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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
PROCESS PARAMETERS IN AWJ CUTTING
1. Hydraulic1. Waterjet Orifice2. Waterjet Pressure
2. AbrasiveG S1. Abrasive Grit Size
2. Abrasive Material3. Abrasive Flow rate
3. Focusing Nozzle1. Bore Diameter2. Tube Length Performance3. Material
4. Cutting Parameters1 T S d
Performance1. Depth of cut2. Kerf Width3 Surface Roughness1. Traverse Speed
2. Standoff Distance3. Angle of Attack
3. Surface Roughness4. Material Removal
Rate5. Cutting Efficiency
February 3, 2011 65. Work / Target Material
CUT SURFACE TOPOGRAPHYKERF GEOMETRY
INTRODUCTION …contd.CUT SURFACE TOPOGRAPHYKERF GEOMETRY
1
Jet TraverseSmooth zone
2Transition zone
Rough zone
3
1 Smooth zone1. Smooth zone2. Transition Zone3. Striation zone
PERFORMANCE OPTIMIZATION
Criteria employed for optimum performance
Minimise the cost per unit volume of material removed p
High rate of cutting
Achieve consistent quality
Based on the applications, abrasive waterjet cut can be characterised into
Separation Cut - energy efficient, rough surface finish
Application : Rough cutting
Quality Cut - High energy requirement, Good surface finish and kerf quality
Application : Precision cuttingApplication : Precision cutting
Blind Cut - Cutting depends on input energy of AWJ
Application : Pocket millingApplication : Pocket milling
REVIEW OF WORK ON PARAMETRIC STUDIESEFFECT OF PROCESS PARAMETERS
DYNAMIC VARIABLES QUASI STATIC VARIABLES STATIC VARIAB ESDYNAMIC VARIABLES• Waterjet Pressure
• Abrasive Flow Rate
QUASI – STATIC VARIABLES• Orifice diameter
• Focusing nozzle diameter
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);
df – Focusing nozzle size (0.76, 1.2, 1.6 mm) ; P – Waterjet pressure (100, 175 , 250 MPa);
v – Traverse rate (30, 60, 90 mm/min)
February 3, 2011 17
PRELIMINARY STUDIES
EXPERIMENTATION - Design of Experiments (L27 OA)
MEAN RESPONSE CURVE - Kerf Width at Top region
PRELIMINARY STUDIES
1 41.61.8
2
(mm
)
do1
df3df3
df2
0 60.8
11.21.4
erf W
idth
do1do2do3
df2
df1
df2
df1
00.20.40.6
Top
Ke
P1 P3 m1
m3 v1 v3 do1
do3
df1
df3 m1
m3
m1
m3
do1
do3
Process parameters
m – abrasive flow rate (0 03 0 15 0 27 kg/min) ; do – orifice size (0 25 0 3 0 35 mm); m abrasive flow rate (0.03, 0.15, 0.27 kg/min) ; do orifice size (0.25, 0.3, 0.35 mm);
df – Focusing nozzle size (0.76, 1.2, 1.6 mm) ; P – Waterjet pressure (100, 175 , 250 MPa);
v – Traverse rate (30, 60, 90 mm/min)
February 3, 2011 18
PRELIMINARY STUDIES
EXPERIMENTATION - Design of Experiments (L27 OA)
MEAN RESPONSE CURVE - Surface Roughness at upper region
PRELIMINARY STUDIES
8
9
ough
ness
df2df2
d 3
5
6
7
Surf
ace
Ro
(µm
)
df1
df1
df3
do3
do1
do2
3
4
5
Ave
rage
S df3do2
P1 P3 m1
m3 v1 v3 do1
do3
df1
df3
m1
m3
m1
m3
do1
do3
Process parameters
m – abrasive flow rate (0 03 0 15 0 27 kg/min) ; do – orifice size (0 25 0 3 0 35 mm); m abrasive flow rate (0.03, 0.15, 0.27 kg/min) ; do orifice size (0.25, 0.3, 0.35 mm);
df – Focusing nozzle size (0.76, 1.2, 1.6 mm) ; P – Waterjet pressure (100, 175 , 250 MPa);
