Unused extruder "leaky" on dual extrusion prints

[DrMistry]

Hi everyone,

When printing the first 5 or 6 layers of a dual extruder model, the idle extruders are leaking slightly and leaving a "ghost" print to the left and right of the actual print. I'm not sure if this is just a functional limitation of my rig, or if there's something more I can do either in firmware or in S3D to try to mitigate the problem. In almost every other way, the prints are perfect aside from a small cooling issue when doing very fine details on top layers. I'm using both priming pillar and ooze shield, but once the head is significantly off the bed (let's say above 0.5mm) the problem reduces then disappears over the proceeding couple of layers.

I've had a search around but can't find any matching advice. I have a Prusa i3 clone (Anycubic, but with a GT2560 board running Marlin 1.1.5) to which I've added 2 bowden-fed E3D v6 clone hot ends, with 0.2mm nozzles. My print quality with single extruder models is great using either extruder in isolation - I've got my flow rate just so for both extruders, they're well calibrated and I regularly take measures of the filament diameter for each extruder. The nozzles are very carefully aligned to be the same height, and I've used a number of calibration models to get the X and Y offset as close to perfect as I can get it. I've set as generous a tool-change retraction as I can (11mm @15 mm/s) without the filament exiting the hot zone - if I go any further the cooled filament end "bulbs up" and won't go back in to the hot zone, stalling the bowden and killing the print. I clean the nozzles carefully between prints and my in-print retraction and z-hop settings are keeping the prints nice and clean with no zitting or stringing, bed adhesion is good and I'm using an aluminium bed with an inductive bed sensor, which works just as it should. I only ever print in PLA, the hotend temperatures are currently 195 degrees, but I've tried as high as 210 degrees with no issues.

Any advice would be greatly appreciated!

[brian442]

Try larger tool change retraction distances. Or add an ooze shield

[DrMistry]

I've tried with a 2-outline shield, 10mm from the model, vertical. If I increase the tool change retraction any more, the filament cools and forms a "teardrop" and won't go back in to the hot zone. The thing is, there's absolutely no stringing or zitting on the model and no *visible* strings from the idle extruder, but it does leave a ghost on any parts of the print where the nozzles are coincident (if you see what I mean). It's really just a thin "skin" of material deposited on the bed, but there are occasional blobs appearing on these ghost deposits until I get a few layers in. Given the length of the tool change retract, I don't really want to turn off the priming pillar but I'll try it anyway I guess!

I'm starting to wonder if this is just capillary action on the nozzles causing the initial layer 0 ghosts,, and some kind of electrostatic effect drawing small flecks from the idle extruder for the first few layers. It happens on both extruders too, to a more or less identical extent.

Anyway thanks for the response,
Mike

[gearsawe]

photo?

[DrMistry]

I'll try and get one tonight. Got to replace one of my hotends owing to an overheat condition caused by my idiocy!

[shasselberg]

I have a similar problem. The unused extruder is oozing terribly while idle. I have increased retraction, retraction on tool change, and lowered temperature while idle. It's still pretty bad. PLA on Ultimaker 3.

[arhi]

it is normal behavior, larger the nozzle more it is pronounced but it happens even with 0.25mm nozzle .. solution is ooze shield and if ooze shield is not enough ooze shield + prime tower

[shasselberg]

I have tried ooze shield and priming tower. Odd thing is that they do not adhere even though the rest of the model does fine. Don't know how to get them to work on the Ultimaker 3.

https://ultimaker.com/en/community/3855 ... er-problem

[bjarchi]

I posted a related issue to this. I think the reason the ooze shield doesn't perform as expected is that it's sometimes being printed *after* they layer, rather than before. This is true, and especially problematic, on the first layer since that ooze from the idling extruder can mess with first layer adhesion.

[shasselberg]

I finally got some great two-color prints on my ultimaker 3 by ungrouping the processes. See this thread.

https://forum.simplify3d.com/viewtopic. ... 099#p37099

I'm wondering if some seemingly unrelated observations are starting to come together, and it all has to do with how S3D handles dual-extrusion.