Microsoft PowerPoint - Construction and error sources of multi-axis machines

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辈宙温
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Handout 1 工具機整機系統設計 Construction and error sources of

Three axis Machine Tool Multi axis Machines by Serial

three independent translation axes and rotary axes

Precision, accuracy and high throughput are the

rotary axes + one cutting tool axis Multi axis Machines

spindle head Z-axis X-axis Spindle-axis or tool-axis

1 Handout 1 工具機整機系統設計 Construction and error sources of multi axis machines ( 多軸精密機械之構造與誤差源 ) 多軸工具機的座標定義 2 Three axis Machine Tool Multi axis Machines by Serial linked Configuration Cutting spindle Y-axis Combining three independent translation axes and rotary axes according the Cartesian coordinate system Z-axis X-axis Precision, accuracy and high throughput are the fundamental requirements of the precision machinery such as the machine tool. 3 4 Five axis machining Three translation axes + two rotary axes + one cutting tool axis Multi axis Machines by Cartesian Axis Configuration Y-axis 2-axis swiveling spindle head Z-axis X-axis Spindle-axis or tool-axis 2-axis rotary table 5 Combining three independent motion axes according the Cartesian coordinate system 6 1

When you face to the machines, the x-axis is assigned to the lateral motion

2 Coordinate System of Multiple axis Machines Rules: 1. The z-axis is assigned to the spindle axis. 2. When you face to the machines, the x-axis is assigned to the lateral motion of the stage. 3. Using the right hand rule to determine the y-axis. 7 8 y-axis x-axis z-axis y-axis z-axis x-axis

Five axis Machines Why rotary axes are needed?

3 Five axis Machines Why rotary axes are needed? Rule: The A-axis is assigned to the rotation of x-axis, while the B- and C-axis are assigned to the rotation of y- and z-axis Kinematic Loop and Force Loop CNC (computer numerical control) machine tools workpiece Cutting tool Y-axis CNC 技術高速計算和通信能力 Look Ahead AC/DC Control S curve AC/DC Sharp Corner Control NURBS interpolation Servo amplifier Servo motor Digital servo Z-axis force loop 機械設計機器構型設計傳動與導引設計結構最佳化設計熱穩定設計電機伺服控制技術高性能伺服馬達結構振動抑制前饋伺服延遲補償非線性摩擦力補償加減速預視控制切削加工精度的影響因素加工誤差發方式

4 各種控制方式 Linear axis x: unrestrained, other five DOF (degree of freedom) restrained Rotation axis : unrestrained, other five DOF restrained Open-loop Semi-closed loop-a Semi-closed loop-b Closed-loop

5 運動台控制架構圖 Driver Plant Point to point positioning vs. contour motion 指令 Controller 電壓 Servo ROM Amplifier 電流 Motors, mechanical parts, and external loads low power high power 位置速度與電流 ( 加速度 ) B Controller 控制法則 Gcp(S) Servo ROM Amplifier Plant 控制法則 Gcv(S) Ga(S) Gp(S) A 位置 Hp(S) 速度電流 ( 加速度 ) Hi(S) Hi(S) Point-to-point positioning Contouring 25 (dynamics) 26 Importance of velocity and acceleration control of contouring machining

6 Direct measurement (linear scale) Semi-closed loop A closed loop Semi-closed loop B Laser interferometer 0.1 ppm (1x10-7 ) Indirect measurement (rotary encoder) 控制方式的比較精密定位系統之誤差原因 Single Linear axis Flexible coupling for isolation shock and vibration Ballscrew and nut Guideway and sliding pads

7 Ballscrew Thermal error of the ballscrew drive system Using Linear Scale Sensor to Eliminate Ballscrew Thermal Expansion Problem 高速高剛性與高精度驅動系統高速化高剛性滾珠螺桿反應速度

運動平滑度 Prefect kinematic reference 43 The kinematic reference must be prefect

Besides, it must be stable when dynamic load and temperature are changed.

