The machining processes come under the category of the subtractive manufacturing processes in which material is removed, in the form of chips, from the workpiece to get the desired shape.
All the available machining processes may be classified under the following heads.
- Conventional/Traditional Machining Process
- Unconventional/Non-Traditional/Advanced Machining Process
The conventional machining process( also known as the Traditional machining process) works on the principle of relative hardness. According to which the tool hardness must be higher than the workpiece hardness or more precisely for optimal machining condition tool hardness must be higher than or equal to 1.35 times of the workpiece hardness and less than or equal to 1.5 times of the workpiece hardness.
1.35 HW ≤ HT ≤ 1.5 HT
HW = Workpiece hardness
HT = Tool hardness
Other conditions which are required to be fulfilled for the conventional machining process are:-
- There must be direct contact of the tool with the workpiece at a certain point or edge.
- There must be some kind of relative motion between tool and workpiece.
All the above three conditions ( higher tool hardness, direct contact, and relative motion) are required to be fulfilled for the functioning of any conventional machining process.
Examples:- Turing, Drilling Milling, etc
Limitations of Conventional Machining process
Any of the conventional machining processes would not work satisfactorily if
- Workpiece hardness is extremely high.
- Components of intricate/complex shapes are required to be machined
Continuous development in the field of material science and the emergence of advanced materials having extraordinary properties ( especially hardness ) has put certain limitations on the use of conventional machining processes.
To overcome the existing limitations of the conventional machining, the unconventional machining came into existence. The Unconventional machining is also known as Non-Traditional machining or Advanced machining.
Classification of Unconventional Machining
The popular classification of unconventional machining processes can be done based on the form of energy utilized for the machining purpose.
Mechanical Processes:- utilized a mechanical form of energy for machining purposes.
- Abrasive Jet Machining (AJM)
- Water Jet Machining (WJM)
- Abrasive Water Jet Machining (AWJM)
- Abrasive flow machining (AFM)
Electrothermal Processes:- utilized electrical form of energy to induced thermal effect for machining
- Electro discharge machining (EDM)
- Laser Beam Machining (LBM)
- Electron Beam Machining (EBM)
Electrochemical processes:- utilize electrical form energy to induced chemical reaction used for machining purposes.
- Electrochemical Machining (ECM)
Chemical Processes:- utilize a chemical form of energy for machining purposes.
- Chemical Machining (CM)
- Photochemical Machining (PCM)
Common features among all the unconventional machining processes are:-
- Almost all the unconventional machining processes are independent of the tool’s hardness it means tool hardness may be lower than the workpiece hardness.
- There is always a gap(known as stand-off distance) between tool and workpiece. This results in decrease tool wear rate (TWR) which further increases tool life.
- Any type of intricate shape can be machined that’s too with close tolerances.
| Features|| Conventional Machining|| Unconventional Machining|
|Tool Hardness||Must be higher than workpiece hardness||Tool Hardness is independent of workpiece hardness|
No standoff distance.
Tool and workpiece are in direct contact
|There is always a standoff distance.|
|Intricate shapes||Can’t machined||Can easily be machined|
Limitations and future scope of Advanced machining
Advanced machining has overcome almost all the limitations of the conventional machining but still suffering from some limitations. Out of those, the main important is the low Material Removal Rate (MRR).
Advanced machining has a much lower MRR as compared to the conventional machining.
Other limitations are as follows:-
- High initial cost
- The high rate of power consumption
Still, Advanced machining is being used, where no option left for machining, especially in the following field:-
- Aerospace industries
- Nuclear power industries
- Defence equipment industries & others
Researchers are working on the different aspects (special efforts are being made to increase the MRR) of the advanced machining to make them the first choice among the different manufacturing industries.
This is all about Conventional & Unconventional machining.
Hope you find it useful.