Probe Calibration and Form Resutls

1) If you're using more than one tip of the star probe for the cylinder, the calibration could indeed cause that (small discrepancies on one tip, could put it out of sync with the other - check your cal results for high StdDEv and/or tip diameter). As someone else mentioned, a graphical analysis might show hits with one tip to be causing the issue.

2) How big (diameter and length) is the cylinder? 50 hits often seems a lot, but when looking at form you might be getting an incomplete picture. Especially if you're not taking the hits in the exact same locations.

3) The TP20 will exhibit lobing anyway, depending on the length of the build I'd expect 0.005-0.015mm so some of your error might come from that.

4) The normal (Std/Med/Ext) force module aren't really designed for star / T configurations. You can get 6way modules that are (but really I try avoid star probes on TP20s)


In actuality, I'd say it's probably a combination of the above. Have you checked the repeatability (not moving the part) and without recalibrating?

1) If you're using more than one tip of the star probe for the cylinder, the calibration could indeed cause that (small discrepancies on one tip, could put it out of sync with the other - check your cal results for high StdDEv and/or tip diameter). As someone else mentioned, a graphical analysis might show hits with one tip to be causing the issue.

2) How big (diameter and length) is the cylinder? 50 hits often seems a lot, but when looking at form you might be getting an incomplete picture. Especially if you're not taking the hits in the exact same locations.

3) The TP20 will exhibit lobing anyway, depending on the length of the build I'd expect 0.005-0.015mm so some of your error might come from that.

4) The normal (Std/Med/Ext) force module aren't really designed for star / T configurations. You can get 6way modules that are (but really I try avoid star probes on TP20s)


In actuality, I'd say it's probably a combination of the above. Have you checked the repeatability (not moving the part) and without recalibrating?