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6.4.0-RC Firmware for Prusa CORE One  

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hyiger
(@hyiger)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

 

Posted by: @jurgen-7

Tread carefully... this is an emotional topic for Steve. 😉 

IDK. Don't shoot the messenger maybe?

I think the bug before was that if you change the filament and for whatever reason you needed to try again, the bed would move down again. That's why it is supposed to auto home first on a filament change. Unless I'm missing something...

Posted : 28/11/2025 3:31 pm
1 people liked
ssill2
(@ssill2)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

Ok, I just stopped a print because some ninjaflex was under extruding and the the x carriage crashed into the left side when parking the extruder. Back to 6.2.6 for me.

Posted : 28/11/2025 4:33 pm
hyiger
(@hyiger)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

 

Posted by: @ssill2

Ok, I just stopped a print because some ninjaflex was under extruding and the the x carriage crashed into the left side when parking the extruder. Back to 6.2.6 for me.

This doesn't seem like an edge case either. Looks like the XL needs more testing. 

Posted : 28/11/2025 4:47 pm
gb160
(@gb160)
Honorable Member
RE: 6.4.0-RC Firmware for Prusa CORE One

 

Posted by: @ssill2

Ok, I just stopped a print because some ninjaflex was under extruding and the the x carriage crashed into the left side when parking the extruder. Back to 6.2.6 for me.

Ive had something similar on Core One.

Would appreciate if someone else with a C1 could test this also... start a print, then cancel it after a couple of layers...does the extruder hit the back corner and skip a few steps where it should normally park ?

I've noticed it do this once on the last RC, now I've just seen it on this latest version. Initially I put it down to some gcode I've been manually editing, now it's just done it on a standard, untouched print from Prusaslicer.

Posted : 28/11/2025 4:53 pm
Neal
 Neal
(@neal-2)
Trusted Member
RE: 6.4.0-RC Firmware for Prusa CORE One

 

Posted by: @ssill2

I haven't. I need to actually get a fresh set of batteries for my caliper. I've not ever had a problem with PLA requring me to fiddle with extrusion multiplier for it. PETG on the other hand I'm almost never able to use 1.0 and usually end up at like .97 or lower. When I use a new brand of PETG I expect to have to fiddle with the extrusion multiplier. I guess there's a first time for everything.

I am fairly new to 3D printing.   QUESTION:  How do you know when you need to adjust the extrusion multiplier?   Is there a print defect that you look for, or is there some test print people are doing that covers a range of multipliers, similar to a temperature tower?     

Cheers,

Neal

 

Posted : 28/11/2025 4:58 pm
gb160
(@gb160)
Honorable Member
RE:

 

Posted by: @neal-2

 

Posted by: @ssill2

I haven't. I need to actually get a fresh set of batteries for my caliper. I've not ever had a problem with PLA requring me to fiddle with extrusion multiplier for it. PETG on the other hand I'm almost never able to use 1.0 and usually end up at like .97 or lower. When I use a new brand of PETG I expect to have to fiddle with the extrusion multiplier. I guess there's a first time for everything.

I am fairly new to 3D printing.   QUESTION:  How do you know when you need to adjust the extrusion multiplier?   Is there a print defect that you look for, or is there some test print people are doing that covers a range of multipliers, similar to a temperature tower?     

Cheers,

Neal

 

You can do the Prusa extrusion multiplier test, which is basically an open top, hollow cube printed in vase mode, so the wall is only one perimeter thick.
With standard PS settings the wall should be 0.45mm.
You need high quality calipers, or a micrometer is better. If your walls are above 0.45 you need to decrease the EM, if your walls are under 0.45mm you need to increase your EM.
Having the correct EM means that your parts will have better dimensional accuracy, Top/bottom layers will appear cleaner as there shouldn't be any over or under extrusion.

https://help.prusa3d.com/article/extrusion-multiplier-calibration_2257

Posted : 28/11/2025 5:07 pm
hyiger
(@hyiger)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

Another way (which is what I do) is install OrcaSlicer and run the built-in calibration tests. You can also download these from Printables and run them through PrusaSlicer but OrcaSlicer makes it easier to set them up. 

Posted : 28/11/2025 5:51 pm
hyiger
(@hyiger)
Noble Member
RE:

 

Posted by: @gb160

 

Posted by: @ssill2

Ok, I just stopped a print because some ninjaflex was under extruding and the the x carriage crashed into the left side when parking the extruder. Back to 6.2.6 for me.

Ive had something similar on Core One.

Would appreciate if someone else with a C1 could test this also... start a print, then cancel it after a couple of layers...does the extruder hit the back corner and skip a few steps where it should normally park ?

I've noticed it do this once on the last RC, now I've just seen it on this latest version. Initially I put it down to some gcode I've been manually editing, now it's just done it on a standard, untouched print from Prusaslicer.

Interesting. I recall seeing this after I stopped a print a couple of weeks back but didn't pay attention to it at the time. There is no major difference between the release and RC2 except for some changes around crash recovery which wouldn't be related. So final and RC2 should exhibit the same behavior.  I'll try it out and report back. 

This post was modified 3 weeks ago by hyiger
Posted : 28/11/2025 5:53 pm
hyiger
(@hyiger)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

 

Posted by: @neal-2

 

Posted by: @ssill2

I haven't. I need to actually get a fresh set of batteries for my caliper. I've not ever had a problem with PLA requring me to fiddle with extrusion multiplier for it. PETG on the other hand I'm almost never able to use 1.0 and usually end up at like .97 or lower. When I use a new brand of PETG I expect to have to fiddle with the extrusion multiplier. I guess there's a first time for everything.

I am fairly new to 3D printing.   QUESTION:  How do you know when you need to adjust the extrusion multiplier?   Is there a print defect that you look for, or is there some test print people are doing that covers a range of multipliers, similar to a temperature tower?     

