Hello all,
I have a little problem with the Dual Print PETG and PVA.
After changing the nozzle, the PETG and PVA runs quite long, which leads after a few hours to a problem that the nozzle is stuck. I use CURA as slicer and have set 2mm as retraction.
Do you have any tips on how I can adjust or improve the run-on?
Greetings
Michael
You could give some more information. Did you change the nozzle size?
What do you mean by runs long?
What temperature are you printing at?
I use the 0,4 mm nozzle on both sides.
When the print is finished with a nozzle, the filament still runs about 3 cm.
I print the PETG with 210 and the PVA with 205.
I donât think 2mm is enough retraction for tool changes. Luban G-code says that it uses 16mm when printing PLA and thatâs what Iâve used with Simplify3D; PETG tends to ooze more than PLA and I suspect PVA does too. The prime tower has plenty of area to prime the extruder.
Are you sure you not mixing up retraction with purging? 16mm for retraction is kinda crazy.
These comments are in the G-code file, so I can only assume that the G-code is doing it. Software retraction is not an easy thing to find in G-code because it looks mostly like extrusion code, especially when the extrusion amounts are absolute. If youâve ever seen how badly the Snapmaker breakaway filament oozes, youâd understand why they might have to do this.
;nozzle_temperature(°C): 200
;nozzle_0_diameter(mm): 0.4
;Extruder 0 Retraction Distance:1
;Extruder 0 Switch Retraction Distance:16
;nozzle_1_temperature(°C): 220
;nozzle_1_diameter(mm): 0.4
;Extruder 1 Retraction Distance:1
;Extruder 1 Switch Retraction Distance:16
Toolchange retraction in Luban is in fact 16mm, but this can contribute to heatcreep / nozzle clogging.
I would recommend 2mm at toolchange, as do manufacturers of other dual extruder printers.
My experience with this is, that 2mm works without problems, as long as the filament is properly dried.
Think of it like this:
Your filament is molten inside the nozzle, no matter how far or quick you pull, you wont get that molten part back out of it by pulling. The only thing you will retract is the solid part of the filament.
The molten remains in the nozzle will ooze as long as they are not cooled down to solidify enough again. But this takes a few minutes.
So what will happen if you retract 16mm, beyond the throat of the heatbrake? You pull your filament up into the cold zone and drag just a bit of soft material with it, this then solidifies and sticks to the cold walls. If you have enough extruder changes, it will build up and form a liner inside the assemby that will eventually cause a clog.
As said, if you retract too far, your molten filament stays in the tip and the solid filament goes up, making room for an airpocket. This air then heats up and expands, pushing the molten filament out â tada oozing.
Same thing with wet or moist filament. The âwaterâ inside the filament evaporates and expands. This pressure builds up and pushes the soft filament outside the nozzle â oozing.
So, use 2mm retract at extruder change and make sure your filament is dry and especially with pva, printed directly from a filament dryer.
The main problem with the Snapmaker dual extrusion module as I see it is it doesnât cool down quickly enough when the heater is turned off. The breakaway filament appears to be especially prone to ooze in this situation; I have yet to get a print with significant supports to not trap strands of breakaway filament inside the part being printed.
I just avoid using special filament for supports. I now use my regular print filament, which gives pretty clean supports when sliced with Simplify3D. I do use dual extrusion in very limited circumstances, such as highlighting text on the top surface of a print; Simplify3D makes that simple to do.
Thanks for the update. Iâll continue to try - the thing Iâm trying to pint is difficult with âclassicâ support, so I need to get PVA working. Some ideas still there, will eventually get there.
