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.
@fxstein somewhat offtopic nit-pick, but "direct drive" and "direct" are two different things. "Direct drive" usually means an ungeared extruder (while I am nit-picking, I'll nitpick on myself and mention that this should be "filament feeder", with the opposite being geared extruder (like Bondtech or Hemera). The "direct" versus "Bowden" (no drive) are really "short distance" vs "long distance" (between filament feeder and hotend).
I know exactly what you mean. We - no I am are butchering a bunch of terms. Guilty as charged. Having said so, the vast majority will understand the meaning of it - might even be less confused than when we speak more precisely.
I know that the main concern of this type of systems, are the retractions, but from what I have been able to find out, the polymers have certain characteristics, it may be the same polymer but for different types of technologies their characteristics change, for example when they melt they flow as a liquid, but rather as a hot dough, and in theory that prevents material from dripping down the nozzle, but in case these drips occur, I plan to build a pneumatic system that stops and opens the nozzle very fast for extruder displacements .
Here you can find a system that closes and opens the nozzle.
The model in the photo has XY dimensions of 40x40mm, horizontal distance between ribs is around 8mm and with 11mm diameter filament gear, 0.2mm layer height, 0.4mm nozzle, I don't believe there is a correlation there. My math might be wrong though.
Can you post a section of the GCode file showing at least one complete layer (not one of the the first few layers) so that we can see how much extrusion is being done per side of the cube?
@dc42 I will upload a video this weekend of the material change in process, so that everyone can see where the issue lies and better understand how the mechanical side of my filament selector works.
On another note, Thank you for always being so attentive to this forum! I don’t think I’ve ever posed a question that you didn’t have some input on. I really appreciate that!
@dc42 thank you. For all the years I've worked at software and used networking I missed that pronterface was upcasing the line which meant it no longer matched the ssid. I went to repetier and did it there and now the webui is up and running.