Why is the filament fan set to zero for first layer?
Why is the fan set to zero for the first layer, and then goes to almost full speed at the very start of the second layer?
At the same time the bed and nozzle temperatures are dropped.
The result is that the nozzle heater turns off altogether until the nozzle temp has dropped to the lower new temperature, then starts to heat, but not yet compensating for the fan cooling effect.
That in turn makes the nozzle temp drop very significantly, potentially weakening the adhesion between layer 1 and 2, or even causing 'Thermal runaway' errors.
I tried to counter-act this by manually 'tune' nozzle temp up at strt of first layer, but it is too slow to stop the temperature drop, and somehow also causes the (by me) hitherto never seen 'PREHEAT ERROR'.
I think the nozzle temp seting should stay unchanged when the fan comes on, until the nozzle temp is recovering, then gradually reduce to the new, lower setting.
Additionally, or alternatively, the fan should run during the first layer, or start gradually, so that the temperature compensation mechanism has time to kick in without the filament temp dropping too much.
Anyway, maybe I just don't understand why the settings are the way they are, but there might be good reasons.
Any explanations would be much appreciated! 🙂
Re: Why is the filament fan set to zero for first layer?
I usually print the first layer at 215, then remaining layers according to requirements.
I do not start the fan until at least the third layer.
I do however, generate my own profiles (KISS) rather than relying on being supplied with them. It really isn't difficult to change to what you want/need so that the printer works in the manner you want it to.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Why is the filament fan set to zero for first layer?
Peter, do you control the printer via USB and some software live, or just print from SD card?
I prefer the SD card option, and it is indeed quite possible to edit the .gcode files generated by slic3r so that things happen differently.
I just want to understand why the defaults in the Prusa Slic3r are set the way they are. There might be important reasons.
Why did you choose to leave the fan off for the first 3 or more layers? What would happen if the fan was on the entire time?
And how do you prevent the temporary drop in temperature when the fan eventually comes on?
Re: Why is the filament fan set to zero for first layer?
I just had a closer look at the nozzle fan speed in a .gcode file produced by Prusa Slicer:
There are 42 instances of M106 command and the range is from 237.15 to 255 (93% to 100%).
The fan starts at 93% at the time when the temperature for nozzle and bed drops at end of the first layer, then it gradually increases in small steps:
S237.15
S239.7
S242.25
S244.8
S247.35 at z 16.4 (which means layer 108 at 0.15mm layer height).
S244.8
So part of what I was suggesting is already implemented, the question is if there is a more optimal setting for particular print objects.
The fan speed setting for this .gcode file were Min 85% Max 100%. So Slic3r is not using the minimum speed to start the fan at.
Temperature was set to 230/65C first layer, 210/55C other layers.
The nozzle temp drops to 197C before it starts to slowly move back up to 210C.
Re: Why is the filament fan set to zero for first layer?
MrMik
Long story, but in short:
I use OctoPrint to control the printer.
I use KISS to slice the models.
I started 3D printing with a cheap 3D clone, with absolutely not support and not a huge number of understandable on-line reference sources. although it was suggested that I use pronterface and Slic3r, I decided to use Cura to slice models (Cura was also able to print directly from the PC), but there were no profiles for either printer or filament; the results were OK, bun not great. I then found KISS and again generated profiles mainly using trial and error, but had to print via SD card, which for me was a huge PITA
Then came Octoprint and the Mk1. The improvement in quality was unbelievable and when combined with KISS, I generated prints better than I had ever expected, again after a learning period and many hours trial and error.
I found that the settings I use work best for me. It is up to you whether you want to use general defaults which are designed to "work" with every printer running is a whole range of different environments and using every filament available, or to tweak your settings and make your printer work the best it can.
Hope that explains why I use the settings I use...
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Why is the filament fan set to zero for first layer?
I tweak layers as I see fit across my prints, with Simplyfy3d an excellent and fast slicer I use across my three different 3D printers. First two layers are the key for grip to the bed. After that, cooling is required for quality of layers. Depending on print and material you are printing with. I also use octopi / octoprint for some of my printers, but slice with Simlyfy3d and parse that up to octoprint. One printer the other two I print directly from files loaded via an SD card.
My Prusa I3 Mk2 uses PEI on the bed, I print from SD card always. My Ultimaker 2+ has Printbite, and I print from SD card always. My Kossel Mini I print from Duet Web Interface, My Fabrikator Mini is driven by a RaspberryPi running OctoPi.
I passed two of my other printers for free onto a local Makerspace. I needed the space in my workshop.
Nigel
Life is keeping interested and excited by knowledge and new things.