AGMA 99FTM2-1999 Traceability Strategies for the Calibration of Involute Spline Gauges《渐开线花键量规校准所需可追溯策略》.pdf

《AGMA 99FTM2-1999 Traceability Strategies for the Calibration of Involute Spline Gauges《渐开线花键量规校准所需可追溯策略》.pdf》由会员分享，可在线阅读，更多相关《AGMA 99FTM2-1999 Traceability Strategies for the Calibration of Involute Spline Gauges《渐开线花键量规校准所需可追溯策略》.pdf（8页珍藏版）》请在麦多课文档分享上搜索。

1、Traceability Strategies for the Calibration of Involute Spline Gauges by: W. Beyer, Physikalisch-Technische Bundesanstalt I TECHNICAL PAPER Traceability Strategies for the Calibration of Involute Spline Gauges Wolfgang Beyer, Physikalisch-Technische Bundesanstalt me statements and opinions contained

2、 herein are those of the author and should not be construed as an official action or opinion of the American Gear Manufacturers Association. Abstract Much is being reported about the form and shape of running gears, little, however, about the same featuresof splines and serration, although the latte

3、r, too, are installed in every automobile. It is, of c0urse.a well- known fact that the permissible geometrical tolerances for spline and serration gauges are often as narrow as those for running gears. According to IS0 17025 (draft), measuring and test equipment - among which spline and serration g

4、auges are counted - must have been linked up with recognized national or international primary standards through an unbroken traceability chain. Since the sixties, national standards and standard measuring devices have. therefore been available in Germany for running gears, for example for the eleme

5、nts: profile, helix, pitch, tooth thickness, radial run-out of gearing, roughness. On the other hand no direct iink-up with the SI unit mefre has so far been made at PTB for splines and serration. nor has a laboratory been accredited within the framework of DKD. In contrast to this, several laborato

6、ries have been accredited in the United Kingdom, one of which may calibrate up to 70 measurands that have been embodied on spline and serration gauges. If one would proceed according to the DKD traceability criteria valid within the DKD for other geometrical measurands, a large number of PTB calibra

7、tions on reference standards or comparison measurements with the PTB on spline and serration gauges would be necessary. and this would, of course, involve relatively high cost. It might. therefore. be an alternative to ensure traceability for the measuring instrument only (e.g. a CMM) - here referre

8、d to ascategory A - and to estimate the uncertainty budget for the individual measurands. However, the smallest possible uncertainty of measurement according to IS0 15530-4 (draft) would not be achievable in this way. Examples will be given in the paper which prove that, in view of the narrow tolera

9、nces, it will often be necessary to trace splines and serration gauges back with the smallest possible uncertainty (here referred to as category B). The task-specific uncertainty of measurement must then be determined, which is obtained through measurementson a CMM for which traceability has been en

10、sured, in combination with traced-back, precise gear standards applying the so-called substitution method (IS0 15530-4). By bringing up this topic, the author wishes to put up for discussion whether internationally uniform traceability criteria in compliance with IS0 17025 should be specified to ach

11、ieve comparability and mutual recognition of measurement results on the international level. Copyright O 1999 American Gear Manufacturers Association 1500 King Street, Suite 201 Alexandria, Virginia, 22314 October, 1999 ISBN: 1-55589-740-1 Traceability strategies for the calibration of involute spli

12、ne gauges Wolfgang Beyer, Wolfram Pahl, Physikalisch-Technische Bundesanstalt, Braunschweig/Germany I. Introduction Splines are used for torque transmission (in the same ,- axis). They are needed when (a) the driven component must be shifted on the driving component (in the case of change speed gear

13、s and clutches) and (b) when two % / Fig. 6: Two ball method (internal diameter) different measuring methods. These uncertainties could correspond to those achieved in category B calibrations (.e. CMM traced back through the complete traceability chain plus comparison with a precise primary spline s

14、tan- dard of the same kind). The reasons for conducting these investigations are, first, that the tolerances for the gauges often are very small so that it is to be expected that the required small uncertainties cannot be achieved with the hand-held equipment and with coordinate measuring ma- chines

