SERVOMETER®

SMC FLEXIBLE SHAFT COUPLINGS

TRUE PERFORMANCE FLEXIBLE SHAFT COUPLINGS

Servometer® “SMC” Flexible Shaft Couplings meet rigorous requirements of precision positioning systems.Precision motion control applications require mechanicalsystems, especially between motors, driven loads, andfeedback devices, to ensure accurate positioning. Suchsystems often require shaft couplings that are both torsionally rigid, to accurately transmit rotational position,and laterally flexible, to accommodate shaft misalignment.Servometer® “SMC” Couplings are ideal for light industrialapplications such as connecting to encoders or steppermotors. Servometer® “SMC” Couplings are invaluablecomponents in precision positioning mechanisms andmotion control feedback devices.

Servometer® flexible shaft couplings made withServometer® precision electrodeposited nickel bellows provide continuous torque capabilities from 1 Ncm to 2400 Ncm for standard shaft sizes ranging from 2 to 20mm. Because of their flexibility, the low-torque couplings can handle angular misalignment up to 18° or parallel misalignments (shafts parallel but offset) up to 1.7mm, withlow side thrust on the bearings.

In general, as misalignment capability goes up, torquecapacity goes down. SMC couplings exhibit both lowwindup due to radial rigidity, and low side thrust because of lateral flexibility. Other coupling types haveeither low windup or low side thrust, but not both.Servometer® flexible shaft couplings are precision electrodeposited nickel bellows-type couplings. Madeusing Servometer® brand precision nickel bellows, thesecouplings are indispensable for use on critical applications such as resolvers,encoders, servos, motion control devices, and computers. The unique characteristics of the bellows couplings are:

• Zero Backlash• Torque range from 1 Ncm to

2400 Ncm• Very low elastic windup from

less than 1 arc-sec/Ncm• Zero Cyclic Speed variation

during 360° rotation• Low side thrust on bearings• Act to dampen vibration• Low moment of Inertia

In addition, specialized dynamic requirements can becustom designed to fit customer specifications.

Application assistance from our engineering staff is available.

GENERALITIESThe Servometer® Flexible Coupling offers one of the best

size/performance ratios on the market. Two differentmounting types are available: either with 2 set-screws at120° or with an integral clamp hub.

1) SET-SCREW MOUNTING, FOR RELIABILITY - SETSCREW HUBSThese hubs assure tight mounting on shafts and are

suitable for applications that do not require precise adjustment when mounting. The two set-screws at 120°provide perfect balancing of clamping forces. However,vibrations may require the use of self-locking screws or a special threadlocking product. The end pieces are madeof a high strength light weight aluminum. Set-screws supplied in black oxide steel.

PARALLEL MISALIGNMENTANGULAR MISALIGNMENT

ANGLE

Comparison of an “SMC” with major coupling types

SERSERVOMETER...VOMETER...“SMC” Flexible Shaft Couplings

14

12

10

8

6

4

2

0

SMC-17SERVOMETER

2.2

MembraneCoupling

2.5

OldhamCoupling

6.1

Stainless SteelBellow Coupling

8.4

Bronze BellowCoupling

8.4

LateralJoint15.7

Flexible BeamCoupling

25

Side Thrust

Stroke

Angular

Windup: 10 RAD/ Ncm.-5

Mis

alig

nmen

t: C

ombi

ned

Valu

es

4) SERVOMETER ELECTRODEPOSITED NICKEL BELLOWS

Producing nickel bellows using electrodeposition technology offers the following decisive advantages incomparison with rolling, hydroforming, welding, orchemical deposition processes:

The bellows wall thickness (down to 8µm) is uniformand controlled which enables very high sensitivity.Manufacturing tolerances assure bellows concentricity(to within 12.7µm). These are the most flexible bellowson the market, providing exceptional performance.They are designed for long service life (from 100,000cycles to infinity). They are weld-free and non-porous.

These exceptional features were meticulouslydesigned to provide a bellows that is ideal for couplingapplications. Each and every bellows is tested to guarantee its performance. Nickel bellows do not oxidize in the presence of air or alkaline liquids. Firstconsult our engineering department if use in salty oracidic environments is planned. We can design specialElectrodeposited Nickel Couplings adapted to yourspecific applications.

