The changes to the content of ISO 21920 are cautious. The drawings that were created according to the previous standard do not lose their validity and there are no significant differences in the results
There are name changes to existing terms. As the old and new standard are offered in parallel in the software, the previous nomenclature (according to ISO 4287 & ISO 4288) remains in the software:
- „Section length lsc“ replaces the term „single measuring section“
- “Number of sections nsc” replaces “Number of individual measuring sections”
- “Evaluation length le” replaces “Measuring section”
- “Profile S filter (Nis)” replaces “λs profile filter”
- „Profile L filter (Nic)“ replaces „λc profile filter“
The DIN EN ISO 21920 series of standards consists of 3 parts:
- DIN EN ISO 21920-1 replaces DIN EN ISO 1302
- Part 1: Specification of the surface finish
- Contains new definitions of drawing specifications for roughness measurement
- DIN EN ISO 21920-2 replaces the DIN EN ISO 4287 & DIN EN ISO 13565-2/-3
- Part 2: Terms and parameters for the surface finish
- Parameters have been added and deleted from the standard
- Other parameters have been renamed and have a slightly different calculation method (e.g. “Rz - Average roughness depth” becomes “Rz - Maximum height”)
- Division into evaluation length and section length parameters
- DIN EN ISO 21920-3 replaces the DIN EN ISO 4288
- Part 3: Specification operators
- Default settings are defined in the third part of the standard series in order to achieve user-independent measurement results
- The settings for the measurement can be defined via setting classes (Sc classes)
Parameter
- Previous parameter according to DIN EN ISO 4287:
- Ra, Rz, Rt, Rmax, R3z, Rq, Rdq, Rpc, Rmr, Rdc, Rsk
- According DIN EN ISO 13565-2:
- Parameters no longer available in the ISO 21920-2:
- Renamed in the ISO 21920-2:
- Mr1 in Rmrk1, Mr2 in Rmrk2
- New parameter in the ISO 21920-2:
- Rzx (Unit µm, Tol. µm), Rp (Unit µm, Tol. µm), Rv (Unit µm, Tol. µm)
- New calculation method in the ISO 21920-2:
- Subdivision of the parameters (old according 4287 & 13565-2)
- ISO 21920-2 Standard
- Ra, Rz, Rt, Rq, Rdq, Rpc, Rmr, Rdc, Rsk, Rzx, Rp, Rv
- Filtering according ISO 16610-21 (linear Gaussian)
- ISO 21920-2 Exceptions
- Rk, Rpk, Rvk, Rmrk1, Rmrk2
- Filtering according ISO 16610-31 (Robust 2nd order Gaussian)
- Renaming of additional parameters (Tolerance window)
- For Rmr
- „Rmr(c0)“ becomes „p“
- „c“ becomes „dc“
- For Rdc
- „Rmr(c1)“ becomes „p“
- „Rmr(c2)“ becomes „q“
- The Rdc is specified as negative in the evaluation according to ISO 21920 (in ISO 4287 it was positive)
Changes in STI
- Selection of ISO 21920
- Under „Evaluation options” there is the selection “Roughness evaluation”
- There you can choose between “Tolerances according to DIN 4287” & “Tolerances according to DIN 21920”
- Tolerances
- Under ‘Tolerance’ there is a choice between “DIN 4287;13565-2” and “DIN 21920”
- The measurement is analysed according to the tolerances selected in “Evaluation option”
- Changes in measurement & evaluation
- “Machine” menu item → “Settings” (filtering the roughness measurement)
- The micro-roughness filter can now be selected under ‘Measuring positions’
- The filter types are subdivided into ISO 21920-2 standard & 21920-2 exceptions (previous subdivision according to ISO 4287 & ISO 13565-2)
- „Measurement“ menu item → „Measurement positions”
- As before, the cut-off wavelength ‘Lc’ and the scanning distance ‘Lt’ can be set here
- The selection of the micro-roughness filter can now also be set separately for profile and lead (previously under ‘Settings’ - can only be set the same for profile and lead)
- The settings for the measurement can be set automatically via the Sc classes (if these are to be set manually, ‘Free configuration’ must be selected)
- Changes to the measurement sheet
- If measured according to a Sc class, this is output on the measurement sheet
- If evaluated according to the new standard, this is output on the roughness measurement sheet in the top left-hand corner
Further information on settings can be found at
https://wiki.klingelnberg.com/spaces/ME/pages/241075555/Rauheit+ISO+21920