Lecture 05 Flashcards

Non-Traditional Machining Using Mechanical Energy

Abrasive Jet Machining (AJM)

• Material removal:
  • Surface Erosion
  • Mechanical Abrasion
  • Micro-chipping
  • Brittle fracture
• Process parameters:
  • Abrasive material: $Al<em>2O</em>3$ / SiC
  • Size: 10 ~ 50 μm
  • Carrier gas: air, $CO<em>2$, $N</em>2$
  • Velocity: 500 ~ 700 m/s
  • Pressure: 2 ~ 10 bar
  • Abrasive jet velocity: 100 ~ 300 m/s
  • Stand-off distance: 0.5 ~ 5 mm
  • Nozzle impingement angle: 600 ~ 900
  • Nozzle Diameter (internal): 0.2 ~ 0.8 mm
• Nozzle-Tip-Distance (NTD):
  • Cutting: 0.75 mm
  • Cleaning and peening: 5-12 mm
  • Glass frosting: 25-75mm

Water Jet Machining (WJM) and Abrasive Water Jet Machining (AWJM)

• WJM:
  • High-pressure water jet (2500 – 4000 bar, 1000 m/s)
  • Suitable for leather, textile materials, food, polymers, thin metals
• AWJM:
  • Abrasive particles mixed with high-pressure water
  • Used for metals and ceramics
• WJM vs AWJM:
  • WJM: Pure water jet
  • AWJM: Water-abrasive mixture
  • AWJM cost of abrasive is an additional expenditure
  • WJM cuts softer materials, wood, leather, polymer and food items.
  • AWJM applications range from wood and polymer to metal cutting industries
• AWJM Components:
  • High pressure intensifier
  • Waterjet
  • Abrasive feed system
  • Abrasive-jet nozzle
  • Abrasive and water catcher
• AWJM General conditions:
  • Orifice: Sapphires - 0.1 to 0.3 mm
  • Focussing Tube: WC - 0.8 to 2.4 mm
  • Pressure: 2500 to 4000 bar
  • Abrasive: garnet and olivine - #125 to #60
  • Abrasive flow - 0.1 to 1.0 Kg/min

Ultrasonic Machining (USM)

• Abrasives in slurry driven against work by tool oscillating at: low amplitude (25-100 microns) and high frequency (15-30 kHz).
• USM Apparatus:
  • Power generator
  • Electroacoustic transducer
  • Mechanical amplifier
  • Sonotrode
• Transducers:
  • Piezoelectric
  • Magnetostrictive
• Material Removal:
  • Mechanical abrasion
  • Microchipping
  • Surface erosion by cavitation