Unconventional Machining Processes

 

• In conventional machining process the ability of cutting tool is utilized to stress the materials beyond the yield point to start the material removal process.
• In conventional machining cutting tool must be harder than the work piece material.
• The advent of hard materials for aerospace applications have made the machining process by conventional methods very difficult and time consuming. This is due to Material Removal Rate (MRR) decreases with increased hardness of the work material.

Hence the machining process which utilizes other machining methods are termed as unconventional machining or Non-traditional machining or advanced machining processes or modern machining processes.

The main reasons for choosing non-traditional machining processes are:

1. To machine high steel alloys.
2. To generate desired complex surfaces and
3. To achieve high accuracy and surface finish.

Classification:

Classification of unconventional machining processes was mainly on the basis of the nature of energy employed in machining process. They are
1. Chemical Processes

1. Chemical Machining (CM)
2. Photochemical Machining (PCM)

2. Electrochemical Processes

1. Electro-Chemical Machining (ECM)
2. Electro Chemical Grinding (ECG)

3. Electro-Thermal Processes

1. Electrical Discharge Machining (EDM)
2. Electron Beam machining (EBM)
3. Plasma Arc Machining (PAM)
4. Laser Beam Machining (LBM)

4. Mechanical Processes

1. Ultrasonic Machining (USM)
2. Abrasive Jet Machining (AJM)
3. Water Jet Machining (WJM)
4. Abrasive Water jet Machining (AWJM)

General Characteristics of Advanced Machining Processes:

 

S.No	Process	Characteristics	Process parameters and MRR or cutting speed
1	Chemical machining (CM)	Shallow removal on large flat or curved surfaces; blanking of thin sheets; low tooling and equipment cost; suitable for low-production runs.	0.0025-0.1 mm/min.
2	Electrochemical machining (ECM)	Complex shapes with deep cavities; highest rate of material removal among other nontraditional processes; expensive tooling and equipment; high power consumption; medium-to-high production quantity.	V: 5-25 DC; A: 1.5-8 A/mm2; 2.5-12 mm/min, depending on current density.
3	Electrochemical grinding (ECG)	Cutting off and sharpening hard materials, such as tungsten-carbide tools; also used as honing process; higher removal rate than grinding.	A: 1-3 A/mm2; typically 25 mm3/s per 1000A.
4	Electrical-discharge machining (EDM)	Shaping and cutting complex parts made of hard materials; some surface damage may result; also used as a grinding and cutting process; expensive tooling and equipment.	V: 50-380; A: 0.1-500; typically 300 mm3/min.
5	Wire electric discharge machining	Contour cutting of flat or curved surfaces; expensive equipment.	Varies with material and thickness.
6	Laser-beam machining (LBM)	Cutting and hole making on thin materials; very small holes and slots; heat-affected zone; requires a vacuum; expensive equipment.	0.50-7.5 mm/min.
7	Electro-beam machining (EBM)	Cutting and hole making on thin materials; very small holes and slots; heat-affected zone; requires a vacuum; expensive equipment.	1-2 mm3/min.
8	Water-jet machining(WJM)	Cutting all types of nonmetallic materials; suitable for contour cutting of flexible materials; no thermal damage; noisy.	Varies considerably with material.
9	Abrasive water-jet machining (AWJM)	Single-layer or multi-layer cutting of metallic and nonmetallic materials.	Up to 7.5 m/min.
10	Abrasive-jet machining (AJM)	Cutting, slotting, deburring, etching and cleaning of metallic and nonmetallic materials; tends to round off sharp edges; can be hazardous.	Varies considerably with material.