When specifying a coupling for a mechanical system, many factors are involved in the decision. Andy Lechner of R +W America, Ross Rivard of Ringfeder and Bobby Watkins of Ruland Manufacturing Co. will each take some time to help us gain a better understanding of when the different types of couplings make the most sense for an application.
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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
Flexible vs. Rigid Couplings
Bobby Watkins
Vice President of Sales
Ruland Manufacturing Co. Inc.
Meet the speakersâŚ
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Servo Coupling Requirements!
â˘âŻ Backlash-free to maintain positioning accuracy.
â˘âŻ Mass balanced for high rotational speeds.
â˘âŻ Designed for low to moderate torquesâusually to 100 Nm.
â˘âŻ Tolerant of shaft misalignments.
â˘âŻ Maintenance free.
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Servo Coupling Applications!
â˘âŻ Any automation system with shaft-driven linear motion, including:
â˘âŻ Machine tools.
â˘âŻ Packaging equipment.
â˘âŻ Test and measurement systems.
â˘âŻ Semiconductor manufacturing.
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Servo Coupling Choices!
â˘âŻ Two types of servo couplings can meet these requirements:
â˘âŻ Rigid metal bellows couplings.
â˘âŻ For example, Ringfeder Gerwah EKN and DKN Series.
â˘âŻ Flexible servo insert couplings.
â˘âŻ For example, Ringfeder Gerwah GWE Series.
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Servo Coupling Choices!
â˘âŻ Many servo applications do not strongly favor one type of coupling over another.
â˘âŻ Either a metal bellows and servo insert coupling can satisfy basic torque, shaft size and
lifecycle requirements.
â˘âŻ But each type of coupling has its subtle advantages:
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Metal Bellows Coupling!
â˘âŻ Typically constructed of stainless steel bellows with aluminum hubs.
â˘âŻ Integrated clamping hubs or set screws in miniature models.
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Servo Insert Coupling!
â˘âŻ Typically consists of aluminum hubs and elastomer âspiderâ inserts.
â˘âŻ Clamping via set screws or integrated clamping hub
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â˘âŻ Adjustable ďŹexibility by changing elastomer inserts.
â˘âŻ Harder inserts approach metal bellows stiffness.
â˘âŻ Softer inserts maximize damping and misalignment tolerance.
â˘âŻ Optimize vibration damping through insert selection.
â˘âŻ Excellent tolerance of radial, axial and angular misalignment.
â˘âŻ Good torque transmission and angular positioning performance.
Servo Insert Coupling!
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â˘âŻ Keep in mind that servo couplings often work in conjunction with other power
transmission components, such as gear boxes and linear actuators.
â˘âŻ Itâs important to choose couplings whose â¨
designs work well with related
power transmission components.
â˘âŻ Shrink discs
â˘âŻ Locking assemblies
Couplings Are Part Of A System!
35. #DWwebinar Presented by: Bobby Watkins www.ruland.com
Backlash, Windup, and Bearing Loads
Coupling with Windup â˘âŻ Windup is not backlash
â˘âŻ Backlash refers to power transmission error
â˘âŻ Windup is posi>on error without torque error
â˘âŻ All couplings have windup
â˘âŻ Zero-backlash means zero loss in power
transmission
â˘âŻ Bearing loads increase wear
â˘âŻ Excessive bearing loads result in bearing wear
and
â˘âŻ premature failure
â˘âŻ Couplings designed to ďŹex during misalignment
produce bearing load
â˘âŻ Coupling misalignment ra>ngs oNen result from
bearing loads
Coupling with Misalignment
36. #DWwebinar Presented by: Bobby Watkins www.ruland.com
Bearing Loads
â˘âŻ Misalignment exists between
the motor and the driven system
due to tolerances and/or system
incompa>bility
â˘âŻ Bearing loads are generated as a
result and are harmful to system
performance
â˘âŻ Other system design factors
must be considered when
selec>ng a coupling
37. #DWwebinar Presented by: Bobby Watkins www.ruland.com
Managing Misalignment
â˘âŻ Selec>on of the correct coupling
is cri>cal
â˘âŻ Must address the applica>on
misalignment type or types
â˘âŻ Must stay within the coupling
speciďŹca>ons
â˘âŻ Must install the coupling
properly
â˘âŻ Other applica>on criteria must
also be addressed
38. #DWwebinar Presented by: Bobby Watkins www.ruland.com
Rigid Couplings
BeneďŹts
â˘âŻ Best torque transmission capabili>es
â˘âŻ Almost zero-windup = the most precise coupling
available
â˘âŻ Suitable for shaN support and push-pull applica>ons
â˘âŻ Low cost
Drawbacks
â˘âŻ No misalignment capabili>es
â˘âŻ No allowance for thermal expansion
â˘âŻ Extremely high bearing loads if used incorrectly
â˘âŻ Poten>al for damage to system components
â˘âŻ Very high iner>a - not suitable for high RPM applica>ons
39. #DWwebinar Presented by: Bobby Watkins www.ruland.com
Flexible Couplings
BeneďŹts
â˘âŻ Accommodate misalignment
â˘âŻ DiďŹerent styles allow the user to select the best ďŹt for
the applica>on
â˘âŻ High RPM capabili>es
â˘âŻ Many standard size op>ons are available
â˘âŻ Most have low iner>a
Drawbacks
â˘âŻ Some require maintenance
â˘âŻ Installa>on can require specialized alignment systems
â˘âŻ Limited torque capabili>es
â˘âŻ Both shaNs must be bearing supported
â˘âŻ High cost
Oldham Coupling Bellows Coupling Beam Coupling Jaw Coupling Disc Coupling
40. #DWwebinar Presented by: Bobby Watkins www.ruland.com
Product SelecFon
â˘âŻ Mul>ple solu>ons may exist when
selec>ng a coupling
â˘âŻ SpeciďŹc couplings are beser suited
for each type of misalignment, for
example: oldhams with parallel
misalignment or beam couplings for
angular misalignment
â˘âŻ Bearing loads and windup are a side
eďŹect of all couplings
â˘âŻ Proper coupling selec>on requires a
full understanding of the system
requirements
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Mike Santora
Associate Editor -
Moderator
Design World
@DW_MikeSantora
Edward Cole
Engineering Manager
Ringfeder Power
Transmission USA Corp.
Edward.cole@ringfeder.com
Andy Lechner
Product Manager
R+W America
Alechner@rw-america.com
Flexible vs. Rigid Couplings
Bobby Watkins
Vice President of Sales
Ruland Manufacturing Co. Inc.
Robert.watkins@ruland.com
Questions?
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Thank You
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