Factors affecting tool life in machining processes

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Factors affecting tool life in machining processes

  1. 1. Factors Affecting Tool Life In MachiningProcesses
  2. 2. Factors Affecting Tool Life In Machining ProcessesWhat are these??
  3. 3. Factors Affecting Tool LifeIn Machining ProcessesME 572Analysis of Manufacturing ProcessesMohammad AlJuhani
  4. 4. Factors Affecting Tool Life In Machining ProcessesIntroductionTool Life and MachinabilityTool DamageCauses of tool damageFactors Affecting Tool Life in Machining Processes
  5. 5. Factors Affecting Tool Life In Machining Processes• Cutting tool life is important consideration in metal cuttingprocesses.• In machining operations, cutting conditions such as tool angles,cutting speeds and feed rates are usually selected to give aneconomical tool life.• Conditions giving a short tool life are uneconomical becausetool grinding and tool replacement costs are high.• Factors affecting tool life should be carefully monitored tominimize their consequences.
  6. 6. Factors Affecting Tool Life In Machining Processes• A tool that doesn’t perform the desired function can be declared asfailed, or reached the end of its useful life.• At this point of time, the tool is not necessarily unable to cut theworkpiece but is merely unsatisfactory (may not give the desiredsurface finish or dimensional tolerances) for the purpose required• The tool life is defined as the length of cutting time that the toolcan be used.Tool Life and Machinability
  7. 7. Factors Affecting Tool Life In Machining Processes• Tool damage can be classified into two groups, wear and fracture by means of its scaleand how it progresses.• Wear is loss of material on an asperity or micro-contact, or smaller scale, down tomolecular or atomic removal mechanisms. It usually progresses continuously.• There are two main types of tool wear• Flank wear• Crater wear• Fracture, on the other hand, is damage at a larger scale than wear and it occurssuddenly.Tool Damage
  8. 8. Factors Affecting Tool Life In Machining ProcessesTool damage. Flank wear vs. cutting time
  9. 9. Factors Affecting Tool Life In Machining ProcessesMechanical DamageThermal DamageAdhesionCauses of tool damage
  10. 10. Factors Affecting Tool Life In Machining ProcessesMechanical DamageMechanicalDamageFractureChippingAbrasion FatigueIt is independent of temperature.Causes of tool damage
  11. 11. Factors Affecting Tool Life In Machining ProcessesCauses of tool damageMechanical Damage
  12. 12. Factors Affecting Tool Life In Machining ProcessesThermalDamagePlasticdeformationDiffusionChemicalreactionIt increases drastically with increasingtemperatureCauses of tool damage
  13. 13. Factors Affecting Tool Life In Machining ProcessesCauses of tool damage
  14. 14. Factors Affecting Tool Life In Machining ProcessesCauses of tool damage
  15. 15. Factors Affecting Tool Life In Machining ProcessesOccurs when work or chip material welds tothe tool surface.Adhesion DamageCauses of tool damage
  16. 16. Factors Affecting Tool Life In Machining ProcessesCauses of tool damage
  17. 17. Factors Affecting Tool Life In Machining ProcessesFactorsAffectingTool LifeCutting ToolGeometryCutting ToolMaterialCutting ToolCharacteristicsCuttingConditionsWorkpieceMaterial.Cutting Fluid
  18. 18. Geometry ofcutting toolvaries withType ofoperation beingperformed,Surface finishrequirements.Power andspeed ofmachineWorkpiecematerial,Factors Affecting Tool Life In Machining ProcessesCutting ToolGeometry
  19. 19. Cuttingtoolgeometryis directlyaffectsMachinedsurfacequality.Productivityofmachining.Chipcontrol.Magnitude anddirection of thecutting forcesTool life.Distribution ofthe thermalenergyTemperaturedistribution inthe cuttingwedgeFactors Affecting Tool Life In Machining ProcessesCutting ToolGeometry
  20. 20. Factors Affecting Tool Life In Machining ProcessesCutting ToolGeometry
  21. 21. Factors Affecting Tool Life In Machining ProcessesRake angleRake angles are three types, positive, zero and negative.For ductile materials, the rake inclination is a positive angleSince their shearing is low.For brittle materials, the rake inclination is a negative angle.The advantages of increasing rake angle• Reduces the horsepower consumption.• The cutting force and tool-chip contact temperature change inapproximately the same way.The disadvantages of increasing rake angle• The strength of the cutting wedge decreases when the rake angleincreases.• The region of the maximum contact temperature at the tool-chipinterface shifts toward the cutting edge.Cutting ToolGeometry
  22. 22. Factors Affecting Tool Life In Machining ProcessesFlank angleThe flank angle affects the performance of the cutting toolmainly by decreasing the rubbing between the toolsurface and workpiece surface.With increasing the flank angle the following advantagesare obtained:• Cutting edge radius decreases which leads to decrease inthe frictional and deformation components of the flankforce.• The strength of the region adjacent to the cutting edgedecreases.• Heat dissipates through the tool decreases.Cutting ToolGeometry
