ANSI AGMA 1006-A97-1997 Tooth Proportions for Plastic Gears.pdf

1、ANSI/AGMA 1006-A97Reaffirmed May 2009American National StandardTooth Proportions for PlasticGearsANSI/AGMA1006-A97iiTooth Proportions for Plastic GearsANSI/AGMA 1006-A97Approval of an American National Standard requires verification by ANSI that the require-ments for due process, consensus, and othe

2、r 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 interests.Substantial agreement means much more than a simple majority, but

3、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 existence does notin any respect preclude anyone, whether he has approved the s

4、tandards 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 nocircumstances give an interpretation of any American National Standard. Moreover, n

5、operson 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 the American Gear ManufacturersAssociation.CAUTION NOTICE: AGMA technica

6、l 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 theAssociation on the subject matter.Tables or other self-supporting sections

7、may be quoted or extracted. Credit lines shouldread: Extracted from ANSI/AGMA 1006-A97, Tooth Proportions for Plastic Gears, withthe permission of the publisher, the American Gear Manufacturers Association, 1500 KingStreet, Suite 201, Alexandria, Virginia 22314.Approved August 7, 1997ABSTRACTThis st

8、andard 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 contains a description, with equations and sample calculations, of how th

9、e proportions of a spur orhelical gear may be derived from the design tooth thickness and the basic rack data. These equations andcalculations use traditional AGMA symbols and inch units. In several annexes, there are discussions of pos-sible variations from this basic rack and also a procedure for

10、defining tooth proportions without using the basicrack concept.Published byAmerican Gear Manufacturers Association1500 King Street, Suite 201, Alexandria, Virginia 22314Copyright 1997 by American Gear Manufacturers AssociationAll rights reserved.No part of this publication may be reproduced in any f

11、orm, in an electronicretrieval system or otherwise, without prior written permission of the publisher.Printed in the United States of AmericaISBN: 1-55589-684-7AmericanNationalStandardANSI/AGMA 1006- A97AMERICAN NATIONAL STANDARDiiiContentsPageForeword iv.1 Scope 1.2 Definitions and symbols 13 Tooth

12、 proportions and basic rack 34 Standard basic rack for plastic gears 3.5 Gear tooth proportions from basic rack data 8Tables1 Nomenclature: symbols and terms 12 Standard basic racks (based on unit pitch) 4Figures1 AGMA PT basic rack (for Pdor Pnd=1)3.2 Example of AGMA PT basic rack modified with tip

13、 relief 53 Comparison of calculated bending stresses at fillets from AGMA Fine-Pitchand AGMA PT basic racks 6.4(a) Effect of fillet shape on mold flow 74(b) Effect of fillet shape on fiber orientation close to surface (at mid-facewidthlocation) 7.4(c) Effect of fillet shape on fillet surface tempera

14、ture during freezing 7.4(d) Comparison of shrinkage effect in undercut pinion with sharp and roundedfillets 85 Tooth outline features introduced by tip rounding on external gears 11AnnexesA Basic rack description and application 13B Experimental basic racks for plastic gears 21.C Determination of to

15、oth thickness and other design variables 23D Gear tip relief from a modified basic rack 27E Alternate practices for defining tooth proportions 31.F Generating spur gear geometry without racks 37G Sample calculations 43Bibliography 47.ANSI/AGMA 1006- A97 AMERICAN NATIONAL STANDARDivForewordThe forewo

16、rd, footnotes, and annexes are provided for informational purposes only andshould not be construed as a part of ANSI/AGMA 1006-A97, Tooth Proportions for PlasticGears.AGMA has issued standards for gear tooth proportions over a period of many years. Themost recent versions have been AGMA 201.02 (with

17、drawn 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 standardize gear generating cutting tools such as hobsand shaper

18、 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 process. Every mold is inherently“non-standard”. The geometry of t

19、he 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 generally required. Thus, tooth proportions for molded plastic g

20、ears 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 plastic molecules, regardless of processing method,makes the stren

21、gths 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 standard notedabove generally result in relatively sharp fille

22、ts.- 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 for a different tooth form, members of the plastic gear moldingi

23、ndustry 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. Because these toothforms contain the preferential features for m

24、olded 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 working depth, that is the same as in the above mentioned AGMAst

25、andards. 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 on the other three variations areincluded in annex B.The tooth

26、 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 improvement of this standard will be welcome. They should be sent to theAmerican Gear Manufa

27、cturers Association, 1500 King Street, Suite 201, Alexandria,Virginia 22314.ANSI/AGMA 1006- A97AMERICAN NATIONAL STANDARDvPERSONNEL of the AGMA Plastics Gearing CommitteeChairman: I. Laskin Irving Laskin, P.EVice Chairman: H. Yelle Ecole Polytechnique de MontralACTIVE MEMBERSM.A. Bennick RTP Company

