Using linear bushings correctly.
Linear bushing applications in simplified automatic machinery - Example 2
(2) Stepping motor and ball screw drive
Under a ball screw drive mechanism, [1] the motor rotation is directly converted into linear movement and [2] the ball screw pitch functions as a reduction gear. Because of these features, this mechanism excels in drive force transmission and motor efficiency.
[Fig. 4] is a drive mechanism that uses a linear bushing and ball screw on the Y-axis. It is used in applications that require reduced takt times or positioning precision.
Click image to enlarge.
Supplementary notes
a) Characteristics of stepping motors
Stepping motors feature big torques in low rotating speed zones (they can achieve big torques during startup and slowdown). They are therefore suitable for applications that have short moving distances and require multiple positioning controls.
b) Motor precision requirements for the achievement of target positioning accuracies
When a ball screw lead pitch of 10 (mm/rev) is selected to achieve a target positioning accuracy of 0.01 (mm), the precision requirements for the stepping motor can be calculated using the following formula.
Precision requirements of the motor = 360 x Positioning accuracy / Ball screw lead pitch
Precision requirements of the motor = 360 x ( 0.01) / 10 = 0.36 ()
(3) Air cylinder drives
[Fig. 5] shows an air cylinder drive bearing with a clamp. [Photo 2] is an air cylinder drive with a magnet connection. Both applications use linear bushings (indicated with arrows).
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An air cylinder drive does not allow speed control during startup and stop operations. A shock absorber is used to reduce impacts during stop operations ([Photo 2]).
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(4) Example of a vertical guide
A flanged linear bushing can be mounted securely on a vertical guide without special holding devices, allowing for a compact and simple mechanism (a vertical base plate is needed on the slide guide to stabilize the rail) ([Photo 3]).
Click image to enlarge.
Click image to enlarge.
Flanged linear bushings, with structures similar to that shown in [Photo 4], are also used in elevation guides from the lower parts of transfer conveyers ([Fig. 6]), as well as in positioning mechanisms ([Fig. 7]), etc.
Click image to enlarge.
Click image to enlarge.