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Abrasive water jet machining

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  1. Abrasive water jet machining MFET 4210

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

  3. 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

  4. 2. Hardware • Intensifier Pump • Nozzle • Abrasive Delivery System • Catcher • CNC Control

  5. Hardware • Intensifier Pump Components • Hydraulic Pump • Pistons • Cylinders • Check valves • Attenuator

  6. Hardware Delivery System • Nozzle • Jewel • Abrasive inlet • Guard • Mixing Tube

  7. Hardware Delivery System • Nozzle • Jewel • Diameter ranges from .005 - .020” • Usually sapphire, sometimes ruby or diamond

  8. Hardware Delivery System • Nozzle • Abrasive Inlet • Feeds from abrasive feed system • Venturi pulls in abrasive

  9. Hardware Delivery System • Nozzle • Mixing Tube • Abrasive and water mix evenly • Must be exactly in line • Composite carbide

  10. Hardware • Abrasive Delivery System • Provide fixed delivery rate • Gravity or air fed

  11. Hardware • Catcher • Slows jet of water down • Reduces noise and dust • Catches dust

  12. Hardware • CNC Controllers • Traditional control • PCs • Cheaper • Easier to update to newer and faster software

  13. 3. Abrasives • Usage • ½ to 2 pounds per minute • $0.15 to $0.40 per pound • Types • Garnet • Olivine

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

  15. Abrasives • Olivine • Cheaper than garnet • Softer than garnet

  16. 4. Parameters • Pressure • Nozzle or jewel diameter • Feed or traverse rate • Nozzle standoff distance

  17. 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

  18. 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

  19. Parameters • Feed Rate • Varies greatly depending on • Type of material • Thickness • Hardness • Quality of cut needed

  20. Parameters • Standoff • Usually .010 to 0.200”, up to 1” • Higher distance causes frosting • Eliminated by cutting underwater

  21. 5. Capabilities • Tolerances • Materials • Geometries • Examples of use

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

  23. Capabilities • Materials • Cuts basically anything • Diamond, some ceramics • 6.5” Ti

  24. Capabilities • Geometry • Stacking parts • 5-axis milling

  25. Capabilities • Geometry • Very thin to very thick cuts • Flat sheets of material • 10.25” Tool Steel

  26. 6. Avantages • No HAZ • Temp may rise to 120 degrees F • Catch tank and water absorb heat • Very small kerf • .020-.050”

  27. Avantages • Minimal cutting forces • 5 pounds max down force • Very low side forces • Clamping forces are very low • Brittle or fragile work pieces

  28. Avantages • Fast and accurate • Minimal fixturing • Omni-directional • Cuts any type of materials • Nonhomogeneous

  29. Avantages • No tools to sharpen, only “tool” is the nozzle • Environmentally friendly • Garnet can be dumped in landfill • Water can be filtered and reused

  30. 7. Disadvantages • Lag • Only a factor if finish is important • Very similar to cutting torch lag lines

  31. Disadvantages • Taper • Parts cut with taper • Can be compensated for by software • Increases with nozzle wear

  32. Disadvantages • Less accurate than traditional machining • Very hard materials not very practical application • Traverse rate is so slow, costs add up

  33. 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

  34. Disadvantages • Nozzle wear • Consumable nozzle wears • Causes stray cutting • Increases kerf • Decreases finish quality • Very loud • Reduced if cut underwater

  35. Applications • Machine shops • Artists • Stone, glass, marble • Aerospace • Titanium, Inconel, composites • Rapid prototyping • Universities • Automotive industry • Custom flooring work • Tiles

  36. Summary • Very versatile, powerful technology • Growing use and applications • Constantly getting better and more capable

  37. 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/