機(jī)床主軸設(shè)計(jì)及相關(guān)技術(shù)研究-數(shù)控銑床的主軸結(jié)構(gòu)【含8張cad圖紙+文檔全套資料】
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畢 業(yè) 設(shè) 計(jì) 任 務(wù) 書1畢業(yè)設(shè)計(jì)的任務(wù)和要求:掌握機(jī)床主軸的基本知識(shí);掌握機(jī)床主軸設(shè)計(jì)的技術(shù)關(guān)鍵;研究數(shù)控機(jī)床主軸單元的關(guān)鍵技術(shù),掌握其相關(guān)知識(shí)及選型、應(yīng)用、設(shè)計(jì)方法等;完成一種數(shù)控銑床主軸單元的設(shè)計(jì),要求主軸工作的轉(zhuǎn)速可達(dá)8000r/min,輸出功率可達(dá)5kW,使用40柄刀具。2畢業(yè)設(shè)計(jì)的具體工作內(nèi)容:1) 分析題目要求,查閱相關(guān)的國內(nèi)外文獻(xiàn)、設(shè)計(jì)資料、有關(guān)專利文獻(xiàn)等,在此基礎(chǔ)上,了解開題報(bào)告的撰寫方法、基本要求,完成開題報(bào)告;2) 學(xué)習(xí)和掌握機(jī)床主軸的有關(guān)知識(shí),了解主軸單元、電主軸的有關(guān)知識(shí)及發(fā)展現(xiàn)狀;了解數(shù)控機(jī)床、加工中心對(duì)主軸的要求;總結(jié)機(jī)床主軸的設(shè)計(jì)要點(diǎn)、技術(shù)關(guān)鍵及發(fā)展方向;力爭(zhēng)提出主軸設(shè)計(jì)的發(fā)展方向;3) 按題目要求,設(shè)計(jì)一種數(shù)控銑床的主軸單元,完成裝配圖及主要零件圖,給出功率、強(qiáng)度、剛度、軸承等必要的計(jì)算;4) 編寫設(shè)計(jì)說明書;5) 翻譯本專業(yè)外文科技文獻(xiàn)一份。畢 業(yè) 設(shè) 計(jì) 任 務(wù) 書3對(duì)畢業(yè)設(shè)計(jì)成果的要求:1)主軸裝配圖、主要零件圖;2)主軸技術(shù)的研究及設(shè)計(jì)說明書一份;3)本專業(yè)外文科技文獻(xiàn)譯文一份。4畢業(yè)設(shè)計(jì)工作進(jìn)度計(jì)劃:起 迄 日 期工 作 內(nèi) 容2016年 02月29日 03月21日 03月22日 04月30日05月01日 05月20日05月21日 05月31日06月01日 06月05日分析課題要求,查閱相關(guān)文獻(xiàn)資料,了解機(jī)床主軸設(shè)計(jì)的國內(nèi)外現(xiàn)狀及發(fā)展趨勢(shì),提出自己的設(shè)計(jì)思路,完成開題報(bào)告;全面掌握主軸相關(guān)的基本知識(shí),了解高速主軸的關(guān)鍵技術(shù),了解主軸單元的設(shè)計(jì)特點(diǎn);分析總結(jié)主軸技術(shù)的發(fā)展方向;設(shè)計(jì)主軸,完成裝配圖和主要零件圖;完成研究總結(jié)及設(shè)計(jì)說明書撰寫答辯講稿,準(zhǔn)備答辯;學(xué)生所在系審查意見: 同意下發(fā)任務(wù)書系主任: 2016年 2 月 29 日畢 業(yè) 設(shè) 計(jì) 開 題 報(bào) 告1結(jié)合畢業(yè)設(shè)計(jì)課題情況,根據(jù)所查閱的文獻(xiàn)資料,撰寫2000字左右的文獻(xiàn)綜述: 文 獻(xiàn) 綜 述1.1國內(nèi)外機(jī)床主軸研究現(xiàn)狀 (1)國內(nèi)研究現(xiàn)狀 目前國內(nèi)研究高速電主軸的科研機(jī)構(gòu)有我國河南省洛陽軸承研究所 ,他們能自行研究開發(fā)電主軸 ,其DmN值達(dá)到了很高的水平 ;廣州鉅聯(lián)高速電主軸有限公司研發(fā)的大功率靜壓軸承電主軸曾獲得日內(nèi)瓦國際專利技術(shù)博覽會(huì)金獎(jiǎng) ;廣東工業(yè)大學(xué)高速加工和機(jī)床研究所也開發(fā)了數(shù)控銑床高速電主軸。其主要技術(shù)指標(biāo)為 :電主軸的額定功率是 13.5kW ,最高轉(zhuǎn)速為 180 0 0r/min ,在額定轉(zhuǎn)速 5 0 0r/min時(shí)產(chǎn)生最大輸出轉(zhuǎn)矩為 85Nm。在我國的安陽市 ,有一家中外合資的電主軸生產(chǎn)廠家安陽萊必泰機(jī)械有限公司 ,它擁有先進(jìn)的電主軸、機(jī)床主軸設(shè)計(jì)和制造技術(shù)。該公司研制生產(chǎn)的加工中心電主軸 ,采用先進(jìn)技術(shù) ,配有矢量閉環(huán)控制系統(tǒng) ,能對(duì)主軸實(shí)行恒功率調(diào)速 ,準(zhǔn)停制動(dòng)。功率為 3.7 2 5kW ,恒功率段 15 0 0 12 0 0 0r/min。采用進(jìn)口高速精密軸承 ,旋轉(zhuǎn)件經(jīng)高精度平衡。該系列產(chǎn)品具有高精度、高剛度、高速度、低噪聲、低振動(dòng)、低溫升等優(yōu)點(diǎn) ,系99國家火炬計(jì)劃項(xiàng)目。 (2)國外研究現(xiàn)狀 國外高速電主軸技術(shù)由于研究較早 ,技術(shù)水平也處于領(lǐng)先地位 ,電主軸已越來越多地應(yīng)用到工業(yè)制造業(yè)中。