Smart Machining with Abrasive Waterjets (AWJ)

Mohamed HashishFlow International CorporationKent, WA 98032

Overview

• Background

• Discuss factors that affect results and robustness

• Discussions will revolve around the tetrahedron with more focus on the process technology

• Examples of smart machining for selected applications

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AWJ System Platforms

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Smart machining addresses all the platforms

5 Platforms

Smart Pumps

• Pump selection• Hyperjet: 94 Ksi Max pressure

• 87 Ksi operating pressure

• Hyperlife: 75 Ksi Max pressure

• Standard: Max pressure 60 Ksi

• Direct drive: Max 60 Ksi high efficiency

• Pump monitoring and diagnostics

• Ease of maintenance

• iOT

• Pressure profiling

• Networking

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Results- Geometrical- Integrity

- standoff distance- traverse speed- lead angle- taper angle

- pressure- orifice size- mixing tube diameter- mixing tube length- abrasive material- abrasive flow rate- abrasive particle size

Jet

Para

met

ers

Kin

emat

ic

Para

met

ers

• Optimize• Static variables

• Orifice size

• Mixing tube length

• Mixing chamber shape

• Abrasive particle size

• Abrasive material

• Monitor• Quasi static variables

• Orifice edge

• Mixing tube diameter

• Control• Dynamic variables

• Pressure

• Abrasive flow rate

• Cutting speed

• Jet angles

• Stand off distance

Smart Process

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Cutting Observation

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Process Models

Basic Model areas• Jet-Material Interaction• Wear Models• Multi Phase flow

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Static Parameters

Parameters Controls

Orifice size • Orifice size is specified to +-.0002

Water supply tube • High l/d for jet coherency >20

Mixing tube length • Specified to +- 0.005

Abrasive particle size• Supplier size distribution

specification – less fines

Abrasive material• Supplier material specification• Application needs

Abrasive feed line length• Minimal from metering valve to

nozzle – no kinksAbrasive feedline material

• Polyurethane• Minimal friction

Abrasive feedline diameter

• Optimized for the abrasive flow rate range

Mixing tube tip cone• Minimal face area to prevent

abrasive rebound

Jet-mixing tube alignment

• High concentricity > 50% at exit• Pre-aligned Cartridges

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Quasi Static Parameters

ParametersControls/sensor

examples

Orifice edge• Vacuum sensor • Air flow rate below orifice

Inlet mixing tube diameter

• Air flow measurement • Periodic inspection

Exit mixing tube diameter

• Vision • Periodic gauging• Compensation

Inlet air flow rate• Venturi• hot wire anemometry

Inlet air condition• Air condition control

(heating, drying)

Temperature (room and catcher)

• Needed for the room, catcher, and fixture

Mixing chamber wear• Hard materials inserts• Periodic Air flow

measurement

0

100

200

300

400

500

600

700

800

0 5 10 15 20 25 30 35 40

Air Flow Rate (Liter/min)

(Pa

- P

v)

mm

-Hg

AWJ Nozzle

Characteristics

Abrasive Feed Hose

Characteristics

dn=0.457 mm, dm=1.19 mm, lm= 76 mm, lh= 3.05 m

69 MPa

138 MPa

207 MPa

276 MPa

dh= 2.54 mm dh= 2.54 mm

dh= 3.81 mm

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Dynamic Parameters

Parameters Controls

Jet pressureA pressure transducer near cutting head is sometimes used

Abrasive flow rateSelected using an orifice or rotary drum - No feed back control

Lead anglePredicted and machine-controlled to 0.2 degrees

Taper anglesPredicted and machine-controlled to 0.02 degrees

Cutting speedPredicted and machine-controlledto +- 3% with acc-dec flow slowing around corners

Stand off distanceControlled within 0.005 inch with height setters- Dynamic contour followers

Catcher water temperature

Catcher temperature control is required and implemented for some applications

SOD Control

Focal pointTaper control

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More Examples

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More Examples

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Abrasives

Dual abrasive feed metering and mixing mini hoppersUS Patent No: 8,308,525

Al2O3

abrasivesGarnetabrasives

metering

Mixing

MaterialMohs

HardnessKnoop

HardnessSpecific gravity

Diamond 10 7000 3.51

Boron Carbide 2750 2.52

Silicon Carbide 2480 2.2

Titanium Carbide 2470

Aluminum Oxide 2100 1.95-4.0

Tungsten Carbide 1880 15.6

Titanium Nitride 9 1800

Tungsten Carbide 1600

Garnet 1360 3.4 - 4.3

Topaz 8 1340

Zirconia 1160

Steel grit 750 7.8

Quartz/Silica 7 820 1.2

Glass beads 530 1.04

Olivine 6.7 1.5

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Drilling Examples

• Diameter (d) ~ 0.015 inch• Angle ~ 22 degree• Size accuracy ~ 0.001 inch• Spacing ~ d• depth ~ 25 d• Thousands of holes have been

drilled in CFRP and TBC• Acoustic sensing is used to detect

hole breakthrough

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Milling Example

• Damaged composites can be scarfed at shallow angles to create a new surface for bonding

Jedo Technologies, France, 3D Milling examples

Scarfed surface and batch repair

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Surface Integrity Results

Controls

Frosting

• Frosting is eliminated when

cutting under water or using

coherent jets

Embedding• Final conventional finishing

• Pure waterjet pass

Delamination

• Vacuum assist

• Pressure ramping

• Optimal parameters and

Procedures

Chipping/cracking

• Vacuum assist

• Pressure ramping (thick)

• Optimal parameters and

Procedures

Tear drop

• Tilt while drill

• Optimal parameters and

Procedures

Bur• Support

• Grit size

Qualitative Results

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Summary

• Smart Machining with AWJ addresses:• Applications

• Process Technology

• Equipment platforms

• Materials optimization

• Management of environmental effects

• There is a significant knowledge and advances is sensors, controls, and software to propel AWJ to the next industrial revolution

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Thank you!

Mohamed Hashish

Flow International Corporation206-465-5953

www.Flowwaterjet.com

Questions Please