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

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Handout 1 工具機整機系統設計 Construction and error sources of multi axis

Configuration Y-axis Combining three independent translation

Z-axis X-axis 4 Five axis machining Three translation axes + two

spindle head Spindle-axis or tool-axis 2 2-axis rotary table 5

Cartesian Axis Configuration Y-axis Z-axis X-axis Precision,

the precision machinery such as the machine tool.

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 ) Multi axis Machines by Serial linked Configuration Y-axis Combining three independent translation axes and rotary axes according the Cartesian coordinate system Z-axis X-axis 4 Five axis machining Three translation axes + two rotary axes + one cutting tool axis 多軸工具機的座標定義 2-axis swiveling spindle head Spindle-axis or tool-axis 2 2-axis rotary table 5 Three axis Machine Tool Cutting spindle Multi axis Machines by Cartesian Axis Configuration Y-axis Z-axis X-axis Precision, accuracy and high throughput are the fundamental requirements of the precision machinery such as the machine tool. 3 Combining three independent motion axes according the Cartesian coordinate system 6 1

The z-axis is assigned to the spindle axis. 2.

2 Z-axis y-axis x-axis z-axis X-axis y-axis z-axis Y-axis x-axis 7 10 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

Rule: The A-axis is assigned to the rotation of x-axis, while the

Five axis Machines CNC (computer numerical control) machine tools

Corner Control NURBS interpolation Servo amplifier Servo motor

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 13 16 Why rotary

切削加工精度的影響因素 14 17 Kinematic Loop and Force Loop 加工誤差發方式 workpiece

3 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. Five axis Machines CNC (computer numerical control) machine tools 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 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 Why rotary axes are needed? 切削加工精度的影響因素 Kinematic Loop and Force Loop 加工誤差發方式 workpiece Cutting tool Y-axis Force loop 的長度盡量短 Kinematic loop 的傳動剛性與熱穩定性要佳, 且摩擦力穩定易於控制移動件的重量要盡量輕量化機床結構的剛性與熱穩定性要佳 Z-axis force loop 地基與腳座的剛性與穩定性要佳 Floor

各種控制方式 19 22 20 23 Open-loop 運動台控制架構圖 Driver Plant Semi-closed loop-a 指令 Controller

external loads Semi-closed loop-b 位置速度與電流 ( 加速度 ) Closed-loop Controller 控制法則

4 各種控制方式 Open-loop 運動台控制架構圖 Driver Plant Semi-closed loop-a 指令 Controller 電壓 low power Servo ROM Amplifier 電流 high power Motors, mechanical parts, and external loads Semi-closed loop-b 位置速度與電流 ( 加速度 ) Closed-loop Controller 控制法則 Gcp(S) Servo ROM Amplifier Plant 控制法則 Gcv(S) Ga(S) Gp(S) 電流 ( 加速度 ) Hi(S) 位置 Hp(S) 速度 Hi(S)

5 Point to point positioning vs. contour motion 運動路徑變換方向時的加減速控制 B A Point-to-point positioning Contouring (dynamics) A=v 2 /r 速度 V 愈大則加速度 A 隨之增加 Importance of velocity and acceleration control of contouring machining CNC 與伺服電氣控制機械傳動系統 ( 慣量剛性與熱變形 ) Semi-closed loop A closed loop Semi-closed loop B 27 檢測器的安裝位置決定了傳動機構的受力變形誤差振動誤差與熱變形誤差是否被檢測器所偵測到 30 5

6 Direct measurement (linear scale) Single Linear axis 構成組件 : 1. 馬達 : 動力來源 2. 撓性聯軸器 (flexible coupling): 隔離動力源與傳動模組見的震動與組裝誤差底座 Ballscrew and nut Laser interferometer 0.1 ppm (1x10-7 ) 3. 滾珠螺桿與螺帽 : 轉動變成線位移之傳動模組 4. 線性導軌與滑塊 (linear guideway and sliding pads): 導引工作臺之運動方向 Flexible coupling for isolation misalignment and vibration Guideway and sliding pads Indirect measurement (rotary encoder) Ballscrew 滾珠迴流槽控制方式的比較 Thermal error of the ballscrew drive system

7 Using Linear Scale Sensor to Eliminate Ballscrew Thermal Expansion Problem Linear motor stage vs. Ballscrew stage Linear motor stage Ballscrew stage 37 高速化高剛性滾珠螺桿反應速度高速高剛性與高精度驅動系統運動平滑度

