Have you heard of ultrasonic machining? Also known as ultrasonic vibration machining, it’s a manufacturing process that’s used to remove material from a workpiece through the use of high-frequency vibrations combined with particles.
An ultrasonic tool essentially creates many small vibrations that, over time, remove material from the workpiece with which it’s used. To learn more about ultrasonic machining and how it works, keep reading.
What Is Ultrasonic Machining?
Ultrasonic machining is a subtractive manufacturing process that removes material from the surface of a part through high frequency, low amplitude vibrations of a tool against the material surface in the presence of fine abrasive particles. The tool travels vertically or orthogonal to the surface of the part at amplitudes of 0.05 to 0.125 mm (0.002 to 0.005 in.).
The fine abrasive grains are mixed with water to form a slurry that is distributed across the part and the tip of the tool. Typical grain sizes of the abrasive material range from 100 to 1000, where smaller grains (higher grain number) produce smoother surface finishes.
Ultrasonic vibration machining is typically used on brittle materials as well as materials with a high hardness due to the microcracking mechanics.
With ultrasonic machining, a tool creates vibrations that project micro-sized particles towards the workpiece. The particles are typically mixed with water or other liquids to create a slurry.
When the ultrasonic tool is activated, it projects these particles at a fast rate of speed towards the workpiece’s surface. The abrasive nature of the particles helps to grind away material from the workpiece’s surface.
Ultrasonic Machining Process
The tool present in the machine for cutting the materials is made from a soft material as compared to the workpiece. The tool is usually made from materials such as soft steel and nickel. When the tool vibrates, the abrasive slurry (liquid) is added which contains abrasive grains and particles.
The abrasive slurry is added till the workpieces interact with the grains. Due to the particles of liquid added, the work brittleness of the workpiece abrades the surface meanwhile the tool deforms gradually.
Working Principle of Ultrasonic Machining
The time spent on the ultrasonic machine entirely depends on the frequency of the vibrating tool. It also depends on the size of grains of the abrasive slurry, the rigidity, and the viscosity as well.
The grains used in the abrasive fluid are usually boron carbide or silicon carbide as they are rigid than others. The used abrasive can be carried away easily if the viscosity of the slurry fluid is less.
Types of Ultrasonic Machining
1. Rotary ultrasonic vibration machining
In rotary ultrasonic vibration machining (RUM), the vertically oscillating tool is able to revolve about the vertical centerline of the tool. Instead of using an abrasive slurry to remove material, the surface of the tool is impregnated with diamonds that grind down the surface of the part.
Rotary ultrasonic machines are specialized in machining advanced ceramics and alloys such as glass, quartz, structural ceramics, Ti-alloys, alumina, and silicon carbide. Rotary ultrasonic machines are used to produce deep holes with a high level of precision.
Rotary ultrasonic vibration machining is a relatively new manufacturing process that is still being extensively researched. Currently, researchers are trying to adapt this process to the micro-level and to allow the machine to operate similarly to a milling machine.
2. Chemical-assisted ultrasonic vibration machining
In chemical-assisted ultrasonic machining (CUSM), a chemically reactive abrasive fluid is used to ensure greater machining of glass and ceramic materials. Using an acidic solution, such as hydrofluoric acid, machining characteristics such as material removal rate and surface quality can be improved greatly compared to traditional ultrasonic machining.
While time spent machining and surface roughness decrease with CUSM, the entrance profile diameter is slightly larger than normal due to the additional chemical reactivity of the new slurry choice. In order to limit the extent of this enlargement, the acid content of the slurry must be carefully selected to ensure user safety and a quality product.
Applications of ultrasonic Machining
The applications of Ultrasonic Machining are:
- Machining very precise and intricate shaped articles.
- Drilling the round holes of any shape.
- Grinding the brittle materials.
- Profiling the holes.
- Engraving
- Trepanning and coining
- Threading
- Slicing and broaching hard materials.
- Machining the glasses, ceramics.
- Machining the precise mineral stones, tungsten.
- Piercing of dies and for parting off operation.
- This is precise enough to be used in the creation of micro-electro-mechanical system components such as micro-structured glass wafers
- Diamond is cut for the desired shapes.
Advantages of Ultrasonic Machining
There are dozens of other manufacturing processes capable of removing material from workpieces, their applications are typically restricted to workpieces made of strong and durable materials. Ultrasonic machining is unique, however, because it’s capable of removing material from nearly all types of workpieces, including those made of hard and brittle materials.
Whether a workpiece is made of glass, ceramic or even quartz, its physical dimensions can be altered using ultrasonic machining.
Ultrasonic machining doesn’t require heating workpieces. If a workpiece is sensitive to thermal fluctuations, it can be safely altered using this machining process. During ultrasonic machining, the workpiece’s temperature will remain the same. In other words, the process requires neither heating nor cooling the workpiece.
Furthermore, ultrasonic machining offers higher tolerance than many other machining processes. It’s capable of modifying workpieces with high tolerances that aren’t possible with other machining processes.
Disadvantages of Ultrasonic Machining
On the other hand, there are a few disadvantages of ultrasonic machining, one of which is a slower-than-average rate of material removal. It’s not a particularly fast way to remove material from workpieces.
On the contrary, it’s slower than most other machining processes. For manufacturing companies looking for mass-production processes, ultrasonic machining may be a poor choice.
In addition to a slower-than-average rate of material removal, ultrasonic machining doesn’t support the use of deep holes. It’s not uncommon for manufacturing companies to drill holes into workpieces before exposing them to an ultrasonic machining tool. If a hole is too deep, however, the slurry won’t be able to fill it.
