CIRP JANUARY MEETINGS 2011, PARIS MULTI-SENSORY APPROACH FOR CONDITION MONITORING OF ABRASIVE WATERJET CUTTING HEAD ABRASIVE WATERJET CUTTING HEAD N. RAMESH BABU AND J. JOHN ROZARIO JEGARAJ MANUFACTURING ENGINEERING SECTION DEPARTMENT OF MECHANICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY MADRAS INDIAN INSTITUTE OF TECHNOLOGY MADRAS CHENNAI – 600 036
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CIRP JANUARY MEETINGS 2011, PARIS
MULTI-SENSORY APPROACH FOR CONDITION MONITORING OF ABRASIVE WATERJET CUTTING HEADABRASIVE WATERJET CUTTING HEAD
N. RAMESH BABU AND J. JOHN ROZARIO JEGARAJ
MANUFACTURING ENGINEERING SECTIONDEPARTMENT OF MECHANICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY MADRASINDIAN INSTITUTE OF TECHNOLOGY MADRAS
CHENNAI – 600 036
ACKNOWLEDGEMENTS
• Thanks to Volkswagen Stiftung for financial support to this Collaborative Research Project on “Adaptive Control of Abrasive Water Jet Cutting Process with S ft C ti A h ”Soft Computing Approaches”
Th k t P f D I H t t L i W t J t• Thanks to Prof. Dr. –Ing. Hartmut Louis, Water Jet Laboratory, University of Hannover, Hannover, GermanyGermany
• Thanks to Prof Dr – Ing Bach and Prof Dr – Ing• Thanks to Prof. Dr. – Ing. Bach and Prof. Dr. – Ing. Haferkamp, University of Hannover
OUTLINE OF PRESENTATION
Introduction Motivation and Importance of the Work Objectives Objectives Methodology for Monitoring of Cutting Head St t i f it i th diti f tti Strategies for monitoring the condition of cutting
head Conclusions
INTRODUCTION
AWIJ AWSJ
Source: Waterjet laboratory University of HannoverSource: Waterjet laboratory, University of Hannover
TYPES OF ABRASIVE WATERJETS
FOCUS ON AWIJ CUTTING SYSTEM
HP Water
Abrasive
!
Abrasive Waterjet Cutting System Cutting Head Mixing Head
STATIC VARIABLES• Focusing Nozzle Length• Abrasives size and
quality• Traverse Rate diameter
- Hashish (1989)
quality
Controllable Uncontrollable( )
February 3, 2011 9(Momber and Kovacevic 1998)
Parametric Studies
EFFECT OF PROCESS PARAMETERS
OrificeEnergy of jet
Structure of jet
Geometry of
affectPerformance
Focusing nozzleStructure of jet
February 3, 2011 10
(Nanduri et al. 1999)(Momber and Kovacevic 1998) (Nanduri et al. 1999)
IMPORTANCE OF THE WORK
Monitoring of nozzle wear is a key aspect in producing high quality parts on a fully automated abrasive waterjet cutting system
- Kovacevic et al. (1989)
The coherence length of the waterjet depends on the health of theorifice. A long coherence length provides efficient and stable machining conditions.
- Hashish (1993)
Focusing tube is the most critical component for the technical andeconomic performance of AWJeconomic performance of AWJ
- Hashish (1994)
AWJ nozzle wear causes incomplete mixing of the abrasive particles with high p g p gvelocity waterjet results in deterioration in cutting ability, poor surface Quality and affects the precision of machining.
Hence suitable methods to be devised to ensure uniform product quality at
desired levels, by replacing or compensating for the worn nozzle at the right time
- Kovacevic, Hashish, Ramulu, Kim, Geskin (1997)
RECOMMENDED SPECIFICATIONSF AWJ i h di h f 2 2 li / i h For AWJ system with discharge rate of 2.2 litres / min, the recommended specifications of orifice and focusing nozzle are Orifice – 0.25 mm
Focusing nozzle - 0.76 mm (Orifice to focusing nozzle ratio – 1:3)
1 .6Not widely used
1
1 .2
1 .4
ize
(mm
)
y
Not investigated
Acceptable
0 .6
0 .8
1
g no
zzle
s Not investigated
0 .2
0 .4
0 .6
Focu
sin
00 .15 0 .2 0 .25 0 .3 0 .35 0 .4
Orifice s ize (m m )
February 3, 2011 12
Orifice s ize (m m )
ISSUES
ORIFICE AND FOCUSING NOZZLE
Process output Process monitoring
DECISION STRATEGY
OBJECTIVES
To investigate the influence of orifice and focusing nozzle size on tti f ffi i d lit f tti ith b icutting performance, efficiency and quality of cutting with abrasive
waterjets
