A ball screw achieves high efficiency even if driving torque is low because balls roll between the screw The ball screw is composed of a screw, a nut and balls, Screws are classified by processing and Ball

shaft and ball nut to obtain a lower coefficient of friction than a leadscrew. Nuts are classified by recirculation method.

Low Coefficient of Friction and High efficiency

High Velocity and Acceleration.

Long Service Life Time.

-1. Types by Manufacturing Method

There are types, Rolled and Ground Screw Threads.

A rolled screw is manufactured by roll forming a thread form into a rod. A Ground screw is

manufactured by grinding the thread form into a rod. Generally ground screws are much more precise

and smooth.

-2. Circular-arc groove and ball contact structures

Four-point and Two-point Contact Structure

(Contact between ball and Circular-arc Groove)

(Load Angle) (Load Angle)

[Calculating the Lead Angle]

: Lead angle

L : Lead

dp : Ball circle diameter

1-3. Structure of the Screw Shaft The nut is classified by Recirculation method.

[Return Tube Type]

The most common type.

A return plate allows balls to recirculate.

[Deflector Type]

[Screw Diameter : d] [Lead : L]

Compact type, Easy to install

It means screw shaft outer diameter. The amount of linear movement achieved by 1

revolution of screw movement.

[Ball Diameter : Dw] [screw-shaft thread minor diameter : dr]

Ball diameter. The diameter of the screw measured from the

bottom of the thread form.

[Ball center-to-center diameter : dp]

[End-cap Type]

The screw diameter measured from the center of

balls rolling in the thread form. This number is These nut are suitable for long-lead type.

necessary to calculate maximum permissible Balls are recirculating in an end-cap.

speed and lifetime.

[Inner-recirculation Type]

Similar to End-cap type.

There is a passage of balls circulating inside of the nut and return piece allows balls to circulate. It is

suitable for high-speed.

[Ball Screw Requirements] References

Orientation : Horizontal / Vertical

Payload mass : m (kg) ) Acceleration

Linear Bearing Type : Rolling / Sliding

Frictional coefficient of the Linear Bearing :

Linear Bearing Resistance : f (N) ) Acceleration distance

External load in the axial direction : F (N)

Support method of the screw shaft : fixed-free / fixed-supported / fixed-fixed

Desired service life time : Lh (h) ) Even speed distance

Stroke length : Ls (mm)

Operating Speed : Vmax (m/s)

Acceleration time : t1 (sec) ) Deceleration distance

Constant velocity time : t2 (sec)

Deceleration time : t3 (sec)

Dwell time : td (sec)

Acceleration : a (m/s2)

Acceleration distance : L1 (mm)

Constant velocity distance : L2 (mm)

Deceleration distance : L3 (mm)

Number of revolutions per minute : n (min-1)

Positioning accuracy : - (mm)

Positioning repeatability : - (mm)

Backlash : - (mm)

[Motor Requirements]

Motor Type : AC servomotor / stepping motor, etc.

The rated speed of the motor : - (min-1)

Moment of Inertia of the motor : Jm (kg.m2)

Motor resolution : - (pulse / rev)

Reduction ratio : A