v – Traverse rate (30, 60, 90 mm/min)
February 3, 2011 19
PRELIMINARY STUDIES
EXPERIMENTATION - Design of Experiments (L27 OA)
CONTRIBUTION OF VARIOUS PROCESS PARAMETERS ON PERFORMANCE
PRELIMINARY STUDIES
Others2%
Pressure15%
Traverse rate22%
Orif ice size5%
Focusing Abrasive f low rate
7%
Traverse
Others36%
Abrasive
Focusing nozzle size
1%
others 20%
Focusing nozzle size
98%
rate18%
Orif ice size3%
Focusing nozzle size
Abrasive f low rate
33%
20%
Pressure19%(a) (b) (c) 3%nozzle size
21%19%(a) (b) (c)
kerf width at top region
Surface roughness (Ra) at upper region
Depth of cut
February 3, 2011 20
ORIFICE DAMAGE MODES OF WEAR IN FOCUSING NOZZLEMONITORING OF CUTTING HEAD
Modes of wear
1. Impact erosionbeginning atthe entry zone
SMOOTH BORE
the entry zone
2. Sliding erosion inthe downstream areaWATER
ORIFICEJET
SPREADING
RANDOM IMPACT
RANDOM PARTICLE ENTRY
DAMAGED BORESHALLOW IMPACT ANGLES OR ABRASION
ZONE
ANGLES OR ABRASIONMIXING TUBE
ORIFICE DAMAGE
MONITORING OF CUTTING HEAD …contd.
Orifice size : 0.25 mm; 0.30 mm;
0.35 mm; 0.40 mm
Orifice (a) New Orifice
(b) Used Orifice(b) Used Orifice
VISUALIZATION
MONITORING OF CUTTING HEAD …contd.
VISUALIZATION
Comparison of the image of the jet emerging out of new orifice and worn out orifice
Orifice 0.25 mm (new)Orifice 0.40 mm (new)
IMPRINT TAKEN ON COPPER PLATE
Orifice 0.25 mm (old) Orifice 0.40 mm (old)
MONITORING OF CUTTING HEAD …contd.
VISUALIZATION
I f th j t i t f f i lImage of the jet emerging out of focusing nozzle
Pressure - 50 MPa
Focusing Nozzle size - 0.76, 1.02, 1.2, 1.6 mm
LITERATURE – Monitoring studies
MONITORING OF CUTTING HEAD …contd.
Orifice Conditiong
Direct Methods Indirect Methods
Optical Tracking Visual Examination Acoustic based approach Vacuum based approach
Visual Examination
Focusing Nozzle Wear
Direct Methods Indirect Methods
W i ht L Optical Tracking Noise monitoring Weight Loss Wear Profiling X Ray examination
Optical Tracking
Ultrasonic gauging
Vibration monitoring
Noise monitoring
Using Wear Sensor probe
Vacuum Measurement Vibration monitoring Vacuum Measurement in the mixing chamber
MONITORING OF CUTTING HEAD …contd.
Sl. No
Authors and year of Publication
Target parameters
Method of monitoring Remarks(if any)
REVIEW OF LITERATURE – Monitoring studies
No. year of Publication parameters (if any)1. Nanduri et al. (1996) Focusing
nozzle wearWear profiling –Pinning and casting
Offline
2 Kovacevic et al Focusing Optical jet tracking Online2. Kovacevic et al. (1990)
Focusing nozzle wear
Optical jet trackingUltrasonic gaugingVibration monitoringNoise monitoring
Online
3. Kovacevic et al.(1991) Focusing nozzle wear Wear probe sensor Online
4. Zeng et al ( 1994). Focusing nozzle wear, Orifice wear
Vacuum pressure monitoring
Online
5. Hashish et al.(1993)
Orifice wear Acoustic based approachVacuum based approach
Online
6. Knaupp (1993) Orifice wear Optical inspection of jet Online
7. Kovacevic (1992) Depth ofpenetration
Normal Reaction Forcesensing
Online
HIGH PRESSURE SENSOR
MULTI SENSORY APPROACH
MONITORING OF CUTTING HEAD …contd.