To develop an integrated monitoring system for focusing nozzle wear g g y gand orifice wear in AWJ Cutting
Orifice wearOrifice wear
0 25 0 3 0 40.25 0.3 0.4
0.76 1.02 1.2 1.6
Focusing Tube Wear
Waterjet PressureWaterjet Pressure
Abrasive Flow Rate
100 MPa 175 MPa 250 MPa
Abrasive Flow Rate
0.07 kg/min
0.11 kg/min
0.22 kg/min
EXPERIMENTAL STUDIES – Design of Experiments
ORIFICE
• 0.25 mm
FOCUSING TUBE
• 0.76 mm
PRESSURE
• 100 MPa
ABRASIVE FLOW RATE
• 0 027 kg/min
TRAVERSE RATE
• 30 mm/min• 0.30 mm
• 0.35 mm
• 1.20 mm
• 1.60 mm
• 175 MPa
• 250 MPa
• 0.027 kg/min
• 0.149 kg/min
• 0.272 kg/min
30 mm/min
• 60 mm/min
• 90 mm/min
DOE
using L27 OAMaterial
Aluminum 6063 – T6 alloy
Effect of Pressure
Effect of Abrasive Flow RateInteraction of orifice size Effect of Abrasive Flow Rate
Effect of Traverse rate
Effect of Orifice size
Interaction of orifice size and focusing tube size
Interaction of abrasive flow
Depth of cut, Top Kerf width, Surface Roughness (upper)
Effect of Focusing tube sizerate and focusing tube size
PRELIMINARY STUDIES
EXPERIMENTATION - Design of Experiments (L27 OA)
35
MEAN RESPONSE CURVE - Depth of Cut
PRELIMINARY STUDIES
25
30
35
mm
)
do1
do2df3
df2
df1
15
20
h of
cut
(m do3 df2
df1
df1
0
5
10
Dep
t
df3
0
P1 P2 P3 m1
m2
m3 v1 v2 v3 do1
do2
do3
df1
df 2 df3 m1
m2
m3
m1
m2
m3
do1
do2
do3
Process parameters
b i fl t (0 03 0 15 0 27 k / i ) d ifi i (0 25 0 3 0 35 ) m – abrasive flow rate (0.03, 0.15, 0.27 kg/min) ; do – orifice size (0.25, 0.3, 0.35 mm);
MONITORING OF CUTTING HEADMonitoring of force exerted by jetMonitoring of force exerted by jet
IMPACT FORCE
Impact force exerted by the jet is proportional to theImpact force exerted by the jet is proportional to the velocity of the jet, density of the slurry and volume flow rate.
Parameters Operating Rangep g g
Orifice (mm) 0.25, 0.30, 0.35, 0.4
Focusing Nozzle (mm)
0.76, 1.02, 1.2, 1.6(mm)
Pressure (MPa) 100, 175, 250
Instrument used KISTLER 3 component force dynamometerdynamometer
Experiment conditions
FORCE SENSOR
Make : M/s KISTLER, 9257BRange : 5 to 5 kN (F F F )
Condition 1 : Orifice without considering
focusing nozzle
Condition 2 : Orifice considering focusing nozzle
February 3, 2011 46
Range : -5 to 5 kN (Fx, Fy, Fz)Range setting: 0 – 100 N (Fz)
MONITORING OF CUTTING HEADMonitoring of force exerted by jet
Force exerted by pure waterjet emerging from orificeP : 1 0 0 MPa P : 1 7 5 MPa P : 2 5 0 MPa
Monitoring of force exerted by jetStatic Analysis
2 02 5
3 03 5
orce
(N)
05
1 01 5
Impa
ct fo
2P : 100 MPa P : 250 MPa
5P : 100 MPa P : 250 MPa
O ifi 0 25 O ifi 0 40
0 .25 0 .3 0 .3 5 0 .4O r if ic e s iz e (m m )
Signal obtained from the sensor
1
1.5
sor s
igna
l (V)
3
4
sor s
igna
l (V)Orifice : 0.25 mm Orifice : 0.40 mm
0
0.5
Forc
e se
ns
0
1
2Fo
rce
sens
February 3, 2011 47
00 2 4 6 8 10
Time (seconds)
00 2 4 6 8 10
Time (seconds)
MONITORING OF CUTTING HEADMonitoring of force exerted by jet
Force exerted by pure waterjet emerging from orifice
Monitoring of force exerted by jet
Dynamic Analysis
P : 250 MPa DISCUSSION
Force sensor : 1. The impact force increases
with an increase in size of orifice in case of impact produced by direct jet fromproduced by direct jet from the orifice
2. The PSD spectrum shows a sudden increase in PSD
P : 100 MPa P : 175 MPa P : 250 MPasudden increase in PSD value with increase in orifice size greater than 0.35 mm
1
1.5
2
Am
plitu
de
mpl
itude
(V2 )
0
0.5
1
PSD
Pea
k A
PS
D P
eak
A
February 3, 2011 48
00.25 0.3 0.35 0.4
Orifice size (mm)
MONITORING OF CUTTING HEADMonitoring of force exerted by jet
df: 0.76 mm df: 1.02 mm df: 1.2 mm df: 1.6 mm
Force exerted by pure waterjet emerging from focusing nozzle
Monitoring of force exerted by jetStatic Analysis
DISCUSSION
20
25
30
rce
(N) 100 MPa 175 MPa 250 MPa Force sensor :
1. With focusing nozzle, the i t f d ith
0
5
10
15
Impa
ct fo
r impact force decreases with reduction in the orifice to focusing nozzle ratio. This reduction is due to large