We measure a Roughness Specimen to get the roughness graph and result of Ra.
Definition of Ra is the average deviation deviding the area of the part to be surrounded by the sampling curve and the average line by the sampling length (JISB0601:2001).
The formula is given below:
l
Ra = 1/n ? [Z(x)] dx
0
where
Z(x): The absolute average in the part having taken out only sampling length
X: The Mean line direction
? (n): The range of sampled reference length
RP: Levels of average roughness peak
RV: Levels of average roughness valley
According to formula of Ra and roughness graph above, here is the way to calculate the result:
Ra = (RP1+RP2+ ...+RPn)+(RV1+RV2+ ... +RVn)
n
Ra = (3.5 + 4 + 3 + 3.5 + 3 + 4 + 3 + 3.5 + 3 + 4 + 3 + 3.5 + 2.5 + 4 + 3 + 4 + 3 + 4 + 2.5 + 3.5 + 3 + 3.5 + 3 + 3.5 + 3 + 3.5 + 2.5 + 3.5 + 2) + (2 + 3.5 + 2.5 + 3.5 + 2.5 + 3.5 + 2.5 + 4 + 3.5 + 3.5 + 2.5 + 3.5 + 2.5 + 3.5 + 2.5 + 4 + 3 + 3.5 + 2 + 3.5 + 2 + 3.5 + 3 + 3.5 + 3 + 3.5 + 3 + 3.5 + 2.5 + 4) / 61
Ra = (101.5) + (93)/61
Ra = 194.5/61
Ra = 3,188µm
* Conclusion: the result value of Ra from Surfcom Nex 001 with calculation data of graphic curve is similar.
Definition of Rz is the sum of the maximum value (RP) of the peak height (ZP) and the maximum value (Rv) of the valley depth (ZV) of the profile in the sampling length (JISB0601:2001).
The formula is given below:
Rz = RP + RV = max[Zpi] + max[Zvi] = max[Z(x)] + min[Z(x)]
where
RP: The maximum value of the peak height
RV: The maximum value of the valley depth
According to formula of Rz and roughness graph above, here is the way to calculate the result:
RZ = (RP1+RP2+...+RP5)+(RV1+RV2+...+RV5)
5
Rz = (5+5+5.1+5+5) + (5+5+5.1+5.1+5.1)
5
Rz = (25.1)+(25.3)
5
Rz = 50.4/5
Rz = 10.08µm.
* Conclusion: the result value of Rz from Surfcom Nex 001 with calculation data of graphic curve is similar.
Notes