欢迎来到麦多课文档分享! | 帮助中心 海量文档,免费浏览,给你所需,享你所想!
麦多课文档分享
全部分类
  • 标准规范>
  • 教学课件>
  • 考试资料>
  • 办公文档>
  • 学术论文>
  • 行业资料>
  • 易语言源码>
  • ImageVerifierCode 换一换
    首页 麦多课文档分享 > 资源分类 > PDF文档下载
    分享到微信 分享到微博 分享到QQ空间

    AGMA 12FTM01-2012 Balancing - No Longer Smoke and Mirrors.pdf

    • 资源ID:422146       资源大小:314.47KB        全文页数:10页
    • 资源格式: PDF        下载积分:5000积分
    快捷下载 游客一键下载
    账号登录下载
    微信登录下载
    二维码
    微信扫一扫登录
    下载资源需要5000积分(如需开发票,请勿充值!)
    邮箱/手机:
    温馨提示:
    如需开发票,请勿充值!快捷下载时,用户名和密码都是您填写的邮箱或者手机号,方便查询和重复下载(系统自动生成)。
    如需开发票,请勿充值!如填写123,账号就是123,密码也是123。
    支付方式: 支付宝扫码支付    微信扫码支付   
    验证码:   换一换

    加入VIP,交流精品资源
     
    账号:
    密码:
    验证码:   换一换
      忘记密码?
        
    友情提示
    2、PDF文件下载后,可能会被浏览器默认打开,此种情况可以点击浏览器菜单,保存网页到桌面,就可以正常下载了。
    3、本站不支持迅雷下载,请使用电脑自带的IE浏览器,或者360浏览器、谷歌浏览器下载即可。
    4、本站资源下载后的文档和图纸-无水印,预览文档经过压缩,下载后原文更清晰。
    5、试题试卷类文档,如果标题没有明确说明有答案则都视为没有答案,请知晓。

    AGMA 12FTM01-2012 Balancing - No Longer Smoke and Mirrors.pdf

    1、12FTM01AGMA Technical PaperBalancing NoLonger Smoke andMirrorsBy R. Hines Mifsud, HinesIndustries, Inc.Balancing No Longer Smoke and MirrorsRobin Hines Mifsud, Hines Industries, Inc.The statements and opinions contained herein are those of the author and should not be construed as anofficial action

    2、or opinion of the American Gear Manufacturers Association.AbstractWe all experience unbalance and balancing in everyday life:S washing machine on “spin dry” vibrating due to unevenly distributed clothes;S ceiling fan swaying back and forth as it spins;S getting new tires and you are asked if you wou

    3、ld like your wheels “balanced”.Picture or imagine:S spinning a Frisbee with a 1” sphere of clay stuck to one side;S swinging a stone around, overhead, on a string.In all the above examples,S the mass center and geometric center are misaligned;S there is an out of balance condition;S the object is no

    4、t balanced or has unbalance.Whenanunbalancedobjectisspun,itvibratesinrhythmwiththerotationandtheforcescausedbyunbalanceare relative to the square of the rotational speed. Two key equations are:Unbalance = Mass (or Weight) x RadiusDisplacement = Unbalance/Total Mass (or Weight)Inthepagesthatfollow,th

    5、roughstories,equationsandproblemsolving,balancingisdiscussedasmoremathand common sense and less smoke and mirrors.Copyright 2012American Gear Manufacturers Association1001 N. Fairfax Street, Suite 500Alexandria, Virginia 22314October 2012ISBN: 978-1-61481-032-23 12FTM01Balancing No Longer Smoke and

    6、MirrorsRobin Hines Mifsud, Hines Industries, Inc.Introductory story Balancing is smoke and mirrorsIn the late 1970s a balancing machine salesman visited a customers plant who had just received a newbalancer from the salesmans competitor. The plant manager saidthey werevery happywith theirautomaticba

    7、lancingmachineandofferedtoshowittothesalesman. Themanagerwalkedthesalesmanoutonthefloorand the two of them watched the operator and balancer in action.Theoperatorplacedapartonthebalancerandclosedthedoor. Thebalancerspunthepart,stopped,weldedonaweight,spunupagain,stopped,anddisplayed“goodpart”. Theop

    8、eratorremovedthebalancedpart,putin a new part, and closed the door. The balancer spun up the part, stopped, welded on a weight, spun upagain, stopped, and displayed “good part”. This scenario was repeated several more times as the salesmanand the manager watched.The manager commented, “We just love

    9、our new machine. All day long it balances parts by welding onweightsandputsoutgoodparts”. Thesalesmansuggestedhavingthe operatorplace a“balanced part”backinthebalanceragainjusttoseewhatwouldhappen. Sotheoperatorplacedthepreviouslybalancedpartbackin the balancer again and closed the door. The balance

