外文翻譯---機床主軸單元

1、<p><b>　　附錄A 英文原文</b></p><p>　　Machine tool spindle units</p><p>　　A.1 Introduction</p><p>　　Machine tool spindles basically fulfill two tasks:</p><p>

2、　　rotate the tools (drilling, milling and grinding) or work piece (turning) precisely in space</p><p>　　transmit the required energy to the cutting zone for metal removal</p><p>　　Obviously spin

3、dles have a strong influence on metal removal rates and quality of the machined parts. This paper reviews the current state.and presents research challenges of spindle technology.</p><p>　　A.1.1.Historical r

4、eview</p><p>　　Classically, main spindles were driven by belts or gears and the rotational speeds could only be varied by changing either the transmission ratio or the number of driven poles by electrical sw

5、itches.</p><p>　　Later simple electrical or hydraulic controllers were developed and the rotational speed of the spindle could be changed by means of infinitely adjustable rotating transformers (Ward Leonard

6、 system of motor control).The need for increased productivity led to higher speed machining requirements which led to the development of new bearings, power electronics and inverter systems. The progress in the field of

7、the power electronics (static frequency converter) led to the development of compact drive</p><p>　　A.1.2. Principal setup</p><p>　　Today, the overwhelming majority of machine tools are equipped

8、 with motorized spindles. Unlike externally driven spindles, the motorized spindles do not require mechanical transmission elements like gears and couplings. </p><p>　　The spindles have at least two sets of

9、mainly ball bearing systems. The bearing system is the component with the greatest influence on the lifetime of a spindle. Most commonly the motor is arranged between the two bearing systems. </p><p>　　Due t

10、o high ratio of ‘power to volume’ active cooling is often required, which is generally implemented through water based cooling. The coolant flows through a cooling sleeve around the stator of the motor and often the oute

11、r bearing rings. </p><p>　　Seals at the tool end of the spindle prevent the intrusion of chips and cutting fluid. Often this is done with purge air and a labyrinth seal. </p><p>　　A standardized

12、 tool interface such as HSK and SK is placed at the spindles front end. A clamping system is used for fast automatictool changes. Ideally, an unclamping unit (drawbar) which can also monitor the clamping force is needed

13、for reliable machining. If cutting fluid has to be transmitted through the tool to the cutter, adequate channels and a rotary union become required features of the clamping system. </p><p>　　Today, nearly ev

14、ery spindle is equipped with sensors for monitoring the motor temperature (thermistors or thermocouples) and the position of the clamping system. Additional sensors for monitoring the bearings, the drive and the process

15、stability can be attached, but are not common in many industrial applications.</p><p>　　A.1.3. State of the art</p><p>　　Spindles with high power and high speeds are mainly developed for the mac

16、hining of large aluminum frames in the aerospace industry. Spindles with extremely high speeds and low power are used in electronics industry for drilling printed circuit boards (PCB).</p><p>　　A.1.4. Actual

17、 development areas in industry</p><p>　　Current developments in motor spindle industrial application focus on motor technology, improving total cost of ownership(TCO) and condition monitoring for predictive

18、maintenance Another central issue is the development of drive systems which neutralize the existing constraints of power and output frequency while reducing the heating of the spindle shaft.</p><p>　　Particu

19、lar 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 of Increased requirements in reliab

20、ility, life-cycle and predictable maintenance the ‘condition monitoring’ systems in motor spindles have become more important. Periodic and/or continuous observation of the spindle status parameters is allowing detection

21、 of wear, overheating and imminent failures. </p><p>　　Understanding the life cycle cost (LCC) of the spindles has steadily gained importance in predicting their service period with maintenance, failure an

22、d operational costs.</p><p>　　2. Fields of application and specific demands</p><p>　　Spindles are developed and manufactured for a wide range of machine tool applications with a common goal of m

23、aximizing the metal removal rates and part machining accuracy. </p><p>　　The work materials range from easy to machine materials like aluminum at high speeds with high power spindles, to nickel and titanium

