Mechanical Energy Processes: Ultrasonic Machining

Mechanical Energy Processes

• Ultrasonic Machining (USM) uses abrasives contained in a slurry of water and abrasive particles to wash away chips.
• The slurry consists of a mixture of water and abrasive particles such as boron carbides, aluminum oxide, silicon carbide, boron nitride, and diamond.
• The tool, made of soft steel or stainless steel, vibrates at a high frequency (20,000 Hz) and low amplitude (0.076 mm) to remove material.
• The tool oscillation is perpendicular to the work surface, and the tool is fed slowly into the work.
• The concentration of abrasives in water ranges from 20% to 60%, and the less viscous the slurry fluid, the faster it can carry away chips.

Advantages of USM

• Any material can be machined regardless of their electrical conductivity.
• Good surface finish is obtained with little or no surface damage.
• USM is a non-thermal process and is not dangerous.

Disadvantages of USM

• Material removal rates are low.
• The depth of the hole is limited to the size of the tool.
• Tool wear is high, and sharp corners cannot be generated.
• High power consumption is required.

Applications of USM

• USM is suitable for hard, brittle work materials such as ceramics, glass, and carbides.
• USM is also successful on certain metals, such as stainless steel and titanium.
• Shapes include non-round holes, and "coining operations" can be performed.

Water Jet Cutting (WJC)

• WJC uses a fine, high-pressure, high-velocity stream of water directed at the work surface for cutting.
• The nozzle diameter is 0.1-0.4 mm, and smaller openings are used for finer cuts on thinner materials.
• Pressure: up to 400 Mpa, and jet velocity: up to 900 m/s.
• The standoff distance, the separation between the nozzle opening and the work surface, is 3.2mm.

Advantages of WJC

• No crushing or burning of the work surface.
• Minimum material loss because of the narrow cut slit.
• No environmental pollution.
• Easy automation of the process using CNC or industrial robots.

Disadvantages of WJC

• Not suitable for cutting brittle materials (e.g., glass) because of their tendency to crack during cutting.

Applications of WJC

• Used to cut narrow slits in flat stock such as floor tile, food, composites, plastic, carpet, leather, and cardboard.