By: Ryan Carter, Date: 02/10/2018

Ultrasonic Machining uses high frequency oscillation of a hard tool to precisely remove material from a hard and brittle surface. The work material is separated from the tool by a slurry of abrasive particles. This slurry is usually an oil or water base with hard particles infused within. The tool contacts the particles in the slurry, and then the particles chip away material from the work material.

Robert Wood and Alfred Loomis are credited with first discussing the method of ultrasonic machining in a paper they wrote in 1927. The procedure was first patented 18 years later in 1945. Nine years later, in 1954, the first ultrasonic tool was manufactured. Today, the procedure and applications have greatly improved. Many different types of tools can be used in the ultrasonic machining process ranging from rotatory tools, precise drilling mechanisms, and surface polishing instruments.

Hard, brittle materials (composites, ceramics, advanced materials)

This process is ideal for designs that require holes or patterns of complicated shapes in brittle materials. This process is non-thermal, non-chemical, non-electrical and creates no change in metallurgical, chemical, or physical properties of the work material. This makes it ideal for machining advanced materials like cabides and ceramics. Additionally, the process can be used on both conductive and non-conductive materials. The shortcomings of this machining process is that there is a low removal rate of material and the process is limited to brittle materials. The tolerances in ultra sonic machining vary with the material being machined, however, the typical tolerance range is ± 10 to 25 µm.

Low-frequency signal → High-frequency signal → Vibrational motion → Abrasive particles → Microscopic cracking

This machining process works by microchipping. The first step in the process begins when low-frequency electrical energy is converted to a high-frequency signal, which is then fed to a transducer. This transducer converts the high-frequency signal to vibrational motion. This motion is transferred to a hard tool assembly which transfers the vibrational motion to abrasive particles held in a slurry. The transducer usually operates at a frequency of over 20 kHz with an amplitude of 6-50µm. The abrasive particles hammer microscopic cracks in the work material until the material is chipped away. Lastly, the removed material is then carried away by the slurry. The machining processes can be completed with a single operator and requires minimal input.

The cost is purely application driven. Ultrasonic machining services can range from $100 a part to tens of thousands of dollars per part. Furthermore, due to the low material removal rate, ultrasonic machining is not used for high volume manufacturing. Additionally, the oscillating tool must be replaced relatively quickly due to wear. This manufacturing process is mainly used for specialty applications requiring advanced materials.