24、alloys which require spindles having high torque and stiffness at low speeds. Cutting work materials with abrasive carbon or fiber-reinforced plastics (FRP) content need good seals at the spindle front end.</p>&l

25、t;p>　　Spindles for drilling printed circuit boards operate in the angular speed range of 100,000 to 300,000 rpm. The increase in productivity and speed in this application field over the last few years was possible wi

26、th the development of precision air bearings.</p><p>　　Spindles used in die and mould machining have to fulfill the roughing operations (high performance cutting, HPC) at high feed rates as well as the finis

27、hing processes (high-speed cutting, HSC) at high cutting speeds. Depending on the strategy and the machinery of the mould and die shop either two different machine tools equipped with two different spindles are used or o

28、ne machine is equipped with a spindle changing unit. Another possibility is to use a spindle which can fulfill both, HSC and HPC</p><p>　　Aerospace spindles are defined by high power as well as high rotation

29、al speeds. Today’s spindles allow a material removal rate(MRR) of more than 10 l of aluminum per minute.</p><p>　　Grinding is a finishing operation where high accuracy is necessary, which requires stiff spin

30、dles with bearings having minimum runout. The present internal cylindrical grinding spindles have a runout requirement of less than 1 mm. </p><p>　　Spindle units which are used mainly for boring and drilling

31、 operations require high axial stiffness, which is achieved by using angular contact bearings with high contact angles. On the contrary, high-speed milling operations use spindles with bearings having small contact angle

32、s in order to reduce the dependency of radial stiffness on the centrifugal forces. </p><p>　　Contemporary machining centers tend to have multi functions where milling, drilling, grinding and sometimes honing

33、 operations can be realized on the same work piece. The bottleneck for the enhancement of the multi-technology machines is still the spindle, which cannot satisfy all the machining operations with the same degree of perf

34、ormance. Reconfigurable and modular machine tools require interchangeable spindles with standardized mechanical, hydraulic, pneumatic and electrical interfaces.</p><p>　　A.3. Spindle analysis</p><

35、p>　　The aim of modeling and analysis of spindle units is to simulate the performance of the spindle and optimize its dimensions during the design stage in order to achieve maximum dynamic stiffness and increased mater

36、ial removal rate with minimal dimensions and power consumption. The mechanical part of the spindle assembly consists of hollow spindle shaft mounted to a housing with bearings. Angular contact ball bearings are most comm

37、only used in high-speed spindles due to their low-friction properti</p><p>　　Spindle simulation models allow for the optimization of spindle design parameters either to achieve maximum dynamic stiffness at a

38、ll speeds for general operation, or to reach maximum axial depth of cut at the specified speed with a designated cutter for a specificmachining application. The objective of cutting maximum material at the desired speed

39、without damaging the bearings and spindle is the main goal of spindle design while maintaining all other quality and performance metrics, e.g. accurac</p><p>　　does not always lead to accurate identification

40、 of the spindle’s dynamic parameters；</p><p>　　A.3.2. Theoretical modeling</p><p>　　Theoretical models are based on physical laws, and used to predict and improve the performance of spindles dur

41、ing the design stage. The models provide mathematical relation between the inputs F (force, speed) and the outputs q (deflections, bearing loads, and temperature). The mathematical models can be expressed in state space

42、forms or by a set of ordinary differential equations. In both cases linear or nonlinear behavior of the spindles can be modeled.</p><p>　　A.3.2.1. Mechanical modeling of shaft and housing</p><p>

43、;　　Finite element (FE) methods are most commonly used to model structural mechanics and dynamics of the spindles. The method is based on discretization of the structure at finite element locations by partial derivative d

44、ifferential equations. The analysis belongs to the class of rotor-dynamic studies where the axis-symmetric shaft is usually modeled by beam elements, which lead to construction of mass (Me) and stiffness (Ke) matrices.&l

45、t;/p><p>　　Timoshenko beam element is most commonly used because it considers the bending, rotary inertia and shear effects, hence leads to improved prediction of natural frequencies and mode shapes of the spin

