#### Sphere Calibration

1. Select Probe from the main screen.

2. Select Sphere Calibration. The Sphere Calibration screen appears.

Parameters Definition:

- Tip Diameter (Probe/Nominal) - Provides the nominal diameter of the probe tip. The Measured value is updated when calibration completes.

- Diameter (Sphere) – Specifies the diameter of the Calibration/Qualification sphere.

- XYZ (Sphere/Center) - Specifies the center location of the qualification sphere in relation to the Work Offset location. This value should be 0,0,0 if the sphere was accurately positioned at the Work Offset.

- Feed Rate - Sets the speed in millimeters per minute (or inches per minute if in inch units) that the probe will travel during probe calibration.

- Prehit Distance - Specifies the distance from the theoretical hit location to which the probe will move before taking a hit. This is used during probe calibration. This is in millimeters or inches.

- Work Offset - Specifies the Work Offset at which the qualification sphere is located. Choose Machine to move relative to Machine coordinates.

Navigation Bar Soft Keys for this Screen:

| Backward When enabled, this soft key scrolls back to any additional buttons available on the first page for this screen. |  | Find Center Selecting this soft key will cause the software to take sample hits to find the center of the sphere before measuring the sphere for calibration.
| Show Details This soft key will show the tip offset from the nominal location. This acts the same as enabling the Show Details check box. The offsets are deviation values. The form error is also shown. The form error is the least squares best fit error of the points prior to vector compensation. The tolerances are entered under the Calibration Test Settings button. |  | Calibration Test Settings This soft key will show open a new window which will allow the user to indicate the nominal location of the ring and tolerance values. If any measured value differs from its respective nominal by more than the allotted tolerance, a warning will be displayed. The user will be able to continue after accepting the warning.
| Work Offset This soft key selects the named work offset from the list of offsets. Pressing this again will select the next work offset from the list. |  | Delete Calibration This soft key deletes the current calibration.
| Learning and Creating a Command This will only be available after all the necessary probe positions to identify the feature location have been learned. It will cause the machine to measure the feature. |  | Cancel All Steps / Abort This soft key stops and resets the current operation. If learning a feature, it removes all the learned probe positions.
| Select a Probe If the Select Probe screen isn't the current screen then this soft key accesses the Select Probe screen. If the Select Probe screen is already visible then this soft key selects scrolls through each probe in the Probe list with each touch of the soft key. |  | Confirm / Add Command For operations this confirms the selection. For commands, this will append the command to the end of the program. For feature commands, this will become available after the machine has learned the feature location or when you have typed the feature's nominal values.
For constructed and dimension feature commands, this will become available once you have specified the proper input features.

| Help This soft key accesses the NC Gage help file. |  | Return This soft key returns the view up one level to the previous screen.
| Forward When enabled, this soft key scrolls forward to any additional soft keys available on the second page for this screen. |  |

Calibration Process:

1. Select the Work Offset to use for the calibration. The default is the Machine work offset.

2. Input the Diameter and Center Location for the Calibration/Qualification sphere. The user may identify the location center coordinates using the description at the bottom of this page.

3. Input the nominal Tip Diameter and the nominal XYZ Center Location values.

4. Jog the probe tip above the qualification sphere's center.

5. Select Learning and Creating a Command. NC Gage automatically takes hits on the qualification sphere as defined by the Sphere Calibration parameters.

6. Once calibration has completed, the measured values are updated. You are now ready to measure features using your calibrated probe.

The following is the specific feature path and logic built into NC Gage:

- Read position of probe above top of sphere.

- Measure straight down, search distance is probe radius + 2* prehit distance.

- Set clearance plane height = Max of read point Z and prehit distance + probe radius above of contact point.

- Estimate center of sphere to be sphere radius below contact point.

- Set prehit radius = Sphere Radius + probe radius + prehit distance.

- Move to Clearance Plane.

- Move in Clearance Plane to a point that is prehit radius in +X direction from sphere center.

- Drop to height of estimated sphere equator.

- Measure equator with 16 points, extra moves between points if needed.

- Move up to next level (9 degrees above equator).

- Measure level with 16 points.

- Repeat process for all 10 levels.

- Measure point on top of sphere.

- Return to clearance plane.

Identify the Sphere Center Location

Locating XY:

- With Spindle Rotation - If the NC Machine supports spindle orientation (M19Sxxx), then the XY position of the sphere may be found with the Find Center apply function in the Calibration screen. This function rotates the spindle for each point so that runout of the probe tip is not a factor.

- With a Dial Indicator - Load a dial indicator in the spindle of the NC Machine and adjust it so that it is touching at the approximate equator of the calibration. Jog X and Y on the NC Machine so that when rotating the spindle the deviation on the indicator is minimized. The center of the sphere is the X and Y machine position.

Locating Z:

- Insert a reference tool of known length into the spindle.

- With a feeler gage of known thickness, jog the tool down over the top of the sphere until the feeler gage has resistance when moving between the sphere and the tool. Use the smallest jog increment when close to the sphere.

- The sphere Z is then equal to machine Z minus the feeler gage thickness minus the calibration sphere radius.