2. SynopsisSynopsis
• IntroductionIntroduction
• Working principleWorking principle
• Process componentsProcess components
• Working of USMWorking of USM
• Types of transducersTypes of transducers
• ConcentratorsConcentrators
• Nodal point clampingNodal point clamping
• Feed mechanismFeed mechanism
• Process parametersProcess parameters
• AdvantagesAdvantages
• LimitationsLimitations
• ApplicationsApplications
3. Introduction - 1Introduction - 1
• First discovered by American EngineerFirst discovered by American Engineer
Lewis Balamuth in 1950Lewis Balamuth in 1950
• Mechanical type – used to erode holesMechanical type – used to erode holes
and cavitiesand cavities
• Material is removed due to the action ofMaterial is removed due to the action of
abrasive grainsabrasive grains
• For hard (harder than 40 HRc), brittle,For hard (harder than 40 HRc), brittle,
non-metallic materialsnon-metallic materials
• Used for both electrically conductive andUsed for both electrically conductive and
non-conductive work piecesnon-conductive work pieces
4. Introduction - 2Introduction - 2
• Uses a shaped tool, high frequency (>16KHz)Uses a shaped tool, high frequency (>16KHz)
mechanical motion and an abrasive slurrymechanical motion and an abrasive slurry
• Process is non-chemical and non-thermal – soProcess is non-chemical and non-thermal – so
materials are not altered either chemically ormaterials are not altered either chemically or
metallurgicallymetallurgically
• Two methods – UIG and rotary UM (involves theTwo methods – UIG and rotary UM (involves the
ultrasonic vibration of a rotating diamond coreultrasonic vibration of a rotating diamond core
drill or milling tool – similar to the conventionaldrill or milling tool – similar to the conventional
drilling of glass and ceramic with diamond coredrilling of glass and ceramic with diamond core
drills, except that the rotating core drill isdrills, except that the rotating core drill is
vibrated at an ultrasonic frequencyvibrated at an ultrasonic frequency
• UIG –Ultrasonic Impact Grinding,UIG –Ultrasonic Impact Grinding,
7. Working principleWorking principle
• A shaped tool is given a mechanical vibrationA shaped tool is given a mechanical vibration
(oscillation normal to the workpiece). This(oscillation normal to the workpiece). This
vibration causes the abrasive grains in the slurryvibration causes the abrasive grains in the slurry
to hammer against a stationary workpieceto hammer against a stationary workpiece
resulting in material removalresulting in material removal
• Resonance is achieved when the frequency ofResonance is achieved when the frequency of
vibration matches the natural frequency neededvibration matches the natural frequency needed
to generate a standing sonic wave within theto generate a standing sonic wave within the
tool-toolholder assembly – resulting in maximumtool-toolholder assembly – resulting in maximum
vibrational amplitude and maximum materialvibrational amplitude and maximum material
removal efficiencyremoval efficiency
8.
