Surface finish metrology iss1

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Transcript of Surface finish metrology iss1

  • 1. Surface Finish Metrology Centre of Excellence Taylor Hobson Ltd 2000 Taylor Hobson Ltd

2. Contents 1. Why do we need to measure Surface Finish?8. Bearing Area (Material Ratio)2. Measurement Methods9. The Rk Parameter3. Measurement Datums10. Form Measurement4. Reproducing the Surface11. Calibration Methods.5. Terminology12. Conics and Aspherics.6. Filters13. 3D (Areal) Measurement.7. Parameters14. Drawing Indication. 3. Why do we need to measure Surface Finish? 4. Nature of Surfaces The microstructure of the material 5. Nature of Surfaces The microstructure of the material The action of the cutting tool 6. Nature of Surfaces The microstructure of the material The action of the cutting tool The instability of the cutting tool on the material 7. Nature of Surfaces The microstructure of the material The action of the cutting tool The instability of the cutting tool on the material Errors in machine tool guideways 8. Nature of Surfaces The microstructure of the material The action of the cutting tool The instability of the cutting tool on the material Errors in machine tool guideways Deformations due to stress patterns in the component 9. Nature of Surfaces The microstructure of the material The action of the cutting tool The instability of the cutting tool on the material Errors in machine tool guideways Deformations due to stress patterns in the component 10. Unwanted Properties on a Surface Deep valleys which may be susceptible to crack propagation Too many peaks which may cause early surface breakdown and wear when in contact with a mating component Excessive waviness which may cause noise or indicate machining problems 11. Wanted Properties on a Surface Sufficient valleys for oil retention when lubrication is an important factor Sufficient peaks for retention of paint and adhesives Sufficient distribution of valleys for formability Smooth surface profiles for reduced, noise, vibration or high reflectance. 12. Why Do We Need to Measure Surface Finish? Process Control Predicting Component Behaviour Monitoring Component Performance 13. Why Do We Need to Measure Surface Finish?The Ideal Situation 14. Why Do We Need to Measure Surface Finish?The Reality - Process Control 15. Why Do We Need to Measure Surface Finish?Predicting Component Behaviour 16. Why Do We Need to Measure Surface Finish?Back to Contents PageMonitoring Component Performance 17. Measurement Methods 18. Measurement Methods Contact Type InstrumentsNon-Contact Type Instruments 19. How Do We Measure Surface Finish? Comparison Plates 20. Measurement MethodsData Point Spacing (X)Stylus Movement (Z)Traverse Direction (X)Contact Type Instrument 21. Measurement Methods Inductive Type of Transducer Coil Ferrite Slug (Armature) BeamCoilStylus Knife Edge Pivots 22. Measurement Methods Piezo-Electric Type of Transducer BeamStylusPiezo Element 23. Measurement Methods Laser Type of Transducer LaserPhotoBeamDiodeStylus Click Here for Further Information Back to Contents Page 24. Measurement Datums 25. Measurement DatumsTraverse Direction (X)SkidStylus Movement (Z)Skid (surface) Datum 26. Measurement Datums Reduces Effects of Vibration No Surface Levelling Required Instrument Portability Robust DesignBenefits of Using a Skid Datum 27. Measurement DatumsH1H2Actual HeightEffect of Skid to Stylus PitchApparent Height 28. Measurement DatumsResultant Profile P-V = 0mP-V = 10mEffect of Skid to Stylus Pitch 29. Measurement DatumsTraverse Unit DatumTraverse DirectionIndependent Datum 30. Measurement DatumsTraverse Unit DatumTraverse DirectionDatum Skid Optical FlatIndependent Datum Back to Contents Page 31. Reproducing the Surface 32. Reproducing the Surface 2mTraverse Direction2mConisphere StylusTruncated Pyramid StylusStylus Tip GeometryClick Here for Further Information 33. Reproducing the SurfaceStylus Tip - Effects of Tip Size & Shape 34. Reproducing the SurfaceStylus Tip - Flanking 35. Reproducing the Surface Profile produced by StylusB AStylus TipB AStylus Tip - Flanking Back to Contents Page 36. Terminology 37. Terminology Data Points True SignalAliasing SignalSampling IntervalAliasingClick Here for Further Information 38. Terminology Sample SurfaceRoughness, Waviness & Form 39. Terminology FormRoughness, Waviness & Form 40. Terminology WavinessRoughness, Waviness & Form 41. Terminology RoughnessRoughness, Waviness & Form Back to Contents Page 42. Filters 43. TerminologySurface InteractionFiltering-Separates Roughness and Waviness 44. FiltersSampling LengthFiltering Using Graphical Techniques 45. Filters FormCut-offSampleRa,Rq,Rz etc...Roughness Filter 46. Filters FormCut-offSampleWa,Wq,Wz etc...Waviness Filter 47. Filters ISO 2CR Filter 2CR PC Gaussian Electronic & Digital Filter Types 48. FiltersUnfiltered ProfileISO 2CR Filtered ProfileISO 2CR FilterClick Here