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6.5.3 Firmware for CORE One/+  

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Cranky Curmudgeon
(@cranky-curmudgeon)
Active Member
RE: 6.5.3 Firmware for CORE One/+

Does anyone know if the problem where the printer is stuck at "Reloading Filament - 99% Parking " has been fixed?

Described here:

https://forum.prusa3d.com/forum/english-forum-original-prusa-i3-mk4s-hardware-firmware-and-software-help/mk4s-mmu3-6-40-alpha-fw-stuck-at-reloading-filament-99-parking/paged/2/

The problem was present in 6.40 firmware. Downloading to 6.2.6 made the problem go away.

I've been avoiding any firmware upgrade until this issue is fixed.

Posted : 31/03/2026 11:44 am
Cédric
(@cedric)
Estimable Member
RE:

Hmm, the new chamber temperature logic drives me mad when it starts the fan at absolutely full blast when it reaches 60C , this firmware was a big downgrade in that regard, I wish it could at least have some calmer control logic.

This post was modified 4 weeks ago by Cédric
Posted : 05/04/2026 3:04 pm
1 people liked
hyiger
(@hyiger)
Famed Member
RE: 6.5.3 Firmware for CORE One/+

 

Posted by: @cedric

Hmm, the new chamber temperature logic drives me mad when it starts the fan at absolutely full blast when it reaches 60C , this firmware was a big downgrade in that regard, I wish it could at least have some calmer control logic.

Yep. And Prusa didn't even mention this is in the release notes until I raised an issue for it on Github. They either "forgot" or intentionally tried to sneak it past us. 

Posted : 05/04/2026 3:13 pm
Cédric
(@cedric)
Estimable Member
RE: 6.5.3 Firmware for CORE One/+

 

Posted by: @hyiger

 

Posted by: @cedric

Hmm, the new chamber temperature logic drives me mad when it starts the fan at absolutely full blast when it reaches 60C , this firmware was a big downgrade in that regard, I wish it could at least have some calmer control logic.

Yep. And Prusa didn't even mention this is in the release notes until I raised an issue for it on Github. They either "forgot" or intentionally tried to sneak it past us. 

Even before i put my chamber heater in it would reach about 58C when printing high temp materials with high bed temp. Not anymore since it starts to vent regularly, but i dont want any unecessary cold drafts when printing these type of materials 🙁 I would rather have hoped that they went the other way when they got more confident in the hardware and with the HT hot end coming, not reducing the functionality. 

Posted : 05/04/2026 3:21 pm
hyiger
(@hyiger)
Famed Member
RE: 6.5.3 Firmware for CORE One/+

 

Posted by: @cedric

Even before i put my chamber heater in it would reach about 58C when printing high temp materials with high bed temp. Not anymore since it starts to vent regularly, but i dont want any unecessary cold drafts when printing these type of materials 🙁 I would rather have hoped that they went the other way when they got more confident in the hardware and with the HT hot end coming, not reducing the functionality. 

There is also the annoying alarm the goes off (screen goes orange with a warning) when the chamber hits 60. Then the fans kick on aggressively which in my case ruined a print because the draft caused it to warp severely. 

Posted : 05/04/2026 4:22 pm
Zippy
(@zippy)
Active Member
RE: 6.5.3 Firmware for CORE One/+

 

Posted by: @jan-kratochvil

Summary

  • New features and improvements
    • Massively speed up MMU filament changes [MMU]
    • Updated default input shaper profiles [C1+, C1L]

Are IS profiles only updated for C1+, or does original C1 also get same treatment? Got a little bit confused, are C1\C1+ such different or only difference is within the upgrade kit, if so C1+ did ship initially with different IS profiles dissimilar to C1?

Posted : 05/04/2026 7:58 pm
hyiger
(@hyiger)
Famed Member
RE:

 

Posted by: @zippy

Are IS profiles only updated for C1+, or does original C1 also get same treatment? Got a little bit confused, are C1\C1+ such different or only difference is within the upgrade kit, if so C1+ did ship initially with different IS profiles dissimilar to C1?

The C1 and C1+ are the same printer as far as the firmware is concerned. That is, it doesn't treat them differently. Anything stated for the C1+ also applies to the C1

Posted : 05/04/2026 8:40 pm
Zippy
(@zippy)
Active Member
RE: 6.5.3 Firmware for CORE One/+

 

Posted by: @hyiger

 

Posted by: @zippy

Are IS profiles only updated for C1+, or does original C1 also get same treatment? Got a little bit confused, are C1\C1+ such different or only difference is within the upgrade kit, if so C1+ did ship initially with different IS profiles dissimilar to C1?

The C1 and C1+ are the same printer as far as the firmware is concerned. That is, it doesn't treat them differently. Anything stated for the C1+ also applies to the C1

Well that were my thoughts as well, just release summary is all over the place.

For example:

  • Lowered chamber safety temperatures [C1]
  • Tuned parking position during purging [C1, C1+, C1L]
  • Vent grille linked to filament preset [C1+, C1L]

Like the safety temp for C1+ wasn't lowered, same with vent grille or IS where C1 not mentioned, only C1+.

 

I guess, Prusa could add some sort of notice to prevent this sort of ambiguity. 

Posted : 06/04/2026 7:11 pm
Page
 Page
(@page)
Active Member
RE: 6.5.3 Firmware for CORE One/+

With this new firmware, printer goes black screen with beeping, restarts and continue printing. It did it three times in 3,5h printing. Am I alone with this problem?