9. Process components - 1Process components - 1
• Four main elements of USMFour main elements of USM
1.1. Transducer – converts the electrical energy toTransducer – converts the electrical energy to
vibratory motion utilizing either thevibratory motion utilizing either the
piezoelectric or magnetostrictive principlepiezoelectric or magnetostrictive principle
2.2. Tool cone and tip – also called asTool cone and tip – also called as
horn/concentrator/Acoustic headhorn/concentrator/Acoustic head
• amplifies the mechanical energy produced byamplifies the mechanical energy produced by
the transducer and imparts it to the workpiecethe transducer and imparts it to the workpiece
– acts as a resonator to amplify the signal– acts as a resonator to amplify the signal
• It should have adequate strength – titanium,It should have adequate strength – titanium,
monel, stainless steel are generally used asmonel, stainless steel are generally used as
tool cone materials–tool cone materials–
10. Process components - 2Process components - 2
• Tool tip is attached to the base of theTool tip is attached to the base of the
cone by means of silver brazing or bycone by means of silver brazing or by
screwsscrews
• Tool geometry governs the shape of theTool geometry governs the shape of the
impression or cavity to be producedimpression or cavity to be produced
• Tool material should be tough andTool material should be tough and
ductile but should not be too soft -ductile but should not be too soft -
generally low carbon steel and stainlessgenerally low carbon steel and stainless
steel are good tool materialssteel are good tool materials
12. Process components - 3Process components - 3
3.3. Abrasive slurryAbrasive slurry
• Large variety available – should be harder thanLarge variety available – should be harder than
the material being machined – Althe material being machined – Al22OO33, SiC and, SiC and
boron carbideboron carbide
• Abrasive suspended in a liquid with about 30-Abrasive suspended in a liquid with about 30-
60% by volume of the abrasive60% by volume of the abrasive
• Liquid serves several functions – medium toLiquid serves several functions – medium to
carry the abrasive to the cutting zone and carrycarry the abrasive to the cutting zone and carry
the spent abrasive and swarf away; also actsthe spent abrasive and swarf away; also acts
as a coolant on the tool faceas a coolant on the tool face
• Water (most commonly used), benzene andWater (most commonly used), benzene and
glycerol are also used as liquidsglycerol are also used as liquids
13. Process components - 4Process components - 4
4.4. WorkpieceWorkpiece
• Brittle materials – however, now thereBrittle materials – however, now there
appears to be no limitation to the rangeappears to be no limitation to the range
of materialsof materials
• No limitation except that material shouldNo limitation except that material should
not dissolve in the slurry media or reactnot dissolve in the slurry media or react
with itwith it
16. Working of USM - 1Working of USM - 1
• Low-frequency electrical energy converted toLow-frequency electrical energy converted to
high-frequency electrical signal and fed to thehigh-frequency electrical signal and fed to the
transducertransducer
• High-frequency mechanical motion is transmittedHigh-frequency mechanical motion is transmitted
to the tool via a mechanical coupler (tool holder)to the tool via a mechanical coupler (tool holder)
• Tool (shaped conversely to the desired hole orTool (shaped conversely to the desired hole or
cavity) positioned near, but not touching, thecavity) positioned near, but not touching, the
surface of the workpiecesurface of the workpiece
• Gap between the vibrating tool and workpieceGap between the vibrating tool and workpiece
flooded with abrasive slurryflooded with abrasive slurry
17. • Material removal occurs when the abrasiveMaterial removal occurs when the abrasive
particles, suspended in the slurry between theparticles, suspended in the slurry between the
tool and workpiece, are struck by thetool and workpiece, are struck by the
downstroke of the vibrating tooldownstroke of the vibrating tool
• Impact from the tool propels the abrasiveImpact from the tool propels the abrasive
particles across the cutting gap causing them toparticles across the cutting gap causing them to
strike the workpiece with a force up to 150,000strike the workpiece with a force up to 150,000
times their weighttimes their weight
