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X Axis goes past home at completion of job

Discussion in 'CNC Mills/Routers' started by BioMP, Jul 24, 2023.

  1. BioMP

    BioMP New
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    Hi,

    Running into a weird issue where at the completion of a job, my X axis travels past where the machine originally was setup as "home" on start up? it goes to the point that the machine goes to the end of of the X (+) - where the limit switch shuts the motion off.

    We just replaced our Blackbox with an X32 and installed a new power supply. I restored the settings from our older blackbox. Everything else works as it should. Where can I look?

    We use Fusion 360 to prepare the files for milling - and nothing has changed there on our end.
     

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  2. David the swarfer

    David the swarfer OpenBuilds Team
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    Are you using the Openbuilds postprocessor for Fusion360?
    docs:software:fusion360 [OpenBuilds Documentation]

    (edit: just realized I said Z when you said X. All still applies but in addition the OB post does not move to X home unless you select it in the options)

    In the options for that post is an offset for Z, defaulting to -10mm. This is used to move the Z to 10mm below the home Z0 point, where it should be safely high enough to clear all the junk on the table yet far enough from the limit switch to never hit it. This number must always be negative, though -10 is usually much more than enough, -2 is probably fine.

    a GRBL 'feature' is that moving to Z0 will trip the limit switch, so our post is set up to never go there.

    If you are using the builtin Fusion360 GRBL post then it is using G28 for clearance moves, which will always hit the limit switch unless you configure the G28 position, which is an offset from home, so if home moves, so does G28, and some kinds of controller reset will reset the position, making your next job unsafe.
     
  3. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Doesn't seem to be our post (or if it was, its very old, Grbl 0.9 dates back to 2015)

    Using the correct post should resolve, along with David's info
     
  4. Misterg

    Misterg Veteran
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    If you're using the Autodesk GRBL POST you need to set the 'Safe Retracts' option to something other than G53 ('Clearance Height' works OK)

    upload_2023-7-25_12-50-2.png

    (Otherwise, I find the Autodesk POST works OK for me.)
     
  5. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    We do address several bugs (and some features, eg overriding the rapids limitations etc) so still better to use ours
     
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  6. Misterg

    Misterg Veteran
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    I did try the OpenBuilds POST, but didn't notice any difference with rapids (I was expecting to)...
    Perhaps I should try it again.
     
  7. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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  8. Misterg

    Misterg Veteran
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    Yes, and really notice the slow rapids! Probably a topic for a new thread though - sorry to the OP for the drift :oops:
     
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  9. David the swarfer

    David the swarfer OpenBuilds Team
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    anything above retractheight will be rapid, this means that small positioning moves at the bottom of pockets and slots will still be slow, very hard to reliably detect the difference between a carving motion and a positioning motion when below materialtop
     
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