#### Calibrating Extended Lathes

Extended lathes can measure past the spindle centre i.e. X<0. Hembrug lathes are examples of such machines. Calibration of offsets for these machines can be simplified with a single outside circle feature centred at the origin rather than the inside and outside circle as done previously. Simpler still, a spindle mounted sphere can be used and this can also be used to incorporate a 2d Vector Compensation too if required.

The calibration scheme chosen must manage the transition between taking hits at different sides of the spindle center to avoid collisions. To do this, the circle feature centerd at the spindle center is broken up into two semi-circles and a move ClearPlane interposed between the two. This scheme is only adopted to simplify calibration and measurement programs will measure only with X>0.

Extended lathes are setup by indicating a non-zero Minus limit for the X axis and a Rotary Table axis in the Physical tab of the MachineDefinition dialog of the CncServer.exe as shown below.

Physical Tab of MachineDefinition Dialog Box for Extended Lathes

##### Ring Calibration

Select Edit | Preferences | Rotary Table Setup and ensure the Single rotary table is selected and clear the offsets if calibrating from scratch as shown below.

Rotary Table Setup Dialog Box

Construct the probe as normal by navigating to the Insert | Hardware Definition | Probe... option from the main toolbar.

Probe Utilities Dialog Box for Extended Lathes

Once the probe is defined, click on the Edit... button and add a new Ring Tool. Enter the ring diameter in both Diameter and Outside Circle Diameter edit boxes since this will be used to create the circle features - one on the right hand (X>0) side of the spindle and the other on the left hand side (X<0).

Edit Tool Dialog Box for Ring Calibration

The 2d Vector Compensation is shown to be turned off and the Y Tip Compensation omitted although these options are still available if required. Click the OK button and then create the calibration program by clicking the Measure button from the Probe Utilities dialog box to display the Measure Probe screen.

Measure Probe Dialog Box for Extended Lathe

Click the Measure button to create the Calibration Part Program shown below:

Calibration Part Program for Extended Lathe

A single outside circle and a plane are needed on the artifact used for calibration. The part program generated splits the circle into 2 semi-circles.

- The right hand circle will be measured by rotating the artifact - hits are taken along the X axis at X>0.

- The left hand circle will be measured by rotating the artifact - hits are taken along the X axis at X<0.

Calibration Part Program Graphical View

Create and run the part program as normal to generate the Journal file shown below:

Extended Lathe Journal File

From the Probe Utilities dialog box, click on the Active Tip from the list, then click on the Edit... button to open the Edit Probe Data dialog box shown below to view the updated values.

Edit Probe Data Dialog Box for Extended Lathe

Select Edit | Preferences | Rotary Table Setup to view the updated Rotary Table values.

Updated Rotary Table Setup Dialog Box for Extended Lathe

Dimensioning the calibration program is instructive as shown below:

Extended Lathe Dimensioned Calibration Program

The post-calibration sanity check is done by switching off the Ignore Rotary Table in the part program and un-checking the Calibrate Active Tip line and rerunning the Journal file (or better still, run the part program on the machine) to see if a near perfect result is achieved.

Extended Lathe Updated Report

Ring Calibration with 2d Vector Compensation

2d Vector and Y Tip Offset Compensation can be added by enabling it in the Edit Tool dialog. Click the Edit... button from the Probe Utilities dialog to access this screen.

Edit Tool Dialog Box for Ring Calibration with 2d Vector Compensation

Create the calibration part program as before. In this case, the 2d Vector Calibration circle has been edited to measure eight hits instead of five to match to saved Journal file data.

Part Program for Ring Calibration with 2d Vector Compensation

Running the program will display the following in the Graphics Display Window:

Part Program for Ring Calibration with 2d Vector Compensation

This part program generates a Journal file as shown below. In this case the Journal file has been created from parts of a Journal file from outside circle measurements on a Siemens NEF400 machine using the non-extended lathe groove calibration.

Journal File for Ring Calibration with 2d Vector Compensation

Starting again from nominals for the tip and rotary table and using the dimensioning shown above, PC-DMIS produces the following report:

Updated Calibration Report for Ring Calibration with 2d Vector Compensation

Graphically, the Out of Circularity found during calibration is shown below:

Updated Graphical View of Ring Calibration with 2d Vector Compensation

Ring Calibration with 2d Vector Compensation Post Calibration Report

Graphically the results for Circularity are near perfect as shown below:

Ring Calibration with 2d Vector Compensation Post Calibration Graphical View

##### Sphere Calibration

Add a Sphere Tool from the Probe Utilities dialog box by clicking on the Edit... button. Click the OK button when done.

Edit Tool for Adding a Sphere Tool

From the Probe Utilities dialog box, click the Measure button to display the Measure Probe dialog box.

Measure Probes Dialog Box for Sphere Calibration

Make the necessary change then click on the Measure button to create the Calibration Part Program as shown below.

Sphere Calibration Part Program

The Graphical View of this program is shown below. Note that the number of hits for the outside circle has increased.

Graphical View of Sphere Calibration Part Program

Create and run the program as normal and a Journal file will be created similar to the following:

Sphere Calibration Journal File

From the Probe Utilities dialog box, click on the Active Tip from the list, then click on the Edit... button to open the Edit Probe Data dialog box shown below to view the updated values.

Sphere Calibration Edit Probe Data Dialog Box

Select Edit | Preferences | Rotary Table Setup to view the updated Rotary Table values.

Sphere Calibration Rotary Table Setup Dialog Box

Dimensioning the calibration program is instructive as shown below:

Sphere Calibration Dimensioned Calibration Program

Turn the Ignore Rotary Table off, un-check the CALIBRATE ACTIVE TIP and then re-run the Journal file. The report is near perfect as shown below.

Updated Sphere Calibration Report

Sphere Calibration with 2D Vector Compensation

Add the Sphere Tool with 2d Vector Compensation as shown below. Click on the Edit... button from the Probe Utilities dialog to access this screen.

Edit Tool Dialog Box for Sphere Calibration with 2d Vector Compensation

From the Probe Utilities dialog box, click the Measure button to display the Measure Probe dialog box. Make any changes as needed then click the Measure button to created the part program which will by default look the same as a standard Sphere Calibration routine.

Initial Graphical View of Sphere Calibration Part Program with 2d Vector Compensation

Re-running the new Journal file after this kind of calibration emphasizes the effect of 2d Vector Compensation as shown below.

Updated Graphical View of Sphere Calibration Part Program with 2d Vector Compensation

Dimensioning the calibration program is instructive as shown below:

Dimensioned Part Program Report for Sphere Calibration with 2d Vector Compensation