PRECISION ELECTRODEPOSITED NICKEL FLEXIBLE SHAFT COUPLINGS

How To Select A Coupling 1. Determine the maximum instantaneous torque

which the coupling will receive. If there is a clutchstart or brake stop, measure the maximum instantaneous value and use this. If a low inertiamotor with gear reduction drives a massive loadthrough the coupling, the maximum torque will bethe starting torque of the motor multiplied by thegear speed reduction ratio. Acceleration of rotational inertia’s generates resisting torques andthe engineer must compute these and take theminto account. Failure to realize the true maximummay result in frequent coupling failures.

(a) WHEN A COUPLING IS USED COMPRESSED:Use 75% of rated torque as maximum sincebellows buckle more easily when compressed.

(b) WHEN A COUPLING IS USED EXTENDED:Apply the normal torque rating.

2. Determine the maximum parallel misalignment tobe encountered. Misalignment of shafts, withaxes parallel but off-set, is the severest load thatcan be applied to a coupling.

3. Determine the maximum angular misalignment tobe expected of the two shafts and specify it.

4. Specify maximum allowable windup. A shorterlength or larger diameter coupling may be requiredfor low values.

5. Determine whether axial compression or extension will require a special length of bellows.

6. Take the five performance values just determinedand find them on the performance chart. The sizecoupling which will meet all the requirements willbecome apparent. If the size of the coupling is not satisfactory, a larger coupling can be usedwith no loss in performance, whereas a smallercoupling would result in inferior performance anda shorter life.

Servometer can also design special couplings tomeet special application needs.

Couplings can also be used in severe motion applications for a shorter life. Predicted life may bedetermined by applying the factors below to thedynamic characteristics of the coupling. Torque ratings are maximum and should not be exceeded.

NOTES:

1. Minimum life expectancy of 108 cycles for values shown intables (1 Rev. = 2 Cycles).

2. Parallel misalignment, angular misalignment & compressionstroke values are mutually exclusive. If combinations of theseare required, consult factory.

Life Required inCycles 104 105 106 107 108

Life Factor 1.9 1.4 1.14 1.03 1

NOTE: 2 cycles = 1 revolution

LIFE EXPECTANCY TABLE

2) INTEGRAL CLAMP MOUNTING, FOR PRECISION POSITIONINGThese hubs, due to the unique integral clamp

hub configuration, are particularly well suited for applications requiring precise adjustment orrepositioning. They are especially recommended for their resistance to reversal torque and vibration.The unique integral clamp hub will not mar the shaft. The end pieces are made of a highstrength light weight aluminum. Cap-screws supplied in black oxide steel.

3) HIGH TECH ADHESIVE ASSEMBLY - FOR FLEXIBILITY AND PERFORMANCEServometer® SMC Flexible Couplings are assem-

bled using high tech adhesive bonding technology.This gives Servometer® the ability to rapidly cus-tomize couplings to specific bore combinations.

In addition, the use of adhesive technology is particularly recommended for assemblies subject toextreme conditions, such as:

• Temperature (-50°C to +120°C)• Moisture• Mechanical stressThis technology allows different types of hubs to

be assembled in a large variety of combinations.

Note: The adhesive used offers sufficient strength for mostindustrial applications. However, for special applications (e.g.food-processing, nuclear industry), we recommend that youcontact our engineering department for verification.

MINIATURE METAL BELLOWS AND ASSEMBLIES

Servometer manufactures custom electrodeposited nickelbellows ranging from 1 mm (.039") to 76 mm (3") O.D.Exceptional qualities are high flexibility and extreme sensitivity.

ELECTROFORMSServometer manufactures many specialty electroformswhich other electroplating companies cannot produce.Tight tolerances can be held and we solicit your inquiries.

CONTACTSServometer bellows contacts are widely used as electricalspring contacts in radio transmitters and receivers, radarsystems and microwave applications, where negligibleinductance and insertion loss are necessary.

CORPORATEServometer Corporation designs and manufactures precision electrodeposited nickel bellows, bellows assemblies, flexible shaft couplings, electrical contactsand lightweight structural electroforms.

Servometer Electroforms

unusual shapes, close tolerances, light weight, great strength, and highly reflective surfaces

®

SERVOMETER® PRODUCTS