Flexibile vs. Rigid Couplings

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Flexible vs. Rigid Couplings

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Before We Start

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Mike Santora Associate Editor - Moderator Design World

Edward Cole Engineering Manager Ringfeder Power Transmission USA Corp.

Andy Lechner Product Manager R+W America


Bobby Watkins Vice President of Sales Ruland Manufacturing Co. Inc.

Meet the speakers…

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PARALLELSHAFTMISALIGNMENT

• resultsfromlackofpilotsinmoun>ngframes/couplinghousings• mostharmfultobearingsandcouplings• evensmallamounts(e.g.,>0.001”)canplacealargeamountofstressonadjacentshaNbearings,contributetovibra>on,andreducesystemefficiency

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ANGULARSHAFTMISALIGNMENT

• resultsfrommoun>ngsurfacesnotbeingflatorlevel• slightlylessharmfultobearingsandcouplings• rarelyexistswithoutparallelmisalignment

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AXIALSHAFTMISALIGNMENT(ENDPLAY)

• resultsfromthermalexpansionofshaNing• resultsfrommotorshaNend-play• occurstovaryingdegreesindependentofothertypesofmisalignment

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MOUNTINGWITHPILOTS

• protrudingfeatureofaprecisiondiameterandconcentrictotheshaN• existsonalmostallservomotors,steppermotorsandprecisiongearboxes• whenusedinconjunc>onwithaprecisionmachinedhousing,parallelshaNalignmentwithin0.001-0.003”shouldbeguaranteed

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RIGIDCOUPLINGS

• disclaimer–R+Wdoesnotmakerigidcouplings• veryusefulinjoiningshaNswhicharenotbothbearingsupported

• allowsoneshaNtosupporttheother• nomisalignmentloadingifonlyoneshaNisbearingsupported

• usefulwhenoneconnectedcomponenthasaflexibleframe• (e.g.,encoderswithflexiblemounts)• allowsthatcomponenttoflexduringshaNrota>ontocompensateformisalignment

• some>mesusedtocouplealengthofshaNingoneachend• workswellwhentheshaNislongenoughtoflexslightly• mostlyforslowerrota>onalspeeds

• oNenusedincaseswherehighprecisionrota>onisneededbutthenrequiredifficultalignmentprocedures

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FLEXIBLECOUPLINGS

• disclaimer–R+Wdoesmakeandsellflexiblecouplings• generallyconsideredtobeabestprac>cebetweensupportedshaNs

• reducessideloads,whichares>llhighat0.001”misalignment• helpsextendbearinglife• canhelpwithvibra>ondamping

• manyvarie>esandmoun>ngop>onsareavailableonthemarket• torsionallyrigidversions• vibra>ondampingversions• highmisalignmentversions• self-suppor>nglineshaNversions

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BACKLASH

• mechanicalclearancewhichresultsinlostmo>on• necessaryinmostgears,butcanbeavoidedinflexiblecouplings

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TORSIONALWIND-UP

• momentarydeflec>onasaresultoftorqueloading• occurstovaryingdegreesinalldrivecomponentsbutisgenerallygreaterinflexiblecouplingsthaninrigidcouplings

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BELLOWSCOUPLINGS

• unlikeother“spring”typecouplingstheyaretorsionallyrigid• usedtypicallyinhighlydynamicorhighprecisionapplica>ons• offersthebenefitsofreducedbearingloadswithhighperformance• s>llnotastorsionallys>ffasrigidcouplingsbutworthconsidering

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PRECISIONELASTOMERCOUPLINGS

• torsionallysoNforvibra>ondampingbutpreloadedforzerobacklash• offerscompensa>onforsmallamountsofshaNmisalignment• hightorquedensitycomparedwithotherflexiblecouplingtypes

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EXAMPLE:BALLSCREW/LEADSCREWAPPLICATION

• GIVEN:10Nmtorqueload/10mmlead• 10Nmbellowscoupling

• torsionals>ffnessof157Nm/deg=0.064°angulardeflec>on• witha10mmleadthisresultsin0.0018mm(0.00007”)linearerror

• 10Nmelastomercoupling(standardinsert)• sta>ctorsionals>ffnessof4.54Nm/deg=2.2°angulardeflec>on• witha10mmleadthisresultsin0.0611mm(0.00241”)linearerror

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THANKSFORYOURTIME!

Selecting Couplings For Your Servo Applications

Ed Cole, Engineering Manager

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Servo Coupling Requirements!•  Backlash-free to maintain positioning accuracy.

•  Mass balanced for high rotational speeds.

•  Designed for low to moderate torques—usually to 100 Nm.

•  Tolerant of shaft misalignments.

•  Maintenance free.

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Servo Coupling Applications!•  Any automation system with shaft-driven linear motion, including:

•  Machine tools.

•  Packaging equipment.

•  Test and measurement systems.

•  Semiconductor manufacturing.

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Servo Coupling Choices!•  Two types of servo couplings can meet these requirements:

•  Rigid metal bellows couplings.

•  For example, Ringfeder Gerwah EKN and DKN Series.