    10、r spun up the part, stopped, welded on a secondweight, spun up again, stopped, and displayed “good part”. The manager had the operator take anotherpreviously “balanced part”and putit intothe balanceragain. Again, thebalancer spunup thepart, weldedonanother weight, spun up again, and displayed “good

    11、part”. Suddenly the manager was not so happy with hisbalancingmachine. Ithadbecomeclear;thismachinewasnotbalancingthepartsatall. Theyhadpurchasedan expensive welding machine to weld weights on their parts.Balancing Shedding some lightProductionManagerswhohavejustaddedanewbalancertotheirshoporproduct

    12、ionlineoftenask“HowdoIknow if my part is balanced?” This question is usually asked after the person has had some basic training inbalancing and has started balancing some parts. They quickly realize that visually, there is no measurabledifference between a “balanced” part and an “unbalanced” part. T

    13、hey can see the “balanced” part has someholes (or other correction) and the “unbalanced” part has no holes (or other correction.) The balancingmachine says, “Good part,” but they still feel a need to ask “How do I know if the part is REALLY balanced?”and“Whatifthebalanceriswrong?” Iwillattempttoansw

    14、erthesequestionsinthepagesthatfollow,suchthat“if you can fog a mirror” you can probably understand balancing.Basic balancing principalsThe simplest form of unbalance iscalled “Forceunbalance”, “Staticunbalance”, or“Single planeunbalance”.Theseareallwordsforthesamething. Ifyoutakeanunbalancedgear,mou

    15、ntitonashaft,andsetitbetweentwoknifeedges;theheavyspotwillrolltothebottom. Whenthispartisspunupandtheheavyspotisspinningaround,theforcesgeneratedbytheheavyspot,pullthegearinthedirection ofthe heavyspot. This issimilartospinningastoneonastring. Theforcescausedbytheunbalanceincreaseordecreaseasthesqua

    16、reofthechangeintherotationalspeed. Unbalanceisusuallymeasuredandspecifiedinunitsofounce-inches,gram-centimeters, or gram-millimeters. Roughly, 1 oz-in = 72 g-cm = 720 g-mm. See Figure 1 and Figure 2.4 12FTM01Figure 1. Part with unbalanceFigure 2. Part with unbalanceSingle plane unbalanceThe equation

    17、 for calculating the amount of single plane unbalance is:Unbalance = Mass (or Weight)RadiusThis is the mass of the heavy spot multiplied by the gear radius to the center of the heavy spot.Getsomeoilbasedmodelingclay,andweigha1grampiece.Addthe1grammassofclaytoabalancedgear,so the clay is located at a

    18、 radius of 200 mm. The gear now has an unbalance of:Unbalance = 1 g200 mm = 200 g-mm(0.035 oz8 in = 0.28 oz-in)Reflecting on balancing machinesThe following is a very brief synopsis of balancing machines, past and present:Balancingways. A gear assembly (or a gear mounted on a shaft) is placed on two

    19、 knife edges. The heavyside rolls to the bottom to show the unbalance.Bubblebalancers. Theaxisofthepartisheldverticallyandloosely. Thepartdoesnotrotateandabubbleisused to show the location of the unbalance or heavy spot.Soft suspension balancing machines. Hold the part suspended on a fine wire. The

    20、part is spun at highspeeds (above the resonant frequency of the suspension) and the machine measures the displacement.5 12FTM01Partsofdifferentweightsrequireadifferentcalibration. Partswithlarge initialunbalance mustbe balancedinsteps at gradually increasing speeds.Hard suspension balancing machines

    21、. Hold the part on a stiff suspension. The part is spun at relativelylow speeds (below the resonant frequency) and the machine measures the force caused by the unbalance.Calibration is the same for the full range of part weights. This suspension readily allows for on-machine cor-rectionandevenpartsw

    22、ithlargeamountsofunbalancecanbebalancedonthefirstspin. Nonrotatingbalan-cing machines with a hard suspension use what is called a stiff pivot.Forces generated by the unbalance SmokescreenTo calculate the amount of force caused by unbalance in a rotating object, use the following equation:Funb= 1.77

    23、(RPM/1000)2(oz-in)orFunb= 127.41(RPM/1000)2(g-cm)where:Funbis the centrifugal force generated by unbalance in a rotating object, in pounds oz-in is the amount ofunbalance in the residual heavy spot, in ounce-inches.In a gear assembly, operating at 1500 rpm, with 1 oz-in of unbalance:Funb= 1.77 (RPM/

