2. Title of slide
Lesson Objectives
In this chapter we shall discuss the following:
Learning Activities
1. Look up
Keywords
2. View Slides;
3. Read Notes,
4. Listen to
lecture
Keywords:
3. Nontraditional Manufacturing
Processes
• Necessity to use new materials, demanding functional
requirements and miniaturization have led to evolution of
modern manufacturing processes.
• Nontraditional machining refers to a group of processes
which removes excess material without a sharp cutting tool
by various nontraditional means such as mechanical,
thermal, electrical or chemical energy (or combinations) and
developed since World War II (1940’s).
These processes do not use a sharp cutting tool in the
conventional sense.
4. Why We Need NTM Processes?
Nontraditional processes have been developed to meet new
and unusual machining requirements of Aerospace and
Electronics industries which are either not possible with
conventional machining or extremely costly, including the
need:
1. To machine new (harder, stronger & tougher) materials.
2. The need for unusual and/or complex geometries.
3. To achieve stringent surface (finish & texture)
requirements
5. Classification of Non
Traditional Manufacturing
Based on the principle form of energy nontraditional manufacturing
processes can be classified into following groups:
1. Mechanical - Erosion of work material by a high velocity stream of
abrasives and/or fluid
Example: USM, AWJM, WJM, AFM
2. Electrical - Electrochemical energy removes material
Example: ECM, ECD, ECG.
3. Thermal - Thermal energy applied to small portion of work surface,
removes material by fusion and/or vaporization
Example: EDM, WEDM, EBM, LBM, PAM, IBM
4. Chemical - chemical etchants selectively (using a mask) remove a
portion of a workpiece.
Example: Chemical milling, Blanking, Engraving and
Photochemical machining.
6. Principal of NTM Processes
Mechanical Energy Methods
Chemical Methods
Thermal Energy Methods
9. Application Considerations
Workpart Geometry Features
• Very small holes - (below 0.005 in. in diameter) use LBM
• Holes with large depth/diameter ratios - (d/D > 20) use ECM and EDM
• Nonround holes - use EDM and ECM
• Narrow slots that are not straight - use EBM, LBM, wire EDM, WJC and AWJC
11. – Nontraditional processes are generally used when conventional
methods are not practical or economical
Performance of Nontraditional
Processes
12.
13. Parts Made by Advanced
Machining Processes
Figure :Examples of parts produced by advanced machining processes.
(a) Samples of parts produced from water jet cutting.
(b) Turbine blade, produced by plunge EDM, in a fixture to produce the holes by EDM.
(a) (b)
14. Material removal is due to abrading action of
the grit-loaded flowing slurry.
Small amplitudes (10–20 μm) and high
frequency (20–40 kHz) of vibrations are given to
tool.
The hard abrasive particles in the slurry are
accelerated towards the workpiece surface by
the oscillating action of the tool through
repeated abrasions, the tool further machines a
cavity of cross section identical to its own.
The workpiece shape and dimensional accuracy
is directly dependent on the geometry of the tool.
The material removal takes place is the form of
fine grains by shear deformation.
Different mechanisms of material removal
include brittle fracture, impact action of
abrasives, cavitation and chemical reaction due
to the slurry.
Ultrasonic Machining (USM)
15. Features of Ultrasonic Machining
• Material removal mechanism: Mechanical - Erosion of work material
• Tool vibrate at low amplitude (0.05-0.125 mm) & high frequency (20kHz).
• Vibration amplitude equals to grit size, also determines resulting surface
finish.
• Tool oscillation: Perpendicular to work surface
• Tool: Formed Stainless steels tool , fed slowly into work.
• Abrasives – BN, BC, Al2O3, SiC & Diamond
• Abrasive grit size: 100 (rough) to 2000(fine)
• Abrasives: 20-60 % by volume in water
• Time of contact: 10-100μs.
• Work materials – Hard, brittle materials e.g. ceramics, glass and carbides
and stainless steel and titanium
• Shapes include non-round holes (i.e. along a curved axis) and Coining
operations (the pattern on tool is imparted to a flat work surface).
