D. Grandy, P. Koshy McMaster University, Canada F. Klocke RWTH Aachen, Germany

D. Grandy, P. KoshyMcMaster University, Canada

F. Klocke RWTH Aachen, Germany

Pneumatic Non-Contact Roughness Assessment of Moving Surfaces

2/23

Pneumatic Non-contact Roughness Assessment of Moving SurfacesD. Grandy, P. Koshy, F. Klocke

59th CIRP General AssemblyBoston, August 26, 2009

Development towards in-process roughness estimation

Issues with machining debris and cutting fluid

Development of a pneumatic sensor

www.taylor-hobson.comwww.taylor-hobson.com

3/23



Principle of pneumatic gauging

work

pb

xi

air

Pcontrol orifice

pressure transducerps

Back pressure pb depends on xi

pb

xi

ps

Primarily quasi-static applications

work

air piezoelectricpressure transducer

4/23



5 mm

Surface porosity detection in machined castings

cutting tool

workpiece

nozzle

transducer Sensor integrated into the cutting tool holder for in-process application, in the presence of a flood coolant

Menzies & Koshy (2009)

5/23



US patent 2,417,988 (1947)

US patent 7,325,445 (2004)

Reliability of pneumatic gauging deteriorates as the peak-to-valley height of the surface exceeds about 3 µmRelated previous work

Nicolau (1937)

Hamouda (1979)

Tanner (1982)

Wang & Hsu (1987)

Woolley (1992)

Nozzle is in contact with workpiece, and is hence not suitable for in-process application

6/23



work

pb

xi

air

P

frequencydecomposition

The present work pertains to non-contact roughness assessment of moving surfaces

Roughness is related to the frequency content of the back pressure signal

7/23



Working principlenozzle

nozzle traverse

8/23



Experiments on plane surfaces

nozzle diameter (dn) 1.5 mm

control orifice diameter (dc) 0.84 mm

supply pressure (ps) 138 kPa

stand-off distance (xi) 50 µm

nozzle feed rate 0.4 m/min

piezo pressuretransducer

nozzle

9/23



Comparison of stylus and pneumatic signals from milled and turned surfaces of roughness 3.2 µm Ra

-10

-5

0

5

10

15

0 2 4 6 8 10-1.0

-0.5

0.0

0.5

1.0

0 2 4 6 8 10

Distance (mm) Distance (mm)

Hei

ght

(µm

)V

olta

ge (

V)

milled surface turned surface

stylus

pneumatic

10/23



Frequency domain comparison of stylus and pneumatic signals

0

2

4

6

0 1 2 3 4 5 60.00

0.15

0.30

0.45

0 1 2 3 4 5 6

Frequency (mm-1) Frequency (mm-1)

Am

plitu

de (

V)

Am

plitu

de (

µm

) turned surfacemilled surface

stylus

pneumatic

11/23



Frequency spectra corresponding to milled surfaces of various roughness values

5 plots shown for each roughness

??

12/23



Roughness Ra (µm)

Am

plitu

de (

V)

Are

a (V

/mm

)

Roughness Ra (µm)0 3 6 9 12 15

0.00

0.15

0.30

0.45

0 3 6 9 12 15

0.0

0.5

1.0

1.5

Correlation of pneumatic indices to roughness measured using a stylus instrument

Area under the frequency plot

Amplitude of dominant frequency

13/23



Supply pressure (kPa)

Nor

mal

ized

am

plitu

de

0 100 200 300 4000

3

6

9

Effect of supply pressure

work

pb

xi

air

Pdc

ps

dn

14/23



Effect of control orifice diameter dc

work

pb

xi

air

dc

ps

dn

Stand-off distance (µm)

Nor

mal

ized

am

plitu

de dc = 0.84 mm

dc = 0.50 mm

dc = 0.50 mm

dc = 0.84 mm

0

1

2

3

0 50 100 150 200 250 300

0

1

2

3

experimental

analytical

15/23



Experiments on rotating cylindrical surfaces

quenchant

hardness

nozzle

turned surface

nozzle workpiece diameter ~25 mm

surface speed 30 m/min

nozzle feed rate 0.2 mm/rev

stand-off distance (xi) 50 µm

supply pressure (ps) 138 kPa

nozzle diameter (dn) 1.5 mm

control orifice diameter (dc) 0.84 mm

nozzleworkpiece

16/23



Effect of increasing roughness

Frequency (Hz)

Am

plitu

de (

V)

0 8 16 24 32 40 480.0

0.1

0.2

0.3

0.4

0 8 16 24 32 40 48

Frequency (Hz)

quenched endof Jominy specimen

1 mm 1 mm

increasing roughness

1.2 µm Ra 3.8 µm Ra

17/23



Effect of relative speed between nozzle and work

0 20 40 60 80

0.00

0.05

0.10

0.15

Frequency (Hz)

Am

plitu

de (

V)60 m/min

100 m/min

200 m/min

Sensor response can be improved by

minimizing the volume of the

variable pressure chamber

18/23



Effect of application of cutting fluid

Frequency (Hz)

Am

plitu

de (

V)

0 8 16 24 32 40 48

0.0

0.1

0.2

0.3

0.4

without cutting fluid

with cutting fluid

Flood coolant application has minimal influence on sensor performance

19/23



Recent work on extension to fine surfaces

0 5 10 15 20 25 30

0

5

10

15

20

23 24 25 26 27

0

2

4

6 Frequency (mm-1)

Am

plit

ude (

mV

)

0 5 10 15 20 25 30

0

5

10

15

20

20 21 22 23 24

0

2

4

6 Frequency (mm-1)

Am

plit

ude (

mV

)

0 3 6 9 12 15 18 21 24 27 30

0.0

0.3

0.6

0.9

1.2

1.5

Am

plitu

de (

mV

)

Frequency (1/mm)

0 3 6 9 12 15 18 21 24 27 30

0

3

6

9

12

15

Am

plitu

de (

mV

)

vibration

pressure

0.1 µm Ra ground 0.1 µm Ra lapped

Back pressure signals are noisy, and are affected by vibration

X1

X2

X3

P

St1

t2

X1 X2 X3 … …

G1

G2

L1

L2

Variables

Obs

erva

tions

…

20/23



Principal Components Analysis

21/23



Application of principal components analysis

-20

-10

0

10

20

-40 -30 -20 -10 0 10 20 30 40

tPS

[2]

tPS[1]

WorksetPredictionset

SIMCA-P 11.5 - 5/29/2009 9:40:58 AM

t1

t 2ground

lapped

95% limit

Filled symbols refer to test data not

considered when building the model

22/23



Proof-of-concept of pneumatic non-contact roughness assessment of moving surfaces has been established

In its present state of development, the system is best suited for in-situ process monitoring based on appropriate calibration

The system exhibits potential for in-process application in the presence of machining debris and cutting fluid that generally obscure the measurement process when using optical instruments

Future work will focus on the physics of jets impinging on laterally moving surfaces, taking roughness into consideration

Conclusions

23/23

Thank you for

your attention!



Natural Sciences & EngineeringResearch Council of Canada

For more details please see: D. Grandy, P. Koshy, F. Klocke, Pneumatic non-contact roughness assessment of moving surfaces, CIRP Annals 58 (2009) 515-518.

Documents

D. Grandy, P. Koshy McMaster University, Canada F. Klocke RWTH Aachen, Germany