線性馬達工具機範例 Stability of a kinematic reference subjected to

120m/min, 2G Spindle:24000rpm 線性馬達工具機 ( 工研院機械所 ) Dynamic

mechanism: moving the stage to the desired position (desired

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

eliminate the misalignment between the drive mechanism and

47 Prefect kinematic reference Misalignments between the

8 線性馬達工具機範例 Stability of a kinematic reference subjected to dynamic and thermal loads X, Y, Z: 600x800x500mm 3 Feed: 120m/min, 2G Spindle:24000rpm 線性馬達工具機 ( 工研院機械所 ) Dynamic loading Thermal loading 46 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,,, Question: How to eliminate the misalignment between the drive mechanism and guiding mechanism? 47 Prefect kinematic reference Misalignments between the slideway axis and drive axis 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

Types of shaft misalignments Parallel misalignment

9 Types of shaft misalignments Parallel misalignment 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) In-line misalignment Angular misalignment Flexural coupling 液靜壓螺桿 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

10 超精密加工機 : 非接觸式傳動與導軌系統 Geometric errors of a single axis Constrained motion of a single axis Geometric errors of Multiple axis Machines z y Geometric error source: manufacturing errors x+ x

11 Geometric error sources: assembly errors 串聯機構的笨重移動軸 Position 1 Position 2 目標 : 移動件盡量輕量化機台結構要高剛性與良好吸收震動的材料特性 Geometric error sources: installation and foundation 高速切削機台構型範例 good bad Box in Box Structure 輕量化機台與高剛性結構之構型設計 62 Geometric errors of multiple axis machine 精密模具加工用的高速切削工具機範例 6 geometric errors X, Y, Z: 560x410x410mm 3 Feed: 60m/min, 1G Positioning accuracy: m Spindle:25000rpm/15kW/HSK40 Max. Load: 350kg Weight: 4700kg Floor space: 2440x2245mm 2 13 geometric errors 21 geometric errors 63 Mazak FJV-20 11

12 該重則重, 該輕的就盡量輕 Structural Optimization The optimization of a slide for a high speed milling machine ( 2g acceleration) 1.7g, Ra:0.26um, 加工時間 : 粗加工 -2hr 精加工 -3hr a) Traditional box ripping b) Automatic topology optimization Mikron HSM 16% weight reduction 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 ,8 μm max. deflection 1,7 μm max. deflection Courtesy: FE Design 70 DMG DuoBlock Topology shape optimization 應用於移動件輕量化設計 Mori Seiki s original zero overhang structure 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 12

Bryan Alignment Principle 串聯機構之五軸機械 Mori Seiki: Driven at

Machine Design 串聯構造 : 低剛性低精度 workpiece P M thermal

workpiece abbe offset ballscrew ballscrew a) 負荷流線長 b)

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 77

z (N/ m): 104 133 770 690 8 材料去除率 476 531 ( 面銑 ) 23 86.

Variaxs 史都華博士在 1965 年發表的六自由度運動平台從 1965~1990 年,

13 Bryan Alignment Principle 串聯機構之五軸機械 Mori Seiki: Driven at the Center of Gravity 76 Motor Type vs. Machine Design 串聯構造 : 低剛性低精度 workpiece P M thermal distortion cutting tool abbe offset force line M M workpiece 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 Courtesy: Mori Seiki 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 77 Mori Seiki X series 移動件輕量化 2. 力流線縮短與質心往驅動中心靠近 3. 加強腳座剛性 4. 提升主軸剛性與採用硬軌 22 Rigidity X (N/ m): y (N/ m): z (N/ m): 材料去除率 ( 面銑 ) ( 端銑 ) (f50 鑽孔 ) 75 史都華平台之演進歷史史都華平台 Gidding&Leiws 的 Variaxs 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 78 13

14 Giddings & Lewis Variax Portable and Re configurable Series kinematic machine (SKM) vs. Parallel kinematic machine (PKM) Neos Robotics AB Tricept Geodetic G500/G1000 Index V100 Extremely short idle times due to new tripod concept: 1g acceleration and rapid movement up to 60 m/min 81 14

Z 3 Head 工具機發展趨勢年代 ( 西元 ) 進給速度 (m/min) 加減速 (g) 主軸轉速 (rpm) 主軸馬力 (kw) 60-69 70-79 80-89 5

5 >120 >2 >500 >8 40,000 >60,000 >100,000 20 >60 >100 1.

120-kW 30,000-rpm spindle and 80-kW 30,000-rpm spindle 85 88 DST ECOSPEED 1.

輕量化的並連機構主軸旋轉頭 Need More Power and Higher RPM Spindles 800 700 600 500 400 300 200 100 0

cutter-spindle interface will be the major problems of the future spindles.

