What is a coupling (shaft coupling)?
Types and Features.

The primary reason for using a coupling is to connect the drive shaft to the driven shaft.
It is difficult to manufacture a machine connected with one-piece shaft instead of using a coupling. It creates problems in terms of cost and accuracy, but also transportation and assembly are very difficult, so it takes extra man-hour.
Also, in the case of one-piece shaft, it must be replaced in its entirety, if either the drive side or the driven side is broken.

It takes a considerable amount of time to align the drive shaft to the driven shaft with high precision.
If the axes of two shafts are misaligned, an extra force is repeatedly applied to the surrounding parts as it rotates, which causes vibration and noise.
In addition, even though the same parts are used to manufacture units, there are errors such as machining accuracy, so it is very difficult to assemble every unit with accuracy, because the dimensions are different one by one.
Therefore, a coupling should be used to absorb such mounting errors.
Coupling has the role of transmitting power dynamically and accurately even if there is a misalignment (eccentricity / declination angle, axial displacement, etc.) between the two shafts.

Vibration and shock may be transferred to surrounding parts when using the machine.
For example, if the vibration of a motor, etc. in the driving side is transmitted to the ball screw, etc., it deviates the machine from the prescribed position and it is impossible to make the good use of the machine’s performance.
Also, if a machine with no coupling receives an impact from the outside, the impact may be transmitted directly to the motor and may cause damage to the motor.
A coupling is the solution to this problem. It absorbs vibration in order to move the driven side with high accuracy, and/or shock to prevent expensive motors, etc. from damaging.

A motor generates a lot of heat when it is used.
When it is transmitted to the driven side, the ball screw, etc. expand by heat and the length will be changed.
As a result, the positioning accuracy is affected, and the expected machine precision will be not realized.
However, by using a coupling, it is possible to prevent the heat transfer of the motor, etc. so that the parts will not be deformed or shifted from its correct position.

◯: Suitable △: Suitable for some applications

Coupling Models	Photo	Discription	Zero back lash	High torsio nal rigid ity	Damp ing	Oil proof	Indu ction motor	Servo motor	Step per motor	En coder
Metal Disc type		· The flexible metal disc elements allow for varying degrees of misalignment. ・Excellent fit for high speed rotation applicationt.	○	○		○		○	○	○
Rigid type		· Cylindrical simple structure · Ultra-high rigidity with low inertia	○	○		○		○
Spring coupling		· The coil spring element allows for varying degrees of misalignment · High flexibility and high transmittable torque		△		○	○	△	△
Pin and bush type		· The sliding pin and bush allow large misalignment, and very low reaction force			△		○	△	△
Mugnet type		· Permanent magnet force transmitted power without mechanical contacting · These features ideal for clean rooms and food processing application			○	○	○
High vibration damping laminated s rubber type		· High dampening characteristics absorbs resonances of servomotor or stepper motor	○		○			○	○
Jaw type		· Two hubs interpose rubber or elastomer element structure absorbs vibration · Easy installation	△		○	△	○	○	○
Bellows type		· Structure of 2 hubs and plastic bellows · Compact and high flexibility			○	△			○	△
Rubber/ elastomer element type		· Compressed rubber structure, elastomer element structure · Suitable for engine applications for vibration absorbing			○	△	○