WJM

• WATER JET MACHINE PROCESS : Working of abrasive water Jet machining process (animation). - YouTube
• How Does a Waterjet Work? It Slices Steel with Water! - YouTube

Applications and Products

Applications

• Industries: mining, automotive, aerospace
• Operations: machining (cutting, shaping, rimming, machining sheets, machining foils, pocket milling, drilling) and special (paint removal, surgery cleaning, peening, cutting frozen meet)
• Materials: soft is most common (rubber, textiles, plastic, foam, leather, paper) and =hard= (composites, tile, stone, glass)

Products

• Automotive parts

Advantages and Disadvantages

Advantages

• Intricate, complex cuts
• Low maintenance and operation cost (no moving parts)
• Low hazards
  • True cold cutting (no heat affected zones)
  • No mechanical stresses
  • No worker or environmental hazards (clean machining area)
• Cuts and machines non-metallic materials (plastic, wood, rubber)

Disadvantages

• High initial cost
• Very thick material cannot be machined

Working Principle

• Erosive force of high speed (540 - 1400 m/s), high density, ultra-high pressure (150 - 1000 MPa) water stream removes material (water acts like a saw)
• The speed is faster than the speed of sound
• $K.E=0$ -> Pressure; $K.E=0$ after striking
• Water + Alcohols, oil, glycerol
• Erosion (localized compressive failure) means: Pressure > Material strength
• Ductile: erosion due to shearing action

Schematic

Process Parameters

These parameters affect:

• Surface quality
• Material removal rate
• Accuracy

Nozzle

• Standoff distance: small to minimize dispersion
• Nozzle operating diameter: small = fine cuts; large = higher pressure
  Water Jet
• Water pressure: high P = high MRR
• Feed rate: 5-500 mm/s
• Others: fluid type, velocity, flow rate, viscosity
  Workpiece
• Type, thickness, feed rate