ENTRAIMENT VACUUM SENSOR
THICKNESSTHICKNESS MEASUREMENT
TEMPERATURE MEASUREMENT
IMAGE PROCESSING
FORCEFORCE DYNAMOMETER
EXPERIMENTATION PLANMONITORING OF CUTTING HEAD …contd.
EXPERIMENTATION
ORIFICE FOCUSINGNOZZLE
Wear Variation in size WearVariation in size
AB BA
Monitoring StudiesMonitoring Studies
Monitoring Studies
3 0 0 0
d : 0 .2 5 m m d : 0 .3 0 m m d : 0 .3 5 m m d : 0 .4 0 m m
MONITORING OF CUTTING HEAD - HIGH PRESSURE SENSOR
2 0 0 0
2 5 0 0
sing
sen
sor
1 0 0 0
1 5 0 0
ed p
ress
ure
us
(bar
)
RESULTS
CONDITION - A
0
5 0 0
0 5 0 0 1 0 0 0 1 5 0 0 2 0 0 0 2 5 0 0 3 0 0 0
Mea
sure
H y d r a u lic P u m p s e t p r e s s u r e ( b a r )
6
P:100 MPa P:150 MPa
P:200 MPa P : 250 MPa
4
5
put (
Volts
)
1
2
3
Sens
or O
utpu
00.25 0.3 0.35 0.4
Orifice size (mm)
S
RESULTS
MONITORING OF CUTTING HEAD - HIGH PRESSURE SENSOR
d : 0.25 mm; P : 100 MPa6
d : 0.25 mm; P :250 MPa6
CONDITION - A
3
4
5
outp
ut (v
olts
)
3
4
5
outp
ut (v
olts
)
0
1
2
0 2 4 6 8 10
Sens
or o
0
1
2
0 2 4 6 8 10
Sens
or o
0 2 4 6 8 10Time (sec)
0 2 4 6 8 10Time (sec)
d : 0.30 mm ; P :100 MPa d : 0.30 mm; P : 250 MPa
3
4
5
6
put (
volts
)
3
4
5
6pu
t (Vo
lts)
0
1
2
3
0 2 4 6 8 10
Sens
or o
ut
0
1
2
3
0 2 4 6 8 10
Sens
or o
ut
Time (sec) Time (sec)
RESULTS
MONITORING OF CUTTING HEAD - HIGH PRESSURE SENSOR
d : 0.35 mm; P : 100 MPa6
d : 0.35 mm; P : 250 MPa
5
6
CONDITION - A
3
4
5
outp
ut (v
olts
)
3
4
5
r out
put (
volts
)
0
1
2
Sens
or o
0
1
2
0 2 4 6 8 10
Sens
or
0 2 4 6 8 10Time (sec)
0 2 4 6 8 10Time (sec)
d : 0.40 mm; P : 100 MPa6
d : 0.4 mm; P : 250 MPa6
3
4
5
tput
(vol
ts)
3
4
5tp
ut (v
olts
)
0
1
2
3
Sens
or o
ut
0
1
2
Sens
or o
ut
00 2 4 6 8 10
Time (sec)
00 2 4 6 8 10
Time (sec)
RESULTSCONDITION A
MONITORING OF CUTTING HEAD - HIGH PRESSURE SENSOR
Orifice 0.25 mm; P 100 MPa Orifice 0.25 mm; P 250 MPaCONDITION - A
Orifice 0.30 mm; P 100 MPa Orifice 0.30 mm; P 250 MPa
RESULTSCONDITION - A
MONITORING OF CUTTING HEAD - HIGH PRESSURE SENSOR
Orifice 0.35 mm; P 100 MPa Orifice 0.35 mm; P 250 MPa
CONDITION - A
Orifice 0.40 mm; P 100 MPa Orifice 0.40 mm; P 250 MPa
MONITORING OF CUTTING HEAD - HIGH PRESSURE SENSOR
RESULTS
CONDITION - A
0.16
d :0.25 mm d: 0.30 mm d : 0.35 mm d : 0.40 mm
0.08
0.12
valu
e (v
olts
)
0
0.04
100 150 200 250
RM
S v
100 150 200 250
Waterjet set pressure (MPa)
MONITORING SUCTION PRESSURE
MONITORING OF CUTTING HEAD
INSIDE MIXING CHAMBERIn abrasive water injection jets
orifice mixing chamber and focusing orifice, mixing chamber and focusing tube is similar to a jet pump
The suction pressure is proportional to
the quantity of liquid flow through the orifice.
