2. History of Machining
2
In ancient days – hand tools (stones, bones or stick).
Later – hand tools of elementary metals (bronze or iron)
Till 17th Century – tools were either hand operated or driven
mechanically by very elementary methods.
Wagons, ships, furniture, etc. – were produced.
Introduction of water, steam and electricity – power driven
machine tools
Caused a big revolution in 18th and 19th centuries.
1953 – Numerical control machine tools – enhanced the
product productivity and accuracy.
11. Need for Unconventional Machining
11
• Greatly improved thermal, mechanical and chemical properties of
modern materials – Not able to machine through conventional
methods. (Why???)
• Ceramics & Composites – high cost of machining and damage
caused during machining – big hurdles to use these materials.
• In addition to advanced materials, more complex shapes, low
rigidity structures and micro-machined components with tight
tolerances and fine surface finish are often needed.
• To meet these demands, new processes are developed.
• Play a considerable role in aircraft, automobile, tool, die and mold
making industries.
12. Need for Unconventional Machining
12
• Very high hardness and strength of the material. (above 400 HB.)
• The work piece is too flexible or slender to support the cutting or
grinding forces.
• The shape of the part is complex, such as internal and external
profiles, or small diameter holes.
• Surface finish or tolerance better than those obtainable
conventional process.
• Temperature rise or residual stress in the work piece are
undesirable.
18. Mechanical based Unconventional Processes
18
USM – thru mechanical abrasion in a
medium (solid abrasive particles
suspended in the fluid)
WJM – Cutting by a jet of fluid
AWJM – Abrasives in fluid jet.
IJM – Ice particles in fluid jet.
Abrasives or ice – Enhances
cutting action.
26. ELECTRO CHEMICAL ENERGY METHODS
26
CHEMICAL ENERGY METHODS
These methods involve controlled etching of the work
piece material in contact with a chemical solution
27. Chemical & Electrochemical
based Unconventional Processes
27
CHM – uses Chemical
dissolution action in
an etchant.
ECM – uses Electrochemical
dissolution action in
an electrolytic cell.
29. PROCESS SELECTION
29
Based on the following points
1. Physical Parameters
2. Shapes to be machined
3. Process Capability or Machining Characteristics
4. Economic Considerations
42. LIMITATIONS OF Un Conventional Machining
42
1. More expensive process
2. Low Material Removal Rate (MRR)
3. AJM, CHM , PAM and EBM are not commercially
economical Process
43. ADVANTAGES of UCM
43
High Accuracy and surface finish in process
Less Rejected pieces
Increase productivity
Tool material need not be harder than work piece material.
Easy to machine harder and brittle materials
There is no residual stresses in the machined material
