1、AGMAINFORMATIONSHEET(This Information Sheet is NOT an AGMA Standard)AGMA909-A06AGMA 909-A06AMERICAN GEAR MANUFACTURERS ASSOCIATIONSpecifications for Molded Plastic GearsiiSpecifications for Molded Plastic GearsAGMA 909-A06CAUTION NOTICE: AGMA technical publications are subject to constant improvemen
2、t,revision or withdrawal as dictated by experience. Any person who refers to any AGMAtechnicalpublicationshouldbesurethatthepublicationisthelatestavailablefromtheAs-sociation on the subject matter.Tablesorotherself-supportingsectionsmaybereferenced. Citationsshouldread: SeeAGMA 909-A06, Specificatio
3、ns for Molded Plastic Gears, published by the AmericanGearManufacturersAssociation,500MontgomeryStreet,Suite350,Alexandria,Virginia22314, http:/www.agma.org.Approved July 18, 2006ABSTRACTThe objective of this information sheet is to inform the plastic gear designer of the importance to clearly andth
4、oroughly define the gear specifications to the plastic gear producer. This information sheet discusses thespecifications for gear tooth geometry, inspection, other gear features and manufacturing.Published byAmerican Gear Manufacturers Association500 Montgomery Street, Suite 350, Alexandria, Virgini
5、a 22314Copyright 2006 by American Gear Manufacturers AssociationAll rights 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: 1-55589-899-8Am
6、ericanGearManufacturersAssociationAGMA 909-A06AMERICAN GEAR MANUFACTURERS ASSOCIATIONiii AGMA 2006 - All rights reservedContentsPageForeword iv.1 Scope 1.2 Normative references 1.3 Symbols 1.4 Gear tooth geometry data 15 Inspection data 3.6 Other gear feature specifications 57 Manufacturing specific
7、ations 6.Bibliography 25.AnnexesA Plastic gear specifications 7B Simplified approach to plastic gear specifications 15.C An alternative method for specifying molded plastic gears 23.Tables1 Symbols 2.2 Basic gear data for external and internal spur gears 2.3 Basic gear data for external and internal
8、 helical gears 2.4 Tooth proportions data for external spur and helical gears 35 Tooth proportions data for internal spur and helical gears 3.6 Basic rack data for spur and helical gears 37 Composite inspection data 4.8 Master gear data 4.9 Alternate tooth thickness inspection data 5.AGMA 909-A06 AM
9、ERICAN GEAR MANUFACTURERS ASSOCIATIONiv AGMA 2006 - All rights reservedForewordThe foreword, footnotes and annexes, if any, in this document are provided forinformational purposes only and are not to be construed as a part of AGMA InformationSheet 909-A06, Specifications for Molded Plastic Gears.The
10、 committee, responding to the widely recognized need for improving the technicalcommunication between molded plastic gear purchasers and producers, developed thisspecification information sheet. The primary objective of this information sheet is toincreaseunderstandingbythegearpurchaseroftheresponsi
11、bilitytothoroughlydefinethegear requirements to the gear producer.Plasticgeartransmissiondesignandmanufacturingmustconsidertherelationshipofgeargeometry, layout, housings, shafts, bearings, and materials. Molded plastic gears offerconsiderabledesignflexibility. However,physicalpropertiesanddimension
12、swillvaryoverthe range of operating conditions. To accommodate these variations and the moldingprocess, the plastic gear designer must create detailed gear specifications for producingprototype or production gears. This information must clearly communicate to the gearproducer what the gear designer
13、specifies.The first draft of AGMA 909-A06 was made in June, 2001. It was approved by the AGMAmembership in July 18, 2006.Suggestionsforimprovementofthisdocumentwillbewelcome. TheyshouldbesenttotheAmericanGearManufacturersAssociation,500MontgomeryStreet,Suite350,Alexandria,Virginia 22314.AGMA 909-A06
14、AMERICAN GEAR MANUFACTURERS ASSOCIATIONv AGMA 2006 - All rights reservedPERSONNEL of the AGMA Plastics Gearing CommitteeChairman: Edward H. Williams, III GE Plastics - LNP.Vice Chairman: Richard R. Kuhr Enplas USA, Inc.ACTIVE MEMBERST. Barry Phillips-Moldex CompanyF. Eberle Hi-Lex Controls, IncD.S.
15、Ellis ABA-PGT, IncG. Ellis ABA-PGT, IncT. Grula DuPont Engineering - tooth proportions data;- basic rack data.Adherence to these formats is optional providedadequatespecificationsaresupplied. Foradditionalinformation on these features, see ANSI/AGMA1106-A97.AGMA 909-A06 AMERICAN GEAR MANUFACTURERS A
16、SSOCIATION2 AGMA 2006 - All rights reservedTable 1 - SymbolsSymbol Definition UnitsWherefirst usedDbBase diameter mm Table 2d Standard pitch diameter mm Table 2L Lead mm Table 3m Module mm 4.1mnNormal module mm Table 3mtTransverse module mm Table 3N Number of teeth - - Table 2PdDiametral pitch mm 4.