the diameter of focusing tube
Pressure fluctuations
Turbulence
S f Size of suction duct etc.
Monitoring of suction pressure inside chamber is useful to study
Orifice condition
Focusing tube conditionAWJC set up with vacuum sensor
Abrasive flow condition etc.
Vacuum sensor
SIMULATION STUDIES – MONITORING SUCTION PRESSURE INSIDE MIXING CHAMBER
MONITORING OF CUTTING HEAD - VACUUM SENSOR
0.25 0.3 0.35Orifice
CHAMBER0.4
0.76 1.02 1.2 1.6 0.76 1.02 1.2 1.6 0.76 1.02 1.2 1.6
Focusing tube Focusing tube Focusing tube
0.76 1.02 1.2 1.6
Focusing tube
Pressure25 – 300 MPa
Pressure25 – 300 MPa
Pressure25 – 300 MPa
Pressure25 – 300 MPa
SUCTION PRESSURE INSIDE MIXING CHAMBER
Condition abrasive feed line - blocked
VACUUM MONITORING SETUP
MONITORING OF CUTTING HEAD - VACUUM SENSOR
Hopper
Vacuum sensorHP WATER
Vibratory Feeder
Orifice
Abrasive shut off valve
Vacuum Sensor
Mixing CChamber
Focusing Nozzle
Focusing tube
Catcher Tank
MIXING CHAMBER - EJECTOR
MONITORING OF CUTTING HEAD - VACUUM SENSOR
Variation of suction pressure inside mixing chamber (orifice - 0 25mm)
RESULTS CONDITION - A
chamber (orifice - 0.25mm)
600700
FN - 0.76 FN - 1.02mm FN - 1.2mm FN - 1.6mm
300
400500600
olut
e su
ctio
n su
re (m
illib
ar)
0100200
0 50 100 150 200 250 300 350
Abs
opr
ess
Abrasive flow rate : NilCondition : blocked abrasive feed line
Waterjet Pressure (MPa)
SUCTION PRESSURE INSIDE MIXING CHAMBER
MONITORING OF CUTTING HEAD - VACUUM SENSOR
Variation of Suction inside mixing chamber
RESULTS CONDITION - A
250
300
insi
de
illib
ar) d : 0.76 mm d : 1.02 mm d : 1.2 mm d : 1.6 mm
0.25 mm 0.30 mm 0.35 mm 0.4 mm
100
150
200
te p
ress
ure
cham
ber (
m
0
50
50 100 150 200 250 50 100 150 200 250 50 100 150 200 250 50 100 150 200 250
Abs
olut
mix
ing
c
Waterjet set pressure (MPa)
Abrasive flow rate : NilCondition : abrasive feed line - blocked
SUCTION PRESSURE INSIDE MIXING CHAMBER
SUCTION PRESSURE INSIDE MIXING CHAMBER
MONITORING OF CUTTING HEAD - VACUUM SENSOR
2
2.5
tput
(Vol
ts)
2
2.5
tput
(Vol
ts)
0.5
1
1.5
acuu
m s
enso
r out
0.5
1
1.5
acuu
m s
enso
r out
Orifice : 0.25 mm Orifice : 0.25 mm
00 5 10 15 20
Time (sec)
Va 00 5 10 15 20
Time (sec)
Va
Focusing Nozzle : 0.76 mmWaterjet Pressure : 50 MPa
