Hi, I'm about to order and build my first Voron 2.4 kit (from Formbot), but I'm not sure which hotend (and extruder) is the best choice. I print mostly PLA and PET-G, but the ability to print ABS and ASA comes handy occasionally. And I like to print medium to very fast. I think the Rapido 2 UHF is good for me, but I don't know how good it is for printing PLA, because of heatcreep.
#Hotend
fallen wharf
nova snow
i feel like i've seen this message several times around the server now
rapido 2 would be a good, versatile hotend choice
royal crag
While I don't run one myself, I haven't heard anything about Rapido 2 being in any way bad for PLA. It needs proper hotend cooling to avoid heat creep, but so does basically every hotend.
fallen wharf
Thank you! I have some questions. What fan is considered as a good choice for Rapido 2 (or any other hotend) cooling? What CFM value and size,...? Can I use 5V or do I need 24V one? Can I use fan without PWM rotation meter?
royal crag
Either voltage works. While higher voltage means lower current means you can have longer/thinner wires, those fans are generally low-enough power (and wires pretty short) it doesn't matter much. Depends mostly on what specific fan you get and what is easy to wire up on your toolhead (though most toolhead boards, if you have one, can do either voltage easily enough), but for stealthburner it's easy enough to find 24V fans.
You also don't really need a 3-wire fan with a tachometer signal (or a 4-wire fan with dedicated speed control signal), it's not like the hotend fan needs to be very precisely rpm controlled.
I run the regular LDO-branded 4010 24V fan for my Dragon HF in a Stealthburner, and it's been perfectly adequate for my needs (no idea what the airflow is, but it's a rather ordinary fan). Hotends with tiny 25/30mm fans sometimes have issues with inadequate cooling, but I haven't had any.
fallen wharf
ok. Is Rapido 2 UHF better than HF for my use? Are there any differences in cooling?
royal crag
The "U" is supposed to better if you're printing really fast. Allegedly 75mm^3/s for UHF vs 45 for the HF (though those numbers are afaik with PLA at rather high temperatures and maybe a bigger nozzle). Not sure if it needs more cooling though. More cooling might be needed at higher temperatures for melty filaments like PLA, but it doesn't seem obvious that it would due to the flow rate.