17、1pbBase pitch mm Table 2pNNormal base pitch mm Table 3 Pressure angle degrees Table 2nNormal pressure angle degrees Table 3tTransverse pressure angle degrees Table 3 Helix angle degrees Table 34.1 Basic gear dataThese data describe the gear in basic terms. Theydirectly describe the gear itself and d
18、o not includedata that apply to generating or inspection tooling.None of the data are accompanied by tolerances.Anypermittedvariationsfromthedescribedgeome-try or tolerances are expressed by separate dataelsewhere in the specification. Several secondarybasicgeardataareoftenaddedtoprovideadditionalhe
19、lpful information. These data can be calculatedfrom the primary basic gear data, however, and donot necessarily need to be specified. See tables 2and 3. When the diametral pitch, Pd, is specified,rather than module, m, replace m with 1/Pdin theequations.Table 2 - Basic gear data for external andinte
20、rnal spur gearsPrimary data UnitsNumber of teeth, N - -Module, m mmPressure angle, degreesSecondary dataStandard pitch diameter, dd = NmmmBase diameter, DbDb= d cos mmBase pitch, pbmmpb= DbNTable 3 - Basic gear data for external andinternal helical gearsPrimary data UnitsNumber of teeth, N - -Normal
21、 module, mnmmNormal pressure angle, ndegreesHelix angle, degreesHelix hand (left/right) - -Secondary dataTransverse module, mtmmmt=mncos Transverse pressure angle, tdegreest= tan 1tan ncos Standard pitch diameter, d mmd = NmtBase diameter, DbmmDb= dcos tNormal base pitch, pNmmpN= mncosnLead, LL = dt
22、an mm4.2 Tooth proportions dataComplete gear tooth geometry cannot be fullydefined by the basic gear data and basic rack datawithout additional tooth proportions data. Tables 4AGMA 909-A06AMERICAN GEAR MANUFACTURERS ASSOCIATION3 AGMA 2006 - All rights reservedand 5 list the tooth proportions data re
23、quired to fullydefine gear tooth geometry for external and internalspurandhelicalgears. Notethattheseitemsrequirea tolerance range. Sometimes the tooth outline,including the fillet, is fully defined by the toothproportions data. In that case, the basic rack datamay be omitted, see 4.3.Table 4 - Toot
24、h proportions data for externalspur and helical gearsItem Tolerance,mmNormal circular tooth thickness atstandard pitch diameter+/-Outer diameter +/-Root diameter +/-Involute form diameter max.Normal tooth tip radius +/-Effective outer diameter +/-Normal tip relief at effective outsidediameter+/-Diam
25、eter at start of tip relief +/-Normal root fillet radius (reference) min.For spur gears, where the helix angle equalszero, disregard the word “normal”.Table 5 - Tooth proportions data for internalspur and helical gearsItem Tolerance,mmNormal circular tooth thickness atstandard pitch diameter+/-Major
26、 diameter +/-Normal root fillet radius at major di-ameter (reference)min.Involute form diameter min.Minor diameter +/-Normal tooth tip radius at minordiameter (reference)+/-Effective minor diameter +/-For spur gears, where the helix angle equalszero, disregard the word “normal”.The outside diameter
27、of an external gear and theinternal diameter of an internal gear are not definedby the rack form. Therefore, they are required to bedirectly specified as part of the tooth proportionsdata.It is sometimes desirable to make modifications totheinvoluteprofileofageartooth,suchastiprelieforlead crown. Th
28、e tip relief, or other profile modifica-tion, is often not defined by specifying modificationsto the basic rack form, but rather by a separatedescription included in the tooth proportions data.4.3 Basic rack dataThese data apply to a generating form, and there-fore, only indirectly describe the gear
29、. Basic rackdataisincludedwhenthetoothoutline,especiallyinthefilletarea,isdefinedasifageneratingformwereused to create the outline. The basic rack datadescribes the outline of this generating form. Thismethod is used to produce gear sets that are lesslikely to have root fillet interference than usin
30、gcircular arcs and straight lines to describe the rootfillet.There are a number of basic rack standards in usefor plastic gearing. A basic rack specificationconsists of a reference to such a standard, and mayinclude a supplementary detail drawing.In some situations a standardized basic rack is notpr
31、eferred, because the tooth outline it defines maynot be optimal for a specific application. In suchcases the actual basic rack data must be specified,seetable6.Table 6 - Basic rack data for spur and helicalgearsPrimary data UnitsProfile (pressure) angle degreesModule mmDedendum from reference line m
32、mTooth thickness at reference line mmFillet radius mmTip relief features (optional) mm5 Inspection dataThese data consist of tolerances that serve as thebasis for specifying the accuracy of the gear.Included are indicators of gear tooth shape, size,alignment, and other features. If any of theinspect
33、ion data are based on the use of a mastergear or other inspection gage, reference to thatmastergearorgagemustbeincluded. Furthermore,if any of the inspection data are to be evaluated withspecial statistical requirements, reference to suchalsoshouldbeincluded. Someinspectionspecifica-AGMA 909-A06 AME