Focusing Nozzle : 1.02 mmWaterjet Pressure : 50 MPa
2.5
olts
) 2.5
olts
)1
1.5
2
sens
or o
utpu
t (vo
1
1.5
2
sens
or o
utpu
t (vo
0
0.5
0 5 10 15 20
Time (sec)
Vacu
um
0
0.5
0 5 10 15 20
Time (sec)
Vacu
um
Orifice : 0.25 mmFocusing Nozzle : 1.20 mmWaterjet Pressure : 50 MPa
Orifice : 0.25 mmFocusing Nozzle : 1.6 mmWaterjet Pressure : 50 MPa
2 5 2 5
SUCTION PRESSURE INSIDE MIXING CHAMBER
MONITORING OF CUTTING HEAD - VACUUM SENSOR
1.5
2
2.5or
out
put (
Volts
)
1.5
2
2.5
or o
utpu
t (vo
lts)
0
0.5
1
0 10 1 20
Vacu
um s
enso
0
0.5
1
0 10 1 20
Vacu
um s
enso
0 5 10 15 20
Time (sec)
Orifice : 0.40 mmFocusing Nozzle : 0 76 mm
0 5 10 15 20
Time (sec)
Orifice : 0.40 mmF i N l 1 02Focusing Nozzle : 0.76 mm
Waterjet Pressure : 50 MPaFocusing Nozzle : 1.02 mmWaterjet Pressure : 50 MPa
2.5
volts
) 2.5
olts
)
1
1.5
2
m s
enso
r out
put (
v
1
1.5
2
sens
or o
utpu
t (vo
0
0.5
0 5 10 15 20
Time (sec)
Vacu
um
0
0.5
0 5 10 15 20
Time (sec)
Vacu
um s
Orifice : 0.40 mmFocusing Nozzle : 1.20 mmWaterjet Pressure : 50 MPa
( )
Orifice : 0.40 mmFocusing Nozzle : 1.60 mmWaterjet Pressure : 50 MPa
MONITORING OF CUTTING HEAD - VACUUM SENSOR
COMPARISON OF SUCTION PRESSURE INSIDE MIXING CHAMBER OBTAINED WITH NEW AND USED ORIFICE
1200
de
ar)
New orifice Used orifice0.25mm 0.30 mm 0.4 mm
600
800
1000
ress
ure
insi
mbe
r (m
illib
a
200
400
Abs
olut
e pr
mix
ing
cham
00.76 1.02 1.2 1.6 0.76 1.02 1.2 1.6 0.76 1.02 1.2 1.6
Focusing Nozzle Diameter (mm)
A m
Orifice : 0 25 mm; 0 30 mm; 0 40 mmOrifice : 0.25 mm; 0.30 mm; 0.40 mmFocusing Nozzle : 0.76 mm; 1.02 mm; 1.2 mm; 1.6 mmWaterjet Pressure : 50 MPa
MONITORING OF CUTTING HEAD - VACUUM SENSOR
ABSOLUTE PRESSURE INSIDE MIXING CHAMBER UNDER VARIOUS CONDITIONS OF ABRASIVE WATERJET
2500be
r in
1500
2000
ixin
g ch
amb
Blocked focusing tube / orificedamage
1000
1500
ure
insi
de m
mba
r Abrasive free flow condition
Blocked abrasive feed line
Patm
500
olut
e pr
essu
0Abs
o
SIMULATION STUDIES – Variation in suction pressure with abrasive flow rateO ifi i
MONITORING OF CUTTING HEAD - VACUUM SENSOR
Orifice size
0.25 mm
Focusing tube
0.76 mm
Pressure
100 MPa100 MPa
Abrasive Flow Rate
0.027 kg/min - 0.415 kg/min.
