MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?
 
Notifications
Clear all

MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?  

  RSS
Aw Mac 3
(@aw-mac-3)
Active Member
MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

Hi, Everyone. Hope you’re all staying safe.

I’m struggling with en Err: MINTEMP BED problem in an i3 MK3s that seems to be coming from a bad connection, but I’m not sure what else I can do.

Two days ago, after a long run of productive printing, the printer stopped in mid-print with a "MINTEMP fixed” message. I rebooted and started the print again. It preheated fine. During the initial Calibrating Z step, when the bed was already at 60 degrees, it reset the temp to 0 and gave me the Err: MINTEMP BED message and showed the bed temperature as 0/0 degrees. Then after a few seconds it went to MINTEMP fixed message again.

Upon restart some time later, and after checking the connection in the RAMBO board, I did see that  it showed the bed temp as being 0/0, which, when the textile-sleeve was wiggled could be made to read 14/0. There was no apparent damage to the textile-sleeve, nor any sign that the heatbed thermistor cable was not longer firmly attached to the underside of the heated bed with the golden tape, or that it was affected by the bed’s movement. I removed the bottom of the heatbed connector cover and retightened it and it showed 14/0 again and was able to warm the heatbed again. But now I’m just back where I started, with a heatbed that goes to 0 during the Calibrating Z step.

In effect, everything seems to be as it should be (and I never had bedtemp issues until this) except this clue from wiggling the textile-sleeve. What are the new steps for diagnosing this problem?

Thanks - A MacDonald

Best Answer by kennd:

sounds like you have a broken heatbed thermistor wire. Been there.

Start by checking this link

Use chat support chat ( not email ) and see if you can get a replacement if it is still under warranty. They may ask you to unplug it and test continuity with a multi-meter. When re-assembling it make sure that you follow the correct instructions in the assembly manual. Fabric wrap must be secured at both ends.

Replacing heatbed thermistor

Some people have indicated that were able to solder the wire and it worked. Some have replaced the wire. But see what support has to say first.

 

Posted : 23/03/2020 3:12 am
kennd
(@kennd)
Estimable Member
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

sounds like you have a broken heatbed thermistor wire. Been there.

Start by checking this link

Use chat support chat ( not email ) and see if you can get a replacement if it is still under warranty. They may ask you to unplug it and test continuity with a multi-meter. When re-assembling it make sure that you follow the correct instructions in the assembly manual. Fabric wrap must be secured at both ends.

Replacing heatbed thermistor

Some people have indicated that were able to solder the wire and it worked. Some have replaced the wire. But see what support has to say first.

 

Quality is the Journey, not the Destination
MK3S, Nylock mod, Modified Y-axis bearing mounting
MK3S kit waiting to be assembled (still)
Primary CAD program: Trimble Sketchup Make 2017(standalone) with 3D extensions
My limited prints on Prusaprinters.org...
Posted : 24/03/2020 8:09 am
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?
Posted by: @awmac3

Hi, Everyone. Hope you’re all staying safe.

I’m struggling with en Err: MINTEMP BED problem in an i3 MK3s that seems to be coming from a bad connection, but I’m not sure what else I can do.

Two days ago, after a long run of productive printing, the printer stopped in mid-print with a "MINTEMP fixed” message. I rebooted and started the print again. It preheated fine. During the initial Calibrating Z step, when the bed was already at 60 degrees, it reset the temp to 0 and gave me the Err: MINTEMP BED message and showed the bed temperature as 0/0 degrees. Then after a few seconds it went to MINTEMP fixed message again.

Upon restart some time later, and after checking the connection in the RAMBO board, I did see that  it showed the bed temp as being 0/0, which, when the textile-sleeve was wiggled could be made to read 14/0. There was no apparent damage to the textile-sleeve, nor any sign that the heatbed thermistor cable was not longer firmly attached to the underside of the heated bed with the golden tape, or that it was affected by the bed’s movement. I removed the bottom of the heatbed connector cover and retightened it and it showed 14/0 again and was able to warm the heatbed again. But now I’m just back where I started, with a heatbed that goes to 0 during the Calibrating Z step.

In effect, everything seems to be as it should be (and I never had bedtemp issues until this) except this clue from wiggling the textile-sleeve. What are the new steps for diagnosing this problem?

Thanks - A MacDonald

I would recommend soldering but using a more flexible cable (silicone cable). otherwise you have the same problem in a short time.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 24/03/2020 9:33 am
Aw Mac 3
(@aw-mac-3)
Active Member
Topic starter answered:
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

Thanks for your recommendations. It seems folks are pointing to the thermistor wire. Prusa is sending a thermistor replacement since it was still under warrantee, however while that's in the mail I will look to see if there is something I can do with the wire to give it more life.

Any thoughts about why the wire would give out? Generally I don't go above 60 degrees for the bed.

Posted : 24/03/2020 2:04 pm
kennd
(@kennd)
Estimable Member
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

My thermistor broke right where it came out of the heatbed clamp.

It is a very fine wire and did not stand up to the constant flexing. On the version of the kit I got there was only the fabric wrap and no nylon rod to control the flex. On the newer version Josef re-worked the clamp and included a length of 3 mm nylon rod ( and I think it also came with a spiral wrap ). If you search on 'thermistor wire' here you will find a few topics about it, including mine.