• A small crater will be produced at each impactA small crater will be produced at each impact
sitesite
• Each downstroke of the tool can simultaneouslyEach downstroke of the tool can simultaneously
accelerate thousands of abrasive particles – thusaccelerate thousands of abrasive particles – thus
literally millions of chips are removed from theliterally millions of chips are removed from the
workpiece each secondworkpiece each second
Working of USM - 2Working of USM - 2
18. Working of USM - 3Working of USM - 3
• As material is removed, a counterbalancedAs material is removed, a counterbalanced
gravity feed, or servomotor-driven feedgravity feed, or servomotor-driven feed
mechanism, continuously advances the tool intomechanism, continuously advances the tool into
the newly formed hole to maintain a constantthe newly formed hole to maintain a constant
gap between the tool and workpiecegap between the tool and workpiece
19. Types of transducers - 1Types of transducers - 1
1.1. Piezo electric – when an electric current isPiezo electric – when an electric current is
applied to piezo electric materials such asapplied to piezo electric materials such as
quartz or lead zirconate titanate, they increasequartz or lead zirconate titanate, they increase
in size and come to normal size when thein size and come to normal size when the
current is removedcurrent is removed
• Exhibit an extremely high electromechanicalExhibit an extremely high electromechanical
conversion efficiency (up to 96%), whichconversion efficiency (up to 96%), which
eliminates the need for water cooling ofeliminates the need for water cooling of
transducertransducer
• Available with power capabilities up to 900 WAvailable with power capabilities up to 900 W
• Although these transducers are easier toAlthough these transducers are easier to
design, their availability is limiteddesign, their availability is limited
20. Types of transducers - 2Types of transducers - 2
2.2. Magnetostrictive transducerMagnetostrictive transducer
• Ferromagnetic materials when subjected to anFerromagnetic materials when subjected to an
alternating magnetic field exhibit change inalternating magnetic field exhibit change in
dimension. This change in dimension isdimension. This change in dimension is
referred to as magnetostsrictionreferred to as magnetostsriction
• When the material expands on the applicationWhen the material expands on the application
of magnetic field irrespective of its direction isof magnetic field irrespective of its direction is
called as positive magnetostriction andcalled as positive magnetostriction and
similarly when the material contracts, its calledsimilarly when the material contracts, its called
negative magnetostrictionnegative magnetostriction
21. Types of transducers - 3Types of transducers - 3
• Magentostrictive transducers are usuallyMagentostrictive transducers are usually
constructed from a laminated stack of nickelconstructed from a laminated stack of nickel
alloy sheets which, when influenced by a strongalloy sheets which, when influenced by a strong
magnetic field, will change lengthmagnetic field, will change length
• Magentostrictive transducers are rugged butMagentostrictive transducers are rugged but
have electromechanical conversion efficiencieshave electromechanical conversion efficiencies
ranging from only 20 to 35%. The lowerranging from only 20 to 35%. The lower
efficiency results in the need to water-coolefficiency results in the need to water-cool
magnetostrictive devices to remove the wastemagnetostrictive devices to remove the waste
heatheat
• Magnetostrictive transducers are available withMagnetostrictive transducers are available with
power capabilities up to 2400 Wpower capabilities up to 2400 W
• Iron-cobalt, iron-aluminium (alfer) and nickelIron-cobalt, iron-aluminium (alfer) and nickel
exhibit highest magnetostrictionexhibit highest magnetostriction
22. Types of transducers - 4Types of transducers - 4
• The magnitude of the length change that can beThe magnitude of the length change that can be
achieved by both piezoelectric andachieved by both piezoelectric and
magnetostrictive transducers is limited by themagnetostrictive transducers is limited by the
strength of the particular transducer material. Instrength of the particular transducer material. In
both types of transducers, the limit isboth types of transducers, the limit is
approximately 0.025mmapproximately 0.025mm
24. • Provides the link between the transducer and tool.Provides the link between the transducer and tool.
