KNOWLEDGE INSTITUTE OF TECHNOLOGY DEPARTMENT OF

PEMPPrinciple of UltrasonicMachiningDuring one strike, the tool movesdown from its most upper remote position withEMM2512 a starting speed at zero, then it speeds up to finally reach the maximum speed atthe mean position.Then the tool slows down its speed and eventually reaches zero again at thelowest position.When the grit size is close to the mean position, the tool hits the grit with its fullspeed.The smaller the grit size, the lesser the momentum it receives from the tool.Therefore, there is an effective speed zone for the tool and, correspondingly thereis an effective size range for the grits.In the machining process, the tool, at some point, impacts on the largest grits,which are forced into the tool and workpiece.MECH-KIOT

As the tool continues to move downwards, the force acting on these gritsincreases rapidly, therefore some of the grits may be fractured. As the tool moves further down, more grits with smaller sizes come in contactwith the tool, the force acting on each grit becomes less. Eventually, the tool comes to the end of its strike, the number of grits underimpact force from both the tool and the workpiece becomes maximum. Grits with size larger than the minimum gap will penetrate into the tool andwork surface to different extents according to their diameters and the hardnessof both surfaces.MECH-KIOT

Various work samples machined byUSMA plastic sample that has innergrooves that are machined usingUSMA plastic sample that has complexdetails on the surfaceA coin with the grooving done byUSMMECH-KIOT

MechanismAbrasive Slurry The abrasive slurry contains fine abrasive grains. The grains areusually boron carbide, aluminum oxide, or silicon carbide ranging ingrain size from 100 for roughing to 1000 for finishing. It is used to microchip or erode the work piece surface and it is alsoused to carry debris away from the cutting area.MECH-KIOT

MechanismTool holder The shape of the tool holder is cylindrical or conical, or a modified cone whichhelps in magnifying the tool tip vibrations. In order to reduce the fatigue failures, it should be free from nicks, scratchesand tool marks and polished smooth.MECH-KIOT

ToolMechanism Tool material should be tough and ductile. Low carbon steelsand stainless steels give good performance. Tools are usually 25 mm long ; its size is equal to the holesize minus twice the size of abrasives. Mass of tool should be minimum possible so that it does notabsorb the ultrasonic energy.MECH-KIOT

ApplicationsIt is mainly used for DrillingGrinding,ProfilingCoiningPiercing of diesMECH-KIOT

Advantages of USM Machining any materials regardless of their conductivityUSM apply to machining semi-conductor such as silicon, germanium etc.USM is suitable to precise machining brittle material.USM does not produce electric, thermal, chemical abnormal surface.Can drill circular or non-circular holes in very hard materialsLess stress because of its non-thermal characteristicsMECH-KIOT

Disadvantages of USM USM has low material removal rate. Tool wears fast in USM. Machining area and depth is restraint in USM.MECH-KIOT

USM CharacteristicsPrincipleOscillating tool in water-Abrasive slurryAbrasiveB4C, Al2O3, SiC100 to 800 grit sizeFrequency15-30KHzAmplitude0.03 to 0.10mmTool materialSoft tool steelStock removalWC 1.5in (38mm)Glass 100in(254cm)Critical parametersFrequency, amplitude, tool holder shape, grit size, hole depth, slurryMaterial applicationMetals and alloys (particularly hard metals) Non-metallicPart applicationsRound and irregular holesLimitationsLow metal removal rate Tool wearHole depthMECH-KIOT

Water Jet Machining & Abrasive Water Jet Machining Definition In these processes (WJM and AJWM), the mechanical energy ofwater and abrasive phases are used to achieve material removalor machining.MECH-KIOT

Water Jet Machining & Abrasive Water Jet Machining WJM and AWJM can be achieved using different approaches andmethodologies as enumerated below: WJM - Pure WJM - with stabilizer AWJM – entrained – three phase – abrasive, water and air AWJM – suspended – two phase – abrasive and water.o Direct pumpingo Indirect pumpingo Bypass pumpingMECH-KIOT

Water Jet Machining & Abrasive Water Jet Machining - Process Water is pumped at a sufficiently high pressure, 200-400 MPa(2000-4000 bar) using intensifier technology. Water at such pressure is issued through a suitable orifice(generally of 0.2- 0.4 mm dia). Potential energy of water is converted into kinetic energy, yieldinga high velocity jet (1000 m/s).MECH-KIOT