46、dle .The element PIPE16 of the commonly known FEA software ANSYS is also an implementation of the Timoshenko theory and use the mass matrix and stiffness matrix </p><p>　　As an example in the finite element

47、model in Fig. 1, the black dots represent nodes, and each node has three Cartesian translational displacements and two rotations . The pulley is modeled as a rigid disk, the bearing spacer as a bar element, and the nut a

48、nd sleeve as a lumped mass. The spindle in this case has two front bearings in tandem and three bearings in tandem at the rear. The five bearings are in overall back-to-back configuration. The tool is assumed to be rigid

49、ly connected to the tool</p><p>　　Fig. 1. The finite element model of the spindle-bearing-machine-tool system</p><p><b>　　附錄 B 中文翻譯</b></p><p><b>　　機床主軸單元</b>

50、;</p><p><b>　　B.1.介紹</b></p><p>　　機床主軸基本上完成兩個任務：</p><p>　　在空間精確的旋轉刀具（鉆削，銑削，磨削）或工件（車削）。</p><p>　　把所需要的能量傳遞到切削區(qū)</p><p>　　很顯然主軸對切削效率和機加工件的質量有很大影響，

51、這篇文章評論了目前的狀態(tài)和介紹了主軸技術的研究挑戰(zhàn)。</p><p><b>　　B.2歷史回顧</b></p><p>　　典型地，主軸是被皮帶或齒輪驅動的，轉速只能通過改變傳動比或通過電器開關改變驅動級的數(shù)量來改變。</p><p>　　之后，簡單的電氣或液壓控制器開始發(fā)展，主軸旋轉速度通過無級調速方式來改變，要提高生產力就需要更高的速度，

52、加工技術要求發(fā)展新型軸承，電力電子與逆變器系統(tǒng)。在致力于發(fā)展緊湊的電力電子（靜止變頻器）領域的進步</p><p>　　導致在使用高頻三相異步電動機上的低成本維護，對于早在80年代的主軸，高轉速只能利用磁力軸承來實現(xiàn)，在軸承，潤滑，滾動材料和驅動系統(tǒng)(馬達和轉換器)領域的持續(xù)發(fā)展已經允許建造直接驅動電機主軸來滿足目前各種需求</p><p>　　如今，絕大多數(shù)機床都裝配了點主軸。不同于外部

53、驅動主軸，電主軸不需要像齒輪和接頭一樣的機械傳動單元。</p><p>　　主軸至少有兩套主要的球軸承系統(tǒng)。軸承系統(tǒng)是對主軸的壽命影響最大的組成部件。最常見的電機是安裝在兩個軸承系統(tǒng)之間。</p><p>　　而冷卻主要是通過水冷。冷卻劑流過電機定子周圍的冷卻套而還經常流過軸承外圈。</p><p>　　主軸末端的密封件防止碎屑及切削液的侵入，通常這些是做了空氣凈化

54、的。</p><p>　　一個標準的工具接口例如HSK和SK是被放置在主軸前端的。一個夾緊系統(tǒng)是用于快速automatictool變化。理想情況下，一個可以控制夾緊力的未夾緊單元需要可靠的加工。如果切削液一定要通過刀具流到切削上，那么對應的軌道和旋轉機構就要求具有夾緊系統(tǒng)的特點。</p><p>　　今天，幾乎每個主軸都裝配有用于監(jiān)視電機溫度(熱敏電阻或熱電偶)的傳感器和定位夾緊系統(tǒng)。用于

55、監(jiān)測軸承的附加傳感器，可以監(jiān)測驅動過程的穩(wěn)定性，但在許多工業(yè)領域卻不太普遍。</p><p>　　B.1.3當前發(fā)展狀況</p><p>　　大功率、高轉速電主軸是為了加工用于航空、航天工業(yè)的大型鋁制框架而發(fā)展起來的。高轉速、低功率的電主軸用于電子工業(yè)為印刷電子版鉆孔（PCB）</p><p>　　B.1.4工業(yè)方面的實際開發(fā)領域</p><p&