•  Flexible servo insert couplings.

•  For example, Ringfeder Gerwah GWE Series.

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Servo Coupling Choices!•  Many servo applications do not strongly favor one type of coupling over another.

•  Either a metal bellows and servo insert coupling can satisfy basic torque, shaft size and lifecycle requirements.

•  But each type of coupling has its subtle advantages:

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Metal Bellows Coupling!•  Typically constructed of stainless steel bellows with aluminum hubs.

•  Integrated clamping hubs or set screws in miniature models.

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Metal Bellows Coupling!

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Servo Insert Coupling!•  Typicallyconsistsofaluminumhubsandelastomer“spider”inserts.

•  Clampingviasetscrewsorintegratedclampinghub

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•  Adjustable flexibility by changing elastomer inserts.

•  Harder inserts approach metal bellows stiffness.

•  Softer inserts maximize damping and misalignment tolerance.•  Optimize vibration damping through insert selection.

•  Excellent tolerance of radial, axial and angular misalignment.

•  Good torque transmission and angular positioning performance.

Servo Insert Coupling!

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Servo Insert Coupling Application!

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•  Keep in mind that servo couplings often work in conjunction with other power transmission components, such as gear boxes and linear actuators.

•  It’s important to choose couplings whose designs work well with related power transmission components.

•  Shrink discs

•  Locking assemblies

Couplings Are Part Of A System!

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Metal Bellows Servo Insert

Product Examples! EKN, DKN, AKN Series! GWE Series!

Adjustable Rigidity!

Torque Transmission!

Backlash Free!

Misalignment Tolerance!

Damping!

Low Inertia!

Servo Couplings At A Glance!

Thank You Ed ColeEngineering Manager

Tel: (201) 666-3320

Email: [email protected]

#DWwebinar Presentedby:BobbyWatkins www.ruland.com


Presentedby:BobbyWatkins www.ruland.com


Types of Misalignment

Presentedby:BobbyWatkins www.ruland.com


Why is misalignment a concern?

• Addsstresstosystemcomponents

• Causedbytolerancemismatch


Backlash, Windup, and Bearing Loads

CouplingwithWindup • Windupisnotbacklash•  Backlashreferstopowertransmissionerror•  Windupisposi>onerrorwithouttorqueerror•  Allcouplingshavewindup•  Zero-backlashmeanszerolossinpowertransmission

•  Bearingloadsincreasewear•  Excessivebearingloadsresultinbearingwearand

•  prematurefailure•  Couplingsdesignedtoflexduringmisalignmentproducebearingload

•  Couplingmisalignmentra>ngsoNenresultfrombearingloads

CouplingwithMisalignment


Bearing Loads

• Misalignmentexistsbetweenthemotorandthedrivensystemduetotolerancesand/orsystemincompa>bility

• Bearingloadsaregeneratedasaresultandareharmfultosystemperformance

• Othersystemdesignfactorsmustbeconsideredwhenselec>ngacoupling


Managing Misalignment

•  Selec>onofthecorrectcouplingiscri>cal

• Mustaddresstheapplica>onmisalignmenttypeortypes

• Muststaywithinthecouplingspecifica>ons

• Mustinstallthecouplingproperly

• Otherapplica>oncriteriamustalsobeaddressed


Rigid Couplings

Benefits•  Besttorquetransmissioncapabili>es

•  Almostzero-windup=themostprecisecouplingavailable

•  SuitableforshaNsupportandpush-pullapplica>ons•  Lowcost

Drawbacks•  Nomisalignmentcapabili>es

•  Noallowanceforthermalexpansion

•  Extremelyhighbearingloadsifusedincorrectly

•  Poten>alfordamagetosystemcomponents

•  Veryhighiner>a-notsuitableforhighRPMapplica>ons


Flexible Couplings

Benefits•  Accommodatemisalignment

•  Differentstylesallowtheusertoselectthebestfitfortheapplica>on

•  HighRPMcapabili>es

•  Manystandardsizeop>onsareavailable

•  Mosthavelowiner>a

Drawbacks•  Somerequiremaintenance

•  Installa>oncanrequirespecializedalignmentsystems

•  Limitedtorquecapabili>es

•  BothshaNsmustbebearingsupported

•  Highcost

OldhamCoupling BellowsCouplingBeamCoupling JawCoupling DiscCoupling


Product SelecFon

• Mul>plesolu>onsmayexistwhenselec>ngacoupling

•  Specificcouplingsarebesersuitedforeachtypeofmisalignment,forexample:oldhamswithparallelmisalignmentorbeamcouplingsforangularmisalignment

•  Bearingloadsandwindupareasideeffectofallcouplings

•  Propercouplingselec>onrequiresafullunderstandingofthesystemrequirements

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Mike Santora Associate Editor - Moderator Design World @DW_MikeSantora

Edward Cole Engineering Manager Ringfeder Power Transmission USA Corp. [email protected]

Andy Lechner Product Manager R+W America [email protected]


Bobby Watkins Vice President of Sales Ruland Manufacturing Co. Inc. [email protected]

Questions?

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