How does ultrasonic machining use an abrasive liquid to remove material?

In ultrasonic machining (USM), material is removed from a workpiece through the action of abrasive particles suspended in a water slurry. This slurry circulates through a narrow gap between the workpiece and a tool shaped to match the desired cavity.1

The tool oscillates at a high frequency—typically between 19,000 and 40,000 hertz—with an amplitude ranging from 0.013 to 0.062 millimetres. These rapid vibrations drive the abrasive grains against the surface of the workpiece, effectively chipping away material. This process is particularly effective for machining hard, brittle materials, including ceramics, glass, semiconductor materials like germanium, and precious stones. While a slurry containing grit is standard for this method, some variations, such as ultrasonic twist drilling, can operate without it.12