Water Jet Machining In pure WJM, commercially pure water (tap water) is used formachining purpose. However as the high velocity water jet isdischarged from the orifice, the jet tends to entrain atmosphericair and flares out decreasing its cutting ability. Hence, quite often stabilisers (long chain polymers) that hinderthe fragmentation of water jet are added to the water.MECH-KIOT

Abrasive Water Jet Machining In AWJM, abrasive particles like sand (SiO2), glass beads are addedto the water jet to enhance its cutting ability by many folds. AWJ are mainly of two types – entrained and suspended type asmentioned earlier. In entrained type AWJM, the abrasive particles are allowed toentrain in water jet to form abrasive water jet with significantvelocity of 800 m/s.MECH-KIOT

Abrasive Water Jet Machining – Setup Entrained Type LP Booster Hydraulic Drive Additive Mixer Direction Control IntensifierMECH-KIOTnsifier LP Inte HP In Accumulatortensifier

Abrasive Water Jet Machining(entrained) – Cutting Head Diameter of the orifice 0.2 - 0.4mm. The velocity of the water jet isestimated, assuming no losses as vwj (2pw / ρw)1/2 using Bernoulli’s equationwhere, pw is the water pressure and ρwis the density of water. The orifices are typically made ofsapphire.MECH-KIOT

Abrasive Water Jet Machining(entrained) – Mixing Mixing means gradual entrainment of abrasive particles withinthe water jet and finally the abrasive water jet comes out of thefocussing tube or the nozzle. MECH-KIOT

Abrasive Water Jet Machining(entrained) – Mixing Focussing tube is made up of Tungsten Carbide. Usual Dimensions of focussing tube Inner diameter Length : 0.8-1.6: 50-80mm.Tungsten Carbide is used due to its abrasive resistant property.MECH-KIOT

Abrasive Water Jet Machining – Suspended Type In suspension AWJM the abrasive water jet is formed quite differently. There are three different types of suspension AWJ formed by direct, indirect and Bypass pumping method. In suspension AWJM, preformed mixture of water and abrasive particles is pumped to a sufficiently high pressure andstored in pressure vessel.MECH-KIOT

Abrasive Water Jet Machining – Suspended TypeIndirect PumpingBypass PumpingMECH-KIOT

Abrasive Water Jet Machining – Catcher “Catcher” is used to absorb the residual energy of the AWJ and dissipate the same. Other Types: Pocket Type & Line TypeMECH-KIOT

Water Jet &Abrasive Water Jet Machining – Applications Paint removal Cleaning Cutting soft materials Cutting frozen meat Textile, Leather industry Mass Immunization Surgery Peening Cutting Pocket Milling Drilling Turning Nuclear Plant DismantlingMECH-KIOT

Water Jet &Abrasive Water Jet Machining – Materials Steels Non-ferrous alloys Ti alloys, Ni- alloys Polymers Honeycombs Metal Matrix Composite Ceramic Matrix Composite Concrete Stone – Granite Wood Reinforced plastics Metal Polymer Laminates Glass Fibre Metal LaminatesMECH-KIOT

PEMPWater JetMachining Also known as hydrodynamicmachining The water jet acts as a sawand cuts a narrow groove inthe material Pressures range from 60ksi to200ksi (1500- 4000 MN/m2 ) Jet velocity 900m/sMECH-KIOTEMM2512

PEMPWater Jet Machiningc(a) Schematic illustration of water-jet machining.(b) A computer-controlled, water-jet cuttingmachine cutting a granite plate. (c) Example ofvarious nonmetallic parts produced by the waterjet cutting process.MECH-KIOTEMM2512

PEMPEMM2512Water Jet Machining Process capabilities– Can be used on any material up to 1” thick– Cuts can be started at any location without predrilledholes– No heat produced– No flex to the material being cut Suitable for flexible materials– Little wetting of the workpiece– Little to no burr produced– Environmentally safeMECH-KIOT

PEMPEMM2512Pros and Cons Pros:– No work hardening of pieces– Faster than EDM or Laser– Initial cost is less Cons:– Accuracy is poor (0.003 inch)– Nozzle life is short (40 hours)MECH-KIOT

PEMPEMM2512Abrasive Jet Machining Uses high velocity dry air, nitrogen, orcarbon dioxide containing abrasiveparticles Supply pressure is on the order of125psi The abrasive jet velocity can be ashigh as 100 ft/sec Abrasive size is approximately 4002000 micro-inchesMECH-KIOT

