VW_13705-201308
Group standard VW 13705
Issue 2013-08
Class. No.:
02624Descriptors:surface finish, surface roughness, roughness, drawing specification, drawing note, engineering drawing,
average roughness, Ra, Rz, ripple
Specification of Surface Texture
Geometrical Product Specifications – Engineering Drawings
Previous issues
VW 13705: 1967-08, 1971-02, 1974-10, 1975-07, 1983-10, 1983-11, 1992-09, 2003-01, 2007-07,2009-09
Changes
The following changes have been made to VW 13705: 2009-09:
–Technical responsibility changed
–Section 3: Requirement on permissible depth of waviness Wd, without separate drawing speci‐
fication of Wd constrained –Section 4 "Additional conditions for cases of conflicts" added
–Section A.2 "Reference notes" removed
Contents Page Scope .........................................................................................................................2Conversion of Ra to Rz (Rz to Ra), conversion example and examples for surface profiles with Ra value and Rz value ..............................................................2Conversion of Ra values and Rz values ....................................................................2Conversion example with Ra value and Rz value ......................................................3Examples for surface profiles with approximately similar Ra values but different Rz values, see figure 3. ..............................................................................................4Surface requirements on the depth of waviness Wd without separate drawing specification ...............................................................................................................4Additional conditions for cases of conflicts .................................................................5Applicable documents (5)
Former practice (61)
2
2.1
2.2
2.3
3
4
5
Appendix A Always use the latest version of this standard.
This electronically generated standard is authentic and valid without signature.
The English translation is believed to be accurate. In case of discrepancies, the German version is alone authoritative and controlling.
Numerical notation acc. to ISO/IEC Directives, Part 2.Page 1 of 6
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VWNORM-2012-05p
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Scope The surface texture requirements in drawings are specified as per VDA 2005 (for deviation, see section 3).This standard only applies in connection with the application of VDA 2005.The requirements specified in section 2 must be adhered to for indicating Ra values and converting them into Rz values.Surface requirements on the depth of waviness Wd, without separate drawing specification, see section 3.
NOTE 1: The average roughness value Ra is only permitted in exceptional cases as it provides a lower level of information than the roughness depth Rz on account of the fact that different rough‐ness depth values can have the same average roughness value Ra.
Conversion of Ra to Rz (Rz to Ra), conversion example and examples for surface pro‐
files with Ra value and Rz value
Conversion of Ra values and Rz values If engineering drawings or other product documentation are compiled on the basis of partner com‐pany requirements, for example, with Ra values, the Ra values must be converted into Rz values using the following diagram (see figure 1).
The upper limit line of the scatter range is used to determine the Rz limit value for a prescribed Ra value.
The lower limit line of the scatter range is used to determine the Ra limit value for a prescribed Rz value.
The Rz values assigned to the Ra values and the Ra values assigned to the Rz values are subject to scatter. This is why the diagram shows a grid area rather than a graph.
Using the limit lines of the scatter range to determine the Rz and Ra values ensures that a suffi‐ciently high certainty factor is taken into account.
Note that with foreign production requirements the average roughness Ra (term used in UK "centre line average value CLA", term used in the USA "arithmetical average AA") is frequently given in μin (microinch) as compared to μm (micrometer). As a consequence, the Ra values are represented in both units in the diagram.
NOTE 2: There is neither theoretical reason nor empirical proof for a precise conversion of the average roughness value Ra to the roughness depth Rz or vice versa.
1 2 2.1
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Figure 1 – Diagram for converting Ra values and Rz values
2.2
Conversion example with Ra value and Rz value
In the drawings, the converted Rz value must be entered on the symbol along with the original Ra
value as a reference value in parentheses serving as the decisive indication of the conversion, see
figure 2.
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Examples for surface profiles with approximately similar Ra values but different Rz val‐
ues, see figure 3.
Figure 3
Surface requirements on the depth of waviness Wd without separate drawing specifica‐
tion
For all Volkswagen Group drawings that do not contain additional drawing specifications of the depth of waviness characteristic parameter Wd, the following requirement is applicable for static and dynamic sealing surfaces 1) and also for bearing surfaces 2), deviating from VDA 2005, i.e., with‐out separate drawing specification:
If there are no additional specifications for the waviness characteristic parameter (Wd), then the actual, measured Wd value must be less than or equal to the actual, measured Rz value for static and dynamic sealing surfaces and also for bearing surfaces. For an example, please refer to figure 4.
This regulation is applicable only for surfaces with specification of the roughness characteristic pa‐rameter (Rz).
2.3 3 1)
Static and dynamic sealing surfaces are the surfaces between which the sealing function is to be realized. Static sealing surfaces do not move relative to each other. Dynamic sealing surfaces move relative to each other. This movement can be either rotational or translational.
2)Example: Bearing surfaces are the bearing surfaces of plain bearings.
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Figure 4 – Drawing specifications and their meaning
NOTE 3: The surface requirements for the depth of waviness Wd must be specified as per VDA 2005, i.e.,the waviness must be specified directly in the drawing and then only if the function requires it. If the
Wd value is specified below the roughness characteristic parameter Rz, both measured values are applicable independently. For an example, please refer to figure 5.
Figure 5 – Drawing specifications and their meaning
Additional conditions for cases of conflicts
In cases of conflicts, a reference surface probe system with a probe tip radius of 5 μm must be used if the expected roughness value is greater than Rz = 2 μm or Ra = 0,4 μm. If the expected roughness values are smaller, a probe tip radius of 2 μm must be used for measurements.Applicable documents
The following documents cited in this standard are necessary to its application.
Some of the cited documents are translations from the German original. The translations of Ger‐man terms in such documents may differ from those used in this standard, resulting in terminologi‐cal inconsistency.Standards whose titles are given in German may be available only in German. Editions in other languages may be available from the institution issuing the standard.
VDA 2005Geometrical product specification - Technical drawings - Specification of
surface texture; inclusive Appendix 1
4 5
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Former practice If there are simplified roughness specifications in an old drawing, the Rz values in the table in
figure A.1 are applicable.
Figure A.1 – Preferred values for the simplified requirements of roughness depth Rz – former prac‐
tice Appendix A (informative)