15、 which have not been traced back. Secondly, proof was to be established that a task-specific measurement uncertainty of 1 . 2 pm can be achieved only with the very complex measuring equipment available in a national metrology institute. The tooth thickness in external gearings is usually meas- ured

16、indirectly via the size over one or two balls (cylin- ders), in internal gearings additionally in connection with a gauge block (Fig. 6). In the case of external gearings this is usually made with the aid of cylinders and a micrometer screw (Fig. 7) or on a measuring stand with cylinders and dial ga

17、uge. The tooth thickness can also be indirectly de- termined through measurement of the span size (Fig. 8). The PTB carried out measurements with a specially manufactured tooth thickness standard on two different coordinae measuring machines, applying four different measuring straiegies. Basically,

18、the single-ball measuring method was applied, .e. the measurements were related Fig, 7: Two bal, method (external diaineter) m -. to the very good cylindrical reference suriaces. Measurements on CMM-1 with index table (practically size over one ball). The standard was exactly adjusted to the centre

19、of the space width, then rotated on the index table in both directions by half the nominal space width (Fig. sa). The respective involute was traced in positions I and II. The actual space width was calculated from the measured values. Measurement on CMM-1 without index table. The two- flank positio

20、n was realized with the aid of a suitable ball (deviation from the nominal value of 3,O mm: c 1 pm) (Fig. 9b.). In this case, too, the standard was ad- justed to the centre of the space width. -A Fig. 8: Span size measurement one ball method 1 pm maller Ihan . the nominal value I I Fig. 9 a CEE: sta

21、tic Fig. 9b L2 Measurement on CMM-I with index table. On the basis of the measurements according to (a), the size over, i I measuring circle two balls was determined by addition of the results Fiq. 9d Fig. 9c Fig. 9: Tooth thickness measurements with different obtained for the size over one ball of

22、opposite space widths. In addition, the size over two balls was deter- measuring strategies mined from the runout and pitch measurements for op- posite space widths using the CMM program. In both cases, the 3 mm ball in two-flank contact served as a tracing element (Fig. 9c). The following values we

23、re obtained: nominal size. The comparison of the Ll/L3 and Lp/LJ values shows how well the results of the different measurements of the size over two balls agree. However, the actual size of the ball diameter is seldom so close to the d) Measurement on CMM-1 and CMM-2 (practically static). After adj

24、ustment to the centre of the space width, the two flanks are traced around the reference circle (= 5 pm above and below it) (Fig. 9d). 2 : size over one ball (added) = size over two balls: L1 + L3 = 52,5683 mm L2 + L4 = 52,5702 mm CMM measurement of size over two balls (from pitch and runout measure

25、ment): Results: L, + L3 = 52,5682 min The differences between the mean values (of 12 meas- L2 + Ld = 52,5700 mrn urements) obtained by methods (a) to (c) are not greater than 1 pm at most, c 0,5 pm on an average, These values 3 were, therefore, regarded as the most reliable ones. The calculaiion of

26、the uncertainty budget, therefore, furnished an uncertainty of measurement of = 1.0 pm (k = 2). The mean values of the results obtained by method (d) on the two CMMs furnished = 1,7 pm as the greatest difference, 1,5 pm on an average. This result shows that even under optimum conditions - .e. good g

27、eometric quality of the object tested, CMMs in temperature-controlled measure- ment rooms (I 0.1 OK) and traced back with ball plates, and an above-average number of measurement series - using, however, CMMs of different manufacturers, a task- specific uncertainty of measurement will be obtained for

28、 so-called static measurements, which will have to be val- ued at more than f 2 pm (category A). These values will, however, hardly be reached in normal calibrations in a calibration laboratory where the marginal conditions are worse! Be it alone because these laboratories are at a lower level of th

29、e traceability chain and do not have at their disposal such precise and special standards as a metrology institute. The British Calibration Service UKAS in fact accredits at present the tooth thickness with an un- certainty of 2,5 pm on the basis of the size over two balls, for an institute (not usi

30、ng the cylinder or ball method) even with 1,5 pm. The results show that international comparison measurements are necessary to harmonize the uncertainties of measurement. In Europe, within the EA (European co-operation for Accreditation) for example, we are in fact organizing comparison measurements

