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1、工具機切削性能測試工具機切削性能測試財團法人精密機械研究發展中心徐光漢2008.042006/12/01精密機械研發中心2內內容容一.前言二.測試方法三.切削顫振四.測試工件五.討論2006/12/01精密機械研發中心3品質切削效率尺寸 精度表面 品質時間一、前言最大移除 率(MRR)Cycle Time2006/12/01精密機械研發中心4模 態主 軸 熱 變 位循 跡 精 度靜 、 動 剛 性迴 路 增 益高 速 高 精 度 機 能加 減 速 參 數機械特性機械特性伺服特性伺服特性切削應用技術切削應用技術切削性能切削性能刀 具 規 格切 削 路 徑(工 件)切 削 條 件(顫 振)夾 治
2、具評價項目主 軸 迴 轉 精 度2006/12/01精密機械研發中心5影響切削性能因素機台方面結構剛性、功率、轉速、進給速率.刀具方面 材質、硬度、直徑、長度、刀刃數.工件方面 材質、硬度、幾何形狀.周邊 工件夾持、刀具夾持、加工程式、冷卻.2006/12/01精密機械研發中心6材料移除率計算方法條件b = b = 軸向切削深度軸向切削深度a = a = 徑向切削深度徑向切削深度f = f = 進給率進給率= = n n m m c cn = n = 主軸轉速主軸轉速m = m = 刀刃數刀刃數c = c = 切屑厚度切屑厚度chip loadchip load2006/12/01精密機械研發
3、中心7馬力限制一般以主軸馬達負載表達到130%為上限。振動限制發生顫振或振動值太大(振動值在0.4G以上)。工件夾持限制切削過程中夾具無法完全固定工件。刀具限制切刃斷裂或超過刀具可切深。噪音太大限制噪音值超過安全法規(85dBA)或客戶需求值(80dBA)。加工表面粗度不佳加工表面粗度超過規範或客戶需求。材料移除率的限制2006/12/01精密機械研發中心8ISO/CD 230-1 Ed. 3 Test code for machine tools -Part 1: Geometric accuracy of machines operating under no- load or quasi
4、-static conditions ISO 230-2:2006 Ed. 3 Test code for machine tools -Part 2: Determination of accuracy and repeatability of positioning numerically controlled axes ISO/DIS 230-3 Ed. 2 Test code for machine tools -Part 3: Determination of thermal effects ISO 230-4:2005 Ed. 2 Test code for machine too
5、ls -Part 4: Circular tests for numerically controlled machine tools ISO 230-5:2000 Ed. 1 Test code for machine tools -Part 5: Determination of the noise emission ISO 230-6:2002 Ed. 1 Test code for machine tools -Part 6: Determination of positioning accuracy on body and face diagonals (Diagonal displ
6、acement tests) ISO/FDIS 230-7.2 Ed. 1 Test code for machine tools -Part 7: Geometric accuracy of axes of rotation ISO/CD TR 230-8 Ed. 1 Test code for machine tools -Part 8: Determination of vibration levelsISO檢驗標準2006/12/01精密機械研發中心9找出機台-刀具-工件系統之最佳切削條件1.主軸轉速2.進給速度3.切削深度4.切削寬度5.加工路徑6穩定切削穩定切削振動量小振動量小刀具
7、壽命長刀具壽命長材料移除率大材料移除率大.二、測試方法2006/12/01精密機械研發中心10實切測試“Trial and Error”刀具與工件架設完成後，設定轉速、切削深度、進 給，直接進行實際切削，並量測切削過程產生的訊 號，例如切削力、振動、聲音等以進行相關的分析 與評估。Exciter Test “ Predictive ”在刀具架設完成之後，提供一已知的輸入力量 （衝擊槌、激振器）來激勵刀具，並以感測器 （位移計、加速規）量測輸出訊號，以進行相 關的模態參數（頻率、剛性、阻尼）分析與評估2006/12/01精密機械研發中心11切削動力計三向式力感測器量取切削時工件所 承受之x,y,
8、z 三方 向作用力與波型。可建立標準操作程 序，作為日後刀具 判別訊號。2006/12/01精密機械研發中心12單刃切削力量測值2006/12/01精密機械研發中心133D表面粗度量測儀2006/12/01精密機械研發中心14表面粗度紋路頻譜分析轉速頻 18.33 Hz刃頻2006/12/01精密機械研發中心15l顫振是一種切削時，發生於工件、刀具間的自激振動 行為，藉由量測可以評價機台切削能力極限。l顫振時，切削力與振動量將會異常增大，以致刀具或 工件發生損害以及惡劣工件表面。l顫振常發生在高速或高馬力切削過程。三、切削顫振(Chatter)Ref: Dr.Smith2006/12/01精密
9、機械研發中心16 Machine tools are stiff, but not infinitely stiff. Cutting performance becomes limited by the dynamic characteristics of the machine. Insufficient stiffness and damping lead to problems with “chatter” Vibration phenomena are not random, but can be quantitatively described.Basic PrinciplesRe
10、f: Dr.Smith2006/12/01精密機械研發中心17Ref: Dr.SmithlThree kinds of stiffnesses：Static Stiffness (K): known static load, how much does the tool or spindle point deflect.Modal Stiffness (ki): stiffness associated with a given mode at a given natural frequency. fn,i = (ki/mi)1/2Dynamic Stiffness (h): inverse
11、of real flexibility of the system when excited at a natural frequency, inverse resonant flexibility.lHow are they related?Static stiffness is the inverse sum of all the modal stiffnesses. Dynamic stiffness includes the effect of damping and modal stiffness 2006/12/01精密機械研發中心18切削顫振發生的原因 切削過程中令人無法接受的振
12、動多屬 於自激振動(Self-excited Vibration)是何種機制使得主軸穩定能量的輸入 轉換成振動現象？ Regeneration of Waviness 2006/12/01精密機械研發中心19Regeneration of WavinessRegeneration of WavinessRef: Dr.Smith2006/12/01精密機械研發中心20Chatter characteristics. The chatter frequency is usually close to, but not equal to the natural frequency. The lob
13、es are more tightly packed at the left (smaller speed change for the same phase change). Large stable zones exist in the high speed ranges. Surprisingly, the largest such gap occurs where the tooth passing frequency is equal to the natural frequency. Why? When tooth frequency matches natural frequen
14、cy, the surface waves and the tooth vibration are in phase. The chip thickness looks the same as if there were no vibration.Ref: Dr.Smith2006/12/01精密機械研發中心21Chatter Frequency Below the limit of stability, force or sound spectrum (frequencies) are dominated by tooth frequency, run out, harmonics, and
15、 noise. Above the limit of stability, a prominent chatter frequency appears. Stable and unstable machining may be discriminated using the prominent frequency in the spectrum. Additionally, we will see that if the cut is unstable, the chatter frequency gives guidance for correction. Chatter cannot oc
16、cur at the tooth passing frequency or any of its harmonics. Chatter can, but normally does not coincide with rotational frequency or its harmonics.Ref: Dr.Smith2006/12/01精密機械研發中心222006/12/01精密機械研發中心23Frequency Response Functions (FRF)A FRF is a measurement of a systems response to a known excitation as a function of the excitation frequency.Negative Real PeakStatic ComplianceDyna
