KIT – University of the State of Baden-Wuerttemberg and National Research Center of the Helmholtz Association

wbk Institute of Production Science

www.wbk.kit.edu

Machine tool precision determination and compensation approaches Review on research at wbk Institute of Production Science

Daniel Brabandt London, 5th Nov. 2014

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Summary 5

Mechatronic Clamping System 4

Adaptronical Strut 3

Intrinsic Part Scale 2

Introduction 1

Agenda

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Established: 1 October 2009 Courses of Studies: 44 Students: 24.500 Staff: 9.439 (including 346 professors) Total budget: 795 m €

Objectives Positioning the Institute as an institution of internationally outstanding research and teaching in natural sciences and engineering that offers scientific excellence and world class performance in

Research Education Innovation

Karlsruhe Institute of Technology (KIT) wbk Institute of Production Science

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Locations

wbk, Fasanengarten, KIT wbk, Ehrenhof, KIT

wbk at Fasanengarten Production systems Machines, equipment and

process automation wbk at Ehrenhof

Manufacturing and materials technology wbk at Campus Nord GAMI - Global Advanced Manufacturing Institute

Suzhou, China AMTC - Advanced Manufacturing Technology Center

Shanghai, Jiading Campus at Tongji University, China

Tongji University, GAMI, China

wbk Institute of Production Science

Building 276, KIT Campus Nord

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Research Portfolio wbk Institute of Production Science

Prof. Dr.-Ing. Jürgen Fleischer Prof. Dr.-Ing. Gisela Lanza Prof. Dr.-Ing. habil. Volker Schulze

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Introduction Accuracy of machine tools

Accuracies of machine tools is determined by all of the components and their errors

Approaches to improve accuracies:

Workpiece orientation: Intrinsic part Scale

Error compensation within machine tool structure: Adaptronic strut

Error compensation at the tool: Compensation in tool clamping

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Summary 5

Mechatronic Clamping System 4

Adaptronical Strut 3

Intrinsic Part Scale 2

Introduction 1

Agenda

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale

Flexible and exact machining of space-frame structures in automated small batch production

insertion and positioning the profile into the clamping fixture with an industrial robot (IR)

local clamping of the profile

sequential machining

Process

Motivation and Introduction

BMW C1

Aim

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale

2 1 3 4

Metrological approach individual laser markings on the profile surface for a component-specific scale

Profile positioning in the clamping fixture

curved profile IR-gripper

Positioning 4 DOF are constrained with mechanical stops profile displacement and rotation along the longitudinal axis by the IR

displacements inside the IR-gripper limited accuracy of the IR profile contour deviations

Inaccurate positioning due to

mechanical stops

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale Component-specific scale

Required information in the marking x, y coordinates rotation-angle α (centerline – camera CS) orientation absolute allocation

Geometry derivation evaluation of simple ruled geometries and their combinations considered requirements

marking process detection process

Y

X

α (x,y, direction)

repeat accuracy of the position-detection of a single marking: ± 1.2µm (6σ)

Scheme:

Binary image:

camera CS

camera view

profile

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale Marking process

Marking Laser

Additional Axis

marking on the fly

marking inside of a milling-machine positioning and focusing with axis and control of the milling machine during marking-process idle

„Off-line“

„In process“ synchronous with extrusion process (with marking laser) marking on the fly compensation of profile inclination real time control

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale Measuring station

Profile positioning

positioning of two markings calculation of deviation to the default marking position calculation of projected distance

1 2 Setup

measuring the contour of the segment stepwise contour detection with a 2D laser-line triangulation sensor calculation of peak coordinates (x,y,z) by fitting an ellipse with least square method

Scatter plot

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale Metrological approach

generate overlapping areas between two segments align splines in overlapping areas calculate the overall contour by means of cubic spline interpolation coordinate system located in last link

Overall contour determination segment 1 segment 2

reference markings

overlapping area

2 1 3 4 z

x y

z

x y

schematic determination of the entire profile contour

z

x y

z

x y

z

x y

x y

z

z

x y

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale

reference values and measurement results

2

1

3 4

5 6

Validation (results of a planar curved profile)

reference values

measurement results

measurement results

reference values

xy-plane

circular cross-section Ø40x2mm profile with 6 Segments Segment length: 250mm total length: 1500mm overlap length: ± 60mm 12 measurements

marking positions

average deviation

6 1 2 3 4 5

x

y

z

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale Validation (results of a planar curved profile)

2

1

3 4

5 6

xz-plane

positioning accuracy over 6 segments (Δl= 1502.05mm): absolute: - 0.04mm standard deviation: σx= 6µm

max. contour deviation xy plane: - 0.5mm; xz plane: - 0.4mm maximum dispersion: Δxy= ± 0.15mm Δxz= ± 0.25mm

reference values

measurement results

average deviation

6 1 2 3 4 5

marking positions

x

y

z

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Intrinsic part scale Summary

approach for exact profile positioning and contour detection on the basis of a component specific scale metrological approach and design of single markings experimental setup and results of planar curved profile

approach is usable for the precise and flexible positioning and contour detection of curved profiles (e.g. for machining processes)