56、gt;　　當前電主軸的發(fā)展主要集中在電動機的技術，降低用于預防性維護監(jiān)測的成本。另一個核心問題是為了減少主軸上的熱量發(fā)展用于抵消存在的約束力和輸出頻率的驅動系統(tǒng)。</p><p>　　過去注意力主要放在增加可靠的旋轉速度。如今，如今的關注點已經改變，朝著具有高轉速（15000r/min）的同時還要有很高的轉矩。由于在可靠性，產品生命周期和可預測維護方面需求的增加，電機主軸的狀態(tài)監(jiān)測系統(tǒng)變得越來越重要。對主軸各狀態(tài)

57、參數(shù)的定期和或連續(xù)觀測能夠檢測磨損、過熱和即將發(fā)生的故障。</p><p>　　了解主軸的產品壽命周期費用對預測服務期間內的維護、故障和運行成本有很大幫助。</p><p>　　B.2.應用領域和具體需求</p><p>　　主軸被研制和制造的主要目的是實現(xiàn)金屬切削效率和加工精度的最大化。</p><p>　　工件材料可以分門別類，包括簡單的

58、，例如像鋁，要用具有高轉速和大功率的主軸，還包括難加工的，例如鎳鈦合金，要求主軸除了具有較低的轉速，還要具有較大的轉矩和剛度。切削具有磨料碳或碳纖維塑料的工件材料要求主軸前端具有良好的密封性。</p><p>　　給電路板鉆孔的主軸轉速要控制在100 000到300 000轉/每分鐘。隨著空氣軸承的精度的不斷提高，電機主軸應用領域的生產力和轉速也在不斷提高。</p><p>　　用于模具加

59、工的主軸必須以很高的進給率完成粗軋機組操作(高性能切割、HSC)、以很高的切削速度完成切削過程（高切削速度，HSC）.依據磨具和壓鑄車間的實施策略和機械裝置，可以是兩個機床配備兩個不同的主軸或一個機床配備一個主軸切換單元。另一種情況就是用一個主軸來同時完成高速切削和高性能切割，但生產力仍然保持合理的水平。</p><p>　　航空航天用的主軸要求具有大功率和高轉速。如今的主軸要求材料切除率達到每分鐘切除鋁材料10

60、1個單位。</p><p>　　磨削是一個要求高精度的操作過程，需要軸承具有很小的擺動的剛性軸。目前的內部磨床主軸要求軸承擺動不超過1毫米。</p><p>　　主要用于鉆孔的主軸單元要求具有很高的軸向剛度，這需要使用具有高接觸角的角接觸球軸承來實現(xiàn)。相反，高速銑削操作要使用有小接觸角的軸承用以減少由于離心力引起的徑向剛度變化。</p><p>　　現(xiàn)代加工中心往往

61、具有多種功能如銑、鉆、磨，有時珩磨操作可以在相同的工件上實現(xiàn)。提高機床先進性的瓶頸仍然是機床主軸，因為他不能在相同精度的條件下滿足所有的操作?？芍貥嫼湍K化的機床需要有規(guī)范化的機械、液壓、氣動、電氣接口的可互換的主軸。</p><p><b>　　B.3.主軸分析</b></p><p>　　主軸單元的模型和分析的目標是為了實現(xiàn)最大的動態(tài)剛度，以最小的尺寸和功率增加材

62、料去除率，在設計階段模擬主軸的性能和優(yōu)化它的尺寸。主軸裝配的機械部件是由安裝有軸承的空心主軸組成。角接觸球軸承廣泛用于高速主軸，由于其低摩擦性能和可以同時承受徑向和軸向載荷的能力。主軸可以在有限元環(huán)境下用梁、塊、或管道單元來模擬。軸承剛度可以用一個球軸承接觸角的函數(shù)、在操作期間由主軸的外部負載或熱膨脹所引起的預緊力來模擬。運動方程以矩陣的形式導出，包括陀螺和離心效應，還有得到了附在主軸上的工具的固有頻率、振型的形狀和頻率響應函數(shù)。如果軸

