ANSI AGMA 1106-A97-1997 Tooth Proportions for Plastic Gears.pdf

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1、ANSI/AGMA 1106-A97Metric Edition of ANSI/AGMA 1006-A97Reaffirmed May 2009American National StandardTooth Proportions for PlasticGearsANSI/AGMA1106-A97iiTooth Proportions for Plastic GearsANSI/AGMA 1106-A97Metric edition of ANSI/AGMA 1006-A97Approval of an American National Standard requires verifica

2、tion by ANSI that the require-ments for due process, consensus, and other criteria for approval have been met by thestandards developer.Consensus is established when, in the judgment of the ANSI Board of Standards Review,substantial agreement has been reached by directly and materially affected inte

3、rests.Substantial agreement means much more than a simple majority, but not necessarily una-nimity. Consensus requires that all views and objections be considered, and that aconcerted effort be made toward their resolution.The use of American National Standards is completely voluntary; their existen

4、ce does notin any respect preclude anyone, whether he has approved the standards or not, frommanufacturing, marketing, purchasing, or using products, processes, or procedures notconforming to the standards.The American National Standards Institute does not develop standards and will in nocircumstanc

5、es give an interpretation of any American National Standard. Moreover, noperson shall have the right or authority to issue an interpretation of an American NationalStandard in the name of the American National Standards Institute. Requests for interpre-tation of this standard should be addressed to

6、the American Gear ManufacturersAssociation.CAUTION NOTICE: AGMA technical publications are subject to constant improvement,revision, or withdrawal as dictated by experience. Any person who refers to any AGMATechnical Publication should be sure that the publication is the latest available from theAss

7、ociation on the subject matter.Tables or other self-supporting sections may be quoted or extracted. Credit lines shouldread: Extracted from ANSI/AGMA 1106-A97, Tooth Proportions for Plastic Gears, withthe permission of the publisher, the American Gear Manufacturers Association, 1500 KingStreet, Suit

8、e 201, Alexandria, Virginia 22314.Approved August 7, 1997ABSTRACTThis standard presents a new basic rack, AGMA PT, which, with its full round fillet, may be preferred in manyapplications of gears made from plastic materials. It also explains and illustrates the general concept of thebasic rack. It c

9、ontains a description, with equations and sample calculation, of how the proportions of a spur orhelical gear may be derived from the design tooth thickness and the basic rack data. These equations andcalculations use ISO based symbols and metric units. In several annexes, there are discussions of p

10、ossiblevariations from this basic rack and also a procedure for defining tooth proportions without using the basic rackconcept.Published byAmerican Gear Manufacturers Association1500 King Street, Suite 201, Alexandria, Virginia 22314Copyright 1997 by American Gear Manufacturers AssociationAll rights

11、 reserved.No part of this publication may be reproduced in any form, in an electronicretrieval system or otherwise, without prior written permission of the publisher.Printed in the United States of AmericaISBN: 1-55589-685-5AmericanNationalStandardANSI/AGMA 1106- A97AMERICAN NATIONAL STANDARDiiiCont

12、entsPageForeword iv.1 Scope 1.2 Definitions and symbols 13 Tooth proportions and basic rack 34 Standard basic rack for plastic gears 3.5 Gear tooth proportions from basic rack data 8.Tables1 Nomenclature: symbols and terms 1.2 Standard basic racks (based on unit module) 4Figures1 AGMA PT basic rack

13、(for m or mn=1)32 Example of AGMA PT basic rack modified with tip relief 5.3 Comparison of calculated bending stresses at fillets from AGMA Fine-Pitchand AGMA PT basic racks 64(a) Effect of fillet shape on mold flow 74(b) Effect of fillet shape on fiber orientation close to surface (at mid-facewidth

14、location) 74(c) Effect of fillet shape on fillet surface temperature during freezing 7.4(d) Comparison of shrinkage effect in undercut pinion with sharp and roundedfillets 8.5 Tooth outline features introduced by tip rounding on external gears 11AnnexesA Basic rack description and application 13.B E

15、xperimental basic racks for plastic gears 21C Determination of tooth thickness and other design variables 23D Gear tip relief from a modified basic rack 27.E Alternate practices for defining tooth proportions 31F Generating gear geometry without racks 37.G Sample calculations 43.Bibliography 47.ANSI

16、/AGMA 1106- A97 AMERICAN NATIONAL STANDARDivForewordThe foreword, footnotes, and annexes are provided for informational purposes only andshould not be construed as a part of ANSI/AGMA 1106-A97, Tooth Proportions for PlasticGears.AGMA has issued standards for gear tooth proportions over a period of m

17、any years. Themost recent versions have been AGMA 201.02 (withdrawn 1995), Tooth Proportions forCoarse-Pitch Involute Spur Gears, and ANSI/AGMA 1003-G93, Tooth Proportions forFine-Pitch Involute Spur and Helical Gears. These standards and their predecessors wereprepared in response to the need to st

