Phase 2 SRG-4600 - Understanding Roughness Filters and Cutoff; Roughness Filters Explained; Role of Roughness Cutoff (λc); Roughness Cutoff Lengths

RoughnessFilters
•Afilterisusedtoisolatetheroughnesswavelengthband
•FiltersareMechanicalandDigital
–Mechanicalfilters
•DiamondRadius(valleysuppressionbydiamondradius)
•Skid(greaterorlesserskid“bridging”effectofskidonsurface
valleys,dependentonskidgeometry),alsofiltersoutwaviness
–DigitalFilters
•RC(Simulatedoldanalogelectrical“resistorcapacitor”)
•Gaussian
•Theuserselectsthe“Cutoff”settingusedbythefilterto
isolatetheroughnesswavelengthband
•Filterstypicallyhavetransmissioncurves
•Filtereddataiscenteredaroundameanline

TheRoleofRoughness“Cutoff”(λc)
•Forroughness,thecutoffvalueisthelongest
nominalwavelengthtobeincludedinroughness.
•Longerwavelengthsarefilteredout.Shorter
wavelengthsareincludedinroughness.
•Wavelengthslongerthantheroughnesscutoffare
usuallyincludedinwaviness.

(λc)RoughnessCutoffLengths
•Thecutoffselectedmustbeshortenoughtoexcludelong
wavelengths(waviness)
•Thecutoffselectedmustbelongenoughforavalid
sample(atleast10toolmarkspercutoff)
•LengthsaredefinedinASMEandISOstandards
•Cutoffdefaultformerlywas.8mm,nowmustbedefinedon
thedrawing(ASME)
Millimeter Inch
.08 .003
.25 .10
.80 .030
8.0 .300
25.0 1.00