1、 WORLDWIDE ENGINEERING STANDARDS General Specification GMW16676 Surface Roughness (Drawing Entry, Measuring Conditions, Profile Filters, Parameters) Copyright 2012 General Motors Company All Rights Reserved January 2012 Originating Department: GME Specification Center Page 1 of 17 1 Introduction Not
2、e: Nothing in this standard supercedes applicable laws and regulations. Note: In the event of conflict between the English and domestic language, the English language shall take precedence. 1.1 Scope. This standard describes rules for the indication of the surface texture in the engineering product
3、documents (e.g. drawings, specifications) by means of graphical symbols and texts. 1.2 Mission/Theme. Not applicable. 1.3 Classification. Not applicable. 2 References Note: Only the latest approved standards are applicable unless otherwise specified. 2.1 External Standards/Specifications. ISO 1302 I
4、SO 4287 ISO 11562 ISO 13565-2 ISO 3274 ISO 4288 ISO 13565-1 2.2 GM Standards/Specifications. GMW3059 3 Test Preparation and Evaluation 3.1 Resources. 3.1.1 Calibration. The test facilities and equipment shall be in good working order and shall have a valid calibration label. 3.1.2 Alternatives. Alte
5、rnative test facilities and equipment may also be used. However, all measuring variables as specified in this standard shall be determined correctly with respect to their physical definition. 3.1.3 Facilities. According to the relevant specification. 3.1.4 Equipment. According to the relevant specif
6、ication. 3.1.5 Test Vehicle/Test Piece. According to the relevant specification. 3.1.6 Test Required Information. According to the relevant specification. 3.1.7 Personnel/Skills. According to the relevant specification. 3.2 Preparation. According to the relevant specification. 3.3 Conditions. 3.3.1
7、Environmental Conditions. According to the relevant specification. 3.3.2 Test Conditions. Deviations from the requirements of this standard shall have been agreed upon. Such requirements shall be specified on component drawings, test certificates, reports, etc. 3.4 Instructions. According to the rel
8、evant specification. 3.5 Data. According to the relevant specification. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16676 Copyright 2
9、012 General Motors Company All Rights Reserved January 2012 Page 2 of 17 3.6 Safety. This standard may involve hazardous materials, operations, and equipment. This standard does not propose to address all the safety problems associated with its use. It is the responsibility of the user of this stand
10、ard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 3.7 Documentation. Samples of components or material released to this standard shall be tested for conformity with the requirements of this standard and approved by the re
11、sponsible GM Department prior to the start of delivery of production level components or materials. Any change to the component or material, e.g., design, function, properties, manufacturing process and/or location of manufacture requires a new release of the product. It is the sole responsibility o
12、f the supplier to provide the customer, unsolicited, with documentation of any change or modification to the product/process, and to apply for a new release. If not otherwise agreed to, the entire verification test shall be repeated and documented by the supplier prior to start of delivery of the mo
13、dified or changed product. In some cases, a shorter test can be agreed to between the responsible GM department and the supplier. 3.7.1 Test Results. With reference to this standard the test results shall be represented in a test report. 4 Requirements and Procedure 4.1 Statement of Surface Texture
14、in Engineering Product Documents. 4.1.1 Purpose and Application. Preferably the average roughness value Ra shall be indicated. If, due to functional requirements, e.g. for sealing surfaces, it is necessary to restrict the surface roughness, the maximum roughness value Rz1max shall be indicated in ad
15、dition to the average roughness value Ra. For the description of highly stressed technical surfaces (e.g. Sliding surfaces) the specification with Ra and Rz1max is not in most cases sufficient alone. There is the necessity to indicate for such surfaces additional roughness parameters referred to the
