slowly retract inactive tools
-
Hi folks,
i am currently trying out new ways to reduce oozing of inactive tools and came up with the idea of slowly retracting inactive tools (while printing with another tool) to counteract slowly emerging strings on the inactive nozzle. They are not caused by gravity and not preventable by bigger initial retracts.
Is there an easy way for doing such movements (important: WHILE printing with another tool) since in RepRap g-code, it seems like only the active extruder can be commanded?
I am using a Duet 3 6HC board with 3HC expansion and 3 tools with individual hotends and extruders.
Best,
mad_engineer -
@mad_engineer Can't off hand think of how you could do that. But with reference to the oozing, this statement is curious - quote
"..... not caused by gravity and not preventable by bigger initial retracts.".
Given that retraction will eliminate or even reverse any positive pressure in the hot end, and that the filament will either be fully heated or cooling so thermal expansion cannot be a factor, why do you suppose that gravity is not a factor?
-
@mad_engineer Have you established that doing this sort of retract will actually stop the oozing? It should be possible to do that without worrying about doing it at the same time as printing. How long would this retract need to be, over what period etc.
-
I made some experiments where the nozzle is swapped upside down so that gravity cannot pull out a string.
My theory is, that with retracting, some air gets inside the hotend which is caught by surrounding, sealing melt and warmed up then, pressurizing the melt again. Therefore my strategy would be a fast, short retract of about 1mm to remove printing pressure, followed by a very slow retract (for about 15-30sec with about 0.5mm/min and step-wise descending speed) after swapping to the experimental idle position, which should compensate expansion of trapped air or outgassing moisture/other fumes.
I already did some tests with a macro and it reduced the length of the emerging string significantly (about 3mm instead of >10mm) but still not 100% and therefore, I will do some further testing in the next few days.
