why heat the bed when fill the filament?  

RE: why heat the bed when fill the filament?

To get it ready to print?  

RE: why heat the bed when fill the filament?

Sometimes you only want to remove or replace filament, not necessarly to print. But in that case you do not need to heat the bead. You can change only the nozzle temperature from printer menu, or for example from Octoprint. The preheat function is a procedure before print.

Milos

RE: why heat the bed when fill the filament?

You can go into settings / temperature / nozzle and dial a temp for just the nozzle. That will heat just the nozzle and not the heat bed. Similarly you can also heat just the heat bed.

RE: why heat the bed when fill the filament?

thank you, everyone, who give me an answer.  I know how to heat the nozzle in the setting menu. 

my question is, in the menu, there is an option "Unload filament",  based on my understanding, it means I would like to unload the filament if I want to unload the filament, why heat the bed? I mean if I'm loading a filament, it heats the bed, that makes sense, but when I unload the filament, why?

RE: why heat the bed when fill the filament?

Posted by: Snipermax

[...] my question is, in the menu, there is an option "Unload filament",  based on my understanding, it means I would like to unload the filament if I want to unload the filament, why heat the bed? I mean if I'm loading a filament, it heats the bed, that makes sense, but when I unload the filament, why?

I think the firmware just calls the existing preheat function when it detects low temps. The Prusa controller board has very little available memory for firmware, so they probably just saved space by re-using an existing routine rather than create a new one. You certainly don't need a warmed up bed to remove filament or change nozzles.

RE: why heat the bed when fill the filament?

I agree with you @snipermax. I asked this question when it was first introduced in the firmware and never got a decent answer.

RE: why heat the bed when fill the filament?

I never noticed this, I always preheat the nozzle manually and then run unload filament (good habits from times, where firmware did no do thinking part instead of you). And that is also the answer, heat it up first, then choose to unload and you do not need to heat the bed.

Milos

RE: why heat the bed when fill the filament?

preheat the nozzle manually

Same here. My filament removal sequence also includes advancing the extruder a few mm once up to temperature. Advancing the filament before unloading dramatically softens and shrinks the filament tip. That prevents the filament getting jammed during unload. Instead, it glides out with practically no resistance.

RE: why heat the bed when fill the filament?

Come to think of it, I should look into adding an extruder advance as part of filament unload in my firmware branch.

RE: why heat the bed when fill the filament?

If you are just loading or unloading the filament there is no reason to heat the bed.  Just go to settings, temperature and set the hot end temperature for your filament.  The reason the heat bed is on is because I am assuming you selected pre-heat pla,abs,pet, etc.  Doing it from settings/temperature doesn't require you to heat the bed.  But it is extremely beneficial if you are doing a color change in your print.  Both the bed and hot end stay at temperature, the print head moves away from the model and you can change the filament and continue.  And that is why unload/load filament works the way they do.