After each power on, new Core One recalibrates home, bangs the Nextruder against the corner and reports a printer collision  

RE: After each power on, new Core One recalibrates home, bangs the Nextruder against the corner and reports a printer collision

Yes, I did re-calibrate. These are the steps I performed the first and the second time:

1. Loosened both belts up to the point where the belt tensioners were barely holding on the screw.
2. Tightened the looser of the two belts such that it had the same tension as the tighter one; at this point the belts were both still pretty loose. I could pull each belt out of its middle line by approximately 1.5cm without any resistance and without snapping back.
3. Checked that the gantry was square and that there was no gap on either side when I moved the gantry to the front position.
4. Tightened both belts equally and simultaneously until they became tight enough to start vibrating when being pulled (so that the Belt Tuner app could recognize a sound). That was approximately at 60-70Hz.
5. Tightened both belts simultaneously and equally until they were both at the average between 92Hz and 98Hz, i.e. 95Hz
6. Then loosened the lower belt and tightened the upper belt simultaneously by the same amount until they reached 92Hz and 98Hz, resp.

All the time I constantly checked that the gantry did not come out of alignment. Did I also mentioned that I checked the perpendicularity of the mounting brackets of the gantry with a machinest gauge during assembly, because I read in the comments that those brackets are known to be skew?

I also printed the Vernier Skew Test. Intrerestingly, it showed a negative skewness of -0.5mm with the belts being at 98Hz (upper belt) and 92Hz (lower belt). I had to go back to 96Hz and and 94Hz to get a zero.

But either way it didn’t make much of a difference.

Each time, the first auto homing (i.e. directly after th belt calibration) worked nicely: only two bangs and homing was finished. I thought, yeah, that was it. But after the first or second print the homing procedure was running forever again.

I could understand that the belts of a newly built Core One need to settle in, because nee belts might give in after some time and needed re-calibration. But that shouldn’t happen after a single print. Also I could not measure any deviation in the frequencies when it started to happen again. Interestingly, homing sometimes (but rarely, maybe 1 out of 10 times) suceeds instantly.

That is totally annoying.