31、 for simple dial gauges and issue calibration certificates for them, however, for the more complex involute splines there is so far only little activity worldwide. A possible rea- son for this is that only a few countries are interested in these measurands (because of they do not have any production

32、 in this field). 2.2 Major diameter/minor diameter The tolerances for the major diameterlminor diameter must be especially narrow when diameter-fit splines are concerned (Fig. 3). But even in the case of involute splines the major diameters of the internal and external 4 gearings must today be measu

33、red, preferably on coordi- nate measuring machines. Here, too, task-specific uncer- tainties of measurement of 1,25 pm have been accredited for helical external spline gauges which have certainly not been demonstrably traced back. 2.3 circle diameter This runout can only be determined on coordinate

34、meas- uring machines with the object to be measured mounted in relation to a defined axis (Fig. 10). Measurement un- certainties of 1,25 prn, for which accreditation has already been granted, will be traceably realizable only with diffi- Runout of major diameter with respect to reference runout 7- F

35、ig. 1 O: runout between major diameterheference circle diameter culty! The measuring methods for this would have to be defined in directives to guarantee the comparability of the measurement results. The PT6 intends to carry out such measurements in future to find out which uncertainties of measurem

36、ent are achievable. 2.4 Fillet radii, undercuts, chamfers Large measurement uncertainties of 25 pm are in fact stated for these values (UKAS). However, the measuring method alone makes it very difficult to traceably measure these measurands, in particular when small modules are concerned, and to gra

37、nt accreditation which is on a safe basis. International agreements would be of great impor- tance. The PTB is at present not in a position to realize link-up with national standards for these measurands without much effort and outlay. 2.5 Circumferential backlash The circumferential backlash affect

38、s running smoothness and this is the reason why it is measured. The measure- ment is carried out in the form of a composite error meas- urement for which special measuring instruments are available (Fig. 11). However, these instruments are very complex and not absolutely accurate. Suitable instru- m

39、ents today are CMivls with the aid of which the internal and external gearings are determined separately; the ef- fective circumferential backlash is then calculated by simulation. This is an analytical inspection method to find an estimated effective size. With this method, the meas- urement of the

40、 circumferential backlash could become of greater importance than has been the case so far, be- cause the hand-held instruments so far available do not allow the effective tooth thicknesses /space widths (effec- tive spline) to be exactly examined (cf. also 2.5). 2.6 GO composite gauges and NOT GO s

41、ector gauges GO composite gauges are used to check compliance with the tolerance limit of the maximum effective tooth thick- ness and of the minimum effective space width and the, length of the permissible form diameter (Fig. 12). The NOT GO sector gauge is used to check compliance with the toleranc

42、e limit of the minimum actual tooth thickness and the maximum actual space width at the spur-side be- ginning of the gearing (Fig. 13). Precise GO composite gauges are best suited to determine the effective size, .e. the necessary minimum fit clearance. From this it follows that the manufacture of s

43、plines can still be best inspected by means of precise gauges. International comparison measurements for the harmonization of a reliable control of inspection, measuring and test equipment are indis- pensable here. The metrological problems with straight-sided splines and serration splines are simil

44、ar to those described in 2. u/ Fig. 11 : Circumferential Fig. 12: Go composite gauqes backlash measurement (internal/externai)ior - involute splines - Fig. 13: Not go sector gauges (internal/external) uncertainties of measurement achieved for complex ma- chine elements such as splines, and this with

45、 a view to improving the comparability of measurement results on the international level. It is not sufficient to demand, in compliance with IS0 17025 (draft), that all simple meas- uring and test equipment must have been traced back to national standards unless the complex measuring meth- ods for i

46、mportant machine elements are discussed on the international level and appropriate directives drawn up. The draft standard ISOWD 4156-3 concerning splines is, however, a good beginning! The authors should like thank Mr. Rudolf Och from the firm of Frenco for making the literature available. It has been the purpose of this paper to initiate a critical examination of the measuring methods used and of the 5 PUBUSHED BY AMERICAN GEAR MANUFACTURERS ASSOCIATION 1500 KING STRER, ALEXANDRIA, VIRGINIA 22314