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Summary 5

Mechatronic Clamping System 4

Adaptronical Strut 3

Intrinsic Part Scale 2

Introduction 1

Agenda

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Adaptronical Strut Introduction

Influences on accuracy of machine tools Mechanical stiffness and production accuracy of machine components are two main factors which influence the geometrical accuracy of machine tools. Process loads and errors in machine components lead to a displacement of Tool Center Point. Negative impact on machining accuracy

Parallel kinematic machine tool with three degrees of freedom Approach:

Improvement of mechanical stiffness through adaptronics

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Adaptronical Strut Approach

Integration of an adaptronical strut The strut must be able to compensate deformations of the mechanical components from external loads

To increase stiffness of a machine structure, the strut needs to

detect a change in load carry out correction movements

The Approach for the adaptronical strut is based on the principle of oscillating-wire balance.

Concept of the adaptronical strut

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Adaptronical Strut Prototypical Realisation

Control concept

To realize the functionality of the strut a special control concept is necessary

Separation of sensor and actuator signals Stimulation of vibrating string Control of actuator stroke

Simplified control concept

Prototypical adaptronical strut

Prototypical adaptronical strut

The structure consist of an upper and a lower part

Coaxially piezoelectric transducer Vibration string

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Adaptronical Strut Results and Summary

Measurements and Validation

Frequency band 2050 – 2350 Hz

Response time 300 – 400 ms

Resulting stiffness 11 KN/ µm

An approach has been developed and implemented for improving the mechanical stiffness of an strut structure for parallel kinematics through adaptronics. The approach can be applied to other structures in machine tool manufacturing in principle

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Summary 5

Mechatronic Clamping System 4

Adaptronical Strut 3

Intrinsic Part Scale 2

Introduction 1

Agenda

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Mechatronic Clamping System Introduction

Micro-Milling

Application area Very small components Ultra precise geometries

Micro specific challenges

Tool deflection Relatively high cutting edge radii Cutting edge displacement

concentricity error spindle

+ tool tolerance

+ fit errors clamping sytem

= cutting edge displacement 18 µm

10 µm

6 µm

2 µm

aim <1 µm

Cutting edge displacement caused by concentricity errors in the spindle, fitting errors in the clamping system and material tolerances. The main problem is the unpredictability of the wobbling move of the tool.

Application area Very small components Ultra precise geometries

Micro specific challenges

Tool deflection Relatively high cutting edge radii Cutting edge displacement

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Mechatronic Clamping System Introduction

Cutting edge displacement

ideal: diameter = 50 µm displacement = 0 µm

h

real: diameter = 50 µm displacement = 20 µm

h displacement

Worst case scenario: one cutting edge is completely unloded, the opposite edge however has doubled loads.

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Mechatronic Clamping System

Problems due to cutting edge displacement Doubled load for one cutting edge ( tool with 2 cutting edges) Therefore decreased tool lifetime Decreasing process stability

Approach

Mechatronic clamping system for compensation at nominal speed Idea:

Compensation

cutting edge displacement compensation

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Mechatronic Clamping System

Coils for energy transfer

Compensation

Actuation through piezo actuators

Flexibility with solid-state joint

Contactless energy transfer runs a piezo actuater to tilt the flexible, lower part. The solid-state joint enables the tilt ot the chuck to direct the tool center point to its nominal point. A feasible maximum of 10-15 µm correction is possible.

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Mechatronic Clamping System Operation

measurement analysis compensation

Detection of tumbling cutting edges with a Blum-laser. Alternating shading of the laser triggers compensation.

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Mechatronic Clamping System Validation and results

grooves

bars

241,78 µm

225,72 µm

255,81 µm

224,75 µm

239,18 µm

241,17 µm

grooves

bars

Nominal size: 240µm Compensation enables manufacturability of tolerable deviations from the nominal size.

not compensated compensated

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Mechatronic Clamping System

50 test runs uncompensated

Validation and results

35 µm 10 µm

50 test runs compensated

<5 µm

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Summary 5

Mechatronic Clamping System 4

Adaptronical Strut 3

Intrinsic Part Scale 2

Introduction 1

Agenda

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© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Introduction Accuracy of machine tools

Intrinsic part Scale

Adaptronic strut

Compensation in tool clamping

Accuracies of machine tools is determined by all of the components and their errors Increase of machine tool accuracy is possible by scientific approaches using measuring systems

Slide 32 10.11.2014

© wbk Institute of Production Science Prof. Dr.-Ing. J. Fleischer, Prof. Dr.-Ing. G. Lanza, Prof. Dr.-Ing. habil. V. Schulze

Dipl.-Ing. Daniel Brabandt Research Associate

Kaiserstr. 12, 76131 Karlsruhe Tel.: +49 721 608 44016 daniel.brabandt@kit.edu www.wbk.kit.edu

Thanks to:

F. Zanger, P. Hoppen, M. Deuchert, S. Dosch, J. Bauer, D. Berger

Thank you!