AGMA-93FTM12-1993.pdf
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1、93FTM12 The Generationof PrecisionSpurGears ThroughWire ElectricalDischargeMachining by: Roderick and Jack Kleiss, Kleiss Engineering and Scott Hoffmann, Accu-prompt EDM AmericanGearManufacturersAssociation TECHNICALPAPER Copyright American Gear Manufacturers Association Provided by IHS under licens
2、e with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:53:51 MDTNo reproduction or networking permitted without license from IHS -,-,- The Generationof Precision Spur Gears Through Wire ElectricalDischargeMachining Roderickand Jack Kleiss, Kleiss Engineeringan
3、d Scott Hoffmann, Accu-promptEDM Thestatementsandopinionscontained he,_inarethose oft,heauthorand shouldnotbeconstruedas anofficial actionor opinion of the American Gear ManufacturersAssociation. ABSTRACT: The new generationofwire ElectricalDischargeMachines (EDM) arecapableof quite good generating
4、accuracy. We have maximizedtheaccuracyandrepeatabilityofthistoolthroughfixturing,controlledcutting methods,and optimized mathematicalalgorithms forthecuttingpath. Theresultis theverifiedgenerationofprecise spurgearsinpitchesranging from 5 to 41 DP. The advantageofthe methodis short lead timeswith ac
5、curacyapproachingform groundwhilebeing cost competitive. The method is alsosuitable forproducing small to medium lots of very accurate spur gears in any electricallyconductivematerial. Copyright 1993 AmericanGear ManufacturersAssociation 1500 King Street, Suite201 Alexandria,Virginia, 22314 October,
6、 1993 ISBN: 1-55589-624-3 Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:53:51 MDTNo reproduction or networking permitted without license from IHS -,-,- TheGenerationof Preci
7、sionSpurGearsThrough WireElectricalDischargeMachining Roderickand JackKleiss KleissEngineering 3006 EdgertonStreet,LittleCanada,MN 55117 and Scott Hoffmann,President Accu-PromptEDM, Inc. 100 83rd AvenueNorthNE, Fridley,MN55432 Introductionotherforms of gear generation. In plasticgear mold-making,the
8、 wire EDMThe EDM Process is often usedto createthe involuteshapein the mold cavity.This has been a point of contentionElectricalDischargeMachiningis based on withintheplasticcommunityforyears,withthe principaloferosionofanelectricallyconductive traditionalistsarguingthata cavity burnedwith amaterial
9、bycontinuoussparkdischargetoits hob cut electrode is inherentlymore accuratethansurface(1).With wireEDM, a metallicwireis a wire-burnedcavity.Withour own historyofcontinuouslyfedthrougharmssuspendedabove successusingtheEDMmethod,wedecidedtheandbelowtheworkpiece(Fig.1).Thischarged ultimatetest would
10、be to cut externalspur gears inwire is thenguided throughthe specifiedtool path thisfashionandusetraditionalgearinspectionwhile cuttingits way throughthe material.The techniques to quantify theiraccuracy,processisrelativelyslowdependingonwire diameter,workpiecethickness,andmachine Ourexperimentwasmo
11、reoverbasedonsettings.The servo-controlledtool pathis quite need.The plasticgears we had designedfor a gearaccurate,typical for CNC type machinery.And the drivenlawnsprinklerrequireduniquemasterbenignenvironmentof the EDM machinery,with gears.Leadtimesfor formgroundgearswereslow feed rates,extremely
12、low forces, verylittle unacceptable.Withourcustomerssupportwefrictionor vibration,andcontrolledtemperature developeda methodof cuttingthesegearsthatmakeeven finer accuracy possible.The tool path achievedthedesiredshapeson timeandwithincaneitherbe point-to-pointor viasimplearcs. cost constraintsfor f
13、ine pitchmastergears.WeAdvancedmathematicalcurvesarenotdirectly thenemployedthesame techniquesto cut a 19programmablebysoftware;thesemustbe tooth5 DPmastergearinordertodetermineapproximatedwitharcsand/orlinemovements. possibleerrorsof scale.Profile inspectionrevealedBoth the involuteand trochoidalse
14、ctionsof a gear similar accuracy of tolerancewas possible for largefallintothisgeneralcategory.Specified coarse pitchgears as for fine pitch.In the followingdimensionalaccuracyand repeatabilityof the more sections,we will presentthe methodswe employedadvancedwireEDMsareon theorderof .0001 to achieve
15、this level of accuracy,the inspectiondatainches.Surfacefinishesof 16 micro-inchcanbe from our work,comparisonswithprecisionhob cutattainedthroughcarefulselectionofmachining gears,and possibleapplicationsof this methodtoparametersalong with multiplefinishingskim cuts on low powersettings. Copyright A
16、merican Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:53:51 MDTNo reproduction or networking permitted without license from IHS -,-,- Figure1 - Wire EDM gear cuttingsetup GearCuttingWithWireDi
17、fficultieswiththismethodofgenerationare immediatelyapparent.By focusingonlyon the ThewireEDMisprimarilyatwo-involute profile, the trochoidal(or root) area is left dimensionalprocess,althoughthe two wire guidesarbitraryand undefined.No provisionis made for can follow independentpathsallowing slight 3
18、-Dundercutevenifitisrequired.Oneof the modifications.EDM softwareexists that claims toadvantagesof a hob cut gear is thatany similar createa wirepathfor thespurinvolute.Thephysical gear will fit within the envelope created by softwarerequiresstandardgeargeometryto be,the generatinghob.The reason for
19、 this is that the inputalong with tooth thickness,root, and outsidehob removesany possibleinterferingmaterialin diameters.Approximatearc segmentsarethenthe root areathatmay physicallyinterferewith fitted to the involutecurve down to the root or toanothergear.A majorityof non-undercutstandard the bas
20、e circle diameter,whichevercomes first.Ifgearsare not sensitiveto thispossibletrochoidal the base circle is located above the root circle, ainterferencesincethestandardwholedepth straightradiallineis connectedfromthebaseprovidessufficientclearanceandmatingteeth circle to theroot diameter,and the use
21、r has theneverreach below the basecircle.However,as optionofspecifyingafilletradiusforthedesignersmodifygeargeometrytomaximize intersection of those two features (Fig. 2).function or if undercutexists, this areabecomes -_,critical through possibleinterference,or weakened ?_i_by excessiverelief.Thema
22、thematicalgeneration of gearteethmustprovidenotonlyconjugate action but also designedclearancewith any mating gear. _-_._:_-Another not-so-apparent difficultywith the L-_- _-“-_-_,-_-_=_ _“generationofapproximatearcstotheinvolute concernsthe natureof the involuteitself.Withits , _llleTL_everincreasi
23、ngradiusof curvaturefromthe base -RadiusJ“_b (userI_circle,the involuteis anything but a trivial curve specified)J_fittingexercise.Thedesirabilityofmaking BaseRoot 01 a_eter01 ameterintersectingarcstangentattheirendpoints compoundsthe problemof fittingthesearcs to the Typical E0M_ear Involuteinvolut
24、e.Withoutcarefulfittingit is possibleto Figure Z 2 Copyright American Gear Manufacturers Association Provided by IHS under license with AGMA Licensee=IHS Employees/1111111001, User=Wing, Bernie Not for Resale, 04/18/2007 11:53:51 MDTNo reproduction or networking permitted without license from IHS -,
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