16、 function. In addition the roughness characteristics belong Rmr (c) according to ISO 4287 or Rpk, Rk, Rvk, Mr1 and Mr2 for “Surfaces having stratified functional properties” according to ISO 13565-1 and ISO 13565-2. Data on surface roughness, manufacturing methods or machining allowances shall only
17、be made if they are required for functional purposes or the aesthetic or physiological appearance and only on those surfaces where this is necessary. The indication of the surface roughness is not necessary if the usual manufacturing methods already ensure a sufficient finishing state of the surface
18、. Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16676 Copyright 2012 General Motors Company All Rights Reserved January 2012 Page 3 of
19、17 4.1.2 Symbols. Symbols without Specifications see Table 1. Table 1: Symbols without Specifications Index Symbols Meaning / Explanations S1 Basic symbol: The basic symbol consists of two straight lines of different length which are inclined by 60 in relation to the line representing the surface co
20、ncerned. This symbol in itself, without any additional information (for exception see paragraph 4.2.4), is not expressive. It shall only be used if it means “surface concerned”. When the basic symbol is used with additional information, hereby no decision has yet been taken, whether material shall b
21、e removed (Index S2) or whether material removal is not permitted (Index S3) to attain the specified surface quality. S2 Extended symbol for material removal: If material removal by mechanical machining is demanded to reach the specified surface quality, a traverse line shall be added to the basic s
22、ymbol. This symbol with no indication of any other detail shall be used only if it means: surface to be machined. S3 Extended symbol if Material Removal is not permitted: If material removal is not permitted to reach the specified surface quality, a circle shall be added to the basic symbol. This sy
23、mbol may be used for drawings to be created for a certain operation in order to make clear that a surface shall be left in the state of the previous operation, regardless of whether this state was achieved by machining or by another kind of processing. S4 Complete Symbol: If special surface informat
24、ion is required, an additional line shall be added to the longer line of the mentioned symbols. Additional Surface Texture Information in the Complete Symbol see paragraph 4.1.3.2 S5 Symbols of Simplified Drawing Specifications The meaning of the symbols is explained on the drawings. See also Figure
25、 7 4.1.3 Indications added to the Symbols. 4.1.3.1 Surface Texture Requirements. In order to ensure the clearness of a certain surface texture requirement in relation to the function of a certain surface, it is necessary to indicate other requirements such as the transmission characteristic, the sam
26、pling length, manufacturing methods, position and orientation of the surface and possible machining tolerances in addition to the surface parameter and its numerical value. It may be necessary to determine several different surface parameters so that the surface texture requirements clearly ensure t
27、he functional properties of the surface. 4.1.3.2 Positions of Additional Surface Texture Information in the Complete Symbol. The positions of the different surface texture requirements on the symbol are subsequently stated and described: Figure 1: Positions (a through e) for Additional Information (
28、Areas of Designation on the Complete Symbol) Copyright General Motors Company Provided by IHS under license with General Motors CompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16676 Copyright 2012 General Motors Company
29、All Rights Reserved January 2012 Page 4 of 17 Table 2: Designation on the Complete Symbol Position: Designation / Description a If only one surface texture requirement consisting of the surface parameter, the numerical value and the transmission characteristic / sampling length shall be indicated in
30、 the complete symbol. General: Transmission characteristic or sampling length (in mm), one blank, followed by a slash /“, one blank, followed by the designation of the surface parameter, two blanks, followed by its numerical value (in m), for which one line shall be used. Example: 0.0025-0.8 / Ra 1.