  23. 23. Factors Affecting Tool Life In Machining ProcessesNose RadiusNose radius is very critical part of the cutting edge.If the radius is made of sharp angle, the produced finished surface willbe rough and tool life will be short.A large nose radius benefits• Better surface finish.• Faster feed rate.• Stronger tool.• Allow faster cutting speedHowever, large radii have negative sequences such as tool chatter.Cutting ToolGeometry
  24. 24. Factors Affecting Tool Life In Machining ProcessesCutting ToolMaterialFactorsaffectingselectioncuttingtoolmaterialThe cutting operationinvolvedWorkpiece materialProductionrequirementsSurface finish andaccuracy requirements.Machine to be used
  25. 25. Factors Affecting Tool Life In Machining ProcessesCutting ToolMaterialMajor qualities requiredin a cutting toolResistance to heat(hot hardness)Resistance tomechanical impactthermal shock.Resistance to wear(hardness)Resistance to fracture(toughness)Chemical stability to theworkpiece material
  26. 26. Factors Affecting Tool Life In Machining ProcessesCutting ToolMaterial
  27. 27. Factors Affecting Tool Life In Machining ProcessesToday, 50% of HSS, 85% of carbide and 40% of super-hard toolsused in industry are coatedCutting ToolMaterialCuttingToolCoatingImprovewearresistanceReducethermalconductivity.Reducefrictionalcontact.
  28. 28. Factors Affecting Tool Life In Machining ProcessesCutting ToolMaterialUncoated cutting tool Coated cutting tool
  29. 29. Factors Affecting Tool Life In MachiningProcessesCuttingToolCharacteristicsTostandagainsthighstressPressure resistance.Bending strength.Edge strength.Inner bonding strength.High temperature strength.Small propensity to diffusion andadhesion (Chemically stable).Abrasion resistance.Reproducible wear behavior.Cutting ToolCharacteristics
  30. 30. Factors Affecting Tool Life In Machining ProcessesDepth of cutFeed rateCutting SpeedCuttingConditions
  31. 31. Factors Affecting Tool Life In Machining ProcessesCuttingConditionsDepth of cutFeed rateCutting Speed
  32. 32. Factors Affecting Tool Life In Machining ProcessesCuttingConditionsDepth of cutFeed rateCutting Speed
  33. 33. Factors Affecting Tool Life In Machining ProcessesDepth of cutFeed rateCutting SpeedCuttingConditions
  34. 34. Factors Affecting Tool Life In Machining ProcessesCuttingConditionsDepth of cutFeed rateCutting Speed
  35. 35. Factors Affecting Tool Life In Machining ProcessesDepth of cut has least effect upon tool life, so the heaviest (10 times thefeed rate) possible depth of cut should always be used.Depth of cut is limited by• Amount of metal to be machined from the workpiece,• Power available on machine tool,• Rigidity of the work piece and cutting tool• Rigidity of the setup.• Workpiece configuration• Insert size & thicknessCuttingConditionsDepth of cutFeed rateCutting Speed
  36. 36. Factors Affecting Tool Life In Machining ProcessesCuttingConditionsDepth of cutFeed rateCutting Speed
  37. 37. Factors Affecting Tool Life In Machining ProcessesMachinabilityof workpiececriteriaTool lifeSurfaceroughnessSurfaceintegrityMagnitude ofcuttingforcesEnergy(power)consumptionWorkpieceMaterial.
  38. 38. Factors Affecting Tool Life In Machining ProcessesFactorsdetermineconditions ofthe workmaterialMicrostructure.Grain size.Heattreatment.Chemicalcomposition.FabricationYield andtensilestrength.HardnessWorkpieceMaterial.
  39. 39. Factors Affecting Tool Life In Machining ProcessesMain CuttingFluid FunctionsLubrication effect Cooling effectRemoving chipsaway from thecutting zoneCuttingFluid
  40. 40. Factors Affecting Tool Life In Machining ProcessesOtherfunctionsofcuttingfluidsReduction of cutting forces/energy consumptions.Improvement of surface finishand dimensional accuracy.Extend tool life.Facilitate chip removal.Corrosion prevention onworkpiece and machines.Lowering workpiecetemperature.Lubrication of machine toolsliding guidesCuttingFluid
  41. 41. Factors Affecting Tool Life In Machining ProcessesCuttingfluidspropertiesGood lubricatingpropertiesHigh cooling capacityLow viscosity to providefree flow of cutting fluid.Chemically stable.Non-corrosive.High flash point to reducefire risks.Allergy free.Less evaporative.Low cost.CuttingFluid
  42. 42. Cutting FluidsSelectionType of machiningprocesses.Type ofmachinedworkpiecematerial.Type of cuttingtool material.Factors Affecting Tool Life In Machining ProcessesCuttingFluid
  43. 43. Factors Affecting Tool Life In Machining ProcessesCuttingFluidCuttingFluidEffectsEnvironmentalBiodegradabilityLife cycleassessmentBioaccumulabilityandbiomagnificationsEnergy saving andfuel economyRenewabilityHealthRespiratoryproblems.Dermatologicalproblems
  44. 44. Factors Affecting Tool Life In Machining ProcessesEnvironmentalmachiningDry cuttingMinimumquantitylubricantVegetablebased cuttingfluidsCuttingFluid
  45. 45. Factors Affecting Tool Life In Machining Processes
  46. 46. Factors Affecting Tool Life In MachiningProcesses
  47. 47. Factors Affecting Tool Life In Machining ProcessesCutting ToolGeometry

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