• Couplings
  • Disk Type

XGHW-C

Flexible Couplings - The Vibration-Absorption Capable Disk Type

  • Zero Backlash
  • High torsional rigidity
  • High Torque

A new generation of disk couplings


Dimension Drawing

XGHW-CFlexible Couplings - The Vibration-Absorption Capable Disk Type寸法図

Specs/CAD

Part Number AA1L1L2WEHF1F2GM Screw Tightening
Torque (N・m)
Standard Bore Diameter
D1-
D2 (Inertial Rotor Side)
Price
(USD)
CAD Add to Cart Additional Modification
XGHW-27C 19 27 9.2 13.2 29.7 8.5 10 2.6 6.6 7 M2 0.5 - 88.54 CAD Cart       
XGHW-36C 27 36 11 16 37.2 14.5 15 3.3 8.3 10.25 M2.5 1 - 102.48 CAD Cart       
XGHW-41C 34 41 12.5 18.5 42.8 16.5 18 3.75 9.75 13 M3 1.5 - 116.61 CAD Cart       
XGHW-49C 39 49 15.5 22.5 53.6 20.5 22 4.5 11.5 14.5 M4 3.5 - 135.17 CAD Cart       

● Specify the bore diameter in the order D1-D2 (inertial rotor side).
Append the identification code J after the bore diameter of D2 (inertial rotor side).

 Example: XGHW-27C-6-8J

Part Number Max. Bore Diameter
(mm)
Rated
Torque*1
(N・m)
Max. Rotational Frequency
(min-1)
Moment of
Inertia
(kg・m2)*2
Static
Torsional
Stiffness
(N・m/rad)
Max. Eccentricity
(mm)
Max. Angular
Misalignment
(°)
Max. Axial
Misalignment
(mm)
Mass
(g) *2
XGHW-27C 8 1.5 23000 4.6×10-6 300 0.12 2 ±0.2 45
XGHW-36C 14 3.3 17000 1.8×10-5 1400 0.15 2 ±0.4 97
XGHW-41C 16 6.3 15000 3.4×10-5 2500 0.2 2 ±0.5 144
XGHW-49C 20 12 12000 8.9×10-5 4700 0.25 2 ±0.5 260

*1: Correction of rated torque due to load fluctuation is not required.

The shaft's slip torque may be smaller than the coupling's rated torque depending on the shaft bore.

*2: These are values with max. bore diameter.

Part Number Standard Bore Diameter D1
3 4 5 6 6.35 8 9.525 10 11 12 14 15 16 17 18 19 20
XGHW-27C - - - - - - - - - - -
XGHW-36C - - - - - - -
XGHW-41C - - - - - -
XGHW-49C - - -

Part Number Standard Bore Diameter D2 (Inertial Rotor Side)
5 6 8 10 11 14 16 19
XGHW-27C - - - - -
XGHW-36C - - - -
XGHW-41C - - -
XGHW-49C - - - - -

● All products are provided with hex socket head cap screw.
● Recommended tolerance for shaft diameters is h6 and h7.
● Bore and keyway modifications are available on request for D1 only. Please take advantage of our modification services.
● In case of mounting on D-cut shaft, be careful about the position of the D-cut surface of the shaft.


Slip torque

As in the table below, the clamping type XGHW-C has different slip torque according to the bore diameter. Take care during selection.

Unit : N・m

Outside Diameter Bore Diameter (mm)
3 4 5 6 6.35 8 9.525 10 11
27 0.7 1.7 3
36 2 2.9 4 4.2 5.8
41 3.5 4.9 5.5 7.9 10 11 12
49 6 8 13 18 19 23

These are test values based on the conditions of shaft dimensional allowance: h7, hardness: 34-40 HRC, and screw tightening torque of the values described in XGHW-C dimension tables. They are not guaranteed values.
Slip torque changes with usage conditions. Carry out tests under conditions similar to actual conditions in advance.


