CAPPSNC Strain Gauge Probe Calibration

What is involved in a strain gauge probe calibration?

A strain gauge probe is defined as an electronic trigger of internal strain gauges. This means inside of the triggering mechanism are mini strain gauges that instantly trigger upon contact. The strain gauge mechanism allows for the probe to trigger on any portion of the ruby uniformly. This means that once you know the effective radius of your probe, you’ll be able to probe any type of surface uniformly.

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How to calibrate a strain gauge probe with Canned CAPPSNC Routine

1. Inside of CAPPSNC under the Probe Ribbon is a calibrate option.

2. When you open the calibrate option you will be presented with a dialog box that is preconfigured from when your system was setup by AAT3D or AAT3D Partner/Distributor.
   
   
   

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3. Input the Program Number to be used and click write.

4. Transfer program to controller and calibrate your probe.

How to Verify Calibration or Adjust

After a calibration has been performed it is good to practice and verify the calibration to a trusted position.

Process to Verify Calibration

The easiest way to verify the calibration is by finding a trusted position on the machine using the spindle face and some sort of known calibrated distance block to a point. This allows you to set the work offset or origin to that location and then be probed in CAPPSNC.

1. Set the Point you found to the work offset or origin you will want to run a CAPPS program on.

2. Make a program in CAPPS to probe a point at 0,0,0 with the correct vector and post the program.

3. Run your CAPPS program on the machine

4. Look at the deviation of the point relative to the point direction error “Example: Z axis” deviation should be under .0002”/.00508mm

5. Rerun calibration and then test program until the deviation is under the limit.

Process to adjust your Probe Deviation

In the event that your probe did not verify out correctly you will want to adjust the variable in the start file that the AAT3D engineer set for controlling the Tool Length or Radius size.

1. Locate the machines start file located in the CAPPSNC8-->Capp-->MachineStart ”machine name” Or Right click in DMIS window-Click- Create NC Machine Program-Click upper right MachineStart

2. Open text file and look for a line that says “probe length adjust” or “Probe Ruby Radius” if you do not have either of those you will need to adjust the probe length that CAPPS is using.

3. Adjust the value in the variable/macro line and ADD the deviations to the current value present in the verification program.

4. Re Run calibration and run verification test again.

5. If still deviated keep repeating until it checks out to within tolerance.

FAQ

Frequently Asked Questions about Calibration

How do I know if I have a good calibration?

-Click the Select button under the Probe Ribbon, then click the Display Dev. From Nominal. Your form listed is how to know how accurate your calibration was. A lower number the better. The form should be .001”/.0254mm or less. The Diameter deviation should be under .02”/.508mm. The X, Y, Z deviations listed are representative of probe runout.

My probes form is bad, how do I fix it?

-Form is determined by the following: probe length, integrity of ruby, accuracy of calibration sphere size. Verify the probe length by measuring a known surface and probe it in CAPPS if there is deviation the probe length is off. Adjust the length for the probe being used in CAPPSNC system. If length is good, there may be a discrepancy in the cal sphere size input for calibration or there may be a flat forming on the probe’s ruby.

I indicated in my probes runout on the machine do I need to recalibrate?

-Yes. Anytime you physically change/alter the probe you need to run a calibration. The proper procedure would be to redefine your probe and then run the initial calibration and repost the calibration a second time to verify the calibration.