著名的有瑞士的Fisher公司、Ibag公司、德 國的GMN公司、Hofer公司、Siemens公司、意大利Faemat公司、Gamfior公司及美國Ingersoll公司、日本Okuma公司和Fanuc公司等,它們的技術(shù)水平代表了這個(gè)領(lǐng)域的世界先進(jìn)水平。這些公司生產(chǎn)的電主軸較之國內(nèi)生產(chǎn)的有以下幾個(gè)特點(diǎn) :功率大、轉(zhuǎn)速高。采用高速、高剛度軸承。國外高速精密主軸上采用高速、高剛度軸承 ,主要有陶瓷軸承和液體動(dòng)靜壓軸承 ,特殊場(chǎng)合采用空氣潤(rùn)滑軸承和磁懸浮軸承。精密加工與精密裝配工藝水平高。配套控制系統(tǒng)水平高。這些控制系統(tǒng)包括轉(zhuǎn)子自動(dòng)平衡系統(tǒng)、軸承油氣潤(rùn)滑與精密控制系統(tǒng)、定轉(zhuǎn)子冷卻溫度精密控制系統(tǒng)、主軸變形溫度補(bǔ)償精密控制系統(tǒng)等。并在此基礎(chǔ)之上,這些外國廠家如美國、日本、德國、意大利和瑞士等工業(yè)發(fā)達(dá)國家已生產(chǎn)了多種商品化高速機(jī)床。如瑞士米克朗公司 ,就是世界上著名的精密機(jī)床制造商。它生產(chǎn)的機(jī)床配備最高達(dá) 6 0 0 0 0r/min的高速電主軸 ,可以滿足不同的切削要求 ,所有的電主軸均裝有恒溫冷卻水套對(duì)主軸電機(jī)和軸承進(jìn)行冷卻 ,并通過高壓油霧對(duì)復(fù)合陶瓷軸承進(jìn)行潤(rùn)滑。所有的電主軸均采用矢量控制技術(shù) ,可以在低轉(zhuǎn)速時(shí)輸出大扭矩。國產(chǎn)電主軸和國外產(chǎn)品相比較 ,無論是性能、品種和質(zhì)量都有較大差距 ,國產(chǎn)電主軸產(chǎn)品和國外的相比較 ,主要存在以下差距 :(1)國外電主軸低速段的輸出扭矩最大可達(dá) 30 0Nm ,而我國目前僅在 10 0Nm以內(nèi)。(2 )在高轉(zhuǎn)速方面 ,國外用于加工中心的電主軸轉(zhuǎn)速已達(dá) 75 0 0 0r/min ,我國則多在15 0 0 0r/min以內(nèi)。(3)電主軸的軸承潤(rùn)滑 ,國外普遍采用油氣潤(rùn)滑 ,而我國仍用油脂潤(rùn)滑。(4 )其他配套技術(shù)也有較大差距 ,如主軸電機(jī)矢量控制、交流伺服控制技術(shù)、精確定向技術(shù)、快速啟動(dòng)、停止等。(5 )在產(chǎn)品的品種、規(guī)格、數(shù)量和制造規(guī)模等方面 ,國產(chǎn)電主軸仍然處于小量研發(fā)試制階段 ,沒有形成系列化、專業(yè)化 ,遠(yuǎn)不能滿足國內(nèi)數(shù)控機(jī)床和加工中心發(fā)展的需求。所以目前國產(chǎn)的高轉(zhuǎn)速、高精度數(shù)控機(jī)床和加工中心所用的電主軸 ,仍然主要從國外進(jìn)口。1.2主軸技術(shù)的發(fā)展趨勢(shì)1)繼續(xù)向高速度、高剛度方向發(fā)展由于高速切削和實(shí)際應(yīng)用的需要,隨著主軸軸承及其潤(rùn)滑技術(shù)、精密加工技術(shù)、精密動(dòng)平衡技術(shù)、高速刀具及其接口技術(shù)等相關(guān)技術(shù)的發(fā)展,數(shù)控機(jī)床用電主軸高速化已成為目前發(fā)展的普遍趨勢(shì),如鉆、銑用電主軸,瑞士IBAG的HF42的轉(zhuǎn)速達(dá)到140000rmin,英國WestWind公司的PCB鉆孔機(jī)電主軸D1733更是達(dá)到了250000rmin;加工中心用電主軸,瑞士FISCHER最高轉(zhuǎn)速達(dá)到42000rmin,意大利CAMFIOR達(dá)到了75000rmin。在電主軸的系統(tǒng)剛度方面,由于軸承及其潤(rùn)滑技術(shù)的發(fā)展,電主軸的系統(tǒng)剛度越來越大,滿足了數(shù)控機(jī)床高速、高效和精密加工發(fā)展的需要。2) 向高速大功率、低速大轉(zhuǎn)矩方向發(fā)展根據(jù)實(shí)際使用的需要,多數(shù)數(shù)控機(jī)床需要同時(shí)能夠滿足低速粗加工時(shí)的重切削、高速切削時(shí)精加工的要求,因此,機(jī)床電主軸應(yīng)該具備低速大轉(zhuǎn)矩、高速大功率的性能。如意大利CAMFIOR、瑞士StepTec、德國GMN等制造商生產(chǎn)的加工中心用電主軸,低速段輸出轉(zhuǎn)矩到200Nm以上的已經(jīng)不是難事,德國CYTEC的數(shù)控銑床和車床用電主軸的最大扭矩更是達(dá)到了630Nm;在高速段大功率方面,一般在l050kW;CYTEC電主軸的最大輸出功率為50kW;瑞士StepTec電主軸的最大功率更是達(dá)到65kW(S1),用于航空器制造和模具加工;更有電主軸功率達(dá)到80kW 的報(bào)道。 3) 進(jìn)一步向高精度、高可靠性和延長(zhǎng)工作壽命方向發(fā)展用戶對(duì)數(shù)控機(jī)床的精度和使用可靠性提出了越來越高的要求,作為數(shù)控機(jī)床核心功能部件之一的電主軸,要求其本身的精度和可靠性隨之越來越高。如主軸徑向跳動(dòng)在0.001mm 以內(nèi)、軸向定位精度0.0005mm以下。同時(shí),由于采用了特殊的精密主軸軸承、先進(jìn)的潤(rùn)滑方法以及特殊的預(yù)負(fù)荷施加方式,電主軸的壽命相應(yīng)得到了延長(zhǎng),其使用可靠性越來越高。StepTec的電主軸還加裝了加速度傳感器,降低軸承振動(dòng)加速度水平,為了監(jiān)視和限制軸承上的振動(dòng),安裝了振動(dòng)監(jiān)測(cè)模塊,以延長(zhǎng)電主軸工作壽命。