Based on energy used, unconventional machining processes can be broadly classified into five main types. They are:
- Mechanical Energy based Unconventional Machining Processes
- Electrical Energy based Unconventional Machining Processes
- Electrochemical Energy based Unconventional Machining Processes
- Chemical Energy based Unconventional Machining Processes
- Thermo-electrical (or Electro-thermal) Energy based Unconventional Machining Processes
In these processes, unwanted material in the workpiece is removed by mechanical erosion. The mechanical erosion can be facilitated by using any medium. For example, in abrasive jet machining, high velocity abrasive jet is used for eroding material from the workpiece. In water jet machining, high velocity water jet is used for cutting the workpiece material.
The four main mechanical energy based unconventional machining processes are:
- Abrasive Jet Machining
- Water Jet Machining or Water Jet Cutting
- Abrasive Water Jet Machining
- Ultrasonic Machining
Here, electric spark discharge is used to cut and machine the workpiece.
In electrical energy based processes, no arc is produced (as in arc welding). Instead, thousands of sparks are produced every second. These sparks increase the temperature of the workpiece, melt the unwanted portions and vapourise those portions.
A dielectric fluid is used for cleaning the workpiece and facilitating a smooth spark discharge.
Processes that come under this category are:
- Electrical Discharge Machining
- Wire Cut Electrical Discharge Machining
In these processes, unwanted portions of the workpiece are removed by electrochemical effect. The workpiece (in contact with an electrolyte) is machined by ion dissolution. Processes that come under this category are:
- Electrochemical Machining
- Electrochemical Grinding
- Electrochemical Honing
Here, chemical energy is used to remove material from the workpiece.
We know that metal can be easily converted to metallic salt, if suitable reagent is used. Chemical energy based processes exploit this principle.
Material is removed by controlled etching of the workpiece in the presence of a reagent known as enchant.
Chemical machining, chemical milling and photochemical milling (PCM) are the processes that comes under this category.
Unwanted portions of a metal can be easily removed, if it is melted or vapourised. Thermo-electrical energy based unconventional machining processes make use of this principle.
In these processes, electrical energy is converted to a huge amount of heat by some means. This heat is applied on a small region of the workpiece. That particular region is either melted or vapourised. By this way, material is removed.
The following are some of the important thermo-electrical energy based unconventional machining processes:
- Plasma Arc Machining
- Electron Beam Machining
- LASER Beam Machining
- Ion Beam Machining