機床主軸設計及相關技術研究-數控銑床的主軸結構【含8張cad圖紙+文檔全套資料】

喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請放心下載，，有疑問咨詢QQ:414951605或者1304139763 ======================== 喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請放心下載，，有疑問咨詢QQ:414951605或者1304139763 ======================== 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 機床主軸單元 1.介紹 機床主軸基本上完成兩個任務：在空間精確的旋轉刀具（鉆削，銑削，磨削）或工件（車削）；把所需要的能量傳遞到切削區(qū)。 很顯然主軸對切削效率和機加工件的質量有很大影響，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)。 1.1歷史回顧 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量來改變。 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，加工技術要求發(fā)展新型軸承，電力電子與逆變器系統。在致力于發(fā)展緊湊的電力電子（靜止變頻器）領域的進步 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，在軸承，潤滑，滾動材料和驅動系統(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。 1.2 主要結構 如今，絕大多數機床都裝配了點主軸。不同于外部驅動主軸，電主軸不需要像齒輪和接頭一樣的機械傳動單元。 主軸至少有兩套主要的球軸承系統。軸承系統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之間。 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。 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的。 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的特點。 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。用于監(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。 1.3當前發(fā)展狀況 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）。 1.4工業(yè)方面的實際開發(fā)領域 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。 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)測系統變得越來越重要。對主軸各狀態(tài)參數的定期和或連續(xù)觀測能夠檢測磨損、過熱和即將發(fā)生的故障。 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。 2.應用領域和具體需求 主軸被研制和制造的主要目的是實現金屬切削效率和加工精度的最大化。 工件材料可以分門別類，包括簡單的，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。 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。 用于模具加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。 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101個單位。 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。 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。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。 現代加工中心往往具有多種功能如銑、鉆、磨，有時珩磨操作可以在相同的工件上實現。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。 3.主軸分析 主軸單元的模型和分析的目標是為了實現最大的動態(tài)剛度，以最小的尺寸和功率增加材料去除率，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、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。如果軸承剛度與速度有關，或如果主軸在切削載荷下模擬，數值方法用于預測沿主軸軸振動荷載和軸承上的接觸載荷。 主軸仿真模型考慮了主軸設計參數的優(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。 3.1實驗模擬 一個現有的電主軸的動態(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： （1）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； （2）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的測量是相當困難的； （3）運用從測量的輸入和輸出數據中提取的參數進行曲線擬合或其他方法 并不總是得到主軸動態(tài)參數的精確分析。 3.2理論模型 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）之間的數學關系。數學模型可以用狀態(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。 3.2.1軸和外殼的力學建模 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。 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ANSYS中PIPE16單元也是使用了Timoshenko理論與質量和剛度矩陣。 3.3角接觸球軸承的建模 角接觸球軸承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。 圖1 機床—主軸—軸承系統的有限元模型 畢 業(yè) 設 計 任 務 書 1．畢業(yè)設計的任務和要求： 掌握機床主軸的基本知識；掌握機床主軸設計的技術關鍵；研究數控機床主軸單元的關鍵技術，掌握其相關知識及選型、應用、設計方法等；完成一種數控銑床主軸單元的設計，要求主軸工作的轉速可達8000r/min，輸出功率可達5kW，使用40柄刀具。 2．畢業(yè)設計的具體工作內容： 1） 分析題目要求，查閱相關的國內外文獻、設計資料、有關專利文獻等，在此基礎上，了解開題報告的撰寫方法、基本要求，完成開題報告； 2） 學習和掌握機床主軸的有關知識，了解主軸單元、電主軸的有關知識及發(fā)展現狀；了解數控機床、加工中心對主軸的要求；總結機床主軸的設計要點、技術關鍵及發(fā)展方向；力爭提出主軸設計的發(fā)展方向； 3） 按題目要求，設計一種數控銑床的主軸單元，完成裝配圖及主要零件圖，給出功率、強度、剛度、軸承等必要的計算； 4） 編寫設計說明書； 5） 翻譯本專業(yè)外文科技文獻一份。 畢 業(yè) 設 計 任 務 書 3．對畢業(yè)設計成果的要求： 1）主軸裝配圖、主要零件圖； 2）主軸技術的研究及設計說明書一份； 3）本專業(yè)外文科技文獻譯文一份。 4．畢業(yè)設計工作進度計劃： 起 迄 日 期 工 作 內 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，查閱相關文獻資料，了解機床主軸設計的國內外現狀及發(fā)展趨勢，提出自己的設計思路，完成開題報告； 全面掌握主軸相關的基本知識，了解高速主軸的關鍵技術，了解主軸單元的設計特點；分析總結主軸技術的發(fā)展方向； 設計主軸，完成裝配圖和主要零件圖； 完成研究總結及設計說明書 撰寫答辯講稿，準備答辯； 學生所在系審查意見： 同意下發(fā)任務書 系主任： 2016年 2 月 29 日