• Due to the abrasive action of particles, gradually wear of the tool occurs,
16. USM:
Material Removal Mechanism
• The impact of abrasives is mainly responsible for the
removal of material, in the form of small wear particles
which are carried away by the abrasive slurry.
• Mechanisms responsible for the material removal are:
1. Mechanical abrasion: Occurs due to hammering effect
of abrasive particles on work piece through the tool.
2. Impact: Feely moving particles impact with a certain
velocity on the work piece resulting in micro chipping.
3. Erosion: Due to cavitation effect of abrasive slurry,
erosion of the workpiece occurs.
4. Chemical: Due to fluid employed, chemical effect can
come into consideration.
17. USM:
Advantages, Disadvantages
Advantages:
1. Brittle and hard materials can be
machined easily.
2. No direct contact of the tool and
workpiece.
3. No physical, chemical or thermal
changes.
4. W-piece is unstressed, undistorted
and free from heat effects.
5. Process is free from burrs and
distortions
6. Machine any materials, irrespective
of electrical conductivity
7. Process offers good surface finish
and structural integrity
Disadvantages /
Limitations:
1. Can not machine soft
& ductile materials
2. consumes higher
power and has lower
MRR.
3. Fast tool wear.
4. Can not produce
deep holes, sharp
corners and blind
holes.
18. USM:
Applications
1. USM is used in machining of hard and brittle metallic
alloys, semiconductors, glass, carbides and advanced
ceramics for applications in auto-engine components.
2. In machining of small dies for wire drawing, punching or
blanking.
3. Drilling small holes in helicopter power transmission
shafts and gears.
4. For drilling holes in borosilicate glass for the sensors
used in electronic industries
19. Water Jet Machining (Cutting)
Fig. : Schematic illustration of the WJM process
• The term water jet means a high pressure water stream.
• WJM uses a water jet cutter, which acts as a tool in the form of a water-
saw, for cleaning and cutting applications.
• This water-jet at a high velocity and pressure is able to slice materials
and some metals using some abrasive particles mixed in it.
• This process resembles natural water erosion phenomenon of soil and
rocks.
• There is no heat-affected zones and process is environmental friendly.
• Used for cutting, carving and shaping applications in mining to
aerospace industries.
Fig. : A CNC WJM cutting a granite plate
20. Abrasive Water Jet Machining
(AWJM)
Fig. : Schematic illustration of the WJM process
• In AWJM processes, which is an extension of WJC,
abrasive particles such as Al2O3, SiC are added to water,
which further increases the MRR.
• AWJM is used for machining hard, brittle ceramics and
glass and soft metals such as rubber and foam.
Fig. : A CNC WJM cutting a granite plate
21. 1. Water is forced at high pressure, 180-420 MPa through a small orifice
in a nozzle (0.2- 0.4 mm diameter), causing high acceleration of water.
2. Conversion of water’s potential energy into kinetic energy yields a
very high jet velocity of around 1000 m/s.
3. The impact and high pressure of the accelerating water particles
develop fine cracks on the material.
4. These fine cracks propagate further under the impact of high pressure
and abrasives to the extent that the material gets cut.
5. The extended version of WJM is AWJM. In AWJM process the particles
of abrasives such as sand (SiO2) or beads of glass are added in the
water jet in-order to enhance its ability of cutting by many folds.
Principle of WJM & AWJM
22. WJM :Advantages
Advantages of WJM and AWJM
No harmful fume, dust or other particles.
No need of secondary or finishing operations.
In AWJM process, Low cutting forces.
Limited tooling requirements and no tool re-sharpening
cost.
Typical surface finish achieved is in range of 125-250 um Ra.
Reduced material wastages due to smaller kerf sizes.
There is no heat affected zone and thermal distortion.
It can cut metals, plastics, stones, composites, glass, ceramics
& rubber.