4) 快速啟動(dòng)、停止響應(yīng)速度加快為縮短輔助時(shí)間,提高效率,要求數(shù)控機(jī)床電主軸的啟、停時(shí)間越短越好,因此需要很高的啟動(dòng)和停機(jī)加(減)速度。目前,國外機(jī)床電主軸的啟、停加速度可達(dá)到lg以上,全速啟、停時(shí)間在ls以內(nèi)。5) 軸承及其預(yù)加載荷方式、潤(rùn)滑方式多樣化除了常規(guī)的鋼制滾動(dòng)軸承外,近年來陶瓷球混合軸承越來越得到廣泛的應(yīng)用,潤(rùn)滑方式有油脂、油霧、油氣等,尤其是油氣潤(rùn)滑方法(又Oil-air),由于具有適應(yīng)高速、環(huán)保節(jié)能的特點(diǎn),得到越來越廣泛的推廣和應(yīng)用;滾動(dòng)軸承的預(yù)負(fù)荷施加方式除了剛性預(yù)負(fù)荷(又稱定位預(yù)負(fù)荷)、彈性預(yù)負(fù)荷(又稱定壓預(yù)負(fù)荷)之外,又發(fā)展了一種智能預(yù)負(fù)荷方式,即利用液壓油缸對(duì)軸承施加預(yù)負(fù)荷,并且可以根據(jù)主軸的轉(zhuǎn)速、負(fù)載等具體工況控制預(yù)負(fù)荷的大小,使軸承的支承性能更加優(yōu)良。在非接觸形式軸承支承的電主軸方面,如磁浮軸承、氣浮軸承電主軸(瑞士IBAG等)、液浮軸承電主軸(美國Ingersoll等)等已經(jīng)有系列商品供應(yīng)市場(chǎng)。 6)向多功能、智能化方向發(fā)展在多功能方面,有角向停機(jī)精確定位(準(zhǔn)停)、C軸傳動(dòng)、換刀中空吹氣、中空通冷卻液、軸端氣體密封、低速轉(zhuǎn)矩放大、軸向定位精密補(bǔ)償、換刀自動(dòng)動(dòng)平衡技術(shù)等。在智能化方面,主要表現(xiàn)在各種安全保護(hù)和故障監(jiān)測(cè)診斷措施,如換刀聯(lián)鎖保護(hù)、軸承溫度監(jiān)控、電機(jī)過載和過熱保護(hù)、松刀時(shí)軸承卸荷保護(hù)、主軸振動(dòng)信號(hào)監(jiān)測(cè)和故障異常診斷、軸向位置變化自動(dòng)補(bǔ)償、砂輪修整過程信號(hào)監(jiān)測(cè)和自動(dòng)控制、刀具磨損和損壞信號(hào)監(jiān)控等,如Step-Tec 電主軸安裝有診斷模塊,維修人員可通過紅外接口讀取數(shù)據(jù),識(shí)別過載,統(tǒng)計(jì)電主軸工作壽命。參考文獻(xiàn)1鄭修本.機(jī)械制造工藝學(xué).機(jī)械工業(yè)出版社,2012,032韓秋實(shí).械制造技術(shù)基礎(chǔ).北京:機(jī)械工業(yè)出版社,2010 3 谷玉芳.立式加工中心主軸箱的抗振特性研究和拓?fù)鋬?yōu)化設(shè)計(jì)D.陜西科技大學(xué) 2012.4秦大同.謝里陽.現(xiàn)代機(jī)械設(shè)計(jì)手冊(cè)(第1卷).化學(xué)工業(yè)出版社,2011,035孫開元.駱?biāo)鼐?常見機(jī)構(gòu)設(shè)計(jì)及應(yīng)用圖例.化學(xué)工業(yè)出版社,2010,076凌云.朱金生.機(jī)械設(shè)計(jì)實(shí)用機(jī)構(gòu)運(yùn)動(dòng)仿真圖解.電子工業(yè)出版社,2014,017楊雪寶.機(jī)械制造裝備與設(shè)計(jì).西北工業(yè)大學(xué)出版社,2010.8 李國斌.機(jī)械設(shè)計(jì)基礎(chǔ).機(jī)械工業(yè)出版社出版,20109辛文彤.Solidworks2012中文版從入門到精通.人民郵電出版社, 2012,0110詹迪維.Solid Works高級(jí)應(yīng)用教程(2012中文版).機(jī)械工業(yè)出版社,2012,0311 呂建法,閆兵,王文芝.鏜銑床有限元建模及其瞬態(tài)動(dòng)力學(xué)分析J.機(jī)械工程師. 2012(12).12 任小星.BFK150/2鏜銑床主軸夾緊裝置的改造J.制造技術(shù)與機(jī)床.2016(02).13 劉超峰,張功學(xué),張淳,陳英.DVG850高速立式加工中心主軸箱靈敏度分析J.組合機(jī)床與自動(dòng)化加工技術(shù).2010(10).14 張霄.機(jī)床主軸箱的固定聯(lián)接及其結(jié)構(gòu)方案設(shè)計(jì)D.大連理工大學(xué)2015.15 張樂平.面向重載數(shù)控車床的主軸箱結(jié)構(gòu)優(yōu)化D.南京航空航天大學(xué)2014.16 陸暢.重型數(shù)控車床主軸箱的分析及優(yōu)化D.沈陽航空航天大學(xué)2014.17 梁東旭.球面車磨床主軸箱及其關(guān)鍵零件的有限元分析與優(yōu)化D.蘭州理工大學(xué) 2013.18 韓君.組合機(jī)床主軸箱智能設(shè)計(jì)系統(tǒng)的研究D. 河北農(nóng)業(yè)大學(xué) 2012 畢 業(yè) 設(shè) 計(jì) 開 題 報(bào) 告本課題要研究或解決的問題和擬采用的研究手段(途徑):2.1研究或解決的問題 (1)通過對(duì)自己所查找的相關(guān)資料,了解掌握銑床主軸的基本知識(shí)。 (2)熟悉銑床主軸單元的關(guān)鍵技術(shù),掌握其相關(guān)知識(shí)及選型、應(yīng)用、設(shè)計(jì)方法等。 (3)學(xué)會(huì)CAD設(shè)計(jì)軟件,完成相應(yīng)的工程圖設(shè)計(jì)。 (4)編寫說明書。