NON Conventional machining

1. ULTRASONIC MACHINING(USM)
BISHAL DAS(BT14ME001)
DEPARTMENT OF MECHANICAL ENGINEERING
NATIONAL INSTITUTE OF TECHNOLOGY MIZORAM
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2. CONTENTS
WORKING
SCHEMATIC DIAGRAM
MECHANISMS
COMPONENTS
ADVANTAGES
DISADVANTAGES
APPLICATIONS
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3. WORKING
It is a mechanical material removal processes, used to erode material in the form of fine holes
and cavities in hard or brittle work pieces.
It uses firm tools, vibrations of high frequency and a suitable abrasive slurry-mix
The USM process is suitable for machining brittle materials such as:glass,ceramics and
semiconductors ,for increasingly complex operations to provide intricate shapes and work piece
profiles.
The cutting is actually performed by the abrasive particles which are suspended in the
slurry(fluid)
USM accomplishes the material removal through the abrading action of the grit-loaded slurry
which is kept circulated between the tool and the work piece
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4. Schematic Diagram
ULTRASONIC MATERIAL REMOVAL PROCESS ULTRASONIC MACHINE
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5. WORKING
Small amplitudes and high frequency of vibration are given to the tool, typically in the range of (10-
20)µm at 20 -40 kHz.
The hard abrasive particles in the slurry are accelerated towards work piece surface by the
oscillating action of the tool through repeated impacts.
The work piece shape and dimensional accuracy is directly dependent on the geometry of the tool.
In this process, high frequency electrical energy is converted into mechanical vibration through a
transducer.
The high frequency vibrations are transmitted to the abrasive particles in the slurry via an energy
focusing device or horn/tool assembly
A re-circulating pump forces abrasive ,suspended in a liquid medium, between the vibrating tool
face and the work piece
The tool shaped like the cavity to be produced, oscillates at amplitude of about 0.013 to 0.062 mm
at 19 to 40 kHz(cycles per second)
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6. Mechanism of Material Removal
Although the USM process is commercially used since many decades the exact details of
mechanism leading to the removal of fine materials is yet to be understood well.
The main mechanism responsible for the material removal in USM are :
1. MECHANICAL ABRASION: This occurs due to the hammering effect of the abrasive particles
on work piece through the tool.
2. IMPACT: The freely moving particles impact with a certain velocity on the work piece
resulting in micro chipping.
3. EROSION: Due to cavitation's effect of the abrasive slurry, erosion of the work surface occurs.
4. CHEMICAL: Due to the fluid employed chemical effect can come into consideration.
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7. ULTRASONIC MACHINE
The basic ultrasonic equipment consists of the following elements:
1. A generator for high frequency oscillations(Ultrasonic generator): generator transmits
electrical power to the transducer which creates energy impulses in the ultrasonic range i.e.
18-20kHz
2. An acoustic head consisting of transducer and trunk(shank) and
3. Tool and abrasive slurry elements
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8. The Acoustic
Head
This is the HEART of the whole equipment and
consists of two parts :
1. The transducer which converts the high
frequency output of the generator into
linear vibrations and
2. The trunk which mechanically amplifies the
linear vibrations
3. The shape of the tool holder is cylindrical or
conical, or a modified cone which helps in
magnifying the tool tip vibrations.
4. Its function is to increase the tool vibration
amplitude and to match the vibrator to the
acoustic load. Therefore it must be
constructed of a material with good acoustic
properties and be highly resistant to fatigue
cracking.
5. Monel and titanium have good acoustic
properties and are often used together with
stainless steel, which is cheaper.
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9. The tool
The tool is designed to provide the maximum amplitude of vibration at the free end
The selection of the tool material is very important as the tool tip is subjected to vibration and it
must not fail due to wear.
The shape of the tool, mechanical properties of the material used in tool making are some of the
other parameters that may effect the USM process performance significantly
Tool material should be tough and ductile. Low carbon steels and stainless steels give good
performance.
Tools are usually 25 mm long ; its size is equal to the hole size minus twice the size of abrasives.
Mass of tool should be minimum possible so that it does not absorb the ultrasonic energy.
It is important to realize that finishing or polishing operations on the tools are sometimes necessary
because their surface finish will be reproduced in the work piece.
Tool and tool holder are often attached by silver brazing.
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10. Abrasives
 common types of abrasive
- boron carbide (B4C) good in general, but expensive
- silicon carbide (SiC) glass, germanium, ceramics
- corundum (Al2O3)
- diamond (used for rubies , etc.)
- boron silicon-carbide (10% more abrasive than B4C)
 liquid
- water most common
- benzene
- glycerol
- oils
- high viscosity decreases MMR
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11. ADVANTAGES
Machining any material regardless of their thermal conductivity
USM is suitable for precise machining of brittle materials
It does not produce any thermal, chemical or any abnormal surfaces
Can drill circular or non-circular holes in very hard materials
Less stress-concentration because of its non-thermal characteristics
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12. DISADVANTAGES/LIMITATION OF USM
Soft materials like lead and plastics are not suitable for machining by the USM process, since
they tend to absorb the abrasive particles rather than chip under their impact.
The USM process consumes higher power and has lower material removal rates(3-15mm3/min)
compared to traditional fabrication processes.
The holes produced in USM have a tendency to break out at the bottom owing to the static
load and high amplitudes.
While producing deeper holes through USM method, there is ineffective slurry circulation
leading to presence of a fewer active grains under the tool face.Due to this, the bottom surfaces
of blind holes tend to become slightly concave.
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13. APPLICATIONS
USM process is used in machining hard and brittle metallic alloys, semiconductors
,glass,ceramics,carbides,etc
In machining of advanced ceramics for applications in auto-engines components
In machining, wire drawing, punching or blanking of small dies
Drilling,grinding,profiling,coining ,piercing of dies
 welding operations on all materials which can be treated suitably by abrasives.
Used for machining round, square, irregular shaped holes and surface impressions.
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14. Various work
samples machined
by USM
1- The first picture on the left is a
plastic sample that has inner grooves
that are machined using USM.
2- The Second picture (in the middle
is a plastic sample that has complex
details on the surface
3- The third picture is a coin with the
grooving done by USM
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15. Thank you
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