The MTS Ballbar Inspection evaluation calculates the following table of results.
Explanation of the values are calculated as follows:

Circularity

The average value of the difference between the minimum radial deviation and the maximum radial deviation for each trace.

((RMax1-RMin1)+(RMax2-RMin2)+(RMax3-RMin3)+(RMax4-RMin4))/4

Radial Deviation

The average radial deviation of the trace from the programmed radius of the contour.

Min. Radial Deviation

The trace is automatically centered according to the average value for all traces in memory. The minimum radial deviation is then determined as the minimum deviation that occurs on any of the traces, not an average of all traces.

Max. Radial Deviation

The trace is automatically centered according to the average value for all traces in memory. The maximum radial deviation is then determined as the maximum deviation that occurs on any of the traces, not an average of all traces.

Axes Squareness Deviation (um/m)

The average radial deviation at the 45° , 135°, 225°, 315° degrees positions on the trace are used to calculate a value for the squareness deviation of the axes. This value should be calculated using traces in both positive and negative direction. This value should be checked using other measuring methods and is only a guideline. This is the difference between the diameter at 45° and 135° divided by the programmed diameter and is calculated as shown below.

( D R45 + D R225 - D R135 - D R315) ° 2[um]

Squareness deviation= Programmed radius [mm]

Diameter Deviation

The diameter deviation is calculated using the average radial deviation at positions 5* offset from the reversal points. This is necessary to prevent backlash and reversal peaks influencing the results. These values are averaged for each trace.

( D R5 + D R355 + D R175 + D R185)

Diameter Dev. (X) = 2° Radial Dev. + 2

( D R85 + D R95 + D R265 + D R275)

Diameter Dev. (Y) = 2° Radial Dev. + 2

Axes Backlash

The axes backlash for each reversal point are averaged for each trace. The value is positive for an increase in radial deviation in the positive direction with increasing angle.

Backlash (x+) = D R2 - D R358 (DR+)

Backlash (x+) = D R358 - D R2 (DR-)

Reversal Peaks

The peak height is calculated as the difference between the minimum and maximum radial deviation within a range of + 5 measuring points around the position of the peak. The values are average for each trace.

Dynamic Deviation

Dynamic deviation is a measure of the elliptical error form of the trace to take into account the errors on the trace caused by control lag, traversing in different directions.

( D R45 + D R225 - D R135 + D R315)[um]

Dynamic deviation = 4° Direction of rotation

Direction of rotation = +1 (DR+)

= -1 (DR-)

Unidirectional Repeatability

The unidirectional repeatability is the largest difference at any one position between traces carried out in the same direction. Values apply to all traces and are not averaged.

Bi-directional repeatability

The bi-directional repeatability is the largest difference at any one position between traces carried out in the different directions. Values apply to all traces and are not averaged.

Center Offsets

These are the calculated center offsets averaged for all traces that were active when the centering offset was determined.

Explanation of the Values Specified According to ISO 230

The ISO 230 standard specifies that the following values should be quoted with the results of a circular test:

Circularity

Radial Deviation

Circular Hysteresis (=Bi-directional repeatability)

The meaning of these values are explained above.