2.2擬采用的設(shè)計(jì)方案 (1)本次設(shè)計(jì)擬采用數(shù)控銑床的電主軸,其結(jié)構(gòu)如圖所示: 圖1 數(shù)控銑床主軸結(jié)構(gòu)圖 (2)主軸伺服驅(qū)動(dòng)器的選擇:由于本次設(shè)計(jì)要求主軸工作轉(zhuǎn)速達(dá)8000r/min,輸出功率達(dá)5KW,可采用深圳步科的伺服驅(qū)動(dòng)器。具體的相關(guān)的技術(shù)參數(shù)如下:控制器等級(jí),0.75Kw75Kw;調(diào)速范圍,0r/min15000r/min(四級(jí)電機(jī));0r/min30000r/min(二級(jí)電機(jī));本次的電機(jī)的主功率為5Kw,轉(zhuǎn)速8000r/min。 (3)確定主軸的主要結(jié)構(gòu)參數(shù):確定主軸的軸徑、主軸前端懸伸量和主軸主要支承間的跨距。 (4)利用CAD軟件繪制工程圖。2.3擬采用的研究思路和手段初步擬采用理論分析和結(jié)構(gòu)設(shè)計(jì)相結(jié)合的研究方法。針對(duì)銑床主軸單元設(shè)計(jì)主要采取以下方法: 收集國內(nèi)外相關(guān)研究資料,對(duì)其進(jìn)行詳細(xì)分析并總結(jié)各自方案的優(yōu)缺點(diǎn);通過對(duì)比國內(nèi)外研究情況,提出自己的看法,擁有自己的創(chuàng)新點(diǎn)。通過對(duì)機(jī)構(gòu)進(jìn)行總體分析并詳細(xì)設(shè)計(jì),初步確定本設(shè)計(jì)的研究思路??偨Y(jié)自己的思路,并與指導(dǎo)老師、同學(xué)們進(jìn)行交流,最終確保本畢業(yè)設(shè)計(jì)思路的正確性和可行性。在做畢業(yè)設(shè)計(jì)的過程中,如果遇到疑問或問題,及時(shí)與老師溝通交流;最終完成銑床主軸變速箱設(shè)計(jì)。撰寫畢業(yè)設(shè)計(jì)說明書,準(zhǔn)備答辯。進(jìn)度安排:2月29日-3月3日:查閱資料3月4日-3月21日 :撰寫開題報(bào)告 3月22日-5月18日:確定優(yōu)化方案 5月19日-6月1日: 完成畢業(yè)論文初稿6月2日6月5日:根據(jù)指導(dǎo)老師意見,修改論文初稿,完成終稿,準(zhǔn)備答辯 畢 業(yè) 設(shè) 計(jì) 開 題 報(bào) 告指導(dǎo)教師意見:報(bào)告表明,該同學(xué)近期查閱了大量文獻(xiàn)資料,特別是企業(yè)產(chǎn)品的技術(shù)資料,對(duì)數(shù)控機(jī)床、電主軸等有了一些新認(rèn)識(shí)。對(duì)國內(nèi)外采用了什么新技術(shù),關(guān)鍵技術(shù)等還有些不足。但對(duì)設(shè)計(jì)任務(wù)基本明確。 同意開題。 指導(dǎo)教師: 2016 年 3 月 22 日所在學(xué)院審查意見: 同意開題 負(fù)責(zé)人: 2016 年 3 月 22 日 Machine tool spindle units1 IntroductionMachine tool spindles basically fulfill two tasks:rotate the tools (drilling, milling and grinding) or work piece (turning) precisely inspace transmit the required energy to the cutting zone for metal removalObviously spindles have a strong influence on metal removal rates and quality of the machinedparts. This paper reviews the current state.and presents research challenges of spindle technology.1.1.Historical reviewClassically, main spindles were driven by belts or gears and the rotational speeds could only bevaried by changing either the transmission ratio or the number of driven poles by electricalswitches.Later simple electrical or hydraulic controllers were developed and the rotational speed of thespindle could be changed by means of infinitely adjustable rotating transformers (Ward Leonardsystem of motor control).The need for increased productivity led to higher speed machiningrequirements which led to the development of new bearings, power electronics and invertersystems. The progress in the field of the power electronics (static frequency converter) led to thedevelopment of compact drives with low-cost