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Stylus Probe

Apr 03, 2018

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    IPE 381Chapter:11

    Surface Finish

    Abdullah-Al-MamunLecturer, Dept. of IPE

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    Outline

    Importance of Surface Roughness

    Surface Texture

    Surface Roughness Surface Roughness Measurement

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    Surfaces

    The nominal surfaces appear as absolutely straight

    lines, ideal circles, round holes, and other edges and

    surfaces that are geometrically perfect

    Actual surfaces of a part are determined by the

    manufacturing processes used to make it

    Variety of processes result in wide variations in

    surface characteristics

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    Why Surfaces are Important

    Aesthetic reasons

    Surfaces affect safety

    Friction and wear depend on surface

    characteristics

    Surfaces affect mechanical and physical

    properties

    Assembly of parts is affected by their surfaces Smooth surfaces make better electrical contacts

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    Surface Technology

    Concerned with: Defining the characteristics of a surface

    Surface texture

    Surface integrity

    Relationship between manufacturing processes and

    characteristics of resulting surface

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    Surface Texture

    The topography and geometric features of

    the surface

    When highly magnified, the surface is

    anything but straight and smooth It has roughness, waviness, and flaws

    It also possesses a pattern and/or

    direction resulting from the mechanical

    process that produced it

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    11.2 Meaning and Terminologies

    of Surface Texture

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    Elements of Surface Texture

    1. Roughness - small, finely-spaced

    deviations from nominal surface Determined by material characteristics and

    processes that formed the surface

    2. Waviness - deviations of much larger

    spacing

    Waviness deviations occur due to work deflection,vibration, heat treatment, and similar factors

    Roughness is superimposed on waviness

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    Four Elements of Surface

    Texture3. Lay - predominant direction or

    pattern of the surface texture

    4. Flaws - irregularities that occur

    occasionally on the surface

    Includes cracks, scratches,inclusions, and similar

    defects in the surface

    Although some flaws relate

    to surface texture, they

    also affect surface integrity

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    Surface Roughness and

    Surface Finish Surface roughness - a measurable

    characteristic based on roughness deviations

    Surface finish - a more subjective term

    denoting smoothness and general quality of asurface

    In popular usage, surface finish is often used as a

    synonym for surface roughness

    Both terms are within the scope of surface texture

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    Surface Roughness

    Average of vertical deviations from nominalsurface over a specified length surface

    gth

    Figure : Deviations from nominal surface used in the two definitions

    of surface roughness.

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    Surface Roughness

    Mean line of the Profile: It is the line that divides the effective profilesuch that, within sampling length the sum of squares of distances

    (y1, y2, .yn) between effective points and mean line is minimum.

    Center line of the Profile: It is the line for which the area embraced

    by the profile above or below the line is equal.

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    Surface Roughness

    Center Line Average (CLA), Ra is the Arithmetic Average of the

    distance of the filtered or unfiltered Roughness profile from its Mean

    Line.

    Maximum Peak to valley height, Rt or Rmax.

    RMS Value, Rq is the Root Mean Square of the distance of the

    filtered or unfiltered Roughness Profile from its mean line.

    Ni

    i

    y1

    ia ||N

    1R

    Ni

    iiy

    1

    2

    q N

    1

    R

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    Surface Roughness

    Ten Point height of Irregularities, Rz is numerically the average

    height difference between the five highest peaks and the five lowest

    valleys within the assessment length.

    Rz is also known as the ISO 10 point

    height parameter.

    5

    )YYYY(Y)YYYYY((ISO)R

    v5v4v3v2v1p5p4p3p2p1

    z

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    Surface Roughness

    Specification

    Figure : Surface texture symbols in engineering drawings: (a) the

    symbol, and (b) symbol with identification labels.

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    Surface Texture Symbols

    0.030^0.015

    cut-off

    Lay

    Max

    Roughness

    Spacing

    0.002.-263

    32

    Max Waviness Width

    Max Waviness

    Height

    Max

    Ra

    Min Ra

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    11.5. Methods of Measuring

    Surface Roughness Touch Inspection

    Visual Inspection

    Scratch Inspection

    Microscope Inspection

    Surface Photographs

    Micro Interferometer

    Wallace Surface Dynamometer

    Reflected Light Intensity

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    11.6. Direct Instrument

    Measurement Stylus Probe Instrument

    A skid or shoe is drawn slowly over the surface.

    A stylus move over the surface with the skid.

    An amplifying device for magnifying the stylus movement and

    indicator. A recording device to produce trace of the surface profile.

    A mean of analyzing the trace

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    Stylus Probe Instrument

    The Tomlinson Surface Meter:

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    Stylus Probe Instrument

    The Taylor-Hobson Talysurf As the probe moves, Armature

    pivots around a E shaped

    stampings.

    Any movement on the stylus

    causes the air gap to vary.

    Amplitude of a.c. current is

    modulated.

    Signal is demodulated to get

    the vertical displacement ofstylus.

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    Taylor Hobson Telyserf

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    Self Study

    11.9 Analysis of Surface TracesWorked out Qustion and Answers (From page 661-663)

    Thank You