SUCTION PRESSURE INSIDE MIXING CHAMBER
MONITORING OF CUTTING HEAD - VACUUM SENSOR
SUCTION PRESSURE INSIDE MIXING CHAMBER FOR CHANGE IN ABRASIVE FLOW RATE
980
1000
nsid
e m
bar
940
960
pre
ssur
e in
cham
ber,
in
900
920
Abs
olut
em
ixin
g c
0 0.1 0.2 0.3 0.4 0.5Abrasive flow rate, in kg/min
CONDITION :Orifice – 0.25 mm Focusing Tube – 0.76 mmWaterjet Pressure – 150 MPa
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
df : 0.76 mm df : 1.02 mm df : 1.2 mm df : 1.6 mm
0
0.25 0.3 0.35 0.4 0.25 0.3 0.35 0.4 0.25 0.3 0.35 0.4Orifice size (mm)
reduction is due to large friction offered by the walls of the focusing nozzle.
2. The loss of impact force
15
20
25
ct fo
rce
(N)
100 MPa 175 MPa 250 MPa
2. The loss of impact force found increased beyond orifice of 0.3 mm
0
5
10
Loss
in Im
pac
February 3, 2011 49
00.25 0.3 0.35 0.4 0.25 0.3 0.35 0.4 0.25 0.3 0.35 0.4
Orifice size (mm)
L
MONITORING OF CUTTING HEADMonitoring of force exerted by jet
DISCUSSIONOrifice : 0.25 mm Orifice : 0.40 mm
Monitoring of force exerted by jetDynamic Analysis
Force sensor : 1. The PSD spectrum shows the
peak amplitude that p pincreased drastically with orifice wear beyond 0.35 mm
4
5
2Hz
df : 0.76 mm df : 1.02 mm df : 1.2 mm df : 1.6 mm
(V2 )
Frequency : 2 Hz2
3
4
Am
plitu
de a
t 2ea
k A
mpl
itude
0
1
0.25 0.3 0.35 0.4Orifice size (mm)
PSD
AP
SD
Pe
February 3, 2011 50
Orifice size (mm)
MONITORING OF CUTTING HEADMULTI SENSORY APPROACH
HOPPER
Vacuum Sensor
CRO
MULTI – SENSORY APPROACH
VACUUM SENSOR
HP WATERVIBRATORY FEEDER
High Pressure Sensor
AD
CRO
SC
HIGH PRESSURE SENSOR
SHUT OFF VALVE
ROTOMETERAD
CRO
SC
Force Sensor
A
CRO
FORCE SENSOR
AD
SC
Experimental set up showing multi sensors attached to the cutting head
February 3, 2011 51
MONITORING OF CUTTING HEADSUMMARY
ProblemIndications
High Pressure sensor Low Pressure sensor
Blockage in orifice RMS value : Equals to the set pressure
RMS value : Equal to atmospheric pressure when abrasive line is open
Orifice damaged RMS value : Drops beyond RMS value : Higher positive pressure et ives)
11% with respect to set pressure (at 100 MPa)
PSD Value : Very high peak f i l t l
above atmospheric pressure (>1000mbar) (or)RMS value : Very low absolute pressure below 70 millibar at waterjet pressure of u
re w
ate
rje
ho
ut
ab
rasi
power of signal at low frequency
below 70 millibar at waterjet pressure of 50 MPa (Condition : abrasive feed line closed)
Blockage in focusing nozzle
No significant change RMS value : Positive pressure above atmospheric pressure
Pu
(wit
h
nozzle atmospheric pressure
Focusing nozzle worn out
No significant change RMS value : Low absolute pressurePSD value: Very high peak power of signal at low frequency
Blockage in abrasive No significant change RMS Value : Absolute pressure below Blockage in abrasive feed line
No significant change RMS Value : Absolute pressure below 500 millibar
No abrasive in hopper No significant change RMS Value : Absolute pressure equal to atmospheric pressure
bra
sive
W
ate
rjet
February 3, 2011 52
Abrasive free flow No significant change RMS Value : Absolute pressure closer to atmospheric pressure in the range of 900 millibar to 1000 millibar
Ab
W
MONITORING OF CUTTING HEADSUMMARY