18、andardize gear generating cutting tools such as hobsand shaper cutters. Without such standards, the variety of tools needed by gear shopswould have become unlimited.The manufacture of gears by the molding process is not subject to the same practicalconstraints as manufacture by the gear cutting proc

19、ess. Every mold is inherently“non-standard”. The geometry of the mold cavity cannot follow a standard because ofvarying allowances for shrinkage. Furthermore, there are some methods for manufacturingthe mold cavity which do not depend on cutting tools and, even for those that do, specialtools are ge

20、nerally required. Thus, tooth proportions for molded plastic gears need notfollow those established for machined gears.Some of the special properties of plastic materials influence the selection of gear toothproportions as the two following examples illustrate:- The structure and orientation of plas

21、tic molecules, regardless of processing method,makes the strengths of the materials particularly sensitive to sharp internal corners. Asubstantially stronger tooth will result if sharp fillets at the base of the tooth are avoided.The tooth proportions for gears made according to the AGMA fine-pitch

22、standard notedabove generally result in relatively sharp fillets.- In certain applications, the higher expansion properties of plastic materials maycreate the need for a greater depth of engagement between mating gears than permittedby the other standard tooth forms.As a result of this preference fo

23、r a different tooth form, members of the plastic gear moldingindustry have adopted their own individual sets of tooth proportions. One set that has gainedwide usage by plastic gear designers, and is often specified in place of the AGMAFine-Pitch Standard, has been developed by William McKinley 1. Be

24、cause these toothforms contain the preferential features for molded plastic gears and because they arealready well recognized in the industry, they were used, with some changes, as models inthe preparation of this standard. The first of the four variations in this set has a depth ofengagement, or wo

25、rking depth, that is the same as in the above mentioned AGMAstandards. The other three have increased depths of engagement in varying degrees. Thisstandard has selected only the first variation, which is the one in widest use, as the model forthe new tooth proportions. However, data similarly based

26、on the other three variations areincluded in annex B.The tooth forms in this standard are defined with the use of the basic rack concept. For thosethat might be unfamiliar with this concept, a detailed description of the basic rack is includedas annex A.Suggestions for the improvement of this standa

27、rd will be welcome. They should be sent tothe American Gear Manufacturers Association, 1500 King Street, Suite 201, Alexandria,Virginia, 22314.ANSI/AGMA 1106- A97AMERICAN NATIONAL STANDARDvPERSONNEL of the AGMA Plastic Gearing CommitteeChairman: I. Laskin Irving Laskin, P.EVice Chairman: H. Yelle Ec

28、ole Polytechnique de Montral.ACTIVE MEMBERSM.A. Bennick RTP Company.R. Casavant GW Plastics, Inc.D. Castor Eastman Kodak Company.C.M. Denny Consultant.D.S. Ellis ABA-PGT, IncK. Gitchel Universal Tech. Systems, Inc.J.W. Kelley Shell Chemical Company.R. Kleiss Kleiss Engineering.S. Legault Seitz Corpo

29、rationA. Milano Seitz Corporation.S.D. Pierson ABA-PGT, Inc.J.T. Rill Black top land Eq 8saeEEffective top land with tip rounding Eq 30saeRRemaining top land with tip rounding Eq 28saiTooth thickness at inside diameter of spur internal gear; inside tip land Eq 12snNormal tooth thickness at reference

30、 diameter 5.4snaiNormal tooth thickness at inside diameter of helical internal gear; normal insidetip landEq 27snaeNormal tooth thickness at outside diameter of helical external gear; normal toplandEq 23snaeEEffective normal top land with tip rounding Eq 34snaeRRemaining normal top land with tip rou

31、nding Eq 32staiTransverse tooth thickness at inside diameter of internal helical gear Eq 25staeTransverse tooth thickness at outside diameter of external helical gear Eq 21y Rack shift Eq 2z Number of teeth of gear 5.1 Profile angle of basic rack; pressure angle at reference diameter of spur gear;no

32、rmal pressure angle at reference diameter of helical gearFigure 1aiPressure angle at inside diameter of spur internal gear Eq 11naeNormal pressure angle at outside diameter of helical external gear Eq 31aePressure angle at outside diameter of spur gear Eq 7tTransverse pressure angle at reference dia

33、meter of helical gear Eq 17taiTransverse pressure angle at inside diameter of helical gear Eq 24taeTransverse pressure angle at outside diameter of helical gear Eq 20 Helix angle at reference diameter 5.4aiHelix angle at inside diameter of internal helical gear Eq 26aeHelix angle at outside diameter

34、 of external helical gear Eq 22ANSI/AGMA 1106- A97AMERICAN NATIONAL STANDARD33 Tooth proportions and basic rackIt is general practice to establish a system of toothproportions by defining a basic rack. The actualtooth outline for a gear with a specified number ofteeth and value of tooth thickness wi