maintenance using high frequency three-phaseasynchronous motors.Through the early 1980s high spindle speeds were achievable only by usingactive magnetic bearings. Continuous developments in bearings, lubrication, the rolling elementmaterials and drive systems (motors and converters) have allowed the construction of direct drivemotor spindles which currently fulfill a wide range of requirements.1.2. Principal setupToday, the overwhelming majority of machine tools are equipped with motorized spindles.Unlike externally driven spindles, the motorized spindles do not require mechanical transmissionelements like gears and couplings.The spindles have at least two sets of mainly ball bearing systems. The bearing system is thecomponent with the greatest influence on the lifetime of a spindle. Most commonly the motor isarranged between the two bearing systems.Due to high ratio of power to volume active cooling is often required, which is generallyimplemented through water based cooling. The coolant flows through a cooling sleeve around thestator of the motor and often the outer bearing rings.Seals at the tool end of the spindle prevent the intrusion of chips and cutting fluid. Often this isdone with purge air and a labyrinth seal.A standardized tool interface such as HSK and SK is placed at the spindles front end. Aclamping system is used for fast automatictool changes. Ideally, an unclamping unit (drawbar)which can also monitor the clamping force is needed for reliable machining. If cutting fluid has tobe transmitted through the tool to the cutter, adequate channels and a rotary union become requiredfeatures of the clamping system.Today, nearly every spindle is equipped with sensors for monitoring the motor temperature(thermistors or thermocouples) and the position of the clamping system. Additional sensors formonitoring the bearings, the drive and the process stability can be attached, but are not common inmany industrial applications.1.3. State of the artSpindles with high power and high speeds are mainly developed for the machining of largealuminum frames in the aerospace industry. Spindles with extremely high speeds and low powerare used in electronics industry for drilling printed circuit boards (PCB).1.4. Actual development areas in industryCurrent developments in motor spindle industrial application focus on motor technology,improving total cost of ownership(TCO) and condition monitoring for predictive maintenanceAnother central issue is the development of drive systems which neutralize