63、承剛度與速度有關，或如果主軸在切削載荷下模擬，數(shù)值方法用于預測沿主軸軸振動荷載和軸承上的接觸載荷。</p><p>　　主軸仿真模型考慮了主軸設計參數(shù)的優(yōu)化，目的是為了使主軸在全速運行時達到最大的動剛度，用一把指定的專用刀具用指定的速度實現(xiàn)最大軸向切削深度。在不損壞軸承和主軸的前提下以指定的速度，主軸設計的主要目標是實現(xiàn)切除材料的最大化，同時還要保證各項其他指標如精度和可靠性。</p><p&

64、gt;<b>　　B.3.1實驗模擬</b></p><p>　　一個現(xiàn)有的電主軸的動態(tài)行為是通過測量它的力和位移之間的頻率響應函數(shù)得到的。在機械加工過程中，主軸結構會引起振動，可測量的頻率響應函數(shù)可以用曲線來擬合，可用于預測固有頻率、阻尼比和剛度值。頻率響應函數(shù)的實驗測量對于在加工工藝設計階段評估動態(tài)剛度和確定切削顫振條件是實用的。然而，以下困難需要考慮在內：</p><

65、;p>　?。?）只需要測量旋轉軸的一小部分就可行了，因此模擬整個主軸是不可能的；</p><p>　?。?）運算速度和溫度主要影響特征值，但當主軸旋轉時頻率響應函數(shù)的測量是相當困難的；</p><p>　?。?）運用從測量的輸入和輸出數(shù)據中提取的參數(shù)進行曲線擬合或其他方法</p><p>　　并不總是得到主軸動態(tài)參數(shù)的精確分析；</p><

66、p><b>　　B.3.2理論模型</b></p><p>　　理論模型是基于物理定律，在設計階段用來預測和改善主軸的性能。模型提供輸入F（力，速度）和輸出q（撓度，軸承載荷，和溫度）之間的數(shù)學關系。數(shù)學模型可以用狀態(tài)空間形式或通過一系列的微分方程來表達，在這兩種方案中主軸的線性或非線性行為都可以被精確的模擬。</p><p>　　B.3.2.1軸和外殼的力學建

67、模</p><p>　　有限元方法普遍適用于主軸的結構力學和動態(tài)模型。該方法是通過偏導數(shù)微分方程組在有限元區(qū)域基于結構的離散化。該分析屬于轉子動態(tài)研究的類型，具有對稱性的軸通常用梁單元來模擬，可以得到質量和剛度矩陣。</p><p>　　Timoshenko梁單元最為常用，因為它考慮了彎曲、轉動慣量和剪切的影響，因此對主軸的固有頻率和模態(tài)形狀的預測有很大幫助。普遍都知道的有限元分析軟件AN

68、SYS中PIPE16單元也是使用了Timoshenko理論與質量和剛度矩陣。</p><p>　　如圖1中的有限元模型的一個實例，黑點代表節(jié)點，每個節(jié)點以笛卡爾坐標系參考都有三個平動自由度和兩個旋轉自由度?；啽灰暈閯傂詧A盤，軸承隔套作為桿單元，螺母和套筒作為集中質量，在這個方案中主軸前段有兩個串聯(lián)的軸承，主軸后端有三個串聯(lián)的軸承。五個軸承總體上是背靠背安裝的。主軸軸軸頭之間使用了彈簧，它的剛度由實驗獲得。<

69、;/p><p>　　圖B1 機床—主軸—軸承系統(tǒng)的有限元模型</p><p>　　B.3.3角接觸球軸承的建模</p><p>　　角接觸球軸承（圖11）普遍應用于高速主軸。為了保持徑向和軸向的旋轉精度和足夠的剛度以滿足基本的操作要求，軸承需要預緊來防止打滑?；旧?，有兩種類型的軸承預緊力：剛性預緊和恒預緊。</p><p>　　圖B2 主軸的草