34、RICAN GEAR MANUFACTURERS ASSOCIATION4 AGMA 2006 - All rights reservedtion data might be used only during a first-piece ormold-approval inspection, while others will be usedin periodic process-control inspections.5.1 Accuracy systemsClassifyinggearaccuracybytheuseofanaccuracysystem,suchastheAGMAsyste
35、m,iswidelyusedinall parts of the gear industry. An accuracy level canconveniently identify the desired level of the follow-ing tolerances that are normally included in theinspection data:- composite tolerances;- total composite tolerance;- tooth-to-tooth composite tolerance;- elemental tolerances;-
36、radial runout;- pitch tolerance;- profile tolerance;- helix (lead) tolerance.The accuracy system was specifically designed forcut metal gears. It does not reflect the uniquecharacteristics of injection molded gears. Someinspection tolerances areeasier toachieve thanareothers depending on the manufac
37、turing method.The accuracy of metal gears is primarily controlledby its machining tolerances; a plastic gear has theadded variable of material shrinkage. Therefore, itmaybepreferredtospecifyanaccuracylevelandmodify certain individual inspection tolerances tomeet performance and cost requirements.5.2
38、 Composite inspection dataThesimplest,mosteconomical,andcommonlyusedsetofgearaccuracyverificationsisbasedondoubleflank composite testing in which composite mea-surements of tooth thickness, runout, profile, andpitch deviations are made while the test gear isrotated in tight mesh with a suitable mast
39、er gear. Alimiting test radius is a convenient way to specifygear size and errors when using double flankcomposite testing. See table 7.The master gear must be fully specified. Thisspecification is agreed upon between the designerand molder. See table 8.Table 7 - Composite inspection dataData Tolera
40、nce1)Accuracy level - -Total composite tolerance max.Tooth-to-tooth compositetolerancemax.Test radius min./max.Test load basicNOTE1)For definition of basic, see ANSI Y14.5M:1994.Table 8 - Master gear dataData Tolerance1)Master gear identificationClass - -Module basicPressure angle basicHelix angle/h
41、and basicNumber of teeth basicTooth thickness +/-Outside diameter +/-Root diameter max.Test diameter basicNOTE1)For definition of basic, see ANSI Y14.5M:1994.5.3 Elemental inspection dataAnother set of gear accuracy verifications is basedonmeasurementsofindividualgeartoothelements.Elemental inspecti
42、on provides greater detail of theindividual gear tooth elements. These measure-mentsaremadeoncomputer-controlledmeasuringmachines operated with special software. Thistypeof inspection is slower and more expensive thancomposite testing, and is typically used for first-piece or mold-approval inspectio
43、n, or when specialoperating requirements justify the greater expense.There are several elemental inspection standardsavailable. For example, AGMA 2000-A88 lists thefollowing elemental inspection criteria:- quality number (accuracy);- radial runout;- pitch variation;- profile tolerance;- tooth alignm
44、ent (lead) tolerance.AGMA 909-A06AMERICAN GEAR MANUFACTURERS ASSOCIATION5 AGMA 2006 - All rights reservedANSI/AGMA 2015-1-A01 lists the followingelemental inspection data:- accuracy grade;- single pitch deviation tolerance;- cumulative pitch deviation tolerance, total;- profile tolerance, total;- pr
45、ofile slope tolerance;- profile form tolerance;- helix tolerance, total;- helix slope tolerance;- helix form tolerance.5.4 Tooth thicknessAdditional indirect composite tooth thickness mea-surement techniques are available. The two mostcommonmethodsforexternalgearsareameasure-ment over pins or balls
46、and a tooth span measure-ment. The most common method for internal gearsis a measurement between pins or balls. Seetable 9.Table 9 - Alternate tooth thickness inspectiondataData Tolerance1)Pin or ball diameter basicMeasurement over/between pinsor balls+/-Number of pins or balls basicNumber of teeth
47、spanned basicSpan measurement +/-NOTE1)For definition of basic, see ANSI Y14.5M:1994.6 Other gear feature specificationsThere are other features that should be defined aspart of a complete injection molded gear specifica-tion. These features will appear as part of thedimensioned views in the gear dr
48、awing and will beinterpreted in accordance with general draftingconventions and practices.6.1 Datum specificationsIt is necessary to add a call out such as “datumsurface” or “mounting surface” to explicitly definehow the gear is to be positioned for inspectionpurposes. Where practical, the inspectio
49、n datumshould be the same as the datum that positions thegear in its application.6.2 Face widthThe gear face width must be specified. A specifica-tion of perpendicularity and parallelism on one orboth faces acts as a limit on the degree of allowabledistortion.6.3 Geometric featuresThe performance, precision and moldability of aninjection molded plastic gear will be affected by theoverall design of the part. Good plastic part designpractices s