the existing constraintsof power and output frequency while reducing the heating of the spindle shaft.Particular attention was paid to the increase of the reliable reachable rotational speeds in the past.However, the focus has changed towards higher torque at speeds up to 15,000 rpm. Because ofIncreased requirements in reliability, life-cycle and predictable maintenance the conditionmonitoring systems in motor spindles have become more important. Periodic and/or continuousobservation of the spindle status parameters is allowing detection of wear, overheating andimminent failures.Understanding the life cycle cost (LCC) of the spindles has steadily gained importance inpredicting their service period with maintenance, failure and operational costs.2. Fields of application and specific demandsSpindles are developed and manufactured for a wide range of machine tool applications with acommon goal of maximizing the metal removal rates and part machining accuracy.The work materials range from easy to machine materials like aluminum at high speeds withhigh power spindles, to nickel and titanium alloys which require spindles having high torque andstiffness at low speeds. Cutting work materials with abrasive carbon or fiber-reinforced plastics(FRP) content need good seals at the spindle front end.Spindles for drilling printed circuit boards operate in the angular speed range of 100,000 to300,000 rpm. The increase in productivity and speed in this application field over the last fewyears was possible with the development of precision air bearings.Spindles used in die and mould machining have to fulfill the roughing operations (highperformance cutting, HPC) at high feed rates as well as the finishing processes (high-speed cutting,HSC) at high cutting speeds. Depending on the strategy and the machinery of the mould and dieshop either two different machine tools equipped with two different spindles are used or onemachine is equipped with a spindle changing unit. Another possibility is to use a spindle which canfulfill both, HSC and HPC conditions, but this still remains a compromise regarding overallproductivity.Aerospace spindles are defined by high power as well as high rotational speeds. Todaysspindles allow a material removal rate(MRR) of more than 10 l of aluminum per minute.Grinding is a finishing operation where high accuracy is necessary, which requires stiff spindleswith bearings having minimum runout. The present internal cylindrical grinding spindles have arunout requirement of less