23. WJM: Disadvantages
Disadvantages of WJM and AWJM
Cannot cut materials which degrades quickly with
moisture.
Higher cutting speeds (used for rough cutting)degrade
the surface finish.
Greater chance of cracking in brittle materials.
With WJM process, thick parts cannot be cut accurately
and economically.
The equipment used are quite expensive.
There are safety concerns due to noise and high
pressures.
24. WJM: Applications
Fig. : Examples of various nonmetallic parts produced WJM process.
Applications of WJM and AWJM
• Diverse applications in mining to aerospace industries.
• Primarily used for cutting, carving and shaping applications.
• WJC is used in cutting low strength materials like plastics,
wood and aluminum.
• AWJM process can be used for stronger materials like tool
steels.
25. • In AJM material removal occurs on account of impact of high velocity air / gas
stream of abrasive particles on the workpiece (WP).
• Abrasives are propelled at a high velocity by gas to erode material from WP.
• As an outcome of impact of the abrasive particles on WP, tiny brittle fractures
occur at the surface of WP and carrier gas carries away the fractured fragments.
• AJM is also called as abrasive blasting process. It is also known by several other
names such as abrasive micro-blasting, pencil blasting & micro-abrasive blasting.
• Effective method for hard and brittle materials such as glass, and tungsten.
• AJM is used for cutting intricate shapes or forms of specific edges.
• AJM is inherently free from chatter, vibration and heat problems because the tool
never touches the substrate.
Abrasive Jet Machining (AJM)
26. Principle of AJM
High velocity abrasive jet (150-300 m/s)
The principle of AJM process is explained below:
1. Abrasive particles of size between 10µm to 50 µm are accelerated in a gas stream
(commonly air at high atmospheric pressures).
2. The smaller abrasive particles are useful for finishing and bigger are used for
cutting operations.
3. The abrasive particles are directed through the nozzle, towards the workpiece
surface where-ever cutting or finishing is to be done. The distance between the
tip of the nozzle and the work surface is normally within 1 mm.
4. As the abrasive particles impact the surface of the workpiece, it causes a small
fracture at the surface of the workpiece. The material erosion occurs by the
chipping action.
5. The erosion of material by chipping action is convenient in those materials that
are hard and brittle.
6. As the particles impact the surface of workpiece, it causes a small fracture and
wear, which is carried away by the gas along with the abrasive particles.
7. The abrasive particles once used, cannot be re-used as its shape changes partially
and the workpiece material is also clogged with the abrasive particles during
impingement and subsequent flushing by the carrier gas.
27. Advantages of AJM:
o For machining fragile, brittle and heat sensitive materials
o Localized forces and less heat generation than the
conventional machining processes.
o No tool-workpiece contact, hence lesser force and heat
generation.
o There is no damage to the workpiece surface.
o High flexibility.
o Low power consumption.
AJM: Advantages
28. Disadvantages of AJM:
The process is limited to brittle and hard materials
High nozzle wear rate
Low MRR
The process results in poor machining accuracy
The process can cause environmental pollution
AJM: Disadvantages
29. Metal working: De-burring of some critical zones in the
machined parts.
Drilling and cutting of the thin and hardened metal sections.
Removing the machining marks, flaws, chrome and anodizing
marks.
Glass: Cutting of the optical fibers without altering its
wavelength
Cutting of extremely thin sections of glass and intricate curved
patterns
Cutting, drilling and frosting precision optical lenses.
Cleaning and dressing the grinding wheels used for glass.
Grinding: Cleaning residues from diamond wheels, dressing
wheels of any shape & size.
AJM Applications
30. Case Study: Stent Manufacture
Fig: The Guidant MULTI-LINK TETRATM
coronary stent system.
Fig: Detail of the 3-3-3 MULTI-LINK
TETRATM pattern.
Fig: Evolution of the stent surface. (a) MULTI-LINK TETRATM after lasing. Note that a metal
slug is still attached. (b) After removal of slag. (c) After electropolishing.
