Specs/CAD

mm inch

＊1：　Correction of rated torque due to load fluctuation is not required. If ambient temperature exceeds 30°C, be sure to correct the rated torque with temperature correction factor shown in the following table.

The allowable operating temperature of XGS2 is -10℃ to 120℃.

※ The shaft's slip torque may be smaller than the coupling's rated torque depending on the shaft bore. XGT2XGL2

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

● All products are provided with hex socket head cap screw.
● Recommended tolerance for shaft diameters is h6 and h7.
● In case of mounting on D-cut shaft, be careful about the position of the D-cut surface of the shaft. ⇒Mounting and Maintenance
● Bore and keyway modifications are available on request. Please take advantage of our modification services.
● For the shaft insertion amount to the coupling, see Mounting/maintenance. ⇒Mounting and Maintenance

Ambient Temperature / Temperature Correction Factor

Slip torque

As in the table below, the clamping types XGT2-C, XGL2-C, and XGS2-C have different slip torque according to the bore diameter. Take care during selection.

Structure

Clamping Type

XGT2-C Standard type XGT2
XGL2-C Long type XGL2
XGS2-C Short typeXGS2

Internal Structure

Material/Finish

Characteristics

• Recommended Applicable Motor

• Property

• High-gain flexible coupling which surpasses XGT-CXGL-CXGS-C in performance. This is a single-piece construction with the two aluminum hubs molded with high-gain rubber.
• The optimal damping and rigidity design enables realization of even greater servomotor gain, leading to reduced stabilization time.
• Technical information⇒Productivity and stabilization time
• Suppressing speed unevenness control during stepping motor operation is effective.⇒Suppressing speed unevenness during stepping motor operation
• Contributes to improved productivity and quality by suppressing residual vibration during positioning.
• O.D. φ15-φ56 types use high-gain fluoro-resin rubber. Heat resistance, oil resistance, and chemical resistance are excellent.⇒Physical properties and chemical resistance of high-gain type rubber
• Standard type XGT2-C / long type XGL2-C / short type XGS2-C are now standardized.

Application

Semiconductor manufacturing equipment / Mount machines / Machine tools / Packaging machines

Selection

Selection Based on Shaft Diameter and Rated Torque

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

Selection Example

In case of selected parameters of shaft diameter of φ16 and load torque of 7N・m, the selected size is XGT2-34C.

Selection Based on the Rated Output of the Servomotor

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.

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 is not possible to increase the rigidity of the entire rotating system including the ball screw simply by changing the coupling; so changing to a highly rigid coupling such as a disk-type may not be effective.

High-gain Rubber Type

XGT2-C XGL2-C XGS2-C XGT XGL XGS
The high-gain rubber type can be used at even higher gain than high-rigidity couplings such as the disk type, enabling reduction of 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 high-gain rubber types than with disk types?

The Bode plot makes it clear why the high-gain rubber type can increase servomotor gain beyond the capacity of the disk type.
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 with the disk type limit gain (upper limit of the gain in which coupling can be used without hunting) shows not only that the high-gain rubber type features a larger gain margin, but also that the gain margin is over 10 dB. This is why the high-gain rubber type allows greater servomotor gain than the disk type.
To increase the gain margin, both the coupling damping performance and its dynamic rigidity must be high. XGT2XGL2

Gain margin at the disk type limit gain
High-gain rubber type: 17.40 dB
Disk type: 9.90 dB

Bode Plot

● Damping performance comparison of high-gain rubber and disk types

In tests using servo motors and actuators, the following are confirmed.

• Stabilization Time

Increasing the gain shortens the stabilization time, and the gain can be set especially high in the XG2 and XG series.

There were no differences in stabilization time between couplings as long as the gain was the same.

To reduce stabilization time, higher gain settings enabled by the use of the high-gain rubber types, especially the XG2 series, demonstrate clear advantage against 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 XG2 Series allows higher gain settings, 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 XG2 series is effective for shortening the cycle time of devices and equipment.

Test Devices

Actuator: MCM08 Manufactured by NSK Co., Ltd.

＊ Ball screw lead 10 mm

Servomotor: HF-KP13 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: 3.5

Test Operation

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

Test Method

Measure the work movement with a displacement sensor and also measure the work piece's travel distance and stabilization time.

• Measurement of Stabilization Time, Positioning Accuracy and Overshoot

Changes in performance after cycles

• Test Method ①

Rated torque load is applied to a coupling which rotates in a single direction, and the damping ratio and dynamic rigidity are measured.

Couplings

XGT2-25C-12-12

• Changes in Damping Ratio Depending on Number of Cycles (Cumulative Rotation Speed)

• Test Method ②

A motor and coupling are mounted on a single-axis actuator, the workpiece is set in reciprocating motion and the damping ratio is measured.

Test Devices

Actuator: BG46 Manufactured by Nippon Bearing Co., Ltd.

＊ Ball screw lead 10 mm

Servomotor: HF-KP13 Manufactured by Mitsubishi Electric Corporation

Couplings

XGT-25C-8-8

Test Conditions

Motor revolution: 3000 min-1

Acceleration/deceleration time: 10 ms

Workpiece load: 3.0 kg

Ratio of moment of inertia of load: 3.5

Test Operation

Forward rotation (10 rev) → Reverse rotation (10 rev) This operation is repeated.
Stroke 100 mm, total travel distance 4400 km

Test Method

The damping ratio of the coupling is measured before and after the testing.

• Measurement of Damping Ratio and Dynamic Rigidity

Temperature-triggered changes in performance

• Test Method

A coupling is left at the prescribed ambient temperature for 4 hours and damping ratio and dynamic rigidity measured.

Couplings

XGT2-25C-12-12 XGT-25C-12-12

• Temperature-triggered Changes in Damping Ratio

• Temperature-triggered Changes in Dynamic Rigidity

Suppressing speed unevenness during stepping motor operation

Test Devices

Motor: α step AR66AK-1 Manufactured by Oriental Motor Co., Ltd.

Set voltage----24 VDC

Resolution----1000 p/r

Moment of inertia----1250×10-7kg・cm2

Encoder: RD5000 Manufactured by Nikon Corporation

Drive Parameters

Startup speed: 60 min-1

Drive speed: 900 min-1

Rotation angle: 1800°

Acceleration/deceleration time: 100 ms

Eccentric Reaction Force

This is the force generated when placing XGT2-CXGL2-CXGS2-C in an eccentric condition.
As the eccentric reaction force becomes smaller, the force acting on the shaft bearing also becomes smaller.

Thrust reaction force

This is the force generated when compressing XGT2-CXGL2-CXGS2-C in the axial direction. As the thrust reaction force becomes smaller, the force acting on the motor also becomes smaller.

Physical properties and chemical resistance of high-gain type rubber