Effect of Moment Load

Effect of Moment Load (pitch, roll, and yaw)

The accuracy of a motorized stage is influenced by its shape and the moment load it receives. If the load is applied to a position far from the center of the stage table, the stage is influenced by moment load (overhang load) in the direction of pitch, roll, and yaw. As seen in the lllus. 1, if the axis of operation is positioned outside the motorized stage table, the influence of pitch and roll increases. In the lllus. 2, if the axis of operation is inside the table, the influence decreases, although a high table position has a greater influence on the pitch and roll direction.

As seen in lllus. 3 using SGSP 26 Series, if a load of 10kg is applied to the spot 100mm from the center of stage table, the stage is inclined for approx. nine seconds (Approx.0.0025° ) in the yaw direction.

At this time, an error of approx. 0.0001µm in the X axis direction and an error of approx. 4.4µm in the Y axis direction are observed, compared to a normal situation where no load is applied and no inclination occurs.

As illustrated above, the accuracy of motorized stage changes depending on how they are used.

Illus.1 Example where the axis of operation is positioned outside the motorized stage table

Illus.2 Example where the axis of operation is positioned inside the motorized stage table

Illus.3 Example of the effect in the yaw direction

Illus.4 Example of pitch and roll effect

Illus.5 Accuracy mesurement for XY axis stage (reference data)

Effect of Moment Load

The amount of deviation in the stage caused by moment load (pitch, roll and yaw direction) and its effect

Measurement of stage deviation

Here, we will examine how much error occurs in the SGSP/SGAM Series motorized stages by measuring the amount of deviation in the stage table that is caused by moment load.

First, we measured the deviation distance and then the deviation angle(θ) in the overhang position. (Please refer to the following illustrations on how to measure them.)

Moment applied to z-axis stages and prevention of fall Prevention

The allowable load in z-axis direction is much lower than when used in the x-axis direction. Please refer to specification table in our catalog for the maximum load rating. In addition, the further the load is position away from the table, the stage is subject to more bending error and moment force, which results in larger positional error and reduction of stage life. Always try to limit the distance between the load and the table.

When the power is shut off or the automatic current-down function is stopped, the table may fall from its last position. Increase of the stop current to the motor when system is on or adding fall prevention mechanisms can prevent the table from falling.

Please refer to "Prevention mechanisms against falling" section of our catalog for more information.