Verification of the accuracy of motorized stages is generally performed by sampling inspection, according to JIS General Test Method of Machine tools (JIS B6190), using instruments calibrated to a standard traceable to a national standard.

Instruments used

Dynamic Calibrator (HP5529A), manufactured by Agilent Technologies Japan., Ltd. The Dynamic Calibrator has been calibrated using a standard traceable to the U.S. National Institute of Standards and Technology (NIST).

Various other instruments, including a two-axis photoelectric autocollimator manufactured by Nikon Corp. and a laser measuring machine (BG10L or BR10A) manufactured by Sony Precision Technology Inc., have been calibrated using a standard traceable by the manufacturers.

Accuracy verification item (test item)

(1) Length measurement (2) Straightness measurement (3) Perpendicularity measurement (XY-axis stage) To have stages delivered with measurement results, indicate the desired accuracy test items or measurement specifications (e.g., load conditions) when ordering. (An additional fee is charged.)

Positional accuracy, positional repeatability, lost motion, and straightness measurement

Accuracy testing for installed stages

Accuracy testing for a motorized stage is performed for just the stage. Accuracy measurements when the stage is combined with other components - for example, with X, Y and q z axes - are generally not performed at the Sigma Koki factory. Please contact us to request accuracy test under specified conditions. (An additional fee is charged.)

Accuracy measurement at delivery sites

If needed, such testing will be performed by the Japan Quality Assurance Organization or other entities. Please contact us for further information. (An additional fee is charged.)

Positional accuracy

Inspecting regulation: JIS(Japanese Industrial Standards) B 6333 fulfilled. Starting from the origin, uni-directional and equally displaced positioning is accomplished over entire travel of the stage. For each positioning points, deviations between "Measured" (actual displacement from the origin) and "Targeted" (desired displacement based on commands) value are obtained.

Difference between maximum and minimum deviation is then defined as positional accuracy.

Directional position repeatability

Inspecting regulation: JIS (Japanese Industrial Standards) B 6333 fulfilled. At three arbitrary points (both ends and center) of the stage, uni-directional positioning is accomplished for seven times per each points and maximum deviation are obtained. The largest of these maximum deviations is then defined as directional position repeatability.

Lost motion

Inspecting regulation: JIS (Japanese Industrial Standards) B 6333 fulfilled. At three arbitrary points (both ends and center) of the stage, bi-directional positioning is accomplished and displacement between forward and backward positioning is obtained. This measurement is repeated for seven times, and the average is calculated. The largest of these averaged values is then defined as lost motion.

Straightness

Inspecting regulation: JIS(Japanese Industrial Standards) B 6333 fulfilled. Amount of deviation orthogonal to axis of travel. Either horizontal or vertical. Starting from the origin, uni-directional and equally displaced positioning is accomplished over entire travel of the stage. For each positioning point, deviation from the axis of travel is measured. The largest of these deviations is defined as straightness.

Positional repeatability

Inspecting regulation: Sigma Koki's company regulation. Starting from the origin, twelve equally displaced positioning is accomplished over entire revolution of the stage. This positioning is carried out for five round-trips.
For each positioning points, deviations between "Measured" (actual displacement from the origin) and "Targeted" (desired displacement based on commands) value are obtained. From this result, average displacement of uni-directional (CCW direction) positioning and also standard deviation is derived. The largest of (average)?}(standard deviation) is then defined as positional repeatability.

Lost motion

Inspecting regulation: Sigma Koki's company regulation. Starting from the origin, twelve equally displaced positioning is accomplished over entire revolution of the stage. This positioning is carried out for five round-trips. For each positioning point, averages of "Measured" displacement (actual displacement from the origin) are derived for both CW and CCW directions. Differences of the values are lost motion of the point. The largest of these values is then defined as lost motion of the stage.

Wobble

Inspecting regulation: JIS (Japanese Industrial Standards) B 6191 fulfilled. Measuring vertical displacement of the table surface through one revolution (360?). The largest of these values is then defined as wobble.

Note 1) Above described results are value for following stages measured by using accuracy verification software fo rrotation motorized stage (Rotary.xls).

Note 2) The origin of verification is set at point rotated 15 degree to CCW direction after detecting the mechanical origin.

Note 3) Approach direction ↑ indicates rotating to CCW direction and ↓ indicates rotating to CW direction.