Positioning System Guide to Choose the Correct Linear Actuator in 12 Steps –Part III

1. Multiple Centre of Gravity Positions

The center of gravity of the load that is moved keeps changing as it moves across the axes. For every position, the center of gravity with respect to the datum (home) point on the different axes needs to be calculated. As the load/ object travels across the system in accelerated or decelerated movements, its center of gravity relative to a coordinate will keep changing. So, when mounting the linear systems, the different positions and calculations of center of gravity of the object at various points with respect to all the axes will need to be calculated.

Calculating the center of gravity at various positions, in the application and averaging the calculations will assist you in employing the right mounting methods.

2. Load Bearing Capacity

Calculating the mass or geometry of the load at various points on the axes with respect to the coordinates will help determine the load bearing capacity of the system. Stationary loading factors, and rapid moment loads, are other factors to be considered when determining the load capacity. The integrated linear systems, engines, and gearboxes act as overhung loads. This is also a determinant in calculating the load capacity.

3. Stroke Lengths

The stroke length of the actuator for each axis needs to be determined to provide the right direction and magnitude of movement. The extent of movement is largely dependent on the type of actuator used. For example, when using heavy duty ball screw actuators, the ball screw will determine the length of stroke. The stroke length cannot exceed the length of the ball screw. On the other hand, linear actuators utilizing belt drives have no limit on the stroke length. Theoretically, the stroke length can be infinite but in practical application, the length rarely exceeds 10 meters.

4. Precision & Repeatability

Most applications that require movement have definite needs for precision and repeatability. These are two important factors during the design and conception stages. The repeatability and accuracy of every linear actuator is defined upon production. You will need to speak to your manufacturer or supplier and purchase an actuator that fits your specific requirements. Generally, linear actuators with ball screws are more precise compared to those with belt drives.