Drive mechanism and guideways Drive mechanism: moving the stage to the desired

x axis Guide ways: constraining the stage motion to the desired directions

y, z,,, Dynamic loading Thermal loading 45 Question: How to eliminate the

8 運動平滑度 Prefect kinematic reference 43 The kinematic reference must be prefect of geometric errors such as straightness errors. Besides, it must be stable when dynamic load and temperature are changed. 44 Stability of a kinematic reference subjected to dynamic and thermal loads Drive mechanism and guideways Drive mechanism: moving the stage to the desired position (desired DOF), ex. x axis Guide ways: constraining the stage motion to the desired directions (five constrained DOF), ex. y, z,,, Dynamic loading Thermal loading 45 Question: How to eliminate the misalignment between the drive mechanism and guiding mechanism? 46 Misalignments between the slideway axis and drive axis Types of shaft misalignments Parallel misalignment In-line misalignment Angular misalignment

9 Flexural coupling Sliding vs. rolling sliding (a) rolling (b) Velocity Note: Not only the friction level should be kept to low, but more important is that the friction variation should be stabilized 精密滾動軸承雖然被廣泛應用在精密機械上, 但是對於超精密機械而言, 每一顆滾珠間的差異性卻可能精度的侷限 ( 以目前製造技術而言, 滾珠的 form error 大約在 0.1 m) Friction drive mechanisms Capstan friction drive Twist roller friction drive 51 Note: The friction must be maintained to constant during the axis movement. 52 液靜壓螺桿 Non contact screw mechanism

10 非接觸式傳動與導軌系統磁螺桿 Constrained motion of a single axis Geometric errors of Multiple axis Machines z y Geometric errors of a single axis x+ x

11 Geometric error source: manufacturing errors Geometric error sources: assembly errors Geometric error sources: installation and foundation Geometric errors of multiple axis machine 串聯機構的笨重移動軸 6 geometric errors 13 geometric errors 21 geometric errors

12 該重則重, 該輕的就盡量輕 DMG DuoBlock 1.7g, Ra:0.26um, 加工時間 : 粗加工 -2hr 精加工 -3hr Mikron HSM 移動部與樹脂混泥土機體的質量比是 1:10 Mikron HSM Monoblock Closed Epoxy Composite Frame Topology shape optimization 應用於移動件輕量化設計 Structural Optimization The optimization of a slide for a high speed milling machine ( 2g acceleration) a) Traditional box ripping b) Manual optimization c) Automatic topology optimization 15% weight reduction further 2% weight reduction A: D 2 m: D 3 Strain ~ F/A ~ D Combustion Engine Animation(240p_H.263-MP3).flv 許多情況下, 減少動件機械元件的截面積更有助於降低動態負荷進而改善機械元件壽命 69 4,8 μm max. deflection 2,8 μm max. deflection 1,7 μm max. deflection Courtesy: FE Design 70 串聯機構之五軸機械

13 串聯構造 : 低剛性低精度史都華平台之演進歷史 workpiece thermal distortion P M M M force line workpiece abbe offset cutting tool abbe offset ballscrew ballscrew a) 負荷流線長 b) 結構受彎矩負荷 c) 熱不對稱結構 d) Abbe Offset 大開放性結構負荷流線長且承受彎曲負載, 因此結構剛性差由於串聯之故, 各軸之幾何誤差和熱變形會產生累積與放大效應史都華平台史都華博士在 1965 年發表的六自由度運動平台從 1965~1990 年, 主要之應用在於飛行模擬器振動測試台與裝配美國 Ingersoll 和 Gidding&Leiws 工具機公司於 1988 年開始研究史都華平台在工具機切削加工之應用 Gidding&Leiws 在 1994 年 IMTS Show 展出此類構型機器, 工具機業者並喜用 Hexapod 機器名字以便區分其與傳統工具機之不同 73 Gidding&Leiws 的 Variaxs 74 Giddings & Lewis Variax Geodetic G500/G Portable and Re configurable Neos Robotics AB Tricept

Z 3 Head DST ECOSPEED 1. Box in box 封閉式結構 2.

Z: 670mm(0 o )/ 370mm(+-40 o ), 50m/min & 1G, A/B:

120-kW 30,000-rpm spindle and 80-kW 30,000-rpm

1975 1987 1998 2000 79 80 Index V100 High speed

times due to new tripod concept: 1g acceleration

More Power and Higher RPM Spindles 年代 ( 西元 ) 進給速度

75 1.5 >120 >2 >500 >8 40,000 >60,000 >100,000 20

Surface speed Feed per tooth Specific MRR 4700m/min

14 Z 3 Head DST ECOSPEED 1. Box in box 封閉式結構 2. 輕量化的並連機構主軸旋轉頭 Z: 670mm(0 o )/ 370mm(+-40 o ), 50m/min & 1G, A/B: +-40 o, 80 o /sec& 685 o /sec kW 30,000-rpm spindle and 80-kW 30,000-rpm spindle FPV 2500 FPA 2500/24 FPA ECOSPEED Index V100 High speed spindle for machine tools Extremely short idle times due to new tripod concept: 1g acceleration and rapid movement up to 60 m/min 82 工具機發展趨勢 Need More Power and Higher RPM Spindles 年代 ( 西元 ) 進給速度 (m/min) 加減速 (g) 主軸轉速 (rpm) 主軸馬力 (kw) ,000 6,000 15, * >120 >2 >500 >8 40,000 >60,000 >100, >60 >100 Optimal cutting parameters for Al7075 Surface speed Feed per tooth Specific MRR 4700m/min mm 70-80cm 3 /kw*min 83 Bearings, motors and cutter-spindle interface will be the major problems of the future spindles

