Methods for the assessment of departure from roundness - Measurement by two- and three-point methods

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1 nternatonal 4292 YTERNATONAL ORGANlZArOh FOR STANPARDZATON*MEXflYHAPOflHAR OPrAHL43AUL4R fl0 CTAHAAPTM3AUMM.OAGANlSATlON NTERNATONALE DE NORMALSATON Voorbeeld Prevew Dt document mag slechts op een standalone PC worden genstalleerd. Gebruk op een netwerk s alleen. toestaan als een aanvullende lcenteovereenkomst voor netwerkgebruk met NEN s afgesloten. Ths document may only be used on a standalone PC. Use n a network s only permtted when a supplementary lcense agreement for us n a network wth NEN has been concluded. Methods for the assessment of departure from roundness Measurement by two and threepont methods Méthodes d'évaluaton des écarts de crcularté Frst edton Mesuraqe par les méthodes w dec;x et tros ponts UDC Ref. No. S (E) E 3 Descrptors : metrology, surface condton, roundness measurement, error analyss O E Prce based on 8 pages

2 Voorbeeld Foreword S0 (the nternatonal Organzaton for Standardzaton) s a worldwde federaton of natonal standards bodes (S0 member bodes). The work of preparng nternatonal Standards s normally carred out through S0 techncal commttees. Each member body nterested n a subject for whch a techncal commttee has been establshed has the rght to be represented on that commttee. nternatonal organzatons, governmental and nongovernmental, n lason wth SO, also take part n the work. Draft nternatonal Standards adopted by the techncal commttees are crculated to the member bodes for approval before ther acceptance as nternatonal Standards by the S0 Councl. They are approved n accordance wth S0 procedures requrng at least 75 YO approval by the member bodes votng. nternatonal Standard S was prepared by Techncal Commttee SOTC 57, Me frology and propertes of surfaces. Prevew C nternatonal Organzaton for Standardzaton, Prnted n Swtzerland

3 NTE R N AT O N AL STAN DARD S (E) Methods for the assessment of departure from roundness Measurement by two and threepont methods Voorbeeld Prevew Scope and feld of applcaton Ths nternatonal Standard specfes methods of numercal assessment of outofroundness detered by the combnaton of two and threepont measurement : a deteraton by means of twopont measurement (measurement of dameters) : b deteraton by means of threepont measurement, summt (symmetrcal or asymmetrcal settng) : c deteraton by means of threepont measurement, rder (symmetrcal settng). Any statement regardng an outofround secton s ncomplete unless the extent and nature of the departures from roundness are gven. Methods for makng such descrptons and evaluatng them are specfed n S For routne or nprocess nspecton, the procedure specfed n S0 429 rnay ether be needlessly accurate or the tems to be nspected may be too large to be accommodated. The methods specfed gve faster ard cheaper ways of assessng departures from roundness. Ths assessed value wll devate from the true value. The dfference between the measured value and the true value can be estmated wth the help of tables 2 to 8. assug that the undulaton numbers are known and of snusodal nature. For nonsnusodal undulatons, a theory for estmatng such devatons s not yet alable. 2 References S0 429, Methods for the assessment of departure from roundness Measurement of varatons n radus. S0 638, Measurement of roundness Terms, defntons and parameters of roundness. 3 Defntons For the purpose of ths nternatonal Standard, the defntons gven n S0 638 and the followng apply. 3. twopont measurement : Measurement between coaxal anvls, one fxed and one movng n the drecton of measurement. See fgures and threepont measurement : Measurement between anvls, two fxed and one movng n the drecton of measurement. See fgures 3 to summt method : A threepont measurement n whch the two fxed anvls are stuated on one sde and the measurng anvl s stuated on the other sde of the workpece axs n the plane of measurement, See fgures 3, 4, 6 and rder method: A threepont measurement n whch the two fxed anvls are stuated on the same sde as the measurng anvl n the plane of measurement. See fsures 5 and symmetrcal (threepont) settng : A settng at whch the drecton of measurement concdes wth the bsector angle between fxed anvls. See fgures 3, 5, 6 and asymmetrcal (threepont) settng : A settng at whch the drecton of measurement consttutes an angle wth the bsector angle between fxed anvls. See fgures 4 and 7 4 Measurement n order to cover all possble form devatons and numbers of undulatons, a complete measurement should always consst of one twopont measurement and two threepont measurements at dfferent angles between fxed anvls. n ths nternatonal Standard, several alternatves are gven when choosng angles between fxed anvls (see table ). The measurement procedures rnay, under certan precondtons, be amplfed. See tables 2 to 4.