I asked if anyone had the stl file for the new clamp. Nope. I have checked several times and it was not in the 'printable parts' package on Prusa site.

I looked around for a suitable strain relief and did not find one. Someone has modified the original clamp and posted the stl on prusaprinters. check it out.

Still looking for a solution that works for me In the meantime, I have a couple of spares.

 

This post was modified 2 years ago by kennd
Quality is the Journey, not the Destination
MK3S, Nylock mod, Modified Y-axis bearing mounting
MK3S kit waiting to be assembled (still)
Primary CAD program: Trimble Sketchup Make 2017(standalone) with 3D extensions
My limited prints on Prusaprinters.org...
Posted : 24/03/2020 3:44 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

@kennd

I'm working with this heatbad clamp since many months without any broken wire problems (using silcone wires for all connections): https://grabcad.com/library/prusa-mk-series-cable-cover-1

 

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 24/03/2020 5:09 pm
kennd
(@kennd)
Estimable Member
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

@karl-herbert

Cool. If you have replaced your thermistor wire with silicone covered one, you are the one to help with how to 'upgrade' the thermistor wire. I have not done it.

Quality is the Journey, not the Destination
MK3S, Nylock mod, Modified Y-axis bearing mounting
MK3S kit waiting to be assembled (still)
Primary CAD program: Trimble Sketchup Make 2017(standalone) with 3D extensions
My limited prints on Prusaprinters.org...
Posted : 24/03/2020 5:23 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

@kennd

The thermistor cable always breaks in the moving part of the heatbed strand. You have to cut out this part and solder a flexible, heat-resistant silicone cable, e.g. this one here: heatresistant flexible wires

Insulate with a shrink tube after soldering. You can also cut it near the thermistor, soldering it there and mount on the other end a new molex 2-pin connector.

Read also: https://forum.prusaprinters.org/forum/original-prusa-i3-mk3s-mk3-hardware-firmware-and-software-help/random-print-failures-display-shows-mintemp-fixed-and-please-restart/#post-180269

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 24/03/2020 8:05 pm
Aw Mac 3
(@aw-mac-3)
Active Member
Topic starter answered:
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

@karl-herbert

Karl, I see your printed cable cover at the link you provided. It looks a lot like the cable cover for the MK3s. How do its subtle differences protect the cable better?

Posted : 25/03/2020 1:52 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

@awmac3

Yes, it's the cable cover for my MK3/MK3S. If you have a small enclosure like the Ikea LACK, the 45degree construction changes the orientation of the heatbed cable so that it does not crash into the back of the enclosure. But the better protection against broken wires is to use heatresistant flexible silicone wires.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 25/03/2020 3:01 pm
AchimKoerver
(@achimkoerver)
New Member
Mintemp fixed problem MK3S, latest firmware, my experience

A) mintemp_fixed BED
It is a hardware problem. The cable connector is too loose. Instead of replacing with a
spare part, I fixed the connector with a splinter of wood.
I repeat this, every some days, when I get the BED message. It helps, temporarily.

B) mintemp_fixed
I get this error since some time more and more often. Some objects can be printed, some not.
I wondered, because I had printed out these non-printable objects 4-6 weeks before without problems.
I re-build these objects in my 3D software (FreeCAD) from the scratch and indeed, I detected some slight
inconsistencies in the design, which were not detectable neither in the FreeCAD mesh checker nor in the Prusa slicer software.
After fixing that that inconsistencies the objects could be printed.

Except one, a very simple design, completely error-free.
I tried with the latest version of the slicer (2.3), it didnt help.
I de-installed this version and went back to my old slicer 2.2.8.
After slicing the object with the older version I could print ths object without any problems.

Problem A is a hardware problem - Prusa should use more stable connectors for the mintemp sensors.
Problem B is software problem, mainly caused by the latest slicer version - it is less error tolerant
regarding inconsistencies in the designed objects. But however, in this way I was forced to correct some of my designs.
My recommendation for case B: Try to go back to an older slicer version, thats the most simple way.

P.S: I started my MK3S four months ago and now have used some 30 print days.
So I think I have gained enough experience, not to mention
- a broken front fan (exchanged),
- a broken PINDA sensor (changed),
- my loose BED sensor cable (wood splinter),
- a clogged hotend PTFP tube (cold filament stuck),
- changing the nozzle to 0.25 mm and back to 0.4 mm finally
- and a lot of problems with non-Prusa filaments - I will forever only use Prusa Galaxy Silver 😀 

Posted : 30/03/2020 9:45 am
Aw Mac 3
(@aw-mac-3)
Active Member
Topic starter answered:
RE: MINTEMP BED problem in an i3 MK3s -- suggested next steps for resolving?

Upon receiving the replacement thermistor part from Prusa and following the replacement instructions, the problem is fixed for the time being. It was entirely hardware. While the previous thermistor showed little wear, I believe the wires inside the insulation where the wire entered the back clamp on the heatbed had broken down over the several months in operation. Despite the wire stringing between the thicker headbed power wires, it seems to have developed a crimp.

Posted : 30/03/2020 12:41 pm
Share: