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Surface Roughness

JacobCheverie
Surface Roughness per ASME B46.1

Everywhere I've seen states that the wavelength of the filter is equal to the sampling length. Is this a firm requirement? We are measuring spherical surfaces and we can't quite get the amount of surface measured that we would need to use the filter that matches the roughness requirement. My idea was to measure as much of the surface that we can, and then apply the filter at whatever wavelength we want to for roughness evaluation.

For example, 5 sampling intervals of width .010 are measured with two .010 intervals at the ends to account for end-effects. The evaluation length is .050. Would it be wrong to apply a filter of wavelength .003 (or anything other than .010)?
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  • Surface Roughness per ASME B46.1

    Everywhere I've seen states that the wavelength of the filter is equal to the sampling length. Is this a firm requirement? We are measuring spherical surfaces and we can't quite get the amount of surface measured that we would need to use the filter that matches the roughness requirement. My idea was to measure as much of the surface that we can, and then apply the filter at whatever wavelength we want to for roughness evaluation.

    For example, 5 sampling intervals of width .010 are measured with two .010 intervals at the ends to account for end-effects. The evaluation length is .050. Would it be wrong to apply a filter of wavelength .003 (or anything other than .010)?

    I assume this is due to Z-range of the profilometer you are using, right? But honestly, you shouldn't change it. Are you able to reduce the sample interval to 3 to make sure the correct filter is applied?

    Are you able to check the surface radially versus axially?
Reply
  • Surface Roughness per ASME B46.1

    Everywhere I've seen states that the wavelength of the filter is equal to the sampling length. Is this a firm requirement? We are measuring spherical surfaces and we can't quite get the amount of surface measured that we would need to use the filter that matches the roughness requirement. My idea was to measure as much of the surface that we can, and then apply the filter at whatever wavelength we want to for roughness evaluation.

    For example, 5 sampling intervals of width .010 are measured with two .010 intervals at the ends to account for end-effects. The evaluation length is .050. Would it be wrong to apply a filter of wavelength .003 (or anything other than .010)?

    I assume this is due to Z-range of the profilometer you are using, right? But honestly, you shouldn't change it. Are you able to reduce the sample interval to 3 to make sure the correct filter is applied?

    Are you able to check the surface radially versus axially?
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  • in reply to bfire85
    That is correct. We have had many instances where even cutting the interval to 1 is not sufficient.

    For example, at a required roughness the standard dictates we should use a .030 cutoff, so even a .030 over 1 interval will require .090 of surface to account for end effects. Sometimes we will not even have the .090 required (or are limited by Z-range). My idea is to measure all of the possible surface (maybe .050) and then apply the .030 filter to the measured data.

    Checking radially versus axially is not an option, there is part material in the way.
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