200 150 138 100 50 0 CASE 1 CASE 2 CASE 3 Work: Brake Disk Body, Cast Aluminum Machining

15 Z 3 Head 工具機發展趨勢年代 ( 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 > 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 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 Need More Power and Higher RPM Spindles FPV 2500 FPA 2500/24 FPA ECOSPEED Bearings, motors and cutter-spindle interface will be the major problems of the future spindles. 89 汽車零組件加工 High speed spindle for machine tools MACHINING TIME sec CASE 1 CASE 2 CASE 3 Work: Brake Disk Body, Cast Aluminum Machining condition Present Hi-Speed Feed Hi-Speed Feed & Spindle Feed Speed(m/min) Acceleration(g) Spindle Speed(rpm) Time to Maximum Speed Tool Change Spindle Control Positioning Cutting

斜角滾珠軸承 Lower Power Loss and Longer Life Hoursx1000 1000 100 10 1 LIFE vs BALL MATERIAL 1.5x Si3N4 Steel 5200 5x 1.

5 DN (millions) DN value = bearing diameter x bearing rotation speed 91 94 Bearing Loading at Operations Higher

Temperature-induced loading Cold setting preload Steel ball Ceramic ball Steel ball Ceramic ball Relative

92 95 陶瓷與鋼材材料特性 Basic System Design Concepts of Built in Motor Spindle Direct drive by built-in spindle motor

16 斜角滾珠軸承 Lower Power Loss and Longer Life Hoursx LIFE vs BALL MATERIAL 1.5x Si3N4 Steel x 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 DN (millions) DN value = bearing diameter x bearing rotation speed Bearing Loading at Operations Higher Rigidity Bearing Loading Bearing loading at operations Centrifugal force of ball Centrifugal force of inner ring Temperature-induced loading Cold setting preload Steel ball Ceramic ball Steel ball Ceramic ball Relative Acceleration Engineering Units Steel Vibration Si 3 N cer1 cer2 cer3 cer4 cer5 cer6 cer7 Spindle Speed 陶瓷與鋼材材料特性 Basic System Design Concepts of Built in Motor Spindle Direct drive by built-in spindle motor Oil-air lubrication for bearing Angular-contact ceramic-ball bearing Water cooling system for motor 93 Draw-bar mechanism for automatic tool change 16

17 Bearing layout and preload of Hi speed spindle 滾珠軸承高速化要件 Materials Bearing geometry Surface roughness Lubricant Lubricant supply method Courtesy: GMN Centrifugal force and temperature effects NSK Angular Contact Ball Bearings o i Courtesy: FAG 98 Conventional Bearings ROBUST Series Steel balls Ceramic balls S type H type Grease Oil/air Grease Oil/air Grease Oil/air Grease Oil/air Oil/air Grease Oil/air Oil/air Oil/air Oil/air X type Grease Oil/air Oil/air Constant-pressure preload EX type Oil/air Position preload d m n *10 6 廣域切削主軸可變預壓方式軸承潤滑給油方式油壓控制歐洲 SNFA, FAG DLS 剛性噪音振動迴轉精度摩擦熱壽命高速化預壓增加 : 改善 : 惡化日本 NSK Under-race 99 17

18 Hydrostatic and aerostatic bearings 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 105 Applications of aerostatic bearings

19 超精密機械加工範例 Automatic Tool Changer (ATC) & BT Tool Holder Interface Wafer dicing Optical elements Hard disk Printed circuit board 109 磁浮火車 ISO 1947(One Contact Area): BT Tool Holder Interface 2mm gap 110 磁浮軸承高速主軸 BT 7/24 斜度標準刀把之精度等級區分 IBAG HF200 MA rpm/33kW, HSK50E, 1000~1500 N/ DN:360 萬 6000hrs 111 高速切削時最好使用 AT2 級或更佳之刀把 19

20 Good Fit - Bad Fit Test Results AT5/6 AT2 by Kennametal DIN HSK(Two Contact Areas) Interface: 雙面拘束刀把介面 1/10 tapper interface 提升彎曲剛性改善定位精度 Note: 為了確保能雙面接觸與居拘束, 使用較小斜率的錐孔 (1/10) Big Plus Tool Holder Interface Other Tool Holder Interfaces CoromantCapto Kennametal KM Note: 採用傳統 BT 刀把的介面標準, 但是改良端面的接觸條件, 始能達到雙面接觸與拘束之目的 20

21 Kennametal (Three Contact Areas) Tangential Load Deflection Test conducted by Kennametal-Hertel in Furth, Germany 21

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 ) 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