AfM Technology Volumetric Compensation of machine … of machine tools / CMM ... Limitations in aquisition and compensation Aachen colloquium for 5-Axis precision machining

Page 1 © AfM Technology GmbH / Wolfram Meyer

The Engineering & Calibration Service Company

for

Volumetric Compensation of machine tools / CMM Linear and rotary axis calibration of machine tools / CMM


Aachen colloquium for 5-Axis precision machining

Geometric deviations of machine tools

Metrological parameter aquisition

Compensation in the CNC control

Limitations in aquisition and compensation

Trends and challenges

Agenda


Geometric deviations of machine tools



Influences on machine tool accuracy

Dynamic

Drives

Thermal influences

Geometry

Component

deviations

Location deviations

Model fitness

Machine coordinate

system

Page 5 © AfM Technology GmbH / Horst Eckersberger

support

guide

Each linear guide has 6 degrees of freedom, 3 translational und 3 rotational

translational movement

(transverse to the guide axis) / EZX

rotational movement:

around X = roll / EAX

around Y = pitch / EBX

around Z = yaw / ECX

translational movement (position) / EXX

translational movement

(transverse to the guide axis) EYX

Geometric deviations on a linear machine axis


support

Rotary table

Each rotary axis has 6 degrees of freedom, 3 translational und 3 rotational

translational movement (axial runout in Z) / EZC

rotational movement:

around X = wobble / EAC

around Y = wobble / EBC

around Z = position / ECC

translational movement (radial runout in X) / EXC

translational movement (radial runout in Y) / EYC

Geometric deviations on a rotary machine axis


Kinematic chain of a machine tool

3 linear axes

3 rotary axes

1 spindle

coordinate system

Effective deviations

t – S – A – B – Y – Z – MB – X – C – MT – w

Kinematic chain

Tool Work piece

Spindle Machine

base

3 x 6 = 18

3 x 6 = 18

1 x 5 = 5

41

3 x 3 = 9

3 x 5 = 15

1 x 4 = 4

- 6

28

∑ = 69 deviations

Component dev. location dev.

© AfM / Keppler


Resulting errors at the tool center point (linear axes)

The geometrical errors of the linear axes of a 3-axes machine tool cause spatial errors of the TCP concerning position and orientation.

Geometric errors

positioning error

straightness

roll

yaw

pitch

squareness

Resulting error at TCP

positioning error

orientation error

Programmed tool position and tool orientation

Real TCP position

Real tool orientation


Resulting errors at the tool center point (rotary axes)

The component and location errors of the radial axes of a 4/5/6-axes machine tool causes also spatial errors of the TCP concerning position and orientation.

Geometric errors

runout

wobble

position

location of axis

orientation of axis

zero position

Resulting error at TCP

positioning error

orientation error

Real TCP position

Real tool orientation


Metrological parameter aquisition



Measurement methods for error parameters

Direct Measurement Indirect Measurement

Component

deviations

Location

deviations

Component and location deviations

Laserinterferometer

Straightness artefact

& indicator (Wire /

Stone)

Levels

Reference encoders

Reference scales

Autokollimator

Laserinterferometer

90° stone angle,

calibration cube &

dial indicator

Levels

Test mandrel & dial

indicator

Ball bar, ball plate, Tetraeder

Reference parts

Circular test

Ball & 3D-Probe

Lasertracker

LaserTRACER


Straightness laser

Levels Reference scales

Autokollimator

Straightness artefact & indicator (Wire / Stone)

Direct measurement of linear axis with single-purpose tools

A great variety of tools is used


Direct measurement of linear axis with laser interferometer

Laserinterferometer available with 1 up to 6 DOF

High accurate, long range

Alignment effort, particularly for vertical and

straightness measurement is high

Renishaw (1-DOF)

HP Agilent (1-DOF)

API (6-DOF) TSK (3-DOF)

© TSK


Direct measurement of rotary axis

HEIDENHAIN Reference encoder RON 905

Laserinterferometer with Renishaw RX10 API Swivelcheck

Test mandrell

&

dial indicator


Indirect measurement of linear axis with ball bars

Fast and easy measurement

Geometric and drive analysis

Applicable in any plane

Mind the volume size

Renishaw QC-20W

Dreier RoundCheck VA API Ballbar


Indirect measurement of component and location deviation

© IBS Precision Engineering

Tetraeder

© Prof. Knapp ETH Zürich

Ball bars (1D), ball plates (2D), Tetraeder (3D)

Fixed grid, limited dimension, handling complex

Ball bar

© Dr. Trapet

Ball plate


Indirect measurement of linear axis with laser interferometer

Optodyne MCV 500 © Dr. Trapet


Indirect measurement by multilateration with LaserTRACER

Linear axis calibration

Rotary axis calibration

Acceptance test according

to ISO 230-2/4/6 and ISO

10360-2

LaserTRACER MT LaserTRACER


Online multilateration with LaserTRACER

What is Multilateration?

