Chimera+ (air cooled) Oozing

Discussion in 'Multi-Extrusion' started by Luminaerys, Jul 5, 2018.

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  1. Luminaerys

    Luminaerys Member

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    I've been working with a Chimera+ (air cooled) for a few months. I've been having oozing issues the whole time. The hotend will ooze indefinitely when left idle at print temperature.

    This particularly becomes a problem since the idle hotend will eventually starve itself of filament. Then the hotend becomes active but has no filament primed to print.

    Details:
    • PLA
    • Hotend @ 190-200 degrees
    • ~300 mm Bowden tube (as provided in the Chimera+ kit)
    • 4mm retraction and 4mm tool-change retraction
    • 0.4 mm brass nozzles (previously also had 0.3 and 0.4 mm hardened steel nozzles)
    I believe the "proper" solution to oozing is to simply increase retraction distance. However, the old Chimera documentation warns you to avoid increasing retraction past 5 mm. In my experience, 4.5 mm and above of retraction distance reliably clogs the heatbreak with cooling PLA.

    However, I believe it is quite standard for Bowden extruders to require 5-8 mm of retraction. This likely holds up well for the tool-change retraction as well.

    Also to note: The new Chimera+ guidelines say to keep retraction at or below 2 mm. At this distance, I am experiencing constant (fine) stringing. 3-4 mm seems to be the most reliable for me.

    --

    Questions:
    1. How can I get the hotend to stop oozing? The oozing needs to be negligible over >1 minute so that the other (active) extruder can print 2 full layers without interruption. Slic3r can reduce the inactive extruder's temperature, but in the time it takes the extruder to drop ~10 degrees, I get 20 mm of ooze. This is obviously unacceptable for essentially any print.
    2. Do Bowden extruders generally require 5+ mm of retraction? If so, why does the design of the Chimera+ heatbreak preclude this option, especially when the system is designed to be installed in a Bowden configuration?
    Thank you for any help!
     
  2. Dan Kinzett

    Dan Kinzett New Member

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    I too am having unending trouble tuning in retraction settings with my Chimera. After a perfect extruder calibration setup +/-0.01mm deviation on 0.4mm walls test. I can't get either real life prints or calibration prints to print without a decent amount of stringing and blobbing. I have tested print temps from 190 to 220. I have gone through 2 rolls of filament in test prints.
    I can get near close to good retraction settings but this is at like 7.5mm retract and adding a tiny coast and extra restart. This is far far beyond the recommended "no more than 2mm"

    My microswiss hotend on a wanhao i3 is an absolute dream. I can almost put any old rubbish settings into a slicer and get a rock solid looking print. I am regretting a bowden setup heavily. Hopefully you and I can find some solutions from some other who have already traveled this path.
     
  3. Luminaerys

    Luminaerys Member

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    7.5 mm definitely clogs my Chimera! I used to have 2mm with the stock MK9/10 hotend on the Duplicator i3 and I had much less oozing. I have tried to remove the Bowden system from the equation by detaching the tube and just leaving filament loaded at temperature, but the hotend still oozes.

    I have added some new thermal paste and reseated the heatbreaks higher into the heatsink. Perhaps that will allow me to achieve higher retraction distances (though E3D is quite clear that 2mm should be the limit).
     
  4. Luminaerys

    Luminaerys Member

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    Update:

    After resetting all the settings to reasonable defaults and reapplying thermal paste to the heatbreaks, I swapped to a new spool of filament. This seems to minimize the oozing to a level that can be controlled safely with retraction.
     
    Antoine likes this.

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