Calibrating Z offset for X and U carriage for IDEX



  • Hello,

    I'm designing an IDEX (Independant Dual Extrusion) printer and on the IDEX configuration page of the wiki it says the Z probe must be mounted to the X axis. Is there any way to probe both X and U carriages? I'd like to use either two inductive sensors or run 5v through each hotend and have it close a circuit with the bed.

    I'm really just looking for any way to automatically probe the bed to set the Z height of each carriage independently.



  • very much interested in this topic as I am also working on IDEX.

    I plan on using FSR though to probe the Z since my bed would not be metal..

    Stephen



  • Theoretically, I should be able to trick the printer by closing a circuit with the bed and nozzle. If I run 2 wires in parallel to each hotend and 1 to the bed, either hotend would close the circuit. I can use the X carriage to probe for 3 point bed leveling, I'd still have to input coordinates for Z offset for G30. When probing the U carriage the user would just have to store the value manually. Is there any way to automatically save the value to the correct Z offset?



  • Can you post a photo of what your design looks like?



  • Hey Stephen, it's Adam Steinmark from the Google+ community. My design is very similar in movement style to the BCN3D Sigma, I'd post a pic but the CAD is in a weird spot at the moment and it's not extremely clear. I looked at your posts on this forum and saw the following from the developer:

    "The Duet can support multiple Z probes and let you switch between them, so although I am not aware of anyone having used an IDEX system with separate X axes and probes, it is possible in principle.

    You could connect one Z probe to the E1 endstop connector (E0 is not free on an IDEX machine) and the other to the Z probe connector, and use probe types 5 and 6 in the M558 command to select which one. Or you could connect both to the Z probe connector and use an analog multiplexer IC to switch between their outputs, controlled by the MOD pin on the endstop connector, and use probe types 1 and 3 in the M558 command.

    You would probe with one head/probe and save the height map for that. Then with the other. The G29 command on the Duet allows you to specify the name of the height map file, so you can use a different filename for each head. Then in the tool change macro files you would load the height map file for the head you are switching in.

    Bear in mind that if you want to do ditto printing (print 2 copies of an object simultaneously), then you need to match the nozzle heights accurately.

    HTH David"

    Did this work for you?



  • Hi Adam,

    I'm getting close but not there yet

    just got 1 toolhead printing at the moment. next step will be to see if above instruction would actually works…
    link to video of my machine doing first print https://youtu.be/D8RW9LCTViM

    Stephen



  • You only need a z-offset for the second head, why would you use two probes?

    Kulitorum



  • @Kulitorum:

    You only need a z-offset for the second head, why would you use two probes?

    Kulitorum

    So you don't have to calibrate the Z offset of the second head manually. The value might need some tweaking but at least you wont have to manually re calibrate after doing any work on the printer. This becomes especially important if you're not using 2 identical toolheads (i.e. E3D V6 and Volcano)


  • administrators

    In firmware 1.20beta1, which I am about to release, you can use G30 S-2 to probe the bed and adjust the Z offset of the current tool, instead of adjusting the Z=0 position. But if you want to do ditto printing on an IDEX printer, you need to get both nozzles at the same height anyway.



  • I think you can use the very same probe and assign it to different toolhead since all toolhead will be probed 1 at the time right. Maybe David can confirm



  • @dc42:

    In firmware 1.20beta1, which I am about to release, you can use G30 S-2 to probe the bed and adjust the Z offset of the current tool, instead of adjusting the Z=0 position. But if you want to do ditto printing on an IDEX printer, you need to get both nozzles at the same height anyway.

    Works for me! I probably won't do any ditto printing though, but we'll see.


  • administrators

    I'm glad it's working for you. So can you confirm that it is adjusting the tool Z offset in the correct direction?



  • @dc42:

    I'm glad it's working for you. So can you confirm that it is adjusting the tool Z offset in the correct direction?

    Oh no I haven't actually tried it yet, I'm just saying that that method will work for my needs. I'm nearly finished with the design of the prototype, I'm just waiting on quotes back from a few suppliers. I just wanted to make sure I understand as much as I can so I don't waste any money on parts that need to be changed.



  • David

    can you add the G30 S-2 write up of explanation how to use in the G30 section? I checked and it didn't have any S-2 there

    Thanks,
    Stephen



  • @stephenc:

    David

    can you add the G30 S-2 write up of explanation how to use in the G30 section? I checked and it didn't have any S-2 there

    Thanks,
    Stephen

    +1
    Also
    Is the G30 S-2 working in 1.2 firmware? I am in the process making a nozzle touch switch so I can automatically set the nozzle heights for each of my IDEX carriages.


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