Structure

Clamping Type XGHW-C

XGHW-C

XGHW-C_CFlexible Couplings - The Vibration-Absorption Capable Disk Type


Material/Finish

XGHW-C
Hub A2017
Anodized
Spacer A2017
Anodized
Disk Fixing Bolt SCM435
Ferrosoferric Oxide Film (Black)
Disk SUS304
Collar SUS304
Hex Socket Head Cap Screw SCM435
Ferrosoferric Oxide Film (Black)
Inertial Rotor S45C
Electroless Nickel Plating
Elastic Body FKM

Characteristics

  • Recommended Applicable Motor
XGHW-C
Servomotor
Stepping Motor
General-purpose Motor

◎: Excellent ○: Very good ●: Available

  • Property
XGHW-C
Zero Backlash
High-gain Supported
High Torque
High Torsional Stiffness
Allowable Misalignment
Vibration Absorption Characteristics
Allowable Operating Temperature -10°C to 60°C

◎: Excellent ○: Very good

  • Flexible couplings with vibration absorption function added to high rigidity couplings.
  • A structure with both high rigidity and vibration absorption. The individual dynamic vibration absorber*1 is separate from the inertial rotor and elastic body in order to achieve vibration absorption.

XGHW-C_CFlexible Couplings - The Vibration-Absorption Capable Disk Type

*1: The mechanism for suppressing resonant vibration phenomena is achieved by connecting the dynamic vibration absorber to the auxiliary inertial body via the elastic body.

  • Does not use resin elastic materials for the rotation transmission system from the motor shaft hub to the driven shaft hub, for high rigidity.

XGHW-C_CFlexible Couplings - The Vibration-Absorption Capable Disk Type

  • Achieves high positioning accuracy under high loads, in addition to high servomotor gain.

Application

Actuator / Surface-mount machine / High precision XY stage / Index table

Precautions for Use

When installing, be careful not to apply excessive torque, loads or forces to the inertial body. Doing so may result in the inertial body detaching.

Selection

Selection Based on Shaft Diameter and Rated Torque

The area bounded by the shaft diameter and rated torque indicates the selection size.

XGHW-C_CFlexible Couplings - The Vibration-Absorption Capable Disk Type

Selection Example

In case of selected parameters of shaft diameter of φ14 and load torque of 3 N•m, the selected size is XGHW-41C.

Selection Based on the Rated Output of the Servomotor

Rated Output
(W)
Servomotor Specifications*1 Selection Size
Diameter of Motor Shaft
(mm)
Rated Torque
(N・m)
Instantaneous Max. Torque
(N・m)
XGHW-C
50 6-8 0.16 0.48 27C
100 8 0.32 1.1 27C
200 9-14 0.64 2.2 36C
400 14 1.3 4.5 41C
750 16-19 2.4 8.4 49C

*1: Motor specifications are based on general values. For details, see the motor manufacturer's catalogs. This is the size for cases where devices such as reduction gears are not used.


Gain and Stabilization Time of Servomotor

This shows how the servomotor gain movement follows the command.
Increasing the gain helps to reduce stabilization time, but increasing it too far causes hunting, making servomotor control impossible.
Increasing the gain while suppressing hunting requires fine adjustment of the servomotor parameters.
However, when a servomotor is combined with a coupling with a metal disk type in the elastic segment, raising the gain tends to cause hunting, making it difficult to resolve the problem by fine adjustments to parameters.
When hunting occurs, it is generally recommended to change to a coupling with higher rigidity to increase the rigidity of the rotating system.
However, in reality, it may not be effective to increase the rigidity of the entire rotating system including the ball screw simply by increasing coupling rigidity.

XGHW-C_TTechnical Information


The Vibration-Absorption Capable Disk Type

The vibration-absorption capable disk type XGHW-C has a dynamic vibration absorber on the high rigidity disk. It enables vibration absorption and use of higher gain levels when compared to regular disk types, thereby also allowing a shorter stabilization time. The vibration absorption function reduces the amount of parameter adjustment work, and lowers the time required to find optimal parameters.

Why can gain be increased even further with the vibration-absorption capable disk type XGHW-C when compared with the disk type XHW-C?

The Bode plot clearly illustrates why XGHW-C can increase servomotor gain beyond the capacity of disk types XHW-C.
The width of the gain relative to 0 dB when the phase delay on the Bode plot is -180° is called the gain margin and the phase width relative to the frequency intersecting at 180° is called the phase margin.
General guidelines for servo systems call for setting the gain margin between 10 and 20 dB and the phase margin between 40° and 60°, but as the servomotor gain is increased, the gain margin decreases. When the gain margin falls below 10 dB, hunting tends to occur.
A comparison of the XGHW-C and XHW-C limit gain (upper limit of the gain in which coupling can be used without hunting) shows not only that XGHW-C features a larger gain margin, but that in fact the gain margin is over 10 dB. This is why the servomotor gain is greater in XGHW-C compared to XHW-C.