• Some times also called as mechanical amplifier orSome times also called as mechanical amplifier or
resonator and because of its taper shape andresonator and because of its taper shape and
amplification, commonly known as a HORNamplification, commonly known as a HORN
• Main purpose of the concentrator is to increase theMain purpose of the concentrator is to increase the
amplitude to the level needed for cutting – achievedamplitude to the level needed for cutting – achieved
through the principle of resonancethrough the principle of resonance
• Principle of resonance – if a proper length of anyPrinciple of resonance – if a proper length of any
material whose natural frequencymaterial whose natural frequency ωω matches with thematches with the
excitation frequencyexcitation frequency ωωo with amplitude Xo, then ato with amplitude Xo, then at
resonance, i.e. atresonance, i.e. at ωω//ωωo =1 the ratio X/Xo increases, if ito =1 the ratio X/Xo increases, if it
is not critically dampedis not critically damped
• Various types of concentrators are used: exponential,Various types of concentrators are used: exponential,
conical and steppedconical and stepped
Concentrators - 2Concentrators - 2
25. Nodal point clampingNodal point clamping
• Need: In order to make the acoustic system rigidNeed: In order to make the acoustic system rigid
and without enough losses in the mountingand without enough losses in the mounting
• Enables the system to run smoothly without anyEnables the system to run smoothly without any
high frequency vibration in the structuralhigh frequency vibration in the structural
components of the machine ensuring longer andcomponents of the machine ensuring longer and
safer life timesafer life time
• Damping done at the nodal pointsDamping done at the nodal points
• Damping at the nodal point in the transducer isDamping at the nodal point in the transducer is
not permitted because of electrical suppliesnot permitted because of electrical supplies
• Different methods of clamping may be used asDifferent methods of clamping may be used as
per designer’s choiceper designer’s choice
27. Schematic of different nodal point clamping devicesSchematic of different nodal point clamping devices
28. Feed mechanism - 1Feed mechanism - 1
• Functions:Functions:
1.1. Bring the tool very slowly close to theBring the tool very slowly close to the
workpieceworkpiece
2.2. Provide the static load between the tool andProvide the static load between the tool and
workpiece during machining operationworkpiece during machining operation
3.3. Decrease the force at a specified depthDecrease the force at a specified depth
4.4. Overrun a small distance to ensure theOverrun a small distance to ensure the
required hole size at the exitrequired hole size at the exit
5.5. Return the toolReturn the tool
• Can either be given to the acoustic head or theCan either be given to the acoustic head or the
workpiece but in general, the feed motion isworkpiece but in general, the feed motion is
given to the acoustic head so as to permit X-Ygiven to the acoustic head so as to permit X-Y
positioning for the workpiecepositioning for the workpiece
29. Feed mechanism - 2Feed mechanism - 2
• For accurate working it is vital that the feedFor accurate working it is vital that the feed
mechanism be precise and sensitivemechanism be precise and sensitive
• Systems such as those using counter-weightsSystems such as those using counter-weights
attached through a pulley or lever systemattached through a pulley or lever system
although simple, they are insensitive andalthough simple, they are insensitive and
inconvenient to adjustinconvenient to adjust
• Spring-loaded system are compact and quiteSpring-loaded system are compact and quite
sensitivesensitive
• For high rating machines, pneumatic or hydraulicFor high rating machines, pneumatic or hydraulic
systems may be usedsystems may be used
• Some means of reading tool displacement isSome means of reading tool displacement is
often incorporated in the design of machinesoften incorporated in the design of machines
• The guides and other moving parts are designedThe guides and other moving parts are designed
to have low frictionto have low friction
37. Process parametersProcess parameters
• FrequencyFrequency
• AmplitudeAmplitude
• Static loading (feed force)Static loading (feed force)
• Hardness ratio of the tool and theHardness ratio of the tool and the
workpieceworkpiece
• Grain sizeGrain size
• Concentration of abrasive in slurryConcentration of abrasive in slurry
40. Variation of MRR with feed rate / static loadVariation of MRR with feed rate / static load
41. Variation of MRR with hardness ratioVariation of MRR with hardness ratio
42. Variation of MRR with grain sizeVariation of MRR with grain size
43. Variation of MRR with concentrationVariation of MRR with concentration
