How to keep the spindle from rotating when using the MDI function?

[BobS]

My expectation is to end up with +/- 0.001 positional accuracy. So far it has worked.
One concern I have is that the spindle is not kept from rotating. Very little rotational force is placed on the spindle in this setup, However, I would prefer to be able to have the spindle not be able to rotate as it does when using a 3D probe macro.

Question: How do I keep the spindle from rotating when using the MDI function?

I have a simple setup to calibrate the X,Y,Z DRO, see the attached photo.

The procedure is very simple (inch):

1. Set the axis to be calibrated. Setup F1 > Part F1 > Set F10

2. Set the digital indicator to zero when its tip is contacting the reference stop such that the reference stop moves indicating the distance the reference stop has traveled.

3. MDI F3 > M “axis to be calibrated” desired calibration travel (A value less than the maximum range of the digital indicator.)

4. Use the value on the digital indicator to calculate Motor revs/inch as calculated in the following example:

Divide the distance moved (DRO value) by the distance that the axis actually moved (digital indicator). Multiply this result by the current value in the rev/inch field.

Example: If the axis actually traveled was 6”, but the DRO value was 7.5”, then 7.5/6 = 1.25. Next if the current Motor revs/inch is 5.000, then 5.000 * 1.25 = 6.25 is the new value to enter in the Motor revs/inch field.

Also see reference: https://www.centroidcnc.com/dealersuppo ... ads/36.pdf

Set Motor revs/inch: Setup F1 > Config F3 > Mach F2 > Motor F2 > Motor Parameters table Motor revs/inch

After changing revs/in power cycle and re-home the machine and reset and WCS locations

[suntravel]

Do not mount the indicator in a spindle without a brake or without setting the spindle to position mode holding the position....

Uwe

[BobS]

Uwe,
That is my question how to put the spindle in the hold position.
Thanks, Bob

[suntravel]

Uwe,
That is my question how to put the spindle in the hold position.
Thanks, Bob

As already mentioned, a brake or a spindle drive with position or indexing mode.

I use a sturdy dial indicator arm on the spindle housing, because I have no free axis to put the spindle servo in position mode and the arm is stiffer as a servo, so better precision.

Uwe

[BobS]

Good suggestion.
Thanks

[suntravel]

Here you can see the HG arm I am using:



http://www.hoerger-gaessler.de/files/hy ... essler.pdf

about 400€ with 1000 N holding force, but worth it I you want to measure 0.001mm reliable...

Uwe