An unconventional machining process (or non-traditional machining process) is a special type of machining process in which there is no direct contact between the tool and the workpiece. In unconventional machining, a form of energy is used to remove unwanted material from a given workpiece.
Why unconventional machining processes are used?
The answer is simple. In several industries, hard and brittle materials like tungsten carbide, high speed steels, stainless steels, ceramics etc., find a variety of applications.
For example, tungsten carbide is used for making cutting tools while high speed steel is used for making gear cutters, drills, taps, milling cutters etc.
If such materials are machined with the help of conventional machining processes, either the tool undergoes extreme wear (while machining hard workpiece) or the workpiece material is damaged (while machining brittle workpiece).
This is because, in conventional machining, there is a direct contact between the tool and the workpiece. Large cutting forces are involved and material is removed in the form of chips. Huge amounts of heat is produced in the workpiece. This induces residual stresses, which degrades the life and quality of the workpiece material.
Hence, conventional machining produces poor quality workpiece with poor surface finish (if the workpiece is made of hard and brittle material).
To overcome all these drawbacks, we use unconventional machining processes to machine hard and brittle materials.
We also use unconventional machining processes to machine soft materials, in order to get better dimensional accuracy.
Classification of unconventional machining processes:
Unconventional machining processes can be broadly classified into several types based on four main criteria. The classification of unconventional machining processes is given below:
- Based on the type of energy used
- Mechanical Energy based Unconventional Machining Processes (e.g. Abrasive Jet Machining, Water Jet Machining)
- Electrical Energy based Unconventional Machining Processes (e.g. Electrical Discharge Machining)
- Electrochemical Energy based Unconventional Machining Processes (e.g. Electrochemical Grinding)
- Chemical Energy based Unconventional Machining Processes (e.g. Chemical Machining)
- Thermo-electrical (or Electro-thermal) Energy based Unconventional Machining Processes (e.g. Plasma Arc Machining)
- Based on the source of energy
- Hydraulic Pressure
- Pneumatic Pressure
- Ionised Particles
- Based on the medium of energy transfer
- Pressurized gas
- Ultrasonic waves
- Chemical reagent
- Based on the mechanism of material removal
- Electric Discharge
- Chemical Etching
- Ion Displacement