Dept. of Mechanical Engineering, IISc

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Dept. of Mechanical Engineering, IISc

• ME-255 PRINCIPLES OF TRIBOLOGY
• Surface Properties - Measurement Techniques
• Profilometer
• Presented by
• Balasenthil D
• Sr.No. 08993

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CONTENTS

• Introduction
• Types of Profilometer
• Contact
• Non - Contact
• Working Principle
• Optical Principle Basics
• Modes of Operation
• System Performances
• Range , Resolution Accuracy
• Surface Parameters
• Surface Topography Amplitude Parameters
• Profilometers _at_ IISc
• Measurement Examples

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INTRODUCTION

• Definition.
• - A profilometer is a device used to measure
  the roughness of a surface.
• - Gives difference between the high and low
  point of a surface in nanometres.
• Types of Profilometers.
• Non - Contact Profilometers
• Contact Profilometers

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Non - Contact Profilometer

• Optical Methods
• Vertical Scanning Interferometry
• Phase - Shifting Interferometry
• Differential Interference Contrast Microscopy
• Focus Detection Methods
• Intensity Detection
• Focus Variation
• Differential Detection
• Critical Angle
• Astigmatic Method
• Focault Method
• Confocal Microscopy
• Contd

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Non - Contact Profilometer

• Pattern Projection Methods
• Fringe Projection
• Fourier Profilometry
• Moire

Contact Pseudo Contact Profilometer

• Stylus Profilometer
• Atomic Force Microscopy
• Scanning Tunneling Microscopy

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Contact Profilometer

• Height from 10 nanometres to 1 millimetre
• Radius of diamond stylus from 20 nm to 25 µm
• Horizontal resolution is controlled by the scan
  speed and data signal sampling rate.
• Contd ...

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Contact Profilometer

• Advantages Disadvantages
• Acceptance Easy to Use
• Surface Independence
• Resolution The stylus tip radius can be as
  small as 20 nanometres
• Direct Technique No modelling required.
• Not suitable for very soft (or even liquid) and
  easily damageable surface
• Very hard and damage surface can damage the
  stylus
• Only 2D

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Non - Contact Profilometer

• Uses beams of light to read a surface
• They shoot a beam out and measure the time it
  takes to return.
• no wear since none of its parts touch anything
• Contd

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Non - Contact Profilometer

• Advantages of optical profilometers
• Good Resolution Vertical resolution is usually
  in the nm level
• High Speed
• Reliability cannot be damaged by surface wear
  or careless operators
• Spot size or lateral resolution ranges from a
  few micrometres down to sub micrometre.
• Contd

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Non - Contact Profilometer

• Limitations
• Limited by very high slopes, where the light is
  reflected away from the objective, unless the
  slope has enough texture to provide the light.
• Surface Modelling is required to convert the
  digital code to human usable data.

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Working Principle of Profilometer(Non - Contact
Optical Profilometer)
Contd
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Working Principle of Profilometer(Non - Contact
Optical Profilometer)

• A light beam is split, reflecting from reference
  (known/flat) test material.
• Constructive and destructive interference occurs
• Forms the light and dark bands known as
  interference fringes.
•  
• The optical path differences are due to height
  variances in the test surface.
• Contd

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Working Principle of Profilometer(Non - Contact
Optical Profilometer)

• Constructive interference areas as lighter and
  the destructive interference areas as darker.
• Light to dark fringes above represents one-half a
  wavelength of difference between the reference
  path and the test path.
• Contd

Interference Image
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Working Principle of Profilometer(Non - Contact
Optical Profilometer)

• From the above Interference Image
• Lower portion is out of focus means less
  interference.
• Greatest contrast means best focus.

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Modes of Operation(Non - Contact Optical
Profilometer)

• Phase Shifting Interferometry (PSI) Mode
• Vertical Scanning Interferometry (VSI) Mode
• Contd

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Modes of Operation(Non - Contact Optical
Profilometer)
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System Performances

• Range Highest vertical distance the profiler can
  measure.
• Resolution Smallest distance the profiler can
  accurately measure.
• Lateral Resolution
• Vertical Resolution
• Accuracy How closely a measured value matches
  the true value can be obtained by frequent
  calibration.

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Surface Parameters

• Surface Topography 3D representation of
  geometric surface irregularities.
• Contd

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Surface Parameters

• Roughness Closely spaced irregularities
• Waviness More widely spaced irregularities
• Error of Form Long period non cyclic
  deviations
• Flaws Discrete infrequent irregularities
• Roughness Waviness comprise the Surface Texture
  
• Contd

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Surface Parameters

• Amplitude Parameters
• Contd

Term Definition Use
Ra The roughness average (mean height) Gives roughness of the machine surface
Rq RMS roughness Describes the finish of optical surface
Rp Rv Max profile peak max profile valley depth Ra - info of friction wear Rv - retaining of lubricant
Rt Max height of surface Gives overall roughness of the surface
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Surface Parameters

• Amplitude Parameters

Term Definition Use
Rz Average max height of the profile Evaluating surface texture on limited access surfaces
Rsk Skewness - measure of asymmetry of the profile about the mean line. Gives load carrying capacity, porosity characteristic of non-conventional machining processes.
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Profilometers _at_ IISc

• Optical surface profilometer
• Make Veeco NT1100
• Type Non Contact type
• Principle of Operation
• VSI g interferometry (VSI)
• Phase-shifting interferometry (PSI).
• Range
• VSI 2mm
• PSI 160nm
• Resolution
• Vertical Resolution PSI 3Å VSI 3nm
• Lateral Resolution -- Function of magnification
  objective and the detector array size you choose

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Profilometers _at_ IISc

• Nanoscience Profilometer
• Film thickness measurement from 5 microns down
  to 300 nm or less
• 4 million pixel camera for high resolution
• Auto-range and auto-fringe-find for ease of use
  of Single mode of operation over all scan ranges.

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Measurement Examples

• Some of the profiles obtained are shown below
• 600 GRIT SIZE
• UPD (in 2D) UPD (in 3D)

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Measurement Examples

• Surface of steel Block Reflection Intensity
• 3D Image

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Measurement Examples

• Pit on a thin iron plate 2D image
• Plate thickness 0.7mm
• (Depth 0.14494mm)

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Measurement Examples

• 3D image

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References

• Research Papers
• T.V.Vorburger, J.Raja.
• Surface Finish Metrology Tutorial
• June 1990
• WYKO Surface Profilers Technical Reference
  manual
• September 1999, Version 2.2.1
• Webpage
• Profilometer, Wikipedia
• http//en.wikipedia.org/wiki/Profilometer

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THANK YOU