Analysis of high speed machining center spindle dynamic unit structure performance Yuan guowei

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1 Intenational Confeence on Intelligent Systems Reseach and Mechatonics Engineeing (ISRME 0) Analysis of high speed machining cente spindle dynamic unit stuctue pefomance Yuan guowei Liaoning jidian polytechnic,dan dong china Keywods:spindle; dynamic pefomance; finite element Abstact. As the coe components of high-speed machining cente, Electic spindle ealizes zeo tansmission machine, the main content of this pape is the esponse and stability analysis of citical speed, unbalance of spindle unit, and the tansient excitation system in a vaiety of esponse and the tosional natual fequency and esponse. Intoduction Chaacteistic finite element method is geneally used to calculate spindle unit, especially the stiffness chaacteistics, high calculation pecision. But the analysis of the spindle unit, finite element softwae is not easy and beaing analysis theoy combining, need to be calculated though integal genealized load should be elative and beaing load, and the beaing load and defomation elation is lineaized. With the equiements of the dynamic pefomance of the spindle to impove, vaious factos influencing the dynamic chaacteistics of spindle should be compehensive consideation of the dynamic chaacteistics of spindle in analysis at, to make the esults moe close to the actual situation. Calculation and analysis of chaacteistics of spindle beaing As the key technology of high speed spindle beaing in, diectly detemine the load capacity, woking pefomance of spindle(high speed,high pecision, high igidity movement), the woking life and the spindle dynamic, static pefomance. Ball beaing dynamic pefomance is bette than the taditional ceamic ball beaings, theefoe, in the high speed machining cente, ceamic ball beaing electic spindle is usually adopted. Impovement of spindle beaing lubication on spindle speed plays an impotant ole, the geneal use of oil mist lubication o oil injection lubication. )Analysis of axial foce angle contact ball Poduct nominal diamete beaing Dm and spindle speed n (/ min) is called the ated speed coefficient, When the ated speed Dn m 6 coefficient eaches mm / min above, Electic spindle basically ae installed in high speed olling beaing. Angula contact ball beaings fo, When using the constant peload, the centipetal foce o themal expansion adial offset will cause the inne ing adial size boadening o olling body, esulting axial offset beaing cente. When using igid beaing aangement, the causes of beaing inne load incease. Because the beaing pessue angle change caused by the stiffness eduction will cause the spindle dynamic stiffness eduction, then will educe non flutte condition of mateial emoval ate[]. The beaing stiffness KB by the olling body size, olling goove cuvatue and pessue angle decision. But the dynamics pefomance and pe beaing load, cutting foce, speed and heat defomation elated. Beaing shea stiffness in one case only useful: the dynamic pefomance of the spindle is nonlineasystem. Fo angula contact ball beaing, and can bea adial load F and axial load F a. Pessue line stess ball foce afte the intesect at a point on the axis, the so-called pessue angle, As shown in Figue. 0. The authos - Published by Atlantis Pess 88

2 Figue Foce analysis of angula contact ball beaing At the same time unde adial and axial loads, Beaing inne ing and the oute ing ae espectively poduce elative displacement in the adial and axial amd, In this case, each ball beaing load is not consistent. each ball beaing defomation can be calculated by the following fomula: = sin + coscos = 0 In the fomula, is the beaing contact angle; Is the angle between the cente and the maximum load of each ball beaing olling body cente. the ball load 3 Q =.49 0 (D b ) the ball foce balance F = Q cossin F = Q sin ) Beaing axial adial static stiffness estimation Fo appoximate calculation of beaing stiffness, fist assume that the beaing unde load contact angle emains unchanged, and egadless of beaing aceway diamete and the influence on the main cuvatue and function, the deivation of the angula contact beaing stiffness and defomationof simplified calculation fomula. Beaings only bea axial foce, the channel of the beaing foce, theefoe we can obtain axial stain and axial stiffness K = F Z D (sin 0) = (sin 0) K F Z D the adial stiffness k, assuming that only the adial defomation of beaing axial defomation is zeo, at this time the beaings only bea adial foce, you can obtain the adial defomation and adial stiffness k F Z D =.89 0 (sin ),and the K = F Z D (sin ) 3) Stiffness calculation of beaing axial peload of angula contact Beaing pope pe tight can incease in stiffness and the life of shaft, in the suppoting stuctue of spindle, peload mainly fixed pessue petension and positioning petension in two foms, the latte is applied moe widely[3]. In the pactical application, Suppose beaing adial foce, the inne, oute only adial displacement without axialdisplacement. If the beaing peload is F 0, appoximate that each ball defomation consistent, Each ball load is Q= F 0 / (Z0sin ), Among them Z0 is the numbe of balls,fo b F 0 = (Z sin D ) axial beaing elative displacement is = = (Z sin D ) sin b F 0 axial pe tightening afte, as to subject to adial load, the inne and oute ing elative adial displacement, assuming the beaing peload fo axial positioning petension, and then subjected to 89

