Surface finish characterization

Once a satisfactory profile is obtained, it can be analysed and represented by a variety of means. This raises the question of what particular number, parameter or descriptor should be used. Unfortunately, there is no such thing as a universal parameter or descriptor and one must select from the ones published in the ISO standards.

With reference to Figure 6.5, the ADF (Amplitude Distribution Function or height distribution function) is a histogram where the value of p(y) represents the fraction of heights lying in the stratum between y and (y + dy). If the ADF is integrated, the BAC or Abbott-Firestone Curve or Material Ratio Curve is obtained. The BAC can also

Abbott Firestone Curve
Figure 6.5 A profile and the corresponding height distribution function and bearing area curve

be generated by slicing the profile in a straight line parallel to the mean from the highest peak down, plotting the total length revealed as a fraction of the profile length under consideration. This is the equivalent of a perfect abrasion or wear process. Examples of the graphical outputs as well as parameters are shown in Figure 6.6. This is a trace from a fine-turned surface, showing the conventional turning unit event 'cusp' surface form. The peak spacing is approximately 115um and the peak to valley height is 45um.

Profile Trace of a Fine-Turned Surface

Profile Trace of a Fine-Turned Surface

XPI IX)

/FILTER

XPI IX)

/FILTER

Amplitude Distribution Function

8.78 18.12 37.67 31.84 31 .<2 44.64 8.51 2.28 38.22 41.99 33.64 39.49 35.83 26.52 18.12 22.44

HE1SHT

/FILTER

18.8

Freq X

Bearing Area Curve ss-

Engineering Surface Finish

BEflRIHS

Ra

8.78

Rt

44.64

HSC

35

TP1B

33.13

TP28

28.12

TP38

24.17

1P48

28.21

TPS6

15.83

TP68

12.92

TP78

18.62

TP80

8.54

TP98

Figure 6.6 A profile of a fine-turned, surface and the corresponding ADF and BA C curves

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Responses

  • Negisti
    How to represent surface finish in engineering drawings?
    8 years ago
  • Maura
    How to draw a abbott firestone curve?
    3 years ago

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