汽車零組件加工斜角滾珠軸承 MACHINING TIME sec 350 348 300 250 200 150 100 50 0 308 CASE 1 CASE 2 CASE 3 CASE 4 Machining condition Present High-Speed High-Speed High-Speed Feed Speed(m/min)

85 Work: Brake Disk Body, Cast Aluminum 208 138 Tool Change Spindle Control Positioning Cutting 1. 15 度接觸角 : 減少 spin-roll friction 2. 小直徑滾珠與低截面內環 : 減少離心力 3. 陶瓷珠與高強度內環材料 : 減少離心力 4.

Temperature-induced loading Cold setting preload Spindle Speed 87 88 Lower Power Loss and Longer Life Higher Rigidity Hoursx1000 LIFE vs BALL MATERIAL 1000 1.

15 汽車零組件加工斜角滾珠軸承 MACHINING TIME sec CASE 1 CASE 2 CASE 3 CASE 4 Machining condition Present High-Speed High-Speed High-Speed Feed Speed(m/min) Acceleration(g) Spindle Speed(rpm) Time to Maximum Speed Work: Brake Disk Body, Cast Aluminum Tool Change Spindle Control Positioning Cutting 度接觸角 : 減少 spin-roll friction 2. 小直徑滾珠與低截面內環 : 減少離心力 3. 陶瓷珠與高強度內環材料 : 減少離心力 4. 油氣潤滑 : 降低溫升 Bearing Loading at Operations 陶瓷與鋼材材料特性 Bearing Loading Bearing loading at operations Centrifugal force of ball Centrifugal force of inner ring Temperature-induced loading Cold setting preload Spindle Speed Lower Power Loss and Longer Life Higher Rigidity Hoursx1000 LIFE vs BALL MATERIAL x Si3N4 100 Steel x DN (millions) Steel ball Ceramic ball Steel ball Ceramic ball Relative Acceleration Engineering Units Steel Vibration Si 3 N cer1 cer2 cer3 cer4 cer5 cer6 cer7 陶瓷珠在低速或靜止時, 必須注意打刀力或搬運時之衝擊力可能造成之破壞

16 高速主軸之軸承排列與彈簧力預壓廣域切削主軸可變預壓方式油壓控制剛性噪音振動迴轉精度摩擦熱壽命高速化預壓增加 : 改善 : 惡化廣域切削主軸可變預壓方式廣域切削主軸可變預壓方式形狀記憶合金預壓控制利用 a, b, c, d 四組彈簧的不同設定溫度的形狀記憶能力來進行預壓切換定位與定彈簧力切換機構 Heavy cutting Constant Offset Preload spacer 在 25 o C 以下時, 四組彈簧都作用, 最大預壓力 132kg 在 25 o C- 30 o C 之間, 三組彈簧作用 (b-d), 預壓力為 84kg 在 30 o C- 40 o C 之間, 二組彈簧作用 (c-d), 預壓力為 48kg 在 40 o C 以上時, 只有一組彈簧作用 (d), 預壓力為 20kg High-speed cutting Spring Preload spring Hydrostatic and aerostatic bearings

17 靜壓軸承主軸與滾珠軸承主軸 Aerostatic bearing spindle 超精密加工機與精密儀器應用範例 Lithography stage Inspection instrument Precision grinding center Diamond lathe 99 Applications of aerostatic bearings 100 超精密機械加工範例磁浮火車 Wafer dicing Optical elements Hard disk Printed circuit board

18 磁浮軸承高速主軸 IBAG HF200 MA rpm/33kW, HSK50E, 1000~1500 N/ DN:360 萬 6000hrs

Microsoft PowerPoint - Construction and error sources of multi-axis machines

Microsoft PowerPoint - Construction and error sources of multi-axis machines Handout 1 工具機整機系統設計 Construction and error sources of multi axis machines ( 多軸精密機械之構造與誤差源 ) Multi axis Machines by Serial linked Configuration Y-axis Combining three independent translation axes and rotary