Gain margin at the disk type limit gain
XGHW-C: 15.76dB
XHW-C: 8.67dB

Bode Plot

XGHW-C_TTechnical Information


Comparison of The Vibration-Absorption Capable Disk Type and Disk Type

In tests using servomotors and actuators, the following information is confirmed.

  • Stabilization Time

Increasing the gain enables the stabilization time to be shortened, and the gain can be set especially high with the vibration-absorption capable disk type when compared to the disk type.

  • Positioning Accuracy/Repeated Positioning Accuracy

No differences attributable to factors such as gain or coupling were observed.

  • Overshoot

Increasing the gain increases the overshoot, and the same gain resulted in no difference in the overshoot.

  • Conclusion

The vibration-absorption capable disk type allows higher gain to be set than the disk type, enabling shorter stabilization time. The positioning accuracy, repetition positioning accuracy and overshoot did not differ due to coupling.

As a result, it was confirmed that the vibration-absorption capable disk type is effective for shortening the cycle time of devices and equipment.

Test Devices

Actuator: KR30H Manufactured by THK (Co., Ltd.)

* Ball screw lead 10 mm

Servomotor: HG-KR13 Manufactured by Mitsubishi Electric Corporation

Test Conditions

Motor revolution: 3000 min-1

Acceleration/deceleration time: 50 ms

Workpiece load: 3.0 kg

Ratio of moment of inertia of load: 2.3

Test Operation

Normal rotation (1 rev) → Stop (500 ms) → Reverse rotation (1 rev)

Test Method

A displacement sensor is used to measure work movement, travel distance and stabilization time.

XGHW-C_TTechnical Information

  • Measurement of Stabilization Time, Positioning Accuracy and Overshoot

Gain*1 The Vibration-Absorption Capable Disk Type Disk Type Consideration
23 Stabilization Time (ms) 35 32 This is the upper gain limit for the disk type.
The vibration-absorption capable disk type can be used without any problems.
Positioning Accuracy (mm) 0.014 0.014
Repeated Positioning Accuracy (mm) ±0.002 ±0.002
Overshoot (μm) 1 1
32 Stabilization Time (ms) 8 Occurrence of Hunting This is the upper gain limit for the vibration-absorption capable disk type.
The disk type is not usable due to hunting.
Positioning Accuracy (mm) 0.016
Repeated Positioning Accuracy (mm) ±0.001
Overshoot (μm) 2

*1: Values with all gains, such as position control gain and speed control gain, adjusted (Min: 1 - Max: 32)
Positioning Accuracy
: Positioning operation is performed and the absolute value of the difference between the target point and the actual stop position is determined. Max. value is found by performing this measurement from the home position at all positions within the max. stroke range.
Repeated Positioning Accuracy
: Positioning is repeated 7 times from the same direction of movement to a randomly-selected point, the stopping positions are measured, and the difference between the max. and minimum values of the stopping position is determined. This method of measurement is applied at positions at the middle and both ends of the max. stroke range, then the max. value becomes the measured value, halved and prefixed with ±.
The values in the table vary depending on testing conditions.


Eccentric Reaction Force

XGHW-C_TTechnical Information


Thrust reaction force

XGHW-C_TTechnical Information


Change in static torsional stiffness due to temperature

This is a value under the condition where the static torsional stiffness at 20°C is 100%.
The change of XGHW-C in torsional stiffness due to temperature is small and the change in positioning accuracy is extremely small. If the unit is used under higher temperature, be careful about misalignment due to elongation or deflection of the shaft associated with thermal expansion.

XGHW-C_TTechnical Information


Productivity and Stabilization Time

In a production facility which uses servomotors, single-axis actuators and ball screws, the key to improved productivity is operating these components accurately, as directed by a program. However, occasionally the command execution may be delayed.
For example, when trying to stop the actuator at a predetermined position, sometimes it will stop later than the command, which we refer to as a delay in stabilization time. Since the operation does not shift to the next process until the actuator completely stops, it is important to shorten stabilization time and thereby improve productivity.

XGHW-C_TTechnical Information


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