MBN 31007 13.pdf
Mercedes-Benz MBN 31 007-13 Engineering Standard Edition: 2009-04 Category: 31 Total No. of Pages (Including Annex): 3 Person in Charge: Hercke / Schloz Plant 019; Dept.: PWT/VFQ / GR/PQS Phone: 5 67 41 / 3 49 81 Geometrical Product Specifications (GPS) Surface Texture Parameter BZH: Quality number height step Geometrische Produktspezifikationen (GPS) Oberflächenbeschaffenheit Kenngröße BZH: Be- wertungszahl Höhensprung Foreword Steep-walled variations in the level of a surface often impair the functional behavior of components such as the static sealing properties. This Standard defines the parameter BZH which systemati- cally evaluates this characteristic in the profile section. NOTE: No guarantee can be given in respect of this translation. In all cases the latest German-language version of this Standard shall be taken as authoritative. Changes - New edition Copyright Daimler 2009 Unkontrollierte Kopie bei Ausdruck (PTB/11: Julia Bauer, 2010-11-11) MBN 31 007-13, 2009-04, Page 2 Copyright Daimler 2009 Contents 1 Scope.2 2 Normative References.2 3 Abbreviations, Acronyms, Definitions & Symbols2 4 Principles .2 5 Determination of the BZH 2 6 Drawing Note.3 Annex A: Profile illustrations.3 1 Scope The parameter quality number height step BZH is used for surfaces on which a steep profile transition results in functional impairment, e.g. for contact surfaces with static sealing requirements. 2 Normative References See MBN 31007-0 3 Abbreviations, Acronyms, Definitions & Symbols The definitions of VDA 2005 and VDA 2006 apply to this Standard. 4 Principles The characteristics of steep profile transitions (height steps) on the surface cannot be adequately evalu- ated on the basis of the parameters standardized so far. The calculation of the BZH value is based on a slope-related algorithm which reliably evaluates these characteristics. In contrast to the standard case of the profile measurement, the measuring direction for the determination of the BZH may also be parallel to the preferred machining direction. This case must be specified in the drawing note. 5 Determination of the BZH BZH is calculated from the primary profile. For the calculation, a window with a variable width of 1.0 mm to 2.5 mm is shifted from the profile start to the profile end by the step width of the profile point spacing. For each step, the greatest absolute value of the relevant profile height difference is calculated. In order to increase the weighting of the height struc- tures, the calculated greatest absolute value is multiplied with the larger of the two profile values analyzed. The BZH results from the maximum value of all values analyzed in this way, divided by the value of the associated lateral window width in mm. BZH is indicated in µm²/mm. Annex A contains profile illustrations with associated BZH values. Unkontrollierte Kopie bei Ausdruck (PTB/11: Julia Bauer, 2010-11-11) MBN 31 007-13, 2009-04, Page 3 Copyright Daimler 2009 6 Drawing Note The drawing note consists of the basic symbol of the surface tolerance with a horizontal line for material- separating machining. The evaluation length must be indicated before the code BZH, separated by an oblique stroke. If the measuring direction deviates from the standard case (normal to the machining direc- tion), it must be identified by placing ´P´ (parallel to machining structure) before the value of the evaluation length, separated by an oblique stroke. Table 1 shows examples of drawing notes for both specifications. Table 1 Drawing notes (examples). Drawing note Interpretation Measuring direction normal to machining structure Evaluation length 12.5 mm The upper limit value for BZH is 50 µm²/mm Measuring direction parallel to machining structure Evaluation length 4.0 mm The upper limit value for BZH is 80 µm²/mm Figure 1: Drawing notes for quality number height step BZH End of main document # # # # # Annex A: Profile illustrations P / 4 / BZH 80 12.5 / BZH 50 BZH = 663.4 µm²/mm BZH = 44.5 µm²/mm Unkontrollierte Kopie bei Ausdruck (PTB/11: Julia Bauer, 2010-11-11)
