1、 Selection of Sampling Length and Evaluation Length

Sampling length: It is a reference line length used to determine the surface roughness characteristics. It should be large enough to contain sufficient surface details to accurately reflect the roughness characteristics of the surface.

Evaluation length: It is a small length that must be taken to reflect the roughness characteristics of the processed surface when evaluating roughness. It usually includes multiple sampling lengths to ensure the stability and reliability of the measurement results.

In practical operation, the appropriate sampling length and evaluation length should be selected according to specific needs and standards. For example, in ISO standards, the sampling length and evaluation length range corresponding to different roughness grades are specified.

2、 Selection of Filter Types

The type of filter has a significant impact on the roughness measurement results. Common types of filters include Gaussian filters, first-order approximation spline filters, etc. Different types of filters have differences in frequency response, computational efficiency, and other aspects, so the appropriate filter should be selected according to specific needs.

3、 Specific settings for filtering values

Selection of cutoff wavelength: The cutoff wavelength is an important parameter of the filter, which determines the sensitivity of the filter to surface morphology. In roughness measurement, an appropriate cutoff wavelength is usually selected to filter out the influence of surface wave roughness and other non roughness features. The selection of cutoff wavelength should be determined based on specific surface characteristics and measurement requirements.

Adjustment of filtering parameters: In addition to the cutoff wavelength, the filter may also have other parameters that need to be adjusted, such as the bandwidth ratio, high pass or low-pass characteristics, etc. The adjustment of these parameters should be based on specific measuring equipment and standards.

4、 Considerations in practical applications

Surface cleanliness: Before conducting roughness measurements, it is necessary to ensure that the surface being measured is clean and free of dirt to avoid affecting the measurement results.

Calibration of measuring equipment: Measuring equipment should be calibrated regularly to ensure the accuracy of measurement results.

Repeated measurement: In order to obtain more reliable measurement results, it is usually necessary to perform multiple repeated measurements and take the average as the final result.

5、 Example Explanation

Assuming that a Gaussian filter is selected as the filtering method and a cutoff wavelength of 0.8mm is set for surface roughness measurement. This means that parts with surface deviations less than 0.8mm will be considered surface roughness, while parts greater than 0.8mm will be considered surface defects or other non roughness features. In practical operation, these parameters should be adjusted according to specific needs and standards.

In summary, setting the filter value for roughness is a complex process that involves the comprehensive consideration of multiple factors. In practical applications, appropriate sampling length, evaluation length, filter type, and filtering parameters should be selected according to specific needs and standards to obtain accurate and reliable measurement results.