ABRASIVE WATER JET MACHINING

MFET 4210

Topics for Today

1. Basic Principles 2. Hardware 3. Abrasives 4. Parameters 5. Capabilities 6. Advantages 7. Disadvantages

1. Basic Principles

How does it work? High pressure water with abrasive eroding

material Small diameter orifice or “jewel” to focus

energy Erosion of material Jet of abrasive and water

20,000 – 90,000 psi Up to 600 mph

2. Hardware

Intensifier Pump Nozzle Abrasive Delivery System Catcher CNC Control

Hardware

Intensifier Pump Components Hydraulic Pump Pistons Cylinders Check valves Attenuator

Hardware Delivery System

Nozzle Jewel Abrasive inlet Guard Mixing Tube

Hardware Delivery System

Nozzle Jewel

Diameter ranges from .005 - .020”

Usually sapphire, sometimes ruby or diamond

Hardware Delivery System

Nozzle Abrasive Inlet

Feeds from abrasive feed system

Venturi pulls in abrasive

Hardware Delivery System

Nozzle Mixing Tube

Abrasive and water mix evenly

Must be exactly in line Composite carbide

Hardware

Abrasive Delivery System Provide fixed delivery rate Gravity or air fed

Hardware

Catcher Slows jet of water down Reduces noise and dust Catches dust

Hardware CNC Controllers

Traditional control PCs

Cheaper Easier to update to newer and faster software

3. Abrasives

Usage ½ to 2 pounds per minute $0.15 to $0.40 per pound

Types Garnet Olivine

Abrasives

Garnet Most common at 80 mesh Naturally occurring mineral Less dusting Typical to reuse 2 or 3 times

Abrasives

Olivine Cheaper than garnet Softer than garnet

4. Parameters

Pressure Nozzle or jewel diameter Feed or traverse rate Nozzle standoff distance

Parameters

Pressure Ranges from 20-90,000 psi

Less than 60,000 psi most common Higher pressure for harder materials and

thicker cuts Harder on equipment

Parameters

Nozzle Diameter Large range depending on application Jet usually .020-.050”

Horsepower = 0.58*P*Q P = pressure in ksi Q = flow rate in gpm

Parameters

Feed Rate Varies greatly depending on

Type of material Thickness Hardness Quality of cut needed

Parameters

Standoff Usually .010 to 0.200”, up to 1” Higher distance causes frosting

Eliminated by cutting underwater

5. Capabilities

Tolerances Materials Geometries Examples of use

Capabilities

Tolerances +-.004 to +-.008” Vast majority of industry cuts at +-.010” or

more

Capabilities Materials

Cuts basically anything Diamond, some ceramics

6.5” Ti

Capabilities

Geometry Stacking parts 5-axis milling

Capabilities

Geometry Very thin to

very thick cuts Flat sheets of

material

10.25” Tool Steel

6. Avantages

No HAZ Temp may rise to 120 degrees F Catch tank and water absorb heat

Very small kerf .020-.050”

Avantages

Minimal cutting forces 5 pounds max down force Very low side forces Clamping forces are very low

Brittle or fragile work pieces

Avantages

Fast and accurate

Minimal fixturing

Omni-directional

Cuts any type of materials Nonhomogeneous

Avantages

No tools to sharpen, only “tool” is the nozzle

Environmentally friendly Garnet can be dumped in landfill Water can be filtered and reused

7. Disadvantages

Lag Only a factor if finish is important Very similar to cutting torch lag lines

Disadvantages Taper

Parts cut with taper Can be compensated for by software Increases with nozzle wear

Disadvantages

Less accurate than traditional machining Very hard materials not very practical

application Traverse rate is so slow, costs add up

Disadvantages

Can delaminate some materials Fiberglass, some composites Preventable with pilot hole from drill

Cost Setup ranges from $20,000-$300,000

Average machine runs $150,000 Thickness of cut

Price increases dramatically for >2” metal cuts

Disadvantages

Nozzle wear Consumable nozzle wears Causes stray cutting Increases kerf Decreases finish quality

Very loud Reduced if cut underwater

Applications

Machine shops Artists

Stone, glass, marble Aerospace

Titanium, Inconel, composites Rapid prototyping Universities Automotive industry Custom flooring work

Tiles

Summary

Very versatile, powerful technology Growing use and applications Constantly getting better and more

capable

Sources

Nontraditional Machining Processes, E. J. Weller

http://www.jetedge.com http://waterjets.org/ http://www.h2ocut.com/ http://www.universalminerals.com/ http://www.flowcorp.com/