Filament Rewind while Homing

  • I have delta build with a direct drive extruder (no bowden tube) and a stepper motor setup to rewind the filament spool that is located on top of the printer. I'm trying to figure out a way to rewind the filament (U-axis) while homing. The plan is to have have the XYZ axis home at the same rate that the filament spool rewinds. I'd like the spool axis to stop rewinding as soon as either the X, Y, or Z limit switch is tripped. I need to take out about 18" of slack in the filament each time the delta is homed. Do any of you have any ideas on how I can do this?

    Also, is there any way to trick a delta into thinking it is homed so I can control motion before homing?

  • I need to make something similar, for my filament multiplexer.

    The spools I used all have a 50mm bore. So, I'm using a 50mm PVC pipe to put them on. My idea is to put a DC motor (or a stepper motor once there is a speed control in RRF, allowing me to make it always turn) on this pipe, to constantly rewind the spools. The friction between the spools and the PVC is perfect, whatever the spool are made of (cardboard or plastic), and the extruder has no issue to drag the filament.

    This system addresses two problems: start/stop the motor according to the retract, and drive it at the correct speed, depending on the spool size, or how much filament left on it.

  • Moderator

    Have you considered using a REVERSE bowden tube? One end is fixed to the frame near the filament spool and detached at the direct drive end. This keeps the filament that is spooled out contained and there is enough friction to keep it from pushing the filament back out over the spool edges. Helps keep it from getting tangled and caught up as well.

  • Unfortunately a Reverse Bowen Tube will not work with my setup as I am limited by multiple space constraints. I'll need a software solution. Thanks for the idea though.

  • What space constraints limit you from running a PTFE tube to the effector?

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