Cheers,

Neal

 

@gb160's recommendation is a good test. Another you can try but I find difficult to interpret sometimes is the YOLO test. You can find it in OrcaSlicer with a description of the tests here: https://github.com/OrcaSlicer/OrcaSlicer/wiki/Calibration

Posted : 28/11/2025 5:57 pm
hyiger
(@hyiger)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

@gb160 I wonder if what you are seeing on the C1 is the same (or related) to what is happening on the XL: https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/4984

Posted : 28/11/2025 6:43 pm
ssill2
(@ssill2)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

so I'm seeing interesting behavior since switching back to 6.2.6 on the XL that I've never seen before. If I abort a print and it moves back to the back left position as normal with whatever toolhead was loaded when I aborted the print, 2 in this case. If I tell it either unload one filament by picking a tool OR I tell it to change filament in all tools and pick extruders 1 - 4, it attempts to home but crashes into parked tool 1! it's able to recover but that's NEW behavior. Sigh. I'm done for today lol

Posted : 28/11/2025 10:30 pm
gb160
(@gb160)
Honorable Member
RE: 6.4.0-RC Firmware for Prusa CORE One

 

Posted by: @hyiger

@gb160 I wonder if what you are seeing on the C1 is the same (or related) to what is happening on the XL: https://github.com/prusa3d/Prusa-Firmware-Buddy/issues/4984

Its weird, sounds kinda similar but no idea why other C1 users aren't reporting the same problem...

Posted : 28/11/2025 11:02 pm
Tim
 Tim
(@tim-21)
Member
RE: 6.4.0-RC Firmware for Prusa CORE One

The Prusa PS is at heart a simple 24v LED supply designed to power commercial LED lamp systems. Prusa had the OEM add the power fail catch circuit. 

Turning it off remotely via a smart switch or wall switch is acceptable. If a well designed zero crossing smart switch, it's actually easier on the supply than the supply's own power switch.

Posted : 29/11/2025 7:22 am
Steve
(@steve-33)
Trusted Member
RE: 6.4.0-RC Firmware for Prusa CORE One

 

Posted by: @hyiger

 

Posted by: @steve-33

Unload/Load filament Z moves. Heads up - in total the bed will still move several times downward for a total of 110 mm from power on if you try to change filament! Depending on where your bed was on power off this action may cause bed to hit the bottom stops! 

!t is impossible to move it up manually as Z thinks it's at 0 height and the only way out is to auto Home where real Z zero will get set,

I believe this is by design. This prevents the head front running into a print if it was accidentally left on the bed since the last X,Y,Z position is not saved between power cycles. If you need to manually move the bed, select "Auto Home" then afterwards you can manually move it. 

Poorly thought out design if deliberate  -  It can't hit anything left on bed from parked position unless you deliberately choose to do that. All it does is move head from back right corner parked position straight to front right corner, zero X and Y then go into a series of move Z down ignorant of where Z actually is.  

Posted : 29/11/2025 7:59 am
Tim
 Tim
(@tim-21)
Member
RE:

Boy, at the end of the day I may hold off installing 6.4.0 even longer. Waiting until I get my C1+ upgrade kit. Seems even this release is more than buggy.  Though, thinking back to my Mk3 early days, Prusa had a reliable reputation for shipping broken firmware.  I always waited for the next release or two before installing any "upgraded" releases.  Using 1.1.3, wait until 1.1.7 is released before installing 1.1.5 ... that level of consideration.

While they often fixed something in a release, they also broke something. In-house regression testing is NOT in their vocabulary. It appears this dev process hasn't changed.

Posted : 29/11/2025 4:29 pm
mnentwig
(@mnentwig)
Reputable Member
RE:

>> Prusa had a reliable reputation for shipping broken firmware

 I considered for a second an "unreliable" reputation for shipping broken firmware but it gave me a headache... Well at least while I'm writing this, the printer is printing happily... hey what's that noise ... 

EDIT "that noise" was noises of a core one while printing happily... just for the record 😀

Posted : 29/11/2025 4:41 pm
hyiger
(@hyiger)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

Unless you have an XL, this firmware seems stable enough for a Core One and, so far, fixes issues with nozzle cleaning failures, less aggressive homing and a much more convenient way to tune the belts. I haven't had any failures (BSOD's or otherwise) during a print in the last 2 months. 

Posted : 29/11/2025 5:21 pm
1 people liked
ssill2
(@ssill2)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

I would concur.  on my CoreOne and my MK4S it seems fine.  Just not on the XL.  I'm curious how stable the 6.5.1 firmware is on the core one L lol.   I've not been checking out that forum yet.

Posted : 29/11/2025 5:25 pm
Kachidoki
(@kachidoki)
Trusted Member
RE: 6.4.0-RC Firmware for Prusa CORE One

I have made several prints mixing two-color PETG with PLA supports on the XL with this firmware. There are some strange behaviors regarding the automatic retraction feature that I have not yet investigated, but printing and parking work well. I have never experienced a print head collision since I got the printer.

Posted : 29/11/2025 7:46 pm
ssill2
(@ssill2)
Noble Member
RE: 6.4.0-RC Firmware for Prusa CORE One

The head crash I saw on the XL was when canceling prints.  the two color prints I was doing in PLA went perfectly fine.  Printing with ninjaflex, or tpu in general usually requires a couple cancelled prints until I get things dialed in, so it's not an edge case for me at all. 

Posted by: @kachidoki

I have made several prints mixing two-color PETG with PLA supports on the XL with this firmware. There are some strange behaviors regarding the automatic retraction feature that I have not yet investigated, but printing and parking work well. I have never experienced a print head collision since I got the printer.

 

Posted : 30/11/2025 12:58 pm
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