35、ll be generallydetermined by the generating action of this rack-shaped outline. (Some features of the tooth outlinemay be determined by additional considerations.See 5.8.1, 5.8.2 and 5.8.3.) A description of thisbasic rack concept and how it is applied to varioustypes of gears is given in annex A.4

36、Standard basic rack for plastic gearsA standard basic rack is established in this AGMAstandard. Plastic gears with tooth forms defined bythis basic rack will mesh properly with both AGMAfine-pitch and ISO coarse-pitch gears. (Threeexperimental basic racks with greater workingdepths are defined in an

37、nex B.)NOTE: This basic rack is an optional alternative to oth-er AGMA basic racks. It will often be preferred for thoseapplications in which tooth bending strength is a majorfactor in the design of plastic gears. See 4.4.4.1 DesignationsThis basic rack is designated as:AGMA Plastic Gearing Toothfor

38、m, abbreviatedas: AGMA PT.4.2 ProportionsThe basic rack is shown in figure 1. The figureidentifies all the features described in A.2. Values ofthe dimensional features are listed in table 2 alongwith comparative values for the AGMA fine-pitchstandard and the ISO mostly coarse-pitch standard.All of t

39、hese values are referenced to unit module.Actual values are found by multiplying the tablevalues by the module.sBR=2eBR=2rfBR= 0.43032PitchLinehaBR=1.00htBR=2.33hfFBR= 1.04686hfBR= 1.33pBR= cBR=0.33hkBR=2.00 =20Dimensional features:cBR= clearance hfFBR= form dedendum rfBR= fillet radiuseBR= space wi

40、dth hkBR= working depth sBR= tooth thicknesshaBR= addendum htBR= whole depth = profile anglehfBR= dedendum pBR= circular pitchFigure 1 - AGMA PT basic rack (for m or mn=1)ANSI/AGMA 1106- A97 AMERICAN NATIONAL STANDARD4Table 2 - Standard basic racks (based on unit module)Basic rack feature AGMA PTANS

41、I/AGMA 1003- G93fine- pitchISO 53 (1974)coarse pitchProfile angle, 1)20 deg. 20 deg. 20 deg.Circular pitch, pBR3.14160 3.14160 3.14160Tooth thickness, sBR1.57080 1.57080 1.57080Addendum, haBR1.00000 1.00000 1.00000Whole depth, htBR2.33000 2.20000 (+0.05000)2)2.25000Fillet radius, rfBR0.43032 0.00000

42、3)0.38000Dedendum, hfBR1.33000 1.20000 (+0.05000)2)1.25000Working depth, hkBR2.00000 2.00000 2.00000Clearance, cBR0.33000 0.20000 (+0.05000)2)0.25000Form dedendum, hfFBR4)1.04686 1.20000 (+0.05000)2)1.05261Space width, eBR1.57080 1.57080 1.57080NOTES:1) is also the pressure angle at reference diamet

43、er of spur gear or the normal pressure angle at reference diameterof helical gear.2)After multiplying the table value by the module, add the value in parentheses.3)ANSI/AGMA 1003-G93 states: “A zero fillet radius implies a sharp corner on the tip of the generating tool. In actualpractice, the corner

44、 is made with a small radius.”4)hfFBRis the distance from pitch line to start of fillet radius.4.3 Optional modificationsCertain modifications may be made to these basicracks without deviating from their essential charac-ter. When any such change is desired, a descriptionin an appropriate form must

45、be included in the gearspecifications.4.3.1 Profile modificationIt is sometimes desirable to make slight modifica-tions to the involute profile of the gear. One suchexample is tip relief. This is the removal of a smallsliver of material along a portion of the involuteleading to the tooth tip. Tip re

46、lief will often benefitgear action by reducing the abrupt action accompa-nying load transfer between adjoining teeth,especially when the teeth are deflecting under aheavy load. Such modification to the tooth profilecan be introduced by an appropriate modification tothe straight-sided flank of the ba

47、sic rack tooth.When this is desired, a drawing of the modified basicrack is required as part of the gear specifications. Anexample of such a modification applied to the AGMAPT tooth form is shown in figure 2. Annex D providesequations for calculating the effect of thismodification on certain feature

48、s of the generatedtooth.4.3.2 Tooth- tip diameter modificationIt is sometimes necessary to change the outsidediameter of external gears or the inside diameter ofinternal gears from the diameters defined by thebasic rack. Some of these considerations arediscussed in 5.8.1 and annex C. Such adjustment

49、sdo not significantly depart from the standard basicrack and do not require a special basic rack drawingshowing the modification. The specification of theoutside or inside diameter is, by itself, sufficient todefine the modification.4.4 Comparison to other AGMA basic racksThis new basic rack is similar to the other listedAGMA basic racks. Gears derived from all of themwill generally operate together. However, there aredifferences which, for the new basic rack, may resultin plastic gear designs of enhanced load capacityand, particularly