PEMPEMM2512Abrasive Jet MachiningSchematic illustration of Abrasive Jet MachiningMECH-KIOT

PEMPAbrasive Water JetMachining Very similar to water jet machining– Water contains abrasive material Silicon carbide Aluminum oxide– Higher cutting speed than that of conventional waterjet machining Up to 25 ft/min (7.5 m/min) for reinforce plastics– Minimum hole diameter thus far is approximately0.12 inches (3 mm)– Maximum hole depth is approximately 1 inch(25mm)MECH-KIOTEMM2512

Surface Roughness and Tolerancetable M.S Ramaiah School of AdvancedStudies - BangaloreMECH-KIOTPEMPEMM251249

UNIT III - ELECTRICAL ENERGY BASED PROCESSESElectric Discharge Machining (EDM)- working Principle- equipment's -Process ParametersSurface Finish and MRR- electrode / Tool – Power and control Circuits-Tool Wear –Dielectric – Flushing – Wire cut EDM – Applications.MECH-KIOT

PEMPEMM2512Electrochemical Machining An electrolyte acts as a current carrier whichwashes metal ions away from the workpiece(anode) before they have a chance to plate on thetool (cathode). The shaped tool is either solid or tubular. Generally made of brass, copper, bronze orstainless steel. The electrolyte is a highly conductive inorganicfluid. The cavity produced is the female mating imageof the tool shapeMECH-KIOT

PEMPEMM2512V CItR grA I EAgrV C(EAt)grV CErAtV: Volume of Metal Removed; C: Specific Removal RateR: Resistance; g: Gap between Electrode and Workr: Resistivity of Electrode; E: Applied VoltageI: Current; t: Time; fr: Feed RateMECH-KIOTf r CIAgrf

PEMPEMM2512Electrochemical Machining Process capabilities– Generally used to machine complex cavities and shapes in highstrength materials. Design considerations– Not suited for producing sharp square corners or flat bottoms.– No irregular cavities.MECH-KIOT

PEMPEMM2512Typical parts made by electrochemical machining. (a) Turbine blade made of a nickel alloy, 360 HB;note the shape of the electrode on the right. (b) Thin slots on a 4340-steel roller-bearing cage. (c)Integral airfoils on a compressor disk.MECH-KIOT

PEMP Pulsed electrochemical machining (PECM)–––––EMM2512Refinement of ECM.The current is pulsed instead of a direct current.Lower electrolyte flow rate.Improves fatigue life.Tolerance obtained 20 to 100 micro-meters.(a)(b)(a) Two total knee replacement systems showing metal implants (top pieces) with an ultrahighmolecular weight polyethylene insert (bottom pieces) (b) Cross-section of the ECM process asapplied to the metal implant.MECH-KIOT57

PEMPEMM2512 Electrochemical grinding (ECG)– Combines ECM with conventional grinding.– Similar to a conventional grinder, except that the wheel is a rotating cathode with abrasiveparticles. The abrasive particles serve as insulators and they remove electrolytic products from theworking area.– Less then 5% of the metal is removed by the abrasive action of the wheel.Schematic illustration of the electrochemical – grinding process. (b) Thin slot produced ona round nickel – alloy tube by this process.MECH-KIOT

PEMPEMM2512 Electrochemical honing– Combines the fine abrasive action of honing withelectrochemical action.– Costs more than conventional honing.– 5 times faster than conventional honing.– The tool lasts up to 10 times longer. Design considerations for ECG– Avoid sharp inside radii.MECH-KIOT

PEMPEMM2512Electric Discharge Machining (EDM) Principle of operation– Based on the erosion of metal by spark discharge Components of operation– Shaped tool Electrode– Workpiece Connected to a DC power supply– Dielectric Nonconductive fluidMECH-KIOT

PEMP(a)(b)(c)(a)Schematic illustration of the electrical-discharge machining process. This is one of the mostwidely used machining processes, particularly for die-sinking operations.(b)Examples of cavities produced by the electrical-discharge machining process, using shapedelectrodes. Two round parts (rear) are the set of dies for extruding the aluminum the aluminumpiece shown in front.(c)A spiral cavity produced by ECM using a slowly rotating electrode, similar to a screw thread.MECH-KIOTEMM2512

Electric Discharge Machining When the potential difference is sufficiently high, thedielectric breaks down and a transient spark dischargesthrough the fluid, removing a very small amount ofmaterial from the workpiece Capacitor discharge– 200-500 kHz This process can be used on any electrically conductivematerialMECH-KIOT

