Cut-off length in iso 4288

In ASME, all profile parameters are defined and calculated on the evaluation length. It also reintroduces the parameter Rmax that was once part of ISO and is a good complement to Rz.

This standard defines special parameters for the evaluation of periodic surfaces, especially in the field of mating surfaces. It is usually referred to as Dominant waviness. It defines three parameters calculated after a special zero bandpass filter :. These parameters are part of the Automotive module. This internal standard provides methods and parameters to analyze lead-reduced dynamic sealing surfaces.

It is referred to as Lead or Twist analysis. The following parameters are calculated:. This standard is available in the Lead Analysis Twist module. Wst, maximum absolute height difference of the waviness profile. MountainsMap offers several options to comply to these standards. ASME B VDA can be implemented by disabling the microroughness option in the Preferences.

Toggle navigation Guide. Can we Compare Ra and Sa? Profile Parameters Surface texture of mechanical components has been checked over 80 years in order to improve performances of manufactured products. The first roughness testers recorded surface heights using a stylus tip in contact with the surface and a traverse unit.

The measured profile was drawn on a carbon paper and a value of roughness was given on a galvanometer. Sampling length vs Evaluation length In order to overcome problems arising in the early profilometers, such as noise or repeatability, some parameters are meant to be calculated on profile segments sampling lengths and then averaged. Basically, the new structure will consist of at least three parts: Part 1 - Drawing indications. Will incorporate the content of ISO , plus new symbols.

Part 2 - Definitions and parameters. The total distance spanned by the consecutive Roughness Profile Sampling Lengths is called the Evaluation Length of the profile. The ends of the profile not part of the Evaluation Length are indicated by color shading. The roughness parameters can be calculated from the primary, the roughness and the waviness profile and to distinguish the parameters the names are preceded by a letter identifying the source profile:.

Where n is the number of points within a sampling length, and Z i ,is the height value at point i. Where n is the number of points within a sampling length, and Z i is the height value at point i. If this parameter is zero it means that the height distribution is symmetric, for example Gaussian distributed. Peaks will cause Xsk to become positive and valleys will cause Xsk to become negative. The Kurtosis describes the sharpness of the height distribution, A Gaussian distribution has a Kurtosis close to 3.

Wider distributions have a kurtosis less than 3 and narrower distributions a kurtosis greater than 3. High peaks or deep valleys will influence the kurtosis strongly. Percentage of the profile with height values greater than Zmax — c calculated over the entire Evaluation Length.

Zmax is the maximum height value within the Evaluation Length. In practice this is a read out of the abscissa value for a given ordinate, Zmax — c , on the Material Ratio Curve Abbott-Firestone curve. Material Ratio Curve. The relative amount of material above a certain height level in percent. Mean width of profile elements within the Evaluation Length Profile elements are neighboring peak-valley pairs.

National metrology laboratories such as NPL [ 36 ] and PTB [ 39 ] recommend calculating the profile element parameters over the evaluation length rather than for one sampling length at a time as stated in the ISO standard. This gives much more robust estimates for the profile element parameters. This differs from the ISO standard where local Rz values Rz1, Rz2 … for each sampling length interval are used. The roughness cut-off is identical to the roughness sampling length. An algorithm proposed by NPL [ 36 ] for merging peaks and valleys which fall below the height or spacing discrimination criteria is used.

Profile Elements consist of neighboring Peak and Valleys fulfilling the height and spacing criteria. Each profile element is described by its height and its width. Maximum profile peak height: R p , W p ,P p. The maximum height value within a Sampling Length. Maximum profile valley depth: R v , W v , P v. The minimum height value within a Sampling Length.