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Motor(s) mis-stepping.  

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stephen.w10
(@stephen-w10)
New Member
Motor(s) mis-stepping.

Hi I have a 2.5s which I've had for a number of years now with no issues (it doesn't get a lot of use, just a few hours a month).
Recently it's been getting an hour or two into a print and then the motor stalls and the print skews by several millimetres although sometimes it'll print happily for 4 or 5 hours.
This can happen on either the X or the Y axis. I'm rarely in the room when it happens but when I have been you can hear the motor stall. It could also be happening on the Z axis but I've seen no evidence and a stall would have less effect.
I've replaced the bearings on both axis but it's had no effect on the issue and both axis seem to move smoothly enough.
Has anyone else seen this? ATM I'm struggling to think what it can be beyond replacing the control electronics.

Posted : 14/05/2024 10:47 am
Eef
 Eef
(@eef)
Estimable Member
RE: Motor(s) mis-stepping.

I have an MK2.5 too. And over years things get a bit worn out. Let's try to analyze what you write: 
- It shifts on the X- and Y- axis and maybe Z-axis. That is probably why you think this is related to the electronics? 
All motors have direct cables to the PCB with own connectors. So one issue happening to all motors (if an electronic problem) can only be a problem on the PCB. That would be very rare. Because then the whole computer would have more errors and stop working, with messages (or just a black or white screen).  So, I would not start there. 
- If it as shifting only in one direction (X- or Y), then it is evident that we check that axis and functiong, like smooth moving; belts-tension, screws on the axis of the motor. You did check that and no issues there. 
- So let's go to the other point where all movements come together, the nozzle. 
If the nozzle cannot move, because it is stuck on the object (for what ever reason), then it cannot move anymore (or not enough), the stepmotor looses steps and eventually get's it going again. -> Shift. This could as easy be in the X- and Y direction. (not in Z-direction. then it would probably pull the print of the sheet.. 

So I think that while printing there grows a blob on the nozzle (and or) the object is warping, so a hard part of the object get's in the way of the nozzle. -> beng. 
- There is also the thing, as you mention, that it happens after several hours. why not at the first layers? What could be different because of the time, or the higher layers? 
With higher layers, I think about, maybe the warping.
Because of the time, it could be that there is a temperature-problem. The whole machine gets hotter and hotter (is it placed in an enclosure with closed doors? Then even more heat. When everything get's hotter, it may influence what is happening in the extruder (clogging in the heatblock and/or just above where the PTFE ends against the heatbreak.. This happened in my machine a couple of times!). 

OK. maybe this gives some ideas to work from. Regards, Eef 

Posted : 14/05/2024 5:13 pm
stephen.w10
(@stephen-w10)
New Member
Topic starter answered:
RE: Motor(s) mis-stepping.

Hi Eef, thanks for your reply.

So the reason I suspect the electronics is because this suddenly started happening on both axis at the same time. I appreciate it seems a bit weird since the motor drive sections are independent but perhaps a power supply glitch - enough to stall the motor but not reset the system?

Blobs on the nozzle do occasionally happen but they always have and I've never seen issues with them before. I give the nozzle a good clean between prints to minimise this.
I've also seen the issue happen on the first layer so blobs, warping and overheating shouldn't be an issue.

I'll buy some high quality bearings (the ones I used were just cheap Amazon ones) and strip the machine properly.
Since I need the machine I'm currently building a Mk4 as a replacement but having the 2.5 working again would be nice.

Cheers.

Posted : 16/05/2024 9:04 am
Eef
 Eef
(@eef)
Estimable Member
RE: Motor(s) mis-stepping.

 

Posted by: @stephen-w10

So the reason I suspect the electronics is because this suddenly started happening on both axis at the same time. I appreciate it seems a bit weird since the motor drive sections are independent but perhaps a power supply glitch - enough to stall the motor but not reset the system?

Blobs on the nozzle do occasionally happen but they always have and I've never seen issues with them before. I give the nozzle a good clean between prints to minimise this.
I've also seen the issue happen on the first layer so blobs, warping and overheating shouldn't be an issue.

The power supply has big capacitors, so supply glitches are (kind of) impossible. I can only imagine this happens if somewhere else there is a shortcut. But hard to believe, that this could be more then, the glitches there always are when the hotend + heatbed heating switch on at the same moment. 

I have also seen it happen in combination of blob + warping. But rarely. 

The last two days a couple of prints of myself were ruined by shifting several times in one print. Nothing mechanical to find. 
So I think it could be an error when uploading the file (octoprint) and then to printer. If g-codes are  is missed, it would give strange errors. When I ran it again, no problem, so as strange 

Posted : 16/05/2024 10:20 am
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