Moving additional axes in different secnarios



  • Hi,
    so I was thinking about this for some time now and I wanted to discuss this.
    I have a BigBox upgraded to an IDEX setup with the Duet Wifi and a Duex2.
    Everthing is working fine so far but I am a guy who wants to have things tidy and want a thing to be usable without the least amount of effort.
    For everday printing I just want to switch on the box, upload a file and print it.

    My point is that I have no real option to move every axis as I want to in different stages when preparing the printer for a print.
    WItrh an IDEX setup I have four axes, X, Y, Z and U for the second extruder carriage.
    So when I start the printer no tool is selected, to get back to that stae I can "T-1".
    When I am in that state I can move my first extruder by moxing X axis and the second one by moving U axis.

    Because a slicer does not know about those additional axes you make that mapping of axes to X when selecting a tool.
    So in T0 I moxe first carriage with X and second carriage wiht U.
    But in T1 I move second with X and with U also the second. I am not able to move the first one in that state.
    Previously I used G1 command with S2 option, which is just used for Delta printers as a direct move of a tower motor according to the documentation, but it worked for me as well.
    But this command I meant to be a raw move as discussed here: https://www.duet3d.com/forum/thread.php?id=1730

    My problem with that whole situation is that it is not really straight forward to understand how this all works together.
    Thinking of the three main axes X, Y and Z as the working axes and then the additional axes U, V and W and the mapping between them is not helpful because the first carriage is driven with X unless you mapped another axis on it. When maaping is active there is no way to drive the first carriage axis in a normal manner (G1 S2 would do it but ignores ednstops).
    I'd like to think of it as three working axes and additional carriage axes which are mapped to X when I select a tool.

    I want always be able to move every axis by a constant axis identifier regardless of which tool is active. X moves the selected tool.
    Would it be possible to create and axis "T" just before "U" which always moves the first carriage?


  • administrators

    Have you considered designating the carriages U and V instead of X and U, and having no real X axis at all, i.e. map it to a non-existent motor? Then you will always be able to move U nd V, and you can map X to either U or V (or both) in the tool definitions. You could fake homing X by just putting G92 X0 in homex.g (although I have a report that this may not work in 1.19beta7).

    Mesh bed probing would need some thought because it normally moves X and Y to the probe points.



  • Yes I have but didn't know it is possible and didn't try it yet.

    But if mesh bed leveling is a problem then that's not an option for me…


  • administrators

    I guess we may need an option to specify an X axis mapping for G29 bed probing.



  • @dc42:

    I guess we may need an option to specify an X axis mapping for G29 bed probing.

    That'll be great… Seems to be the less intrusive change as it would be perfectly fine to assing a non-existant motor to X as you said...


  • administrators

    One thing to consider is if a 4 head axis IDEX type design was developed then XUVW would all be used by individual axis. A solution which used a XYZ to move the currently selected tool axis, while allowing UWV? to represent the actual drives makes sense.

    Extending this logic further it could be conceivable that someone would want to build an IdeY (independent Y axis) or similar, or even have multiple Z axis for different tools in a tool changer type situation (OK I admit this is getting far fetched and I can't see how the mechanical design would work but bear with me).

    With that in mind should IdeX type machines not be required to map "special" drive designations (U,V,W,?,?,?….) to the actual drives and then use XYZ only for the currently selected drives. If a tool specifies that multiple drives are mapped to X, Y or Z then this would of course not be a problem.


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