Ultrasonic Machining

Ultrasonic machining is an unconventional machining process. Ultrasonic machining is a method of grinding that uses an abrasive liquid rather than direct tool contact.

 
Principle

In ultrasonic machining, a liquid filled with abrasive material flows through over the work piece, and the work tool vibrates against the abrasives. The abrasive materials affect the work piece and remove material. For vibration we use a piezoelectric material, which vibrates on providing an emf.

Construction

The basic mechanical structure of USM is very similar to that of drill machine, howevee it can also be used on brittle materials also. The workpiece is mounted on a vice, which can be located at the desired position under the tool using a 2-axis table. The table can further be lowered or raised to accommodate work of different thickness.

 The basic elements of a USM are:

• Slurry delivery and return system,
• Feed mechanism to provide a downward feed force on the tool during machining,
• The piezoelectric material, which generates the ultrasonic vibration,
• The horn or concentrator, which mechanically amplifies the vibration to the required amplitude of 15-50 microns and accommodate the tool at its tip.

Working

In an ultrasonic machining, a tool of desired shape is vibrates at an ultrasonic frequency of 19-25 kHz with an amplitude of around 15-50 microns over the workpiece. Generally the tool is pressed downward with a feed force, F. Between the tool and the workpiece, the machining zone is flooded with hard abrasive particles generally in the form of water based slurry. As the tool vibrates over the workpiece, the abrasive particles acts as indenters and indent both the workpiece and the tool.