Comparing Material Removal Rates in EDM to USM

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Comparing Material Removal Rates in EDM to USM

• Andrew Chapman
• Amelia Halim
• Douglas Ramos

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EDM Material Removal Rate (MRR)

• Ranges from 0.1 to 600 mm3/min
• 300 mm3/min typical
• Proportional relationship between MRR and surface
  roughness
• High removal rates gives rough finish, molten and
  recast structure, low fatigue strength
• MRR is also dependent on pulse conditions
  (voltage, current, and duration), electrode
  material and polarity, and the dielectric.
• Lower the melting point of the material, the
  higher the MRR.

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Sink EDM Cont.

• The closer the gap between the electrode and the
  conductive work piece the more intense the
  electric field is between the two and thus a
  greater MRR is able to be achieved.
• The material removal rate, MRR, in EDM is
  calculated by the following foumula
• MRR 40 I / Tm 1.23 (cm3/min)
• Where, I is the current amp,
• Tm is the melting temperature of workpiece in 0C
• The volume of the material removed per spark
  discharge is typically in the range of 10-6 to
  10-6 mm3

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Ultrasonic Stock Removal

• This machining process is nonthermal,
  nonchemical, and nonelectrical. It does not
  change the metallurgical, chemical or physical
  properties of the workpiece. 2
• All brittle materials glass, technical
  ceramics, ferrite, quartz, tungsten carbide,
  sapphire, ruby and even diamond can be abraded
  in this way. 1
• Typical penetration removal rates vary from
  0.025-25 mm/min.
• Grinding force never exceeds 2 lbs of force 3
• The best surfaces finishes result from using
  800-grit abrasives. They leave a surface finish
  on the order of 25 microns.

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Ultrasonic Stock Removal Rate (SRR)

• when machining electrically conductive
  materials, a limited MRR as compared with ECM and
  EDM is realized
• 50mm3/min is typical
• SRR is dependent on the work material, amplitude
  and frequency of tool oscillation, abrasive size
  and type, static pressure, abrasive concentration
  (mixing ratio) in the slurry,
• Also the higher the ratio of tool to work piece
  hardness, the lower the MRR.
• Higher the oscillation amplitude or abrasive grit
  size, the higher the SRR
• SRR increases with applied static pressure, but
  then decreases after a point
• Optimum concentration of slurry mixing ratio,
  abrasives to water, is 40.