Self test fails on heatbed, but everything works as intended
 
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Self test fails on heatbed, but everything works as intended  

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Ignaciobfp
(@ignaciobfp)
Member
Self test fails on heatbed, but everything works as intended

Hello,

I just finished assembly my MK4 kit. For now everything seems to be working fine, but this test fails (tried twice) and I see the same prompt to perform self test on boot.

Running firmware 4.7.2, and have been printing some parts with PETG and the heatbed at 85ºC so it is obviously working. On the test that theoretically fails, the printer sets the extruder temperature to 290ºC and the heatbed to 110ºC. When the extruder is at about 240ºC and the bed at about 60ºC it ends the test (for what I see on reddit and this forum, this is normal behavior)

Any ideas what can be wrong? I double checked wiring but cannot see any issue. Since it seems like a false alarm, a way to disable the prompt on boot will also be sufficient for me.

Photos of the messages (remember that despite this the heatbed seems to work properly)

 

Posted : 24/08/2023 9:42 am
Ignaciobfp
(@ignaciobfp)
Member
Topic starter answered:
RE:

I contacted Prusa support via the chat, and while this is not a proper solution, here is a workaround in case anyone faces the same issue. This could be related to setting up the printer in hot environments (>30ºC):

1) Skip the self test, and preheat the printer for PLA
2) Restart the printer (without waiting for it to cool) and this time do the self test. The printer will wait for cooldown as needed, both for the tapping (don't remember the temperature) and for the heatbed until it is below 40ºC
3) Let the printer finish its thing

That did the trick in my case.

Note that the issue appeared on both 4.7.2 and 4.7.1 versions of the firmware, since I tried downgrading as suggested.

This post was modified 6 months ago 2 times by Ignaciobfp
Posted : 24/08/2023 1:09 pm
bobasaurus
(@bobasaurus)
Active Member
RE: Self test fails on heatbed, but everything works as intended

Maybe try a firmware update (5.0.0-RC is available on github now), it could be that you have a newer hardware revision that isn't fully supported by 4.7.2. 

Posted : 24/08/2023 3:48 pm
Tom De Winter
(@tom-de-winter)
Trusted Member
RE: Self test fails on heatbed, but everything works as intended

I’ll throw a guess into the ring. Perhaps the test is looking at the rate it’s heating or the current draw and seeing it out of specifications. 

I’d be on the Chat for Prusa’s help.

Posted : 24/08/2023 4:02 pm
Hello
(@hello)
Noble Member
RE: Self test fails on heatbed, but everything works as intended

 

Posted by: @tom-de-winter

I’ll throw a guess into the ring. Perhaps the test is looking at the rate it’s heating or the current draw and seeing it out of specifications. 

I’d be on the Chat for Prusa’s help.

Yes the thermistor could be on its way out

Please help me out by downloading a model it's free and easy but really helps me out https://www.printables.com/@Hello_474427/models

Posted : 24/08/2023 6:58 pm
Ignaciobfp
(@ignaciobfp)
Member
Topic starter answered:
RE: Self test fails on heatbed, but everything works as intended
Posted by: @bobasaurus

Maybe try a firmware update (5.0.0-RC is available on github now), it could be that you have a newer hardware revision that isn't fully supported by 4.7.2. 

I am tempted to try the new 5.0.0 RC firmware, but I was (correctly) advised to stay in the stable branch until the problem is solved.

Now I am a bit afraid to try the self test on the new version, since if it does not pass I will be stuck again in square one.

Posted by: @tom-de-winter

I’ll throw a guess into the ring. Perhaps the test is looking at the rate it’s heating or the current draw and seeing it out of specifications. 

I’d be on the Chat for Prusa’s help.

I think this is exactly what happens. And maybe it is related to the hot environment (there is a heat wave in Spain currently, so 31-34ºC in the room) so the temperature rises faster than the firmware expected. I suggested via chat that the firmware guys look into this if possible, could be a faulty or missassembled unit, but I think the prior option is more likely.

Posted by: @hello

Yes the thermistor could be on its way out

I hope that is not the case.

Thank you for all the answers.

Posted : 24/08/2023 7:36 pm
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