Ideal realization of the Abbe Principle: All measurement

lines pass directly through the measurement point.

Principle is used in Global Positioning System (based on

time of flight measurement).

With LaserTRACERs, the principle can be downscaled to

submicron accuracy in a medium measurement volume.

If four LaserTRACERs are used, the system is self calibrating

Characteristics

Mobile, Self calibration

Contactless, 3D measure

Working volume up to 10 m x 10 m x 10 m.

Direct traceability by stabilized laser interferometer.

Highest resolution and accuracy (down to sub-micron range)

© Etalon


3D Messung mit LaserTracker

Lasertracker Moving Active Target (AT)

Stationary T3 Laser Tracker (with Pan & Tilt)

© API


Rotary axis calibration with ball and 3D probe

Fork Head Calibration

Trunion Table Calibration

Rotary and swivel axis as well as trunion table are

supported

Fixed ball, moved probe or fixed probe and moved ball

Fast, easy and automatic cycle

Up to 3 rotary axis at once

© HEIDENHAIN © Fidia © IBS Engineering Precision


Compensation in the CNC control



Geometric compensations in CNC controllers

Geometric compensations (stand alone or as combination)

Linear encoder error compensation (slope)

Non linear encoder error compensation (arbitrary form)

Cross error compensation

Grid compensation

Volumetric compensation

Stand alone or as part of geometric compensation

Backlash compensation


Linear and non linear encoder error compensation

linear encoder error compensation (slope)

Non linear encoder error compensation (arbitrary form)

-40,0

-20,0

0,0

20,0

40,0

60,0

80,0

100,0

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

dev

iati

on

[µ

m]

Position deviation y-axis

yTy / EYY Linear (yTy / EYY)


Cross error compensation

Crosstalk of any axis combination can be compensated

Compensation of straightness and squareness

© HEIDENHAIN


3D Grid compensation

The volume is divided in cubes or a spherical grid

Each corner of the cube is represent by an error vector

Used for linear axis as well as rotary axis

∆Xi ∆Yi = f(A,C) ∆Zi

© Siemens © FANUC

© Bosch Rexroth

http://www.4teachers.de/?action=download&downloadtype=image&downloadid=2796&oldaction=keywordsearch&searchtype=images&searchstring=Gitternetz

http://www.4teachers.de/?action=download&downloadtype=image&downloadid=2795&oldaction=keywordsearch&searchtype=images&searchstring=Gitternetz


Volumetric compensation

E = Te + Rem * Pm + Ret* Pt


Backlash compensation

Backlash compensation As single axis parameter

As data set along the axis

-40,0

-30,0

-20,0

-10,0

0,0

10,0

20,0

-29,0 -24,0 -19,0 -14,0 -9,0 -4,0 1,0 6,0 11,0 16,0 21,0 26,0

Position deviation B-Axis (forward & backward travel)

without CEC [0,001°] with CEC [0,001°]

without CEC [0,001°] with CEC [0,001°]

z.B. Siemens 840D sl

MD 32450 Backlash compensation

$MA_BACKLASH[0]=0.002 mm

Backlash U / U1


Limitations in aquisition and compensation



Limitation by model fitness (I)

yTz = yTz(y) + Ytz(y,z) *z

yRx = yRx(y) + yRxz(y,z) * z

EZY = EZY(y) + EZYZ(y,z) *z

EAY = EAY(y) + EAYZ(y,z) * z

Crosstalking from Z-axis to Y-axis

Z

Y

Z

Y

Y

Z

EAY (y,z)

yRx (y,z)

EZY (y,z)

yTz (y,z)

0

100

200

300

400

500

600

700

800

900

21 Error Model

0

200

400

600

800

1000

1200

1400

1600

23 Error Model

±3s ≈ ±18,3 µm ±3s ≈ ±30,6 µm


Limitation by model fitness (II)

-10,00,0

10,020,030,040,050,060,070,080,090,0

100,0

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

dev

iati

on

[µm

/m]

Bending of Column

YTZZ with 21 model YTZZ with 23 model

-5,0

0,0

5,0

10,0

15,0

20,0

25,0

30,0

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

dev

iati

on

[µra

d/m

]

Yaw of Column

YRXZ with 21 model YRXZ with 23 model

0,000000

1,000000

deviation [µrad]