Electric Discharge MachiningExampleA certain alloy whose melting point 1100 C is to be machined in an EDMoperation. If discharged current 25 amps, what is the expected metal removal rate?Use Equation (MRR KI/T 1.23), themanticipated metal removalrate is MRR 664 (25)/(11001.23) 3.01 mm3/sMRR KIT1.23MECH-KIOT

Electric Discharge Machining Movement in the X&Y axis iscontrolled by CNC systems Overcut (in the Z axis) is the gapbetween the electrode and theworkpiece– Controlled by servomechanisms– Critical to maintain a constant gapMECH-KIOT

Electric Discharge Machining Dielectric fluids– Act as a dielectric– Provide a cooling medium– Provide a flushing medium Common fluids––––Mineral oilsDistilled/Deionized waterKeroseneOther clear low viscosity fluids areavailable which are easier to clean butmore expensiveMECH-KIOT

Electric Discharge Machining Electrodes––––GraphiteBrassCopper-tungsten alloysFormed by casting, powdermetallurgy, or CNC machining– On right, human hair with a0.0012 inch hole drilled throughMECH-KIOT

Electric Discharge Machining Electrode wear– Important factor in maintaining the gap between the electrodeand the workpiece– Wear ratio is defined as the amount of material removed to thevolume of electrode wear 3:1 to 100:1 is typical– No-wear EDM is defined as the EDM process with reversed polarityusing copper electrodesMECH-KIOT

Electric Discharge Machining Process capabilities– Used in the forming of diesfor forging, extrusion, diecasting, and injectionmolding– Typically intricate shapesMECH-KIOT

Electric Discharge Machining Material removal rates affect finish quality– High removal rates produce very rough surface finish with poor surfaceintegrity– Finishing cuts are often made at low removal rates so surface finish canbe improved Design considerations– Design so that electrodes can be simple/economical to produce– Deep slots and narrow openings should be avoided– Conventional techniques should be used to remove the bulk of materialMECH-KIOT

PEMPSchematic illustration of producing an inner cavity by EDM, using a specially designedelectrode with a hinged tip, which is slowly opened and rotated to produce the large cavity.MECH-KIOT

Wire EDM Similar to contour cutting with a bandsaw Typically used to cut thicker material– Up to 12” thick– Also used to make punches, tools and dies from hard materialsSchematic illustration of thewire EDM process.As much as 50 hours ofmachining can be performedwith one reel of wire, which isthen discarded.MECH-KIOT

Wire EDM Wire––––––Usually made of brass, copper, or tungstenRange in diameter from 0.012 – 0.008 inchesTypically used at 60% of tensile strengthUsed once since it is relatively inexpensiveTravels at a constant velocity ranging from 6-360 in/minCutting speed is measured in cross sectional area per unit time (varies withmaterial) 18,000 mm 2/hour 28 in 2/hourMECH-KIOT

Wire EDM Multiaxis EDM– Computer controls for controllingthe cutting path of the wire and itsangle with respect to the workpieceplane– Multiheads for cutting multipleparts– Features to prevent and correctwire breakage– Programming to optimize theoperationMECH-KIOT

Electric Discharge Grinding Similar to the standard grinder Grinding wheel is made of graphite or brass and contains no abrasives Material is removed by spark discharge between the workpiece and rotatingwheel Typically used to sharpen carbide tools and dies Can also be used on fragile parts such as surgical needles, thin-wall tubes,and honeycomb structures Process can be combined with electrochemical discharge grinding Material removal rate is similar to that of EDM– MRR KI where K is the workpiece material factor in mm 3/A- minMECH-KIOT

Laser BeamMachining The source of the energy is the laser– Light Amplification by Stimulated Emission of Radiation The focus of optical energy on the surface of the workpiecemelts and evaporates portions of the workpiece in a controlledmanner– Works on both metallic and non-metallic materials Important considerations include the reflectivity and thermalconductivity of the material The lower these quantities the more efficient the processMECH-KIOT

(a) Schematic illustration of the laser-beam machining process. (b) and(c) Examples of holes produced in nonmetallic parts by LBM.MECH-KIOT

Laser BeamMachining Lasers may be used in conjunction with a gas such as oxygen, nitrogen, orar

Mechanical Engineering Design Manufacturing Primary Manufacturing Secondary Manufacturing Thermal . INTRODUCTION What is Manufacturing? . The Primary manufacturing process provides basic shape and size to the material as per designer’s requirement. For example: Casting, forming, powder me