Bed Thermistor - failing - MINTEMP BED - known issue?
 

Bed Thermistor - failing - MINTEMP BED - known issue?  

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Mr.Shaky
(@mr-shaky)
Active Member

Guess that's a paid feature?  see attached.

I didn't have any problems printing with PETG Prusament and the .20 Quality preset in PrusaSlicer.  Just remember to split the tube in the slicer and put the split face on the bed.  Note that the modified cable cover and tube may not be a rigid assembly--I haven't seen a need to make it one so far.

 

I've done about 20 full-bed prints since my last post, and the cable seems to be holding up pretty well (for now...)

Posted : 06/04/2021 4:50 am
Richard D
(@richard-d)
Active Member

Interesting!  I knocked up something similar in terms of supporting the cable at the heatbed end with a 90-degree tube.  Not as elegant as yours - I just created something that slid onto the existing covers where the cables meet the heatbed.

One question - if the cables now exit the buddy board box at the back, is a 90-degree bend at the heatbed required - or even desirable?

Posted : 06/04/2021 8:40 pm
Mr.Shaky
(@mr-shaky)
Active Member

After performing 2 sensor replacements in 3 months and finding that the short was near the heatbed clamp both times, I decided to recharacterize the cable motion.  Just making a portion of the cable rigid would also keep the cable from hitting an enclosure, but the overall cable motion is still a flex so the failure mode hasn't changed.

Without the tube in the new configuration, the cable would still endure a flex focused at the heatbed clamp.  With it installed, there is arguably still some flexing motion in the arrangement, but it is minimal by comparison.  

 

Posted : 07/04/2021 2:55 pm
Richard D
(@richard-d)
Active Member

Good points.  I've printed most of your design, which by some coincidence has exactly the same dimensions as mine.  Although I'll probably stick with my tube as I put in 3 30-degree bends in the space of about 20mm rather than a single 90-degree bend.

Although my replacement thermistor arrived today, I haven't experienced any more failed prints since installing my "mark 3" cable support 🙂 

Posted : 07/04/2021 4:22 pm
cwbullet
(@cwbullet)
Illustrious Member

Interesting idea.  I fought through this on my Mk3S.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 07/04/2021 5:06 pm
xenomorphih
(@xenomorphih)
New Member

I built a cable chain for my Mini and so far it works fine.

prusa mini cable chain

prusa mini cable chain

Posted : 11/04/2021 1:16 pm
j3zm0n7e
(@j3zm0n7e)
New Member
Posted by: @mgtarallo

Hi Guys - just curious how many of you have experienced bad thermistors?

I love Prusa's printers - I have 2 MK3s - both of which have had failed Thermistors at different times. BOTH replaces under warranty. Support has been great. I inquired if they are doing anything about this, being it seems to be a known issue. Even though the wire seems fine, testing with a multi-meter reveals it is not.

I even made a video here to send to Prusa:

https://fb.watch/2Y81Ln0PND/  

After replacing it - ohms read consistent 124 - and I have had 4 jobs complete already.

If you guys have some creative solutions to prevent this, I'd love to know about them

Thanks and stay well.

 

 

My thermistor cable started failing yesterday when the bed moves back.

I had been printing fine in the morning with no signs of a problem and I tried to set a new print going and then I got the warning message.

The videos shows it only does it when the bed moves back and the temp drop at roughly the same point when the y axis moves either by hand or during a test.

I am contacting prusa support shortly.[video width="1920" height="1080" mp4="https://forum.prusaprinters.org/wp-content/uploads/2021/04/PXL_20210420_101626033-1.mp4"][/video]

Posted : 20/04/2021 12:06 pm
j3zm0n7e
(@j3zm0n7e)
New Member
j3zm0n7e
(@j3zm0n7e)
New Member

I recieved the replacement heat bed thermistor this morning by DHL, I wasn't expecting to get it so quick so big thanks to Prusa support and the the agent who dealt with my problem.

now to read through the online knowledge base guide before I dismantle things.

Posted : 22/04/2021 1:11 pm
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