    24、1000)2(oz-in) = 1.77(1500/1000)21oz-in=4lbforceIn another gear assembly, with 4X the amount of unbalance, the Force is 4larger:Funb= 1.77 (RPM/1000)2(oz-in) = 1.77(1500/1000)24oz-in=16lbforceIn the first gear assembly, operating at 4X the original speed, the Force is 16X larger:Funb= 1.77 (RPM/1000)

    25、2(oz-in) = 1.77(6000/1000)21oz-in=64lbforceThe problems caused by the unbalance are relative to the overall weight, age, and use of the gear assembly.Displacement = Distance between geometric axis and mass axisOn a balanced gear the geometric axis and mass axis are the same. The geometric axis is th

    26、e axisdeterminedduringmanufacture;itisthecenteroftheshaftthatthegearismountedontospin. Themassaxisis the line or axis thatthe gearwill naturallyrotate aroundif itis tossedup intothe airand spun. SeeFigure 3.Figure 3. Balancing is alignment mass axis to geometric axis6 12FTM01Ifyouaddsomemasstothegea

    27、rononeside,thecenterofmassormassaxisofthegearshiftsinthedirectionof the added mass. The distance between the mass axis and the geometric axis is called displacement.Displacement = Amount of unbalance/Total mass (or weight)Tocalculatethedisplacement,youtaketheamountofunbalance,200g-mm,anddivideitbyth

    28、etotalmassofthe gear or gear assembly, 50 kg or 50,000 g.Displacement = 200 g-mm/50,000 g = 0.004 mm of displacement0.28 oz-in /1764 oz = 0.00016” (1.610- 4) of displacementBalancing = Alignment of geometric axis and mass axisGearsmaybebalancedbyaddingweight,180fromtheheavyspot,bywelding, riveting,a

    29、dding epoxyputty,etc.,seeFigure 4. Whenwebalancethegearfromtheaboveexample,weremovematerialattheangleoftheheavy spot, either by drilling, milling, or grinding. If we precisely remove 1 gram of mass, at a radius of 200mm,attheangleoftheheavyspot;themassaxisandgeometricaxisarerealignedandthegearis“bal

    30、anced”,see Figure 5. We could also remove 2 gram at a 100 mm radius or 20 gram at a 10 mm radius. Thesmallestcorrections for unbalance are made as close to the outer diameter of the part as possible.Figure 4. Welding on a weight to correct unbalanceFigure 5. Drilling holes to correct unbalance7 12FT

    31、M01Balance toleranceOne method of setting a balance tolerance is using the API equation:Balance tolerance = 4W/N = 4Weight in pounds per stanchion/rpmUsing a 50,000g (110 lb) gear assembly, that rotates at 5000 rpm in use:455 lb/5000 rpm = 0.044 oz-in /stanchion = 32 g-mm/stanchionItisimportanttonot

    32、ethatalthoughtherpmisusedintheequationtodeterminetheamountofunbalance;thisdoes not mean the part must be spun at5000 rpmto measurethe unbalance. Somebalancers donot spinatall; they measure the weight on all sides of the geometric center of the part.Unbalance = (1 g32 mm)/stanchion2 stanchions = 64 g

    33、-mm = 0.088 oz-inThegearassemblywillhave64g-mmofunbalance,whetheritissittingstill,spinningat100rpm,3500rpm,or10,000rpm. Theforcescausedbytheunbalancewillbevastlydifferent,buttheamountofunbalanceremainsthe same. It is important to list the rpm assumed for a particular balance tolerance. Thebalance to

    34、leranceisoften listed as “32 g-mm at 5000 rpm”. Again,the “5000rpm” isspecifying theoperating speedand doesnotrefer to the balancing speed. If the part will spin faster or slower than 5000 rpm in use, a different balancetolerance should be calculated.Theonlyreasontobalanceattheoperatingspeedisifpart

    35、sorcomponentsof theassembly swingout orshiftatahigherspeed. Manyturbinesandcombineshavebladesorhammersthatshiftoutwardasthepartisspunuptotheoperatingspeed,sotheyshouldbebalanced atthat speed. Whencomponents areshifting atdiffer-entspeeds,theunbalanceisalsochanging. Forultraprecisionbalancing,replica

    36、tingtheoperatingtemperat-ure and pressure for the part in use, should be considered. See Figure 6.Two plane unbalanceIn the case of two gears mounted on a shaft, one gear may have unbalance, caused by a heavy spot at oneangle, and the second gear may have a different amount of unbalance at a differe

    37、nt angle. Thisis called“dy-namic unbalance”, “two plane unbalance”, or “a combination of couple unbalance and force unbalance”. Inthis case, the mass axis and geometric axis are no longer parallel but skewed. To correct the unbalance, theheavy spot on each gear will need to be removed.Figure 6. Crad

    38、le style balancer with 2 stanchions to support the part8 12FTM01As the two correction planes are moved closer together, along the geometric axis, the amount of correctionrequired increases to infinity. The smallest corrections are made closest to the part outer diameter and withthe correction planes

    39、 the furthest apart. See Figure 7.Importance of small variations where theres smoke.If a balanced gear with a mass of 50 Kg (110 lb) is mounted on a balanced shaft and the clearance, oreccentricity, is such that the gear is held off center by 0.00006” (or 610- 5inch) it will cause the assembly tobe

    40、unbalanced.110 lb16 oz/lb610- 5= 0.106 oz-in (63 g-mm), 0.053 oz-in/stanchionComparethistoourbalancetoleranceof0.04oz-in/stanchion. Theassemblyisoutoftolerance,notbecauseof any unbalance in the gear but because the gear is held off center in the assembly. The shaft may haverunout (TIR) or clearance

    41、of 0.00012” (1.210- 4)or0.003mm.Dontletyourtimespentbalancing“goupinsmoke”. Itisinefficienttobalancecomponentstotighttolerancesunless part dimensions, clearance, and runout are held to equally tight tolerances in the final assembly.Wherepossible,itisoftenbesttobalancethefullassemblyinitsownbearings;

    42、radialorpreloadedaxial. SeeFigure 8 and Figure 9.Figure 7. Two plane unbalanceFigure 8. Small variations (exaggerated view)9 12FTM01Figure 9. Small variations (exaggerated view)Problem solvingProduction line gears mirror imagesWhen balancing gears in a production environment, it is important to cont

    43、inually monitor the final “balanced”product. Are they actually balanced? Is the machine still calibrated and set up correctly? And how do youknow? Toconfirmthatthe“balanced”gears,inyourcrate,areactuallybalanced,youshouldtake5or10fromeach lot, back to the balancer and run the following tests:S Measur

    44、e unbalance. Is it below tolerance?S Turn the part 180 on the tooling and measure unbalance again. Is it still below tolerance?S Measure each of the parts in this manner. If they are not all clearly below tolerance, you should run theentire lot through the balancer again. The moral check early and o

    45、ften until you gain confidence in thebalancer.S Add a test weight, either to the spindle or a master part. Is the balancer calibrated? = does the balancerdisplay the amount of unbalance expected for the test weight?S Check the rest of the set up related to your part and correction methodIt is import

    46、ant to keep “scrap” parts from getting accidentally mixed in with the “good” parts. There are manystandard, balancing machine features available to help with this, including:S password required to remove scrap parts from the balancerS locked scrap binsS ink marking only good parts or only scrap part

    47、sS automatic transfer of parts to conveyors for good or scrap partsProblem solving gear assembly blowing smokeWhen balancing gears that will be assembled later, it makes sense to balance the assembly as well. Eventhough the individual gearsand shaftare balanced,the finalassembly mayhave unbalancedue

    48、 toclearanceandrunout. See“ImportanceofSmallVariations”. Totestthatthegearsorassembliesaretrulybalanced,youcan use the list given in “Production line gears” = measure, turn 180 to measure again, and test calibration.Sometimes a gear assembly is balanced, the machine setup is changed and another part

    49、 or assembly isbalanced, then the setup is changed again and the first assembly is put back into the balancer. Thereadingsmaybequitedifferentwhy? See“Importanceofsmallvariations”. Whenyouarereadingfinelevelsofunbal-ance,smallchangescanmakeabigdifference. Ifthebalancerbearingslocateinonelocationontheshaftone10 12FTM01timeandanotherlocationthenexttime,andthereisrunoutintheshaft,thenthegeometriccenterlinechangesandsodotheunbalancereadings. Forthisreason,itisoftenbesttobalancetheassemblyinitsownbearings;


    注意事项

    本文(AGMA 12FTM01-2012 Balancing - No Longer Smoke and Mirrors.pdf)为本站会员(visitstep340)主动上传,麦多课文档分享仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对上载内容本身不做任何修改或编辑。 若此文所含内容侵犯了您的版权或隐私,请立即通知麦多课文档分享(点击联系客服),我们立即给予删除!




    关于我们 - 网站声明 - 网站地图 - 资源地图 - 友情链接 - 网站客服 - 联系我们

    copyright@ 2008-2019 麦多课文库(www.mydoc123.com)网站版权所有
    备案/许可证编号:苏ICP备17064731号-1 

    收起
    展开