ASME B46.1 pdf free download
ASME B46.1-2019 pdf free download.Surface Texture (Surface Roughness, Waviness, and Lay).
In cases of disagreement regarding the interpretation of surface texture measurements, It Is recommended that measurements with skidless stylus-based instruments with Gaussian filtering be used as the basis for interpretation. The following key measurement parameters must be established for proper surface texture specification and measurement.
2 FILTERING
The spatial wavelengths to be included in a surface texture measurement are generally limited by digital band-pass filtering. For measurement of roughness, short-wavelength cutoff, As, specifies the short spatial wavelength limit and is defined as the wavelength where the Gaussian filter will attenuate the true profile by 50%. Spatial wavelengths less than As are severely attenuated and minimally contribute to the roughness measurement.
The roughness long-wavelength cutolt Ac. specifies the long spatial wavelength limit and is defined as the wavelength where the Gaussian filter will attenuate the true profile by 50%. Spatial wavelengths greater than Ac are severely attenuated and minimally contribute to the roughness measurement.
The ratio of Ac to Ac (Ac:As) is the bandwidth of the measurement. Some instruments allow the selection of Ac and As individually and/or the selection of a bandwidth, typically 100:1 or 300:1. The spatial wavelengths comprising the texture between As and Ac are minimally attenuated by the Gaussian filter.
The cutoffs, Ac and As. should be chosen by the designer in light of the intended function of the surface. When choosing Ac and As, one must be cognizant that the surface features not measured within the roughness cutoff bandwidth may be quite large and may affect the intended function of the surface. Thus in some cases it may be necessary to specify both surface roughness and waviness.
When surface waviness control is important, digital band-pass filtering is applied similarly as it is for roughness filtering. For waviness, the waviness short-wavelength cutoff. Asw, and waviness long-wavelength cutoff, Acw, are applied to obtain the waviness profile. An important consideration is the correspondence of the roughness long-wavelength cutoff and the waviness short-wavelength cutoff. When these respective cutoff values are not equal. the discrimination of the roughness and waviness features of a given surface can become confounded.
On all surface texture specifications as of January 1997, Ac and As must be stated. When Ac and As are not specified, guidelines are given in paras. 3-3.20.1 and 3-3.20.2 for the metrologist to establish Ac and As. These guidelines are intended to Include the dominant features of the surface in the measurement whether these surface features are relevant to the function of the surface or not.
3 STYLUS TIP RADIUS
The stylus tip radius may be chosen by the designer or metrologist based on the value of As (i.e.. the short-wavelength cutoff). For As equal to 2.5 pm, the tip radius should typically he 2 pm or less. ForAs equal to H pm, the tip radius should typically be 5pm or less. For As equal to 25 pm. the tip radius should typically be 10 pm or less.
4 STYLUS FORCE
The maximum static measuring force is determined by the radius of the stylus and is chosen to assure minimal damage to the surface and that constant contact is maintained with the surface. Specific recommendations for stylus force may be found in para. 3-3.5.2.
5 MEASUREMENT PARAMETERS
Many surface finish height parameters are in use throughout the world. From the simplest specification of a single roughness parameter to multiple roughness and waviness parameter specifications of a given surface, product designers have many options for specifying surface texture to control surface function. Between these extremes, designers should consider the need to control roughness height (e.g., Ra or Rz), roughness height consistency (e.g., Rmax), and waviness height (e.g., Wi). Waviness Is a secondary longer wavelength feature that is only of concern for particular surface functions and finishing processes. A complete description of the various texture parameters may be found in Section 1.
6 SURFACE TEXTURE SYMBOLS
Once the various key measurement parameters are established, ISO 1302:2002 may be used to establish the proper indication on the relevant engineering drawings.ASME B46.1 pdf download.