Squareness yWz / AOZ

yWz/AOZ

yWz/AOZwith 23 model

-25,0

-20,0

-15,0

-10,0

-5,0

0,0

5,0

10,0

15,0

20,0

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

3200

3400

de

viat

ion

[µra

d]

Pitch y-axis

yRx / EAY with 21 model yRx / EAY with 23 model


Volumetric Compensation of machine tools

Limitation by volumetric backlash

Volumetric backlash analysis

Position 1 Position 2 Position 3 Position 4 Position 5 Position 6 Total Maximum 0,0187 0,0290 0,0170 0,0271 0,0142 0,0087 0,0087

Minimum -0,0281 -0,0234 -0,0255 -0,0183 -0,0149 -0,0153 -0,0153

Range 0,0468 0,0524 0,0426 0,0454 0,0290 0,0240 0,0240

Std. dev. σ 0,0101 0,0119 0,0089 0,0092 0,0056 0,0061 0,0061

±3σ (99,73%) 0,0607 0,0717 0,0532 0,0549 0,0338 0,0369 0,0369

Drift 0,0000 0,0000 0,0000 0,0000 0,0000 0,0000 0,0000

x ̅ + 3σ 0,0303 0,0358 0,0266 0,0275 0,0169 0,0184 0,0184

Average x̅ 0,0000 0,0000 0,0000 0,0000 0,0000 0,0000 0,0000

x ̅ - 3σ -0,0303 -0,0358 -0,0266 -0,0275 -0,0169 -0,0184 -0,0184

-0,040

-0,030

-0,020

-0,010

0,000

0,010

0,020

0,030

0,040

1 26 51 76 101 126 151 176 201 226 251

Backlash single values

x ̅- 3σ x ̅+ 3σ Pos1 Pos2

Pos3 Pos4 Pos5 Pos6

0

20

40

60

80

100

120

140

160

180

-0,0

300

-0,0

270

-0,0

240

-0,0

210

-0,0

180

-0,0

150

-0,0

120

-0,0

090

-0,0

060

-0,0

030

0,00

00

0,00

30

0,00

60

0,00

90

0,01

20

0,01

50

0,01

80

0,02

10

0,02

40

0,02

70

0,03

00

Backlash distribution


Volumetric Compensation of machine tools

Limitation by temperature conditions

13,0

14,0

15,0

16,0

17,0

18,0

19,0

20,0

21,0

22,0

10:1

5:00

12:0

0:00

13:4

5:00

15:3

0:00

17:1

5:00

19:0

0:00

20:4

5:00

22:3

0:00

00:1

5:00

02:0

0:00

03:4

5:00

05:3

0:00

07:1

5:00

09:0

0:00

10:4

5:00

12:3

0:00

14:1

5:00

16:0

0:00

17:4

5:00

19:3

0:00

21:1

5:00

23:0

0:00

00:4

5:00

02:3

0:00

04:1

5:00

06:0

0:00

07:4

5:00

09:3

0:00

11:1

5:00

13:0

0:00

14:4

5:00

16:3

0:00

18:1

5:00

20:0

0:00

21:4

5:00

23:3

0:00

01:1

5:00

03:0

0:00

04:4

5:00

06:3

0:00

08:1

5:00

10:0

0:00

11:4

5:00

13:3

0:00

15:1

5:00

17:0

0:00

18:4

5:00

20:3

0:00

22:1

5:00

00:0

0:00

01:4

5:00

03:3

0:00

05:1

5:00

07:0

0:00

Temperature over time

X-Achse (min) [°C] X-Achse (max) [°C] Z-Achse [°C] Y-Achse (min) [°C] Y-Achse (max) [°C] Luft [°C]

Calibration

with AC-Head Verification

With AC-Head

Calibration

With AC-Head Calibration

W-Axis

Verification

W-Axis Calibration

With Quill Verification with Quill






Dynamic data collection

Advanced kinematic error models

MPE for volumetric accuracy

Thermal models for machines

Kinematic measurement at once

Online connection


Thank you for your attention

Vielen Dank für Ihre Aufmerksamkeit

Grazie per la vostra attenzione

AfM Technology GmbH

Gartenstraße 133

73430 Aalen / Germany

Fon: +49 (0)7361 889608-0

Fax: +49 (0)7361 889608-99

www.afm-tec.de • [email protected]

AfM Technology Italia Srl

Via Giotto 25 / Giotto Straße 25

39100 Bolzano / Bozen / Italy

Fon/ Fax: +39 0471 911953

Mobile: +39 348 4221124

www.afm-tec.it • [email protected]

http://www.afm-tec.de/



http://www.afm-tec.it/



Documents

AfM Technology Volumetric Compensation of machine … of machine tools / CMM ... Limitations in aquisition and compensation Aachen colloquium for 5-Axis precision machining