Revo Fan does not spin fast
I just installed the Revo Micro on my Mini, and it worked great so far,.
However, I noticed on larger prints where the first layer takes a long time, I have big problems with heat creep.
The revo cooling fan does not spin very fast (during printing). When it starts spinning, it is getting close to 5V (and spinning fast...), but only for one or two seconds. Then it slows down and has only 1.7V available.
I think this should be the reason for my heat creep.
Do you have any ideas on how I can fix this?
Do I need to upgrade the firmware, since the new fan does not give any feedback to the mainboard (only using 2 pins)?
Thanks in advance!
Best Answer by Oliver-Andre:
Actually hotend fan output on buddy-board is PWM. Firmware sets it to about 38%. This is coded in firmware, not to be set by user.
Pruser uses a cheep loud oversized fan and makes it quite by turning it down this way to spare the money for a Noctua. The correct way to connect the e3d fan: put red wire of revo fan to the middle pin of the hotend fan connector and black wire to pin 2 of j21, as you get permanent ground there (black wire is marked green here).
Even the stock fan with PWM is often to much throddled down, I often had headcreep with stock hotend. Just did this change to the stock fan. While the Mini now sounds like a Creality-Printer with the stock-fan, 100% power on a noctua should give more airflow than 38% on stock fan and be less noisy. Luckly I have a black noctua for mk3 as a spare (they are not been produced anymore, but you still can get them in the colourful noctua-coloursheme...). So I will use version2 of the revo micro hotend, but with 100% power and noctua. But version 1 should also work with e3d fan if connected this way. It is not a fault of e3d and the fan is not to small - it is just Prusa's firmware being the problem...
Downside of this mod: The fan is always on now.
Speed of hotend fan not being adjustable is an issue on github for more then 1.5 jears now. Quite a shame Prusa have not done anything there for now. Many people have heatcreep with stock setup, a the original fan has variations in quality. If it would be possible to set the speed (f.e. in experimental menu) a simple speedup to 50 or 60% would solve all problems without any hardware change.
Someone even used an Amtel microcontroller to:
- check if there is pwm on hotend fan connector (so detect if fan should turn)
- check a potentiometer to adjust own PWM ratio
- generate own PWM
Nice idea, but a bit overkill. I still hope Prusa integrate setting of PWM in firmware (f.e. to be set in gcode by as M106 P2 S... or in Experimental settings). Till than I will use the simple permanent-on mod.
RE: Revo Fan does not spin fast
I don't have my Micro on my Mini (yet), but I do think the fan is awfully tiny. I suspect it is the reason for all the heat creep issues people are posting. I have seen some mounts that use the stock larger Mini fan, I would use that instead.
My Micro is on my Voron Trident with a larger fan and has nearly 200 hours of trouble-free printing.
Mini+ (kit) - Revo Micro | Antler Cooling | WiFi (4.4.0RC1)
RE: Revo Fan does not spin fast
Actually hotend fan output on buddy-board is PWM. Firmware sets it to about 38%. This is coded in firmware, not to be set by user.
Pruser uses a cheep loud oversized fan and makes it quite by turning it down this way to spare the money for a Noctua. The correct way to connect the e3d fan: put red wire of revo fan to the middle pin of the hotend fan connector and black wire to pin 2 of j21, as you get permanent ground there (black wire is marked green here).
Even the stock fan with PWM is often to much throddled down, I often had headcreep with stock hotend. Just did this change to the stock fan. While the Mini now sounds like a Creality-Printer with the stock-fan, 100% power on a noctua should give more airflow than 38% on stock fan and be less noisy. Luckly I have a black noctua for mk3 as a spare (they are not been produced anymore, but you still can get them in the colourful noctua-coloursheme...). So I will use version2 of the revo micro hotend, but with 100% power and noctua. But version 1 should also work with e3d fan if connected this way. It is not a fault of e3d and the fan is not to small - it is just Prusa's firmware being the problem...
Downside of this mod: The fan is always on now.
Speed of hotend fan not being adjustable is an issue on github for more then 1.5 jears now. Quite a shame Prusa have not done anything there for now. Many people have heatcreep with stock setup, a the original fan has variations in quality. If it would be possible to set the speed (f.e. in experimental menu) a simple speedup to 50 or 60% would solve all problems without any hardware change.
Someone even used an Amtel microcontroller to:
- check if there is pwm on hotend fan connector (so detect if fan should turn)
- check a potentiometer to adjust own PWM ratio
- generate own PWM
Nice idea, but a bit overkill. I still hope Prusa integrate setting of PWM in firmware (f.e. to be set in gcode by as M106 P2 S... or in Experimental settings). Till than I will use the simple permanent-on mod.
RE: Revo Fan does not spin fast
Thanks for your recommendation, I took quite similar approach and hooked up the fan to a dcdc converter that gets 24v from the Mini´s power supply, and converts it to 5v. Now the fan is spinning as fast as it is supposed to and all the problems ar gone.
(24V on buddy board was easyser to solder )
The other solution would have been to install the old fan on another revo mount, but i like the slim Design of the Gen1 mount.
Thanks for your help!
RE: Revo Fan does not spin fast
Yes, stepdown was also my first thought. But I remembered on all my boards mosfets always switched ground, not Vcc. So the 5V on hotend fan connector is a permanent 5V, its the GND being switched. So all 2 do was to find a permanent GND - and its less than a cm away on J21 Pin 2. I could not belive it is so easy. Just to remove one wire from one connector, put a dupond-plastic part on it and plug it to a near pin. Over one year not using the Mini (I gave up after trying Bondtech heatbreak, extuder upgrade etc.) now I have a solution. This night I printed a test object wich always ended in heatcreep - but now it printed with stock hotend (prusa fan at 5V, so overkill in coldend cooling) succesfully.
I will use v2, but not with prusa fan but Fysetc (for mk3s clones) or Noctua. Fysetc at real 5V should blow a bit more air than prusa fan at 38% if I understand the datasheets correctly. This should solve both heatcreep issues and make the printer more silent.
But before installing the Revo I first will test stock hotend with this mod. I have 4 Mini's (one original, 3 clones) and converting them all to Revo at once is a bit out of budget. But if Fysetc to j21p2 works, I definitly will convert them all to Fysetc (and to SuperPinda, just got 4)
RE: Revo Fan does not spin fast
you have a link to the Fystec Fan ?
RE: Revo Fan does not spin fast
have you tried using the stock prusa fan? this might solve your heat creep issue
https://www.printables.com/model/151007-prusa-mini-upgrade-edition-2-revo-micro
RE: Revo Fan does not spin fast
There is an custom firmware ( https://github.com/matthewlloyd/Llama-Mini-Firmware ). It allows to set hotend fan speed in menu. Sadly the developer sold his mini and stopped developing, latest vesion is based on Buddy firmware 4.3.3, so one step behind. But maybe Prusa will support this feature in future versions directly, making the fork obsolent.
I will give the Llama a try, as the changes between 4.3.3 to 4.3.4 mostly effect supporting preview and showing settings from Prusa slicer 2.4 (not needed if you know what you do, so only nice2have), supporting timezones (if I want to know the time, I ask Alexa...) and add Satin Sheet (wich I do not have...). So I can live with the older version.