3 adial loading, axial displacement axial displacement of pe tight, Such is the elastic defomation of the ball at = sin + coscos 0 load of each ball is 3 0 Q =.49 0 D b ( sin + cos cos ) accoding to stess analysis, adial load component, 3 = = + 0 b F Q coscos.49 0 D ( sin coscos ) coscos F is equal to the algebaic each ball load and adial As can be seen fom the above equation, With inceases, F Inceases, but the situation vaies inceased peload changes. the fomula fo the deivative, you can get the adial stiffness 3 K =.49 0 Db cos ( 0 sin ) cos Fo ceamic ball beaings, peload available unde the action of its adial stiffness is cos 3 3 K = Db (Z D b) (F 0) (N/ m m) sin 3 as can be seen fom the above analysis, the elationship between the beaing load and defomation non-linea elationship. beaing stiffness is a function of the load, load, the geate stiffness. This is the calculation of the ceamic ball beaing peload must account fo the cause. In actual calculation, always want to have a stiffness value fo efeence. When the extenal load can not be detemined, Computing often taken as a dynamic load beaing 0 ated load beaing. 3 Spindle cell stuctue analysis of the inheent chaacteistics of computing Establishing an electic spindle and beaing suppot finite element model, beaing with sping dampe units, dynamic chaacteistics of a moto spindle machining cente model calculation model shown in Figue, figue thee, fou as the main component of the second and fouth-ode mode shapes. Figue spindle dynamic chaacteistic calculation model Vibational stuctue can be expessed as each ode natual vibation mode of the linea combination. Whee low-level natual modes of vibation of the stuctue of the highe ode effects of lage, the moe low-level the geate the impact, low ode modes of the dynamic chaacteistics of the stuctue play a decisive ole[4]. So the use of Subspace modal extaction method to calculate the spindle fist five natual fequencies and mode shapes as shown in Table Ⅰ. Table Ⅰ. Table Natual Fequencies And Mode Shapes Of A Spindle Ode Fequency /HZ Modes 0 Revese 70. A fist bending A fist bending Second-ode bending 9.9 Second-ode bending One can see fom the table, wo, thee natual fequencies ae equal, Modes wee fist bending and fist swing, So its pefomance is othogonal modes; Similaly, fou, five bands as well. Figue III and IV, espectively, a fist bending axis and second bend, As can be seen made by Ansys spindle modal analysis, get a good space simulation esults. 90

4 To ensue the machining accuacy and secuity, When the electic spindle wok can not exceed 7% of the maximum speed of one of the fist citical speed. As can be seen fom Table, This aticle fist citical speed electic spindle is =7030/min, the maximum opeating speed is 30000/min, fa less than the fist-ode citical speed, So the electic spindle design is easonable, Can effectively avoid the esonance egion. To ensue the pecision of the spindle[]. Figue 3 second-ode modes Figue 4, fouth-ode modes 4 the impact on the pe-load and speed spindle unit pefomance Geneally, All modes of natual fequencies incease with inceased peload, because the beaing stiffness inceases will follow; Simultaneously with the incease of spindle speed deceases, Because the centifugal foce will be inceased. To moe clealy compae the simulation and measuement esults, Figue gives a fixed spindle speed o pe-load, second-ode effects on the natual fequency of the pe-load and the spindle speed. When the pe-load is inceased fom 600N to 800N when a lage, Natual fequency inceases fom 068Hz to 4Hz. Coespondingly, When the spindle speed is inceased by a stationay, The natual fequency is educed fom 40Hz to 090Hz. Expeiments and analysis show that, Pe-load and speed on the dynamic chaacteistics of electic spindle unit has a cetain impact. Figue peload affects spindle speed and the natual fequency of the second ode Conclusions Though the analysis of high-speed machining cente electic spindle stuctue dynamic pefomance, spindle cells impoved dynamic pefomance measues:() select the appopiate pecision beaings and elated pats of pecision, spindle otation accuacy can be impoved.() Choose the ight spindle stuctue size, choose a good beaing stiffness, powe tansmission and easonable layout position and oientation can be good to impove the igidity spindle unit.(3) Minimize the length of the font end potion of the beaing stuctue of the spindle, to maximize the stiffness and damping of the font beaing, the font beaing to maximize the accuacy of the spindle unit can be impoved vibation esistance. Refeences [] High-speed electic spindle CNC machine contol technology Science Pess, Wu yuhou, Zhang Lixiu edito. [] CNC machine tool spindle cell electic technology Yu-thick edito Machiney Indust y Pess. 9

5 [3] High-speed machining cente pefomance modeling and optimization Science Pess edito Wang Shuting [4] CNC Machine Tool Spindle cell technology Machiney Industy Pess Wu yuhou e dito. [] Key technology eseach powe pemanent magnet synchonous moto spindle dive Beijing Univesity Pess Yujiabin edito. 9