Err:Print Fan Error  

  RSS
AcE Krystal
(@ace-krystal)
Eminent Member

I'm opening this topic both to search for help as for logging my finding and solution(s).

Since a short time my Prusa MK3 is stopping in the middle of a PETG print with cooling fan set on min 30% - max 50%.
It display's the error "Err:PRINT FAN ERROR".

In most cases I suspect the fan cable to have breaks in it. After 2 years my printer had multiple breaks in the original blower/part Fan wires going towards the PCB. Back then I replaced the moving/bending part of the wire with a piece of wire coming from an old mouse as these wires are more suited for a lot of moving and bending.

This time however I get the feeling I don't have a line break, but something else is going on.
The fan is spinning normally when I manually set is to 255 in the printer settings on the printer itself. It also registers the RPM correct even though I move the head or pull/pushe/twist the wire bundle in every direction.

But when I manually set the fan speed on the printer below a value of 75 I alway's get a reading of 0, just as if the prusa firmware dissables RPM tracking at speeds lower then 75.
- I would like it if someone can confirm this for me on their good working printer. Does setting the Blower speed below 75 indeed always result in 0 RPM being read

In my case the g-code seems to set my printer to a speed of 76 while printing most of the times, but for some reason my RPM reading is jumping from 120 to 480 to 1800 and back to 120 and sometimes also 0. This is also what is causing the error. While looking at the fan, I can clearly see it spinning faster then 120 all the time.

I have done a firmware update to the latest firmware, but this did not have any effect.

I suspect there is something wrong with either the FAN itself causing causing the RMP to not being delivered correctly, or maybe even a defect on my PCB causing it to not being able to read out the rpm reliable. The FAN also seems to rotate a bit strange, it is rotating without noticable resistance, but it seems to have a bit of difficulty spinning up at low speed as if one of the coils might be damaged. Also, it seems to tower down every ~5 seconds or so, then update the RPM on the display, and then give a short power boost to the fan making it spin up faster for a brief moment. It is not doing this when setting the speed under 75.

For now I have disabled the FAN CHECK on the printer itself so I can continue printing, but I would like to solve this issue and document it here.

In the future I  plan on doing the following :
1. Measure the wire continuity while bending/pulling/twisting it to make sure the wires are good and do not have breaks.
2. Clean the FAN contacts on the PCB.
3. Buy a new FAN from Prusa, cut the old one off and solder on the new FAN.

 

If someone can test the 0 RPM for me that would be of great help. And if someone has or has had this problem, please let me know 😉

Creative Engineer and 3D printing @ AcEcraft.eu...
Posted : 20/01/2021 5:40 pm
jsw
 jsw
(@jsw)
Noble Member

I had this a while back, and when it started getting more frequent I just said {f-bomb} it and ordered a new fan for a slam-dunk fix.  When I disassembled things to take out the old fan I realized that the fan cable was going through a significant point of strain as it entered the cable bundle.  I rerouted the new cable to avoid this.  I think this is one design flaw in the system.

Posted : 20/01/2021 11:00 pm
AcE Krystal
(@ace-krystal)
Eminent Member

@jsw

I think you are referring to a broken cable problem then I guess. I my case I suspect something else then the cable is going wrong as I replaced it already with a computer mouse cable. But I will do a measurement soon the make sure I don't have new breaks.

Creative Engineer and 3D printing @ AcEcraft.eu...
Posted : 21/01/2021 12:08 am
jsw
 jsw
(@jsw)
Noble Member

Yes, it could be the fan itself, or the connection to the board, or the board itself.

I didn't want to futz around with it any more than I absolutely had to so I just replaced the fan.  IIRC it was US$8 and change.

Posted : 21/01/2021 1:15 pm
cwbullet
(@cwbullet)
Illustrious Member

Check to make sure there is not a Ditzel of filament in the fan.  I have had that happen with a failed print.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 21/01/2021 2:49 pm
AcE Krystal
(@ace-krystal)
Eminent Member

@cwbullet

Thank cw, I checked this and the fan is spinning free, It keeps turning a bit after I give it a little push with my finger. I have had this happen in the past and because of that I added little fan/grills. Never had a problem of failed 3D print ending up in my fan after that. I also opend up the fan housing already to check if there might be something I was missing. I also checked the bearing lubrication, but this was fine. And I checked the wire solder joints and these seemed fine too.

I wanted to try and pull the fan blades from the PCB/motor so I could maybe look underneath of a motor winding has come lose, but it seems like this fan does not have a removable ring on the axle and thus seems to be permanently fixed on the PCB and backplate.

 

I'm to busy at the moment to disassemble my 3D enclosure, so I'm just gonna print without fan-checks for a while. But I will give an update here as soon as I have solved it and also hope to be able to report what actually failed.

Creative Engineer and 3D printing @ AcEcraft.eu...
Posted : 22/01/2021 11:17 am
cwbullet
(@cwbullet)
Illustrious Member

Just make sure the fan spins before you do any long prints.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 22/01/2021 12:30 pm
Share:

Please Login or Register