28、.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 CorporationA. Milano Seitz Corporation.S.D. Pierson ABA-PGT, Inc.J.T. Ri

29、ll Black inside tip land Eq 12tnNormal tooth thickness at standard pitch diameter 5.4tnINormal tooth thickness at inside diameter of helical internal gear; normal inside tiplandEq 27tnONormal tooth thickness at outside diameter of helical external gear; normal top land Eq 23tnOEEffective normal top

30、land with tip rounding Eq 34tnORRemaining normal top land with tip rounding Eq 32tOTooth thickness at outside diameter of spur external gear; top land Eq 8tOEEffective top land with tip rounding Eq 30tORRemaining top land with tip rounding Eq 28ttITransverse tooth thickness at inside diameter of int

31、ernal helical gear Eq 25ttOTransverse tooth thickness at outside diameter of external helical gear Eq 21y Rack shift Eq 2 Helix angle at standard pitch diameter 5.4IHelix angle at inside diameter of internal helical gear Eq 26OHelix angle at outside diameter of external helical gear Eq 22 Profile an

32、gle of basic rack; pressure angle at standard pitch diameter of spur gear;normal pressure angle at standard pitch diameter of helical gearFigure 1IPressure angle at inside diameter of spur internal gear Eq 11nONormal pressure angle at outside diameter of helical external gear Eq 31OPressure angle at

33、 outside diameter of spur gear Eq 7tTransverse pressure angle at standard pitch diameter of helical gear Eq 17tITransverse pressure angle at inside diameter of internal helical gear Eq 24tOTransverse pressure angle at outside diameter of external helical gear Eq 20ANSI/AGMA 1006- A97AMERICAN NATIONA

34、L 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 will be generallydetermined by the generating action of this rack-sh

35、aped 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 Standard basic rack for plastic gearsA standard basic rack is esta

36、blished 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 annex B.)NOTE: This basic rack is an optional alternative toother AG

37、MA basic racks. It will often be preferred forthose applications in which tooth bending strength is amajor factor in the design of plastic gears. See 4.4.4.1 DesignationsThis basic rack is designated as:AGMA Plastic Gearing Toothform, abbreviatedas: AGMA PT.4.2 ProportionsThe basic rack is shown in

38、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 these values are referenced to unit pitch.Actual values are found by

39、dividing the table valuesby the diametral pitch.tBR=2sBR=2rfBR= 0.43032PitchLineaBR=1.00htBR=2.33bFBR= 1.04686bBR= 1.33pBR= =20cBR=0.33hkBR=2.00Dimensional features:aBR= addendum hkBR= working depth sBR= space widthbBR= dedendum htBR= whole depth tBR= tooth thicknessbFBR= form dedendum pBR= circular

40、 pitch = profile anglecBR= clearance rfBR= fillet radiusFigure 1 - AGMA PT basic rack (for Pdor Pnd=1)ANSI/AGMA 1006- A97 AMERICAN NATIONAL STANDARD4Table 2 - Standard basic racks (based on unit pitch)Basic rack feature AGMA PTANSI/AGMA 1003- G93fine- pitchISO 53 (1974)coarse pitchProfile angle, 1)2

41、0 deg. 20 deg. 20 deg.Circular pitch, pBR3.14160 3.14160 3.14160Tooth thickness, tBR1.57080 1.57080 1.57080Addendum, aBR1.00000 1.00000 1.00000Whole depth, htBR2.33000 2.20000 (+0.00200)2)2.25000Fillet radius, rfBR0.43032 0.000003)0.38000Dedendum, bBR1.33000 1.20000 (+0.00200)2)1.25000Working depth,

42、 hkBR2.00000 2.00000 2.00000Clearance, cBR0.33000 0.20000 (+0.00200)2)0.25000Form dedendum, bFBR4)1.04686 1.20000 (+0.00200)2)1.05261Space width, sBR1.57080 1.57080 1.57080NOTES:1) is also the pressure angle at standard pitch diameter of spur gear or the normal pressure angle at standard pitchdiamet

43、er of helical gear.2)After dividing the table value by the diametral pitch, 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 is made with a small radius.”4)bFBRis the distance from

44、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 be included in the gearspecifications.4.3.1 Profile modifi

45、cationIt 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 relief will often benefitgear action by reducing the abrupt

46、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 basic rack tooth.When this is desired, a drawing of the modi

47、fied 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 features of the generatedtooth.4.3.2 Tooth- tip diameter modifica

48、tionIt 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 adjustmentsdo not significantly depart from the standard basicrack a

49、nd 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 in the case of molded plastic gears,also of greater accuracy