Warning: nasty firmware bug
The firmware silently stops extruding if the nozzle temp drops below 190C. I know this is by design, but I think it is a bug.
First, 190C is way too high to be the minimum temperature. There are filaments that are optimal at that temp or lower. And there are official Prusa provided filament profiles at 190C. I think the minimum used to be 175 or 180C which is much better, IMO.
I just spent hours debugging a problem that I finally tracked down to this "feature". I was getting strange gaps in my print. It was not consistent at all and not repeatable. By dumb luck I switched filaments to one that has a 190C profile. While I was watching it just stopped extruding (a nice feature of my skelestruder is you can watch the wheel turning when extruding) but kept on printing. Dumbfounded, I started the print over and this time it would not even extrude the intro line. I happened to notice the temp was 189C. Even with a good PID tune you can get 1-2C variation. I raised the temp +2C in Tune and printed the same gcode without issue. I had recently removed my e3d sock which threw off the PID tune and, now that it is summer, I think my AC kicks on at random times, enough to swing below 190C. I will correct these, but it should be able to print through this without issue.
I am going to hack my firmware to remove this bug, but thought I'd try to get some support from folks to get Prusa to fix this. I'm sure they don't want the extra support tickets dealing with random strange printing problems. But I am guessing they think they have a good reason for 190C and won't change it.
Re: Warning: nasty firmware bug
The firmware silently stops extruding if the nozzle temp drops below 190C. I know this is by design, but I think it is a bug.
First, 190C is way too high to be the minimum temperature. There are filaments that are optimal at that temp or lower. And there are official Prusa provided filament profiles at 190C. I think the minimum used to be 175 or 180C which is much better, IMO.
"I was getting strange gaps in my print"
Yep, I noticed this too.
Polymaker PolyPlus, a great PLA, recommended 180°C to 220°C . . . . I was printing something with lots of overhangs / bridges / fine detail . . . and after laying down a few base layers at the default 215°C to ensure good adhesion I slowly lowered the temperature to 185°C (over 10 minutes or so . . . in 5 degree increments) as it's generally advised to print at the lowest recommended temperature if you have tricky overhangs / bridges / fine detail . . . . I also lowered the speed from 100% to 50%, so was expecting a really clean print . . . came back 30 minutes later to see all the gaps / patchy layers !
Re: Warning: nasty firmware bug
Hm... very strange... and, should i say unacceptable! If Prusa thinks that temp is too low then printer should not only stop extruding but also stop PRINTING while temp is too low! I agree that this is very nasty bug and model destroyer!
Thanks for this info!
Re: Warning: nasty firmware bug
Yea i came across this some time ago. I habe food filament sitting at home that i could not use due to this. I dont need to use it right now so i didnt deal with the Problem.
I never contacted support over it. Maybe they just dont know its a real problem yet.
I guess its there so auto filament loading doesnt mess your stuff up if the nozzle is to cold with pla. Still a stupid threshold.
https://shop.prusa3d.com/forum/others-archive--f66/i-can-not-print-below-200-c-wtf-t14253.html
Re: Warning: nasty firmware bug
No need to change firmware, just add M302 S170 to your start g-code, or even better, to your filament specific g-code in the same manner you set up linear advanced.
I have some rigid.ink PLA in which I get the best prints at 180°C. You can always put M302 S190 in your end g-code to go back to the 'safe' extrusion temperature. I've used 170°C in the above example as I've found that the 2nd layer can fall around 7-8°C lower than needed before climbing up to the specified layer temp.
Re: Warning: nasty firmware bug
No need to change firmware, just add M302 S170 to your start g-code, or even better, to your filament specific g-code in the same manner you set up linear advanced.
I have some rigid.ink PLA in which I get the best prints at 180°C. You can always put M302 S190 in your end g-code to go back to the 'safe' extrusion temperature. I've used 170°C in the above example as I've found that the 2nd layer can fall around 7-8°C lower than needed before climbing up to the specified layer temp.
Awesome! Thanks for the info. Sometimes I forget to scour the gocdes looking for solutions.
Still, I consider this a work-around. Silently failing is bad behavior.