than 1 mm.Spindle units which are used mainly for boring and drilling operations require high axialstiffness, which is achieved by using angular contact bearings with high contact angles. On thecontrary, high-speed milling operations use spindles with bearings having small contact angles inorder to reduce the dependency of radial stiffness on the centrifugal forces.Contemporary machining centers tend to have multi functions where milling, drilling, grindingand sometimes honing operations can be realized on the same work piece. The bottleneck for theenhancement of the multi-technology machines is still the spindle, which cannot satisfy all themachining operations with the same degree of performance. Reconfigurable and modular machinetools require interchangeable spindles with standardized mechanical, hydraulic, pneumatic andelectrical interfaces.3. Spindle analysisThe aim of modeling and analysis of spindle units is to simulate the performance of the spindleand optimize its dimensions during the design stage in order to achieve maximum dynamicstiffness and increased material removal rate with minimal dimensions and power consumption.The mechanical part of the spindle assembly consists of hollow spindle shaft mounted to a housingwith bearings. Angular contact ball bearings are most commonly used in high-speed spindles dueto their low-friction properties and ability to withstand external loads in both axial and radialdirections. The spindle shaft is modeled by beam, brick or pipe elements in finite elementenvironment. The bearing stiffness is modeled as a function of ball bearing contact angle, preloadcaused by the external load or thermal expansion of the spindle during operation. The equation ofmotion is derived in matrix form by including gyroscopic and centrifugal effects, and solved toobtain natural frequencies, vibration mode shapes and frequency response function at the toolattached to the spindle. If the bearing stiffness is dependent on the speed, or if the spindle needs tobe simulated under cutting loads, the numerical methods are used to predict the vibrations alongthe spindle axis as well as contact loads on the bearings.Spindle simulation models allow for the optimization of spindle design parameters either toachieve maximum dynamic stiffness at all speeds for general operation, or to reach maximum axialdepth of cut at the specified speed with a designated cutter for a specificmachining application.The objective of cutting maximum material at the desired speed without