4 P S ( E l Table Svrnrnetrcal settng Angle between fxed anvls, f j anr ' 2 0 d:g Asymmetrcal settng j Angle hetween drecton of measurement and bsector of anqle between fxed anvls, fl 60 30' Angle hetween fxed anvls, n ' Vo 77 and 08" There 5 a lmt OP the mum number of undulatons t o be used when selectng F, accordny t o whether the number of d u l a t e n ç s known and whether ths number s an odd or even value Ths Drscondton S shown n tables 2 to 4 A n g l e s b e t w e e n fxed anvls?he c o r r e r t dvalue of the departure from roundness < qve? bv the eqaton For 90" and 20 settngs, the lmt s 22, whch assumes that a greater number of undulatons than ths wll not he any apprecable effect on the factor F'. For 72" and 0 8 O settngs, the lmt s detered by the fact that for 9 undulatons the factor F cannot be detered. S 'j l Factors F for threepont measurement, symmetrcal settncj, are gver n table 8. NOTE When usnq tables 5 to 8 other combnatons of çettnq besdes those gven!r tables 2 to 4 can he made F. where rhe correcton facror t has a value extracted from tables 2 t o 8 las a frst approxmaton, F may be gven a value of 2) F S 6 Measurng condtons and nstrument or 5 the measured departure from roundness t s the largest value obtaned from the precedng t w o or three cornbnatow of angles receved n the requred measurements 6. Measurng anvl statc force The statc measurng force should not exceed N. The force should, preferably. be adjustable and set at the lowest value that wll ensure cmtnuous contact between anvl and the surface beng measured 6.2 Measurng anvls 5 Dependng on the form of the object, the measurng anvl shall be selected from table 9, unless otherwse specfed. For thnwalled workpeces, a hgh measurng force may affect the measurng result. Therefore t s necessary t o reduce the force t o the mum value possble. be ew ev Pr Wher: measurng workpeces wth a known even or odd number of undulatons, the threepont measurement wth symmetrcal settng at 60 angles between fxed anvls may be used accordng t o table 8. Ths angle s usefu as t gves measured values of hgher correcton factors than the other angles n ths nternatonal Standard. When usng the 6ûo angle, the measured value shall be corrected wth the factor F' gven n table 8. Evaluaton of measurement errors Tables 5 t o 7 gve true factors F for any gven number of snusodal undulatons and measurng method. t s not possb!e t o calculate exactly the departure from round ness f the number of undulatons s unknown. n these cases a mum, erage and mum value of 6 can be calculated from the equaton n clause 4 usng the largest L value and the factors obtaned fron tables 2, 3 or 4. Fxed anvls eld f the number of snusodal undulatons k known, the calculaton of the departure from roundness s made by usng the F factors drectly from tables 5, 6, or 7 as ndcated n tables 2, 3, or Pont or lne contact shall always be used. The followng are recommended : for external measurement: Vsupport wth a small radus; the medan plane of the Vsupport shall be n the same plane as the plane of measurement. for nternal measurement : sphere wth a small radus; the medan plane of the sphere shall be n the same plane as the plane of measurement, 2

5 S (E: Voorbeeld \ Adjustable support Fgure Twopont measurement Fgure 2 Twopont measurement Prevew Fgure 3 Threepont measurement Summt method Symmetrcal settng / Fgure 4 Threepont measurement Summt method Asymmetrcal settng 80"U / Fgure 5 Threepont measurement Rder method Symmetrcal settng Fgure 6 Threepont measurement Summt method Symmetrcal settng 80" a \ Fgure 7 Threepont measurement Summt method Asymmetrcal settng Fgure 8 Threepont measurement Rder method Symmetrcal settng 3

6 S (El Number of undulatons. Table 2 90" and 20". symmetrcal settng Combnaton of settngs 2" and 3R 90" 2. and 3 R 20r 5 qj Factors unknown, put assumed to be 2ao,*22? mr 24 rnax mr, 95 Vo.. O O0 2 O0 + but assumed _.!, rs even and known odd ard known 2 O0... A 3R 90" 4' and 3R n 2 4' 47 O 42?,O0 80 'O0 Tn n s even but unknown, but assumed to be 2 C \ d 22 o. odd but unknown, to be 3 n, < 2 3 s 90' 2 and 3 s 20" 2 4' ma7 2 O0 80 way * exact 6' exact 6' exalt 5' exact 6)?O 00 O0 Twopon? measurement or 2 Threepont measurement, summt, O: = 90". 3) Threepont measurement, summt, a = 20" 4 Threepont measurement, rder, n = 90'. 5 Threepont measurement. rder, a = 20". 6 f multpled bv facrors F accordng to table 5. be ev Pr ew Table O and 0 8 O. symmetrcal settng Combnaton of 2 ' and 3 s 72" 2) and 3 s 08@3' of undulatons, rs ns unknown, but assumed to be 2 < nç < 8 ns even but unknown, but assumed to be 2 6 n s < 22 ns odd but unknown, but assumed to be 3 < ns 6 7 rs even and known n5 odd ard known tnn. l ,09.38, 2 l and 3R 72@4 ' 2 and 33 08O 5 rnax, 3 s 72" 2 3R 72' and 3s 08" 3' r Factors ' T + y 200 ' 2,oo 4 RC 3R 08 5' eld O0 O 38 Tax O 62 2, ,38 2, exact 6 4 exact 6'

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