@deckingman okay, thanks. That's very insightful. Yes, I did some google-fu, on how to add a second stepper for the Z-axis, and the answer was to simply add a second extruder to the configurator, then re-map it in the config file, which is probably how I ended up with double values for two extruders.
As others have pointed out, that's not the way to add a second drive to an axis. Here is some info which might help your understanding.
Any axis can have a number of drives assigned to it but things like acceleration, steps per mm, instantaneous speed change, motor currents etc are all applied on a per axis basis. That is to say, any drives associated with an axis will all be assigned the same values. If you think about, that's the way it has to be because you can't have two motors driving the same axis using different acceleration values for example - they have to synchronised. For that reason, we don't use colon separators for individual drives on the same axis - every drive will have the same values by default.
Extruders are treated similarly to axes but each extruder can only have one drive assigned to it. Tools can have one or more extruders assigned to them but that's another matter. For machines which have multiple extruders, we have to stipulate the acceleration, jerk, steps per mm etc for each extruder, just as we would for separate axes (X,Y and Z might use the same values but they might equally use different values depending on pulley size or lead screw lead). We do that by using multiple values separated by a colon. It's just a shorthand way of saying the first value applies to extruder 0, the second the extruder 1, the third to extruder 2 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.
@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.