for Further Information 49. FiltersMean Line Established By FilterModified Profile Relative to Filtered Mean LineISO 2CR Filter Effect 50. FiltersUnfiltered Profile2CR PC Filtered Profile2CR PC Filter 51. FiltersMean Line Established By FilterModified Profile Relative to Filtered Mean LineISO 2CR PC Filter 52. FiltersUnfiltered ProfileGaussian Filtered ProfileGaussian Filter 53. Filters ZProfile Filter Unfiltered Profile Mean LineCut-offSampling LengthGaussian FilterX Click Here for Further Information 54. Filters Unfiltered ProfileRoughness Amplitude = 20mRoughness Wavelength = 0.25 mmWaviness Amplitude = 100mWaviness WavelengthThe Effects of Filtering= 8.0 mm 55. Filters Roughness Amplitude8.0 mm Cut-off filter= 20mRoughness Wavelength = 0.25 mmWaviness Amplitude = 75m Waviness Wavelength = 8.0 mmThe Effects of 2CR Roughness Filter 56. Filters 2.5 mm Cut-off filter Roughness Amplitude = 20mRoughness Wavelength = 0.25 mmWaviness Amplitude = 24mWaviness Wavelength = 8.0 mmThe Effects of 2CR Roughness Filter 57. Filters 0.8 mm Cut-off filter Roughness Amplitude = 20mRoughness WavelengthWaviness Amplitude = 2m= 0.25 mmWaviness Wavelength = 8.0 mmThe Effects of 2CR Roughness Filter 58. Filters 0.25 mm Cut-off filter Roughness Amplitude = 15mRoughness WavelengthWaviness Amplitude = 0m= 0.25 mmThe Effects of 2CR Roughness Filter 59. Filters 0.08 mm Cut-off filterRoughness Amplitude = 4mRoughness WavelengthWaviness Amplitude = 0m= 0.25 mmThe Effects of 2CR Roughness Filter 60. Filters Traverse LengthOver travelRun-upSampling Length (Cut-off) Assessment (Evaluation) LengthRelationship of Sampling, Assessment & Traverse Length (ISO 2CR) 61. Filters ISO 2CR- 1st 2 Cut-offs discarded 2CR PC-1st & Last Cut-offs discardedGaussian- Half 1st & Half Last Cut-off DiscardedFilter Types 62. Filters0.8mmSampling Length (Cut-off)Cut-off Selection 63. Filters0.25mmSampling Length (Cut-off)Cut-off Selection 64. Filters Traverse Direction1.25 mmChoosing the Correct Cut-off Value 65. FiltersCut-off SelectionUnless otherwise indicated on a drawing the table above should be used to determine the cut-off 66. FiltersLsLcBandwidth=Ratio of Lc/Ls Back to Contents Page 67. Parameters 68. ParametersRoughness -Prefix RWaviness -Prefix WPrimary -Prefix PAnalysis Types 69. Parameters Amplitude Parameters defined from Z co-ordinatesParameter Types 70. Parameters Amplitude Parametersdefined from Z co-ordinates Spacing Parameters defined from X co-ordinatesParameter Types 71. Parameters Amplitude Parametersdefined from Z co-ordinates Spacing Parameters defined from X co-ordinates Hybrid Parameters X & Z co-ordinatesParameter Types 72. ParametersRaAmplitude Parameters - Ra 73. Parameters Ra Ra RaRaAmplitude Parameters - Limitations of Ra 74. Parameterslr =Sampling LengthAmplitude Parameters Rq (RMS) 75. Parameterslr =Sampling Lengthln =Assessment LengthAmplitude Parameters Rt 76. ParametersSampling LengthAmplitude Parameters Rp 77. ParametersSampling LengthAmplitude Parameters Rv 78. ParametersRz 2Rz 1Rz 3Rz 4Rz 5Rz = Maximum peak to valley in each sample length divided by n sampling lengthsAmplitude Parameters Rz 79. Parameters Rp1ma xRz1maxRv1maxAmplitude Parameters Rz1max, Rp1max & Rv1max 80. Parameters A=Slice levellr =Sampling Length (Cut-off)B= Mean Lineln =Assessment LengthSpacing Parameters HSC (High Spot Count) 81. ParametersTall narrow peaks tend to work hardenHardened peaks will eventually break off and the surface will breakdownSpacing Parameters HSC (High Spot Count) 82. Parameters A=Selectable BandwidthB= Mean LineSpacing Parameters Rpc (Peak Count) 83. ParametersPainted Surface Base Sheet Steel Orange Peel Effect Due to Peaks on Sheet Steel Base SurfaceSpacing Parameters Rpc (Peak Count) 84. ParametersMean Linelr =Sampling Length (Cut-off)Spacing Parameters Sm (Mean Spacing) 85. Parameters Hybrid Parameters- Rdq (Pdq, Wdq) (Rms Slope) 86. Parameters Effects of Surface Slopes on vibration & noiseNo Vibration/QuietLow Frequency Rumble High Frequency ScreamHybrid Parameters- Rdq (Pdq, Wdq) (Rms Slope) 87. ParametersWith low surface slopes more light is reflected into the eye and hence has a good appearanceWith high surface slopes less light is reflected into the eye and hence has a poor appearanceHybrid Parameters- Rdq (Pdq, Wdq) (Rms Slope) Back to Contents Page 88. Bearing Area (Material Ratio) 89. Bearing Area (Material Ratio) Upper surface defines run-in characteristicsBody of surface defines wear/life characteristicsValleys define lubrication characteristicsHybrid Parameters - Rmr 90. Bearing Area (Material Ratio) Lapping PlateBearing LineRmr= a+b+c+d+elnx100ln =Assessment LengthHybrid Parameters - Rmr 91. Bearing Area (Material Ratio) Level pTp (%) at level p0tp(%)Material Ratio Curve (Rmr)100 % 92. Bearing Area (Material Ratio) Level pTp (%) at level p0tp(%)Material Ratio Curve (Rmr)100 % 93. Bearing Area (Material Ratio) Level pTp (%) at level p0tp(%)Material R