PC-DMIS. Calibration of a disk styli
Hi there!
Here is a guide on how to calibrate a disk styli in PC-DMIS.
The first thing is to determine the angle range for calibration. As a disk probe is a slice of a sphere, we need to calibrate it on a certain range on a calibration sphere.
We also use only 70% of disk thickness for calibration. The formula is the following:
Sin(A) = (0,5 * 70% of disk thickness) / disk radius
In my example, I have a ceramic ⌀14mm disk with 2mm thickness. Sin(A) = 0,7/7 = 0,1. So Angle is 5,7 degrees. Let's round it and take 6 degrees. Our range will be:
Start angle: -6° and end angle: 6°, following +Z calibration sphere orientation.
As we cannot take exact location of calibration sphere with a disk styli, firstly, we get location of the sphere with a master probe and then use ONLY DCC mode in calibration window (not DCC + DCC as for regular styli).
Also, we use User Defined Mode to put our adjustments there. We use 3 rows of points for calibration as PC-DMIS will not allow you to use 2 rows. The first move of the disk is taking point on the very top of the calibration sphere, then it takes 4 more points with a circular move to construct a plane for the calculation of the whole length of construction including extension. I use carbone fiber one to get the best results as carbon fiber has almost zero thermal expansion coefficient. Then, it takes a point on each row (6°; 0°; -6°). Then, it takes circular rows of points for calibration.
The last step is to evaluate standard deviation and the results. I compared results with master probe on a master ring gage. Got 5 micron difference with 23°C temperature in our room. Not bad for disk styli, but I guess with more stable temperature, we'll get even more stable results. We're working on it.
Hope this was useful. Thank you for watching ✌️
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Musician: Carl Storm
