hotend / heatbreak temperatures
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On my neverending path to migrate my Tronxy X5SA to use a Duet Wifi as controller I removed the original hotend and replaced it with a better (so I hope) one: Phaetus Dragon. with my first tests I managed to have cloggend filament in the heatbreak part which took a complete disassembly and cleaning for the next test. Finally I modified the hotend cooling fan with small airflow guides that the heatbreak with its lower side has now about 36 deg when I set the nozzle temp = 195 (for at least 10 minutes). W 220 deg nozzle the heatbreak only went up to about 41 deg. I did a search here for any recommended cooling temps for the heatbreak side but could not find something. Are there goal temperatures which I should target for so that retracting (for filamanent change) is easy and error-free?
Btw: I did the hotend tuning and the new hotend heating works fine. -
Retracting is likely the cause of your problems.
You don't need to retract to change filaments - do you?
I have two of those hotends and never had a clog that required taking it apart.
And the only time I had any clogging type issues was with certain filaments with additives, like those often labeled as "silk", when trying to use retraction.
Frederick
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@fcwilt Hi, how change filament without retracting? I certainly could just push through the current directly following a new color but I kept the Tronxy bowden feeding and that is about 450 mm PTFE between the extruder and the hotend.
Yes, I know I could detach the PTFE at the hotend and cut the filament there, retract and attach everything and push new filament again but I feel that this is not very "elegant"
I - as a guy very new to all this stuff - believed that this is done more simply. With my current temp in the heatbreak it looks as if I have resolved the clogging and can get the current fillament out, push new, properly cut filament back into the hotend and have a color change.I just wanted to gather some confirmation that I am on a proper path to a good printer...clogginf is really annoying!
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Well I don't use bowden setups but with my setup (Zesty Nimble) I just:
- pull back on the filament guide tube
- cut the filament near to the Nimble and extract from guide tube
- feed the new filament through the guide tube
- heat the hotend
- issue a extrusion command for 100m at 1mm/sec
- feed the new filament into the Nimble making sure it enters the hotend
- issue additional extrusion commands until I'm sure the old filament has been purged
It may not be elegant but it works and never has caused any problems.
Frederick
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@hlwerschner Having spent almost 2 years and having done an awful lot of work in trying to develop a mixing hot end, I have learned much about heat breaks - especially all metal ones. At one time, I was using 6 off genuine Slice Engineering Mosquito heat breaks of which the Dragon is a clone.
These are undoubtedly the most efficient style of heat break. BUT, if the filament is static and heated but not moving forward, then heat will creep up through the filament itself even though very little heat creeps up through the metal part of the heat break. It's especially a problem with PLA because of the low glass transition temperature. So even though the temperature of the heat break might only be 40 deg C, the temperature of the (static) filament inside the heat break can exceed 60-70 deg C which is greater than the glass transition temperature for PLA.
So the moral of the story is to never, ever, heat the hot end for an extended period of time without the filament moving forward. If you do, heat will creep up into the heat break zone through the filament itself, where is will soften. As son as you try to extrude, this softened filament will simply swell and block the tube.
BTW, with a mixing hot end one or more filaments will always be static so for this reason, all metal heat breaks can not be used - they have to be PTFE lined.
