr Formation in O rthogonal Precision 1995-2005 Tsinghua Tongfang Optical Disc Co., Ltd. All rights reserved. diffractometerthroughcalculation.A ndthe form ing process of cutting2direction burr ismade on the basis of high2speed shooting during the metal cutting process . 3 EXPERI M ENTAL RESULTS AND ANALYSES 3. 1 Form ing process of cutting-direction burr Fig.2show s theformation ofcutting2 directionburronthebasisofhigh2speed shooting during the orthogonal cutting process . From Fig. 2, it is know n that cutting2direction burrapproxi matelyformedinfivestages: normalcutting,flexuredeformationofend surface of workpiece, plastic effect, continuous cutting and shear2break separation in orthogonal cutting. Fig. 2 Form ing processes of cutting2direction burr (a)Normal cutting A fter the cutting tool cuts into the workpiece,chip flow s smoothly along the face of cutting tool, then metal cutting continues normally. (b)Flexure deformation The workpiece materials in end surface begins to have flexure deformation under the function of cutting force, w ith cutting tool approaching gradually to the end surface of workpiece.The value of flexure deformationincreases w iththedecreaseof distance betw een the tool tip and the end surface of the workpiece. (c)Plastic effect W henthe distance betw een the tool tip and the end surface of workpiece isl0, the stress ofmaterials in the end of workpiece caused by cutting tool reaches the li2m it value of plastic shear ofmaterial, and then resultsinthevalue offlexuredeformation increasing constantly. (d)Continuous cutting W ith cutting tool moving forw ard continuouly,the undeformed chipthicknessreducesandcuttingforce decreasestoo,keepingthelargestvalue of flexure deformation of end material constant. So cutting tool is still machining partialmaterial of workpiece to be cut. (e)Shear2breakseparation W henthe cutting tool tip continuously reaches on the end surface of workpiece, the support rigidity at the endofthe workpiecebecomessmallerand smaller, making that shear2break separation of end material take place at the same ti me w ith deformation along shear2sliding direction.The cutting2direction burr then is formed at the end surface. 3. 2 Effect of undeformed chip thicknesshDon burr A fter changing undeformed chip thickness hD,experi mental results are show n in Fig. 3 w hich show s that burr heightHand burr root thicknessBincrease w ith the undeformed chip thicknesshD, w hile the ratio(H?B)of burr heightHand the burr root thicknessBremains approxi matelyconstant.Theexperi mental result is si m ilar to the effect of the underformed chip thicknesshDon the side2direction burrs 2. This is because the greater the undeformed chip 691T ransactions of N anjing U niversity of A eronautics ( 2 )A newphenomenoni