Numerical - CLA value of roughness - Metrology & Quality Control

Q.  Calculate CLA value of roughness for a graph, having 100 horizontal magnification and 10000 vertical magnification for a sampling length of 1.2 mm. The areas above the datum line are 100 mm2, 120 mm2, 140 mm2, 40 mm2 and below the datum line are 80 mm2, 40 mm2, 150 mm2, 90 mm2.
- Published on 07 Aug 15

a. 0.6333 micron
b. 6.333 micron
c. 0.912 micron
d. 0.079 micron

ANSWER: 0.6333 micron
 

    Discussion

  • Lahu pawar   -Posted on 08 Oct 17
    Definition of CLA.
  • Lahu pawar   -Posted on 08 Oct 17
    Definition of CLA.
  • Sravanthi   -Posted on 26 Oct 15
    - Centre line average method is used to calculate arithmetic average value of ordinates. It also measures surface ordinates relative to mean line at different points.

    Given: Horizontal magnification = 100, vertical magnification = 10000, sampling length = 1.2 mm

    Areas above datum line are : A1 = 100 mm2, A2 = 120 mm2, A3 = 140 mm2, A4 = 40 mm2
    Areas below datum line are: A5 = 80 mm2, A6 = 40 mm2, A7 = 150 mm2, A8 = 90 mm2

    Formula:
    1) Calculate total area below and above the datum surface i.e ΣA = A1 + A2 + A3 ------ A8

    2) Centre line average (yCLA) = ΣA / (L x horizontal magnification x vertical magnification)

    Solution:

    CLA value is measured in microns and area in mm2 if an irregular trace is magnified along horizontal and vertical directions.

    ΣA = A1 +A2 + A3 ------ A8

    = 100 + 120 + 140 + 150 + 40 +80 + 40 + 90

    = 760 mm2

    Centre line average value (yCLA) = ΣA / (L x horizontal magnification x vertical magnification)

    = 760 / (1.2 x 10000 x 100)

    = 0.633 micron

    CLA value of roughness for a graph, having 100 horizontal magnification and 10000 vertical magnification for a sampling length of 1.2 mm is 0.6333 micron.

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