Posted : 14/04/2026 8:51 am
chmax
(@chmax)
Reputable Member
RE: 6.5.3 Firmware for CORE One/+

did you ground the belt motors screws? For the vast majority of the people that had this kind of issues, they were solved by making sure that the motor grounding screw(s) had electrical connection to the grounded frame (either by scratching away the pain under the screw head, adding a toothed washer, or running a cable to a ground point .. or any combination of those 3).

Posted by: @page

With this new firmware, printer goes black screen with beeping, restarts and continue printing. It did it three times in 3,5h printing. Am I alone with this problem?

 

Posted : 14/04/2026 9:41 am
Page
 Page
(@page)
Active Member
RE: 6.5.3 Firmware for CORE One/+

When I am measuring connection between motor screwes these are connected even with screwes on the bottom together. So I guess everything is connected together and grouded. I have never had this issue and I own core one for 1 year. 

Posted : 14/04/2026 10:20 am
Protoncek
(@protoncek-2)
Estimable Member
RE: 6.5.3 Firmware for CORE One/+

That tells you nothing. Multimeter will also show short if that goes long way, not directly via shortest - nearest screw.

Posted : 14/04/2026 2:04 pm
Page
 Page
(@page)
Active Member
RE: 6.5.3 Firmware for CORE One/+

You are right. OK I will try it tomorrow. Thank you guys!

Posted : 14/04/2026 2:06 pm
Page
 Page
(@page)
Active Member
RE: 6.5.3 Firmware for CORE One/+

You were right. It just works now without restarting. Thank you once again 🙂

Posted : 15/04/2026 11:48 am
Jürgen
(@jurgen-7)
Famed Member
RE: 6.5.3 Firmware for CORE One/+
Posted by: @protoncek-2

That tells you nothing. Multimeter will also show short if that goes long way, not directly via shortest - nearest screw.

Electrical current will happily take a detour too. Hence, as we are concerned with very small currents from static charge, the ground connection indicated by the multimeter should be just fine.

Posted : 15/04/2026 12:13 pm
Protoncek
(@protoncek-2)
Estimable Member
RE:

Electrical current will happily take a detour too. Hence, as we are concerned with very small currents from static charge, the ground connection indicated by the multimeter should be just fine.

Sorry to say, but it seems that you really don't know much about ground loops and consequent problems from them, do you? It's exactly  such "detours" which are causing them, creating a small inductor - this "inductor" then creates noise (note that all inductors create even a small electromagnetic charge when powered - even a single wire is already a small inductor!). Multimeter only measures if resistance is below a certain point, it doesn't really care about noise etc... that's why it's useless to search for ground loop problems with it. At least oscilloscope is needed, and even that one doesn't always finds the loop. If it's of a small value conneting an oscilloscope probe can already cause ground loop to dissapear (momentarily).

And it's not (only) static charge, but real current which causes that. That's why it's important to have a proper grounding. ideally ground should be connected in star and only connected in one point. In our specific case exactly "detour" creates a loop which causes noise and thus reboots. And Page's answer prooves that... By correcting screw contact he eliminated such "detour".

 

In my 40+ years of soldering i created, explored and eliminated more such loops i can count...

Posted : 17/04/2026 12:16 pm
shrap
(@shrap-2)
Estimable Member
RE: 6.5.3 Firmware for CORE One/+

My printer was overdue for some maintenance. I needed to adjust the belt to eliminate layer shifting and fix that obnoxious home mistake, err, banging.

Come to find out I was way back on 6.3.something. Well, I updated it today to 6.5.3 and so far so good. The revised homing seems to be better, at least for now anyway.

I do wish it didn't need to home just to unload filament... That' seems redonkulous to me.

Vehemently against AI. I've seen that film. It ends badly.

Posted : 18/04/2026 2:41 am
Jürgen
(@jurgen-7)
Famed Member
RE: 6.5.3 Firmware for CORE One/+
Posted by: @shrap-2

I do wish it didn't need to home just to unload filament... That' seems redonkulous to me.

I believe the intent is to move the head to a position where the PTFE tube has the widest bend radius, to mimimize friction while filament is loaded or unloaded.

Posted : 18/04/2026 4:05 am
1 people liked
Jürgen
(@jurgen-7)
Famed Member
RE:
Posted by: @protoncek-2

Sorry to say, but it seems that you really don't know much about ground loops and consequent problems from them, do you? [...]

I know about ground loops, but don't think the Core One issue we are solving by grounding the stepper motors has anything to do with them. But I'm not interested in a contest with you about who has more years of soldering or oscilloscope experience.

The CoreXY frame is always part of the chassis ground, by design. The stepper motors are either grounded to the CoreXY frame via their mounting screws, or they are not. What other complex grounding scenario would you envision?

Posted : 18/04/2026 4:16 am
shrap
(@shrap-2)
Estimable Member
RE: 6.5.3 Firmware for CORE One/+

 

Posted by: @jurgen-7
Posted by: @shrap-2

I do wish it didn't need to home just to unload filament... That' seems redonkulous to me.

I believe the intent is to move the head to a position where the PTFE tube has the widest bend radius, to mimimize friction while filament is loaded or unloaded.

Thats fine. It just doesnt have to bang every time.

It should be able to move a tad off of home if it knows it. Say 1/2 inch or so.

Vehemently against AI. I've seen that film. It ends badly.

Posted : 18/04/2026 4:42 am
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