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Evaluation of surface roughness
Mar 16, 2018

1. Sampling length

The sampling length is defined as the length of a reference line for the evaluation of the surface roughness. Should be formed on the surface of the parts based on the actual situation and the texture feature, selection can reflect the characteristics of the surface roughness of the section length, measuring the sample length should be based on the actual surface profile of the general direction. The rule and selection of sampling length are to limit and reduce the effect of surface waviness and shape error on the surface roughness measurement results.

2. Evaluation length

The length of the evaluation is the length required to assess the contour. It may include one or several sample lengths. Because the surface of each part surface roughness is not necessarily very even, on a sampling length often cannot reasonably reflect the characteristics of a surface roughness, so need to take a few sample length on the surface to surface roughness. The evaluation length generally contains 5 sampling lengths.

3. The baseline

The baseline is the contour line used to evaluate surface roughness parameters. The base line has two types: the least squares of the contours: in the sampling length, the square of the contour of each point on the contour line is the smallest and has the geometric outline shape. Contour arithmetic mean median line: in the sample length, the area of the upper and lower sides of the midline is equal. Least squares line is the ideal line in theory, but in practice it is difficult to obtain, so generally substitute the arithmetic average line of contour, and when measuring approximate straight line instead of a position.

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