Components used to transmit motor's torque (force) and rotation (moving distance) to a ballscrew may largely affect the system accuracy, reliability, and ease of assembly. Couplings are explained in this tutorial.

(1) Role of couplings

When connecting both shafts of a motor and a ballscrew, the arrangement may be accurate statically but can include possible variables dynamically, as show below.

	1.	Ballscrew shaft deflection when rotating.
	2.	Shaft deformation and stress due to heat expansion.
	3.	Deformation of ballscrew support unit.
	4.	Friction resistance variances due to bearing wear, after extended usage.

Therefore, couplings that can solve the variables from issues 1~4, instead of using a rigid body to connect the two shafts.

(2) Coupling types, construction, and characteristics