31、0 (position a, see also Note 2) Note 1: The transmission characteristic is indicated by the values of the cut-off wavelengths of the filters (in mm), separated by a separation sign (“). First of all, the short-wave filter Os is indicated, then the long-wave filter Oc. It is also possible to indicate
32、 only one of the two filters. In this case the second filter has the default value. If only one filter is indicated, the separation sign is maintained in order to distinguish between Os- or a Oc-filter. Example: 0.008 (Os -indication) or 0.25 (Oc -indication) Note 2: The transmission characteristic
33、shall only indicated if it shall be ensured that the surface is clearly defined by the surface texture requirement. If no transmission characteristic is indicated, the default transmission characteristic is applicable (paragraph 4.3.9, Table 6). b For a second (third or more) surface texture require
34、ment. If a third or more requirements are to be indicated, the symbol shall be extended accordingly in the horizontal direction. Example: Ra 0.8 (position a) Rz1max 7 (position b) c If it is demanded that the final state of the surface shall be attained by a certain manufacturing method, machining,
35、coating or other requirements to the manufacturing process (such as turning, grinding, rolling or other types), this process shall be written in a full text version or by a sign to be explained in the left hand lower corner of the drawing, over the horizontal line of the symbol. Example: MILLED (pos
36、ition c) d If the direction of lay shall be determined, this shall be stated by an additional symbol according to Table 1. The direction of lay is determined by the prevailing surface pattern which usually is produced as a result of the manufacturing method applied. Example: M (position d) e Indicat
37、ion of the machining allowance (in mm). The machining allowance is generally only indicated in those cases in which several process stages are indicated on the same drawing, e.g. on drawings of unmachined parts illustrating cast and rolled workpieces which contain the finished workpiece. Example: 1
38、(position e) 4.1.3.3 Statement of Numerical Values. With ISO 1302 the graduation of numerical values for roughness variables, which had to be used with preference in earlier versions of the standard according to ISO 468, has become obsolete. The indications are therefore no longer subject to a gradu
39、ation (e.g. Ra =.0.8; 1.6; 3.2; 6.3 .). 4.1.3.4 Tolerances for Numerical Values of Surface Parameters. Two possibilities of interpretation of the specified limits are distinguished: The 16 % - rule or the max- rule. Copyright General Motors Company Provided by IHS under license with General Motors C
40、ompanyNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-GM WORLDWIDE ENGINEERING STANDARDS GMW16676 Copyright 2012 General Motors Company All Rights Reserved January 2012 Page 5 of 17 The max- rule shall be applied, that means, the indicated numerical value for a rou
41、ghness parameter represents the highest value. Note 1: In the case of a tolerancing according to the max-rule, ISO 1302 requires the addition “max“ after the designation of the parameter (e.g. Ramax). Due to the max-rule to be applied to the numerical values of roughness parameters, this may be omit
42、ted. Note 2: With ISO 4288 the roughness parameter Rmax was renamed in Rz1max without explanation. This is already a maximum value. Definition of Rz1max (previously Rmax) see Figure 10. Note 3: The definition of Rz1max according to ISO 1302 can lead to an inevitable wrong interpretation. 4.1.3.5 Bil
43、ateral Tolerance Limits of a Surface Parameter. If it is necessary to establish an upper and a lower limit value, the requirement for the two tolerance limits shall be written in the complete symbol one above the other: The upper specified limit before which a “U” (for upper limit) shall be placed s
44、hall be put over the lower specified limit before which an “L” (“L” for lower limit) shall be placed. Example: U Ra 0.8 (position a) L Ra 0.35 (position b) Note: The data for the two tolerance limits may also be written on the “a” position if, e.g. for lack of space, this shall be necessary. Here, t
45、he upper tolerance limit shall be specified first, followed by a slash, and then the lower tolerance limit. Example: U Ra 0.8 / L Ra 0.35 4.1.3.6 Deviation from the Default Sampling Length. If the number of sampling lengths lr within the evaluation length ln deviates from the default value 5 (ln = 5
46、 x lr) stated in paragraph 4.2, the number of sampling lengths shall be indicated in connection with the filter characteristic according to the roughness parameter designation without any blank (see Figure 2). Note: For workpiece surfaces to which the default sampling length cannot be applied e.g. d
47、ue to the dimensions which are too short, the pre-travel and the post-travel (paragraph 4.2) shall be taken into consideration when indicating the number of sampling lengths. Regarding a Gaussian filter, this is half each of the sampling length ( Oc), i.e. when indicating e.g. three sampling lengths
48、 at least the length of four sampling lengths shall be available to measure the roughness of the workpiece surface. Figure 2: Example of Indicating (here: three) Sampling Lengths in Case of a Deviating Default Sampling Length Meaning/Explanation x The machining process shall be material removing (cl
49、osed roughness symbol) x Unilateral given upper Ra limit with 0.8 m x Transmission characteristic: x cut-off wavelength Oc (or sampling length respectively) = 0.8 mm, x (default value for Os according to the transmission characteristic = 2.5 m) x Evaluation length consisting of three sampling lengths (preset target value) x (Note: Evaluation length = 2.4 mm (3 x Oc), Traversed length lt = 3.2 mm (Evaluation length + Pre- and post- travel
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