damaging the bearingsand spindle is the main goal of spindle design while maintaining all other quality and performancemetrics, e.g. accuracy and reliability.does not always lead to accurate identification of the spindles dynamicparameters; A.3.2. Theoretical modelingTheoretical models are based on physical laws, and used to predict and improve theperformance of spindles during the design stage. The models provide mathematical relationbetween the inputs F (force, speed) and the outputs q (deflections, bearing loads, and temperature).The mathematical models can be expressed in state space forms or by a set of ordinary differentialequations. In both cases linear or nonlinear behavior of the spindles can be modeled.3.2.1. Mechanical modeling of shaft and housingFinite element (FE) methods are most commonly used to model structural mechanics anddynamics of the spindles. The method is based on discretization of the structure at finite elementlocations by partial derivative differential equations. The analysis belongs to the class of rotor-dynamic studies where the axis-symmetric shaft is usually modeled by beam elements, which leadto construction of mass (Me) and stiffness (Ke) matrices.Timoshenko beam element is most commonly used because it considers the bending, rotaryinertia and shear effects, hence leads to improved prediction of natural frequencies and modeshapes of the spindle .The element PIPE16 of the commonly known FEA software ANSYS is alsoan implementation of the Timoshenko theory and use the mass matrix and stiffness matrixAs an example in the finite element model in Fig. 1, the black dots represent nodes, and eachnode has three Cartesian translational displacements and two rotations . The pulley is modeled as arigid disk, the bearing spacer as a bar element, and the nut and sleeve as a lumped mass. Thespindle in this case has two front bearings in tandem and three bearings in tandem at the rear. Thefive bearings are in overall back-to-back configuration. The tool is assumed to be rigidlyconnected to the tool holder which is fixed to the spindle shaft rigidly or through springs withstiffness in both directions translation and rotation. The flexibility of the spindle mounting has tobe reflected in the model of the spindle-machine system. Springs are also used between the spindlehousing and spindle head, whose stiffness is obtained from experience.Fig. 1. The finite element model of the spindle-bearing-machine-tool system
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