Chimera+ idle nozzle hits print

Discussion in 'Multi-Extrusion' started by grumblecakes, Apr 27, 2020.

  1. grumblecakes

    grumblecakes New Member

    Apr 27, 2020
    Likes Received:
    I'm approaching the end of the line with this hotend. I've been working with it for about 5 months (got it for Christmas) nearly every day. I cannot for the life of me get the idle nozzle to stop bumping into the print. I'm printing with PLA. If it doesn't ruin the initial layer(it usually does) it will eventually knock the print off the bed. I think I am on my 4th roll of filament just trying to get this thing stable. Supports and infill (since they are printed first) are usually what the nozzle hits. I'm working with what used to be an Anycubic Kossel Linear Plus (there isn't much left), specs below. I had to design a custom effector to mount this hotend, since everything I could find out there is for a more traditional Kossel with the hotend mounted completely below the effector. I successfully printed a dual extrusion dice and it looks great but I could hear the idle nozzle hitting the ooze shield. This is a genuine E3D Chimera+ from MatterHackers (great company btw). Reverting back to the stock clone v5 hotend with exact same gcode eliminates all issues (no dual extrusion of course).

    Anyone have any suggestions before this hotend meets the sledge hammer in my garage? I welcome any advice. Thanks!

    Printer specs:
    Re-ARM + RAMPS 1.6
    LV8729 stepper drivers configured for 128 microsteps (actively cooled with fan).
    2 Clone Titan extruders (NEMA17 50Nm cm)
    "Ultrabase" glass heated bed
    Cura 4.4.1

    Here is the stuff I have tried:
    Lowered the hotend to just above the bed and used the grub screws to level the nozzles. Countless times.
    Marlin Autocalibration a million times (with and without a probe)
    DC42's least squares calibration
    Automatic bed leveling (I think this is impossible due to this limitation of Marlin)
    Replaced diagonal rods (twice). I am confident backlash has been eliminated.
    Replaced both extruders (twice). Latest is clone Titan extruders which appear to be doing their job properly
    Replaced nozzles
    Replaced thermistors
    Replaced RAMPS (twice)
    Replaced axis steppers
    Verified gears are tight on all steppers
    Change microstepping from 128 to 16
    Print slow (30mm/sec, 500 acceleration, 5 Jerk)
    Print fast (60mm/sec)
    Various versions of Marlin
    Various retractions (0-3 mm)
    Various retraction speeds (35-70mm/sec)
    Various temperatures (180 C - 220 C in increments of 5 between)
    Various belt tensions ranging between stupid tight and stupid loose.
    Calibrate PID more times than I can count.
    Verified cold end fan is running 100% all the time
    Verified part cooling fan turns on after first layer and continues to run
    Reapplied thermal paste 3 or 4 times.
    Rounded the end of the bowden tube to ensure that it is seated as far as possible into the heatbreak.
    Like 5 or more brands of PLA.

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