Understanding Ultrasonic Machining Process

Oct 16, 2024

Ultrasonic Machining

Ultrasonic machining is a non-conventional process used for machining both conducting and non-conducting hard and brittle materials that cannot be machined using conventional methods. This process utilizes ultrasonic vibrations in the frequency range of 20 to 30 kilohertz.

Key Features

  • Ultrasonic Wave: Defined as high-frequency sound waves (>20 kHz) that are inaudible to humans.
  • Machining Method: Combines ultrasonic vibrations with a slurry containing abrasive particles to remove material.

Lecture Overview

  1. Working Principle
  2. Construction
  3. Working
  4. Parameters Affecting the Machining Process
  5. Advantages and Disadvantages
  6. Applications

Working Principle

  • The transducer produces vibrations at the tool tip, which is shaped to create the desired cavity in the material.
  • As the tool lightly presses against the work surface, abrasive slurry is supplied between the tool tip and the workpiece.
  • The high kinetic energy from the vibrations is transferred to the abrasive particles, which then remove material through microscopic abrasion.

Construction Components

  • Power Supply: Provides alternating current (50-60 Hz) necessary for the process.
  • High-Frequency Generator: Converts conventional electrical supply to high-frequency energy (20-40 kHz).
  • Electromechanical Transducer: Converts high-frequency electrical energy into mechanical vibration.
  • Ultrasonic Amplitude Transformer (Horn): Increases vibration amplitude (approximately 0.025 mm) and guides vibrations to the tool tip.
  • Tool Holder: Grips the tool, made from tough and brittle materials like tungsten carbide or stainless steel.
  • Tool: Designed to match the cavity shape to be created.
  • Slurry: Mixture of hard abrasive particles (e.g., silicon carbide, boron carbide) with water or oil, supplied to the machining area.
  • Pump: Supplies the abrasive slurry to the machining area.

Working Process

  1. AC supply is provided to the high-frequency generator which amplifies it to 20-40 kHz.
  2. The electromechanical transducer converts this energy into ultrasonic vibrations.
  3. The horn amplifies these vibrations and focuses them onto the tool.
  4. As the tool vibrates, the abrasive slurry is continuously fed between the tool and the workpiece, resulting in material removal due to abrasion.

Parameters Affecting Material Removal Rate (MRR)

  • MRR is inversely proportional to the cutting area of the tool.
  • Tool vibrations and the type, size, and concentration of abrasives also impact MRR.

Applications

  • Drilling: Creates round holes of various shapes.
  • Step Drilling: Can drill holes at different depths.
  • Grinding: Utilizes the process for brittle materials.
  • Engraving: Capable of engraving designs.
  • Slicing and Broaching: Effective for hard materials like glass and ceramics.

Advantages

  • Can drill both circular and non-circular holes in hard materials.
  • Does not require heating of workpieces, making it suitable for thermally sensitive materials.
  • Applicable to both conductive and non-conductive materials.
  • Operable by semi-skilled personnel.
  • High accuracy can be achieved.

Disadvantages

  • Low material cutting rate.
  • Limited to workpiece surfaces of small size.
  • Shorter tool life compared to conventional machining processes.

Conclusion

  • Ultrasonic machining offers unique benefits for working with hard and brittle materials, making it a valuable process in modern manufacturing.