Duet and bioprinting



  • Hi,

    I am currently working on a design to add bioprinting capability to my 3d printer. It is basically an attachement which replaces the hotend and the extruder with a paste extruder and a syringe. I am normally using BLTouch as a Z endstop and for bed leveling and I still want to use it while bioprinting. The problem with bioprinting is that you are using a petri dish to print on, which contains biogel. The petri dish has to be on the bed at the start of the print. Then, how am i supposed to prevent collision with the BL touch? I can place the petri dish far away from the center of the bed, which would enable the Z homing, but then the only way to prevent collision while printing would seem to be using a very long needle (longer than the difference between the BL touch's pin and the petri's wall height). This could work but it would mean homing without the needle in place in the beginning of the print, rasing the Z height, pausing the print, attaching the needle, and resuming the print. I assume these could be arranged in the slicer but I'd like to hear if there are other suggestions.

    Thanks,



  • @drmaestro I would make sure that the surface is flat (so you don't need mesh compensation, only the Z position) and then use bltouch at areas outside of the petri. If you need the whole area, you could install a block with known height and calculate measure + block height.

    Interesting project!!


  • Moderator

    You could alter your homeall to have the bltouch be away from the area of the dish. Then in your slicer start gcode or in a separate macro you could have some gcode movements that place the needle/printhead where it needs to be before the print starts while avoiding the wall.



  • if the probe offset is smaller than the diameter of the dish it will limt the area inside the dish you can move without hitting the wall wont it?

    if the printer is sufficiently rigid having it calibrated once and homed at power on should give you plenty repeatability - or maybe you could spring load the needle to further remove any need for fine adjustment?


  • Moderator

    @bearer Good point on the offset.

    @drmaestro perhaps you could use manual probing instead by using M558 P0. When you call for a G30 in your homeall it will pop up a dialogue you can use to jog the nozzle to where you want Z0 to be.



  • I have tried to put the syringe at the opposite end of the X car. That way, I should have enough space between the petri dish and BL touch. The height of the syringe will be adjustable. Here's a picture of what I have planned for now:

    Bio1.jpg

    (The hotend won't be there when bioprinting option is active, so you can disregard it)



  • given you have clearance I'd consider using a cam package to make the g-code it will handle fixtures and safe z heights. overkill perhaps, but also easy


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