44. Variation of surface finish with grain sizeVariation of surface finish with grain size
45. Advantages - 1Advantages - 1
• Used for machining hard and brittleUsed for machining hard and brittle
materials to complex shapes with goodmaterials to complex shapes with good
accuracy and reasonable surface finishaccuracy and reasonable surface finish
• Process not affected by the electrical orProcess not affected by the electrical or
chemical characteristics of the workpiecechemical characteristics of the workpiece
materialmaterial
• Holes of any shape can be producedHoles of any shape can be produced
particularly, suited to make holes with aparticularly, suited to make holes with a
curved axiscurved axis
• It has no high speed moving partsIt has no high speed moving parts
• Power consumption is low - about 0.1 wattPower consumption is low - about 0.1 watt
hour/cu.mm for glasshour/cu.mm for glass
46. • Machined surfaces exhibit a good surfaceMachined surfaces exhibit a good surface
integrity and the compressive stress induced inintegrity and the compressive stress induced in
the top layer enhances the fatigue strength ofthe top layer enhances the fatigue strength of
the workpiecethe workpiece
• BurrlessBurrless
• DistortionlessDistortionless
• Single-pass cavity sinkingSingle-pass cavity sinking
• No thermal effectsNo thermal effects
• Possibly the safest of all nontraditional andPossibly the safest of all nontraditional and
conventional processes because it involves noconventional processes because it involves no
high-voltage, burning, cutting, chemicals orhigh-voltage, burning, cutting, chemicals or
dangerous mechanical motionsdangerous mechanical motions
Advantages - 2Advantages - 2
47. SEM picture of machined Si3N4SEM picture of machined Si3N4
48. • Metal removal rates are lowMetal removal rates are low
• Depth of hole produced is limited (2.5 times theDepth of hole produced is limited (2.5 times the
diameter)diameter)
• Tool wear is high and sharp corners cannot beTool wear is high and sharp corners cannot be
producedproduced
• Flat surfaces cannot be produced at the bottom ofFlat surfaces cannot be produced at the bottom of
the cavity because of ineffective slurry distributionthe cavity because of ineffective slurry distribution
• The tendency for holes to break out at the bottomThe tendency for holes to break out at the bottom
owing to static load and amplitude is anotherowing to static load and amplitude is another
limitationlimitation
• Not economical for softer materialsNot economical for softer materials
• Frequent tuning sometimes necessaryFrequent tuning sometimes necessary
LimitationsLimitations
49. • Tungsten and other hard carbides and gemTungsten and other hard carbides and gem
stones such as synthetic ruby (used in watchstones such as synthetic ruby (used in watch
and timer movements) are being successfullyand timer movements) are being successfully
machined by USMmachined by USM
• Coining operations for materials such as glass,Coining operations for materials such as glass,
ceramics etc.,ceramics etc.,
• Threading in glass, ceramics by appropriatelyThreading in glass, ceramics by appropriately
rotating and translating the workpiece/toolrotating and translating the workpiece/tool
• Manufacture of hard alloy wire drawing,Manufacture of hard alloy wire drawing,
punching and blanking diespunching and blanking dies
• Machining semi-conducting materials such asMachining semi-conducting materials such as
germanium and silicongermanium and silicon
• Making components out of porcelain and specialMaking components out of porcelain and special
ceramics – SiC, Si3N4ceramics – SiC, Si3N4
Applications - 1Applications - 1
50. • Round holes and holes of any shape can beRound holes and holes of any shape can be
produced with simple tools – by moving theproduced with simple tools – by moving the
workpiece during cutting. The smallest hole thatworkpiece during cutting. The smallest hole that
can be cut is 0.050mm in diameter, the hole sizecan be cut is 0.050mm in diameter, the hole size
limited by the strength of the tool and thelimited by the strength of the tool and the
clearance required for the flow of abrasive. Theclearance required for the flow of abrasive. The
largest diameter solid tool is 100mm diameter.largest diameter solid tool is 100mm diameter.
Larger holes can be cut by trepanningLarger holes can be cut by trepanning
• USM process offers significant improvements inUSM process offers significant improvements in
the manufacture of graphite electrodes overthe manufacture of graphite electrodes over
conventional techniquesconventional techniques
• Machining of radar components, cutting toolMachining of radar components, cutting tool
inserts, superconductorsinserts, superconductors
Applications - 2Applications - 2
51. Drilling of holes into fragile glass disksDrilling of holes into fragile glass disks
