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

I'm experiencing what seems like the exact same thing you've described. 

It seems like this isn't new, with another thread posted today about it: https://forum.prusa3d.com/forum/prusa-core-one-hardware-firmware-and-software-help/coreone-printing-head-home-position/

And earlier, this thread has more discussion and is from back in February, I believe: https://forum.prusa3d.com/forum/prusa-core-one-hardware-firmware-and-software-help/constantly-recalibrating/

At least it pulls through! But yeah, I'll be holding my breath for some sort of fix or acknowledgement from the Prusa team.

Cheers

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

Hi Matthias, the only time my printer did more banging around was due to the belts being not at the right tension (much like new strings on a guitar, the belts need retuning until they settle on a decently stable config); have you tried returning the belts?

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.

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

Posted by: @matthias-nagel

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.

One thing to try perhaps is the 6.4.0-rc firmware release where there have been improvements made to homing. I've been running it for a few days. There are bugs but they are minor. The new belt tuning strobe is cool. Can always restore to the previous firmware if it doesn't work out. 

RE:

I am not prusa support but I'd look at a couple of things at this point (and please pardon me if you did already):

- cable of the sensor behind the handle not interfering in any way with the gentry movement

- top cable and ptfe tube not allowing enough movement of the head

beyond that I think I'd use support...

RE:

I am not sure to which cable you specifically refer to in your first bullet point (which handle? which sensor? etc.), but Gantry movement is fine. There is not a single cable or PTFE tube which interferes. I am used to be a very nitpicking craftsman, so I am sure that there is nothing wrong with the assembly. At least nothing with the more obvious aspects about which plenty has written in this forum and the comments below the assembly instructions (belt tension, alignment of gantry, obstacles from cables and tubes).

However, reading all the post in the other thread, I believe it might be related to chamber temperature (see my post in Re: Constantly recalibrating). I hadn't made the connection until I read about that aspect in the other thread, but it could be the reason indeed as it would be in line with my observation. Each time after a repeated calibration, the very first homing run smoothly. But it became worse after each single print (not within weeks, but hours). See my text

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 new 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) succeeds instantly.

Obviously, after a repeated calibration the chamber was cold and I print mostly high-temperature material such as PC. My chamber temperature is usually between 55° and 60°C. So a temperature related problem might be indeed the reason. I will give it some observations and then probably contact Prusa support. However, one should assume that Prusa had tested those scenarios.

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

A reboot of the printer helped me out in this case. It looks like a firmware issue for me.