Influence of temperature changes on a linear motion system

Jonathan Abir, Paul Shore, Paul Morantz

Laser Metrology and Machine Performance (LAMDAMAP) 2015

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Research overview

• Design and control of a compact linear motion system for high dynamic performance

• Lightweight structure

• High ratio of moving mass to static mass

• Structural flexibility

• Low damping

• The linear motion system characteristics:

Thermal distortion

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What is the linear motion system?

Slave side guideway

Master side guideway

Carriage

Encoder

491mm

609mm

215mm

• Main material - Aluminium

• Guideways material - Alumina

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Bearing arrangement

Slave side

Master side

Roll

Pitch

Yaw

Z

X

Y

• Over constrained design - Roll

• Symmetric design

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Aluminium 6061

Alumina AD 96

Inverse

specific

stiffness

ρ∙E-1 [s2∙m-2]∙10-6

0.39 0.12

Expansion/

conductivity

α∙λ-1 [m∙W-1]∙10-6

0.14 0.24

Inverse

diffusivity

ρ∙Cp∙λ-1

[s∙m-2]∙10-6

0.01 0.5

CTE α [µm/m·°C]

23.6 @ 23-100 °C

6 @ 25-200 °C

Material properties

Alumina Guideway

Aluminium Frame plate

Lower values – superior material

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Why using Alumina guideways?

FEM simulation @ Free-Free boundary condition

Improving dynamic performance

Mode #

Frequency [Hz] Aluminium guideways

Alumina guideways

Improvement

1 107 103 -4 2 122 134 12 5 361 395 34

8 551 582 31

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What is measured?

Thermal distortion of: guideways and frame

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Where it was measured?

Leitz PMM-F CMM

1.9 ( / 400)

@18 22

MPE L m

C

3000mm

1000mm

2000mm

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Component on a CMM

Measured component

Coordinate Measuring Machine

Three points support

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Heating the component on a CMM

Measured component

Coordinate Measuring Machine

Three points support

Heat sources

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Insulating the CMM

Measured component

Coordinate Measuring Machine

Three points support

Heat sources

Reflection and insulation materials

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Measured component

Reflection and insulation materials

Three points support

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Heating source - lamps

Measured component

Reflection and insulation materials

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Measurement at ambient temperature (reference)

Reference measurement

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Response to applied heat

Reference measurement

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Turning off the heat sources

Reference measurement

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Measurements at elevated temperature

Reference measurement

Measurements at elevated temperatures

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Reference measurement

Reference measurement

Measurements at elevated temperatures

Measurement at ambient temperature (2)

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Reference measurement

Aluminium restraint bar

Alumina guideway

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Aluminium restraint bar

Alumina guideway

Applying heat – lamps

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Measurement(s) at elevated temperature

Aluminium restraint bar

Alumina guideway

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“Bottom up” methodology

Alumina Guideway Aluminium restraint bar

Alumina Guideway

Alumina Guideway

Aluminium Frame plate

D. Distortion of full assembly

A. Expansion of single component B. Bending of two components bolted together

C. Bending of Three components bolted together

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24.32[µm/m·°C] (23.6 [µm/m·°C])

5.72 [µm/m·°C] (6 [µm/m·°C])

Aluminium plate

Alumina Guideway

Linear expansion of single component

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FEM and measurements of two components bolted together

Aluminium restraint bar

Alumina guideway X

Y

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FEM and measurements of three components bolted together

X

Y

Aluminium frame plate

Aluminium restraint bar

Alumina guideway

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Flatness measurements at different temperatures of three components bolted together

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Measuring the thermal distortion of full assembly

Schematic view of bended guideways

Slave side guideway

Master side guideway

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Flatness measurements of slave and master guideways

Summary:

•Thermal distortion can be measured using a CMM

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•Thermal distortion can be measured using a CMM •Heating a component on the CMM requires: Thermal insulation

Temperature monitoring •A “bottom up” methodology improve the measurements confidence •The setup allows a repeatable measurement process

•Thermal distortion can be measured using a CMM •Heating a component on the CMM requires: Thermal insulation

Temperature monitoring

•Thermal distortion can be measured using a CMM •Heating a component on the CMM requires: Thermal insulation

Temperature monitoring •A “bottom up” methodology improve the measurements confidence

Future work:

•Measuring the dynamic performances •Developing a compensation method for the structural flexibility •Improving the servo bandwidth, settling time, position error

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