ProblemIndications
Flow sensor(Air Entrainment)
Flow sensor(Main stream water)
Force sensor(Air Entrainment) (Main stream water)
Blockage in orifice
No entrainment No flow of water Zero impact force
Orifice damaged No entrainment due to Increased flow RMS value : Low impact forceet ives)
positive pressure inside mixing chamber (or)Larger entrainment of air (> 300x10-6 m3/s at 100 MPa)
nearer to the maximum discharge capacity of pump
PSD Value: High peak power of signal at low frequency
ure
wate
rje
ho
ut
ab
rasi
pu p
Blockage in focusing nozzle
No entrainment and entry of water into abrasive feed line
No significant change
RMS value : Zero impact force
Focusing nozzle worn out
Larger entrainment of air ( > 300x10 6 m3/s at 100 MPa)
No significant change
No significant change
Pu
(wit
h
worn out ( > 300x10-6 m3/s at 100 MPa) change
Blockage in abrasive feed line
No entrainment No significant change
RMS value : Impact force equal to that of pure waterjet ( 5 – 10 N at 100 MPa)
No abrasive in hopper
Entrainment of air (< 300x10-6 m3/s at 100 MPa)
No significant change
RMS value : Impact force equal to that of pure waterjet( 5 – 10 N at 100 MPa)
Abrasive free Normal entrainment of air No significant RMS value : Significant impact bra
sive
W
ate
rjet
February 3, 2011 53
Abrasive free flow
Normal entrainment of air (< 300x10-6 m3/s at 100 MPa)
No significant change
RMS value : Significant impact force ( 5 – 10 N at 100 MPa)A
bW
DECISION SUPPORT SYSTEM
DECISION SUPPORT SYSTEM
Condition monitoring strategy
Process performance prediction strategy
Process control parameter selection strategy
Strategy to assess the condition of cutting head
Strategy to determine the size of orifice and focusing
nozzlenozzle
February 3, 2011 54
DECISION SUPPORT SYSTEMCondition monitoring Strategy
Patm - atmospheric pressure
g gy
Strategy to assess the condition of cutting head
(1 bar)P2 - absolute pressure inside
mixing chamberStart the Abrasive Waterjet Machine
Set the waterjet pressure to 100 MPa
Open the abrasive feed line
Read data
P2 from low pressure sensor
If P P If P 0 5 b If 0 9 P P bIf P abs >> P atm If P abs < 0.5 bar If P abs = P atm
Reason :1. Blockage in
Reason :1. Blockage in
Reason :1. No abrasive in
If 0.9 < P 2 < P atm bar
Reason :1. Abrasive free flow
Check the systemCheck the system
gfocusing tube
2. Orifice damage
gabrasive feed line hopper
2. Blockage in orifice
1. Abrasive free flow
February 3, 2011 55If pure waterjet experiment
YESB
NO
DECISION SUPPORT SYSTEMCondition monitoring Strategy
HIGH PRESSURE LOW PRESSURE FLOW SENSOR FLOW SENSOR
g gy
Strategy to determine the size of orifice and focusing nozzle
HIGH PRESSURESENSOR
LOW PRESSURESENSOR
FLOW SENSOR(Main stream)
FLOW SENSOR(Entrainment)
SIGNAL CONDITIONING & INTERFACING
IFU OF
U
DEF
DEFI
NPU
UZZIFI
Rule base for determining
Rule base for determining
Focusing nozzle (For do =0.25- 0.275)
UTP
UZZIFI
FUZZI
FUZZI
B C
UT
USER / AUTOMATIC
ICATI
Orifice
Rule base for determining
Focusing nozzle (For do =0.275- 0.33)
UT
do & df
ICATI
FICAT
FICAT
ON
FUZZY INFERENCE
ON
ION
IONMODULE 2
Determination of size
February 3, 2011 56KNOWLEDGE BASE
FUZZY SYSTEM
of orifice and focusing nozzle