Skirt with Dual Extrusion: Add an offset between loops of different extruders?

[simonkuehling]

I use the skirt feature to easily prime my extruders before printing (its intended primary use, i think) - no need to have any kind of wiper or such.

With a dual extruder setup, both extruders print half of the loops each - which is problematic for extruder-offset calibration. When i want to print a calibration pattern - BUT also use a skirt to prime prior to that, the loops mess up due to the not-yet-calibrated extruder offset.

A solution could be not to distribute the configured skirt loops to all extruders, but to print seperate skirts for each extruder - with the second skirt offset from the first skirt by the same amount as the first skirt from the object.

This would possibly also solve issue #966 by generating each skirt separately with the relevant extruder parameters.

[alranel]

While I do think #966 needs a fix very soon, I'm skeptical on this. Does it really cause noticeable problems?

[simonkuehling]

Actually, i'm not sure how important this really is. On the one hand, accurate calibration of the nozzle offset is essential and needs properly primed extruders as all prints do - on the other hand it is "only" calibration, usually needed once every decade or so...

But then again, calibration is inevitable for multi extruder setups. Another way around this could be some kind of "calibration pattern gcode generator"-wizard, that assembles a gcode file to draw calibration lines with current extruder settings. This could use different, somehow static paths to prime the extruders that do not lay side by side. (I really like this idea! :-) )

I can confirm though, that printing skirt with inaccurate extruder offset can cause slipping filament due to a nozzle "sealed" by the traces of the previous extruder.

[alranel]

@simonkuehling, I'm with you about a wizard to calibrate extruder offsets. And now that Marlin supports firmware-side extruder offset, I think the best place for such wizard would be the host application which can send M218 commands to alter offsets in real time. The LCD panel could be another good place too.

I'm still skeptical about your offset idea. Following that principle, we should take security measures for any other wrong firmware/hardware settings. And that would fix the issue just for skirt, not for perimeters and other object parts. In your post you talk about a calibration pattern with skirt all around. I really think your calibration pattern could just include its own skirt, with the security spacing and without using the Slic3r-generated one which relies on well-calibrated firmware and hardware.

I hope you'll not mind if I close this one! :)