IDEAS adding a "send Z to bottom" menu option

Discussion in 'Guides, Mods, and Upgrades' started by R Design, Jun 8, 2016.

  1. R Design

    R Design Well-Known Member

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    Stian Indal Haugseth likes this.
  2. Alex9779

    Alex9779 Moderator
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    Thanks to @Stefan the Move 10mm menu in my firmware includes Z now...
     
  3. Chase.Wichert

    Chase.Wichert Well-Known Member

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    woot
     
  4. Alex9779

    Alex9779 Moderator
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    Well a few days, since 30.05...
     
  5. R Design

    R Design Well-Known Member

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    Excellent.

    I'm on RC6 but not your version. Will look into it at the next update.

    Quite useful to have a "go to bottom" menu item too, no?

    (Then you can make coffee whilst it goes down!)
     
  6. Alex9779

    Alex9779 Moderator
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    In what situations will you need that? I move it mostly to 50 or 100 to clean the nozzles or to dismount or mount them... Dunno what I should do at the bottom...
     
  7. R Design

    R Design Well-Known Member

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    For maintenance.

    Greasing the rods... Re-doing the rod /motor commissioning. Checking the lead screw behaviour....

    That kind of thing.

    Also to show someone the size of the build volume! ;-)
     
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  8. Alex9779

    Alex9779 Moderator
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    Yay maybe. I'll put it on the list...
     
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  9. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    Like @R Design said. I could have used it the other day when lubricating the shafts. Not needed very often but very handy when you do :rolleyes:
     
  10. PsyVision

    PsyVision Moderator
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    You can use custom buttons in OctoPrint and just make it send a go-to absolute position after a home or similar? Some host software allows a similar thing. But I guess you want it in the firmware :p
     
  11. Alex9779

    Alex9779 Moderator
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  12. PsyVision

    PsyVision Moderator
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  13. R Design

    R Design Well-Known Member

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    Coolio!

    Tested? ;-)
     
  14. Alex9779

    Alex9779 Moderator
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    I tested it. Worked after homing without homing and right after start it homes first. Tough it is problematic if you are at Z300 and home because the firmware wants to do a 4mm lift...
     
  15. Alex9779

    Alex9779 Moderator
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    Oh well think we have to discuss this a bit more.

    The problem is that we have configure to raise Z before homing by 4mm. The is done if the machine is not homed and you home, then Z is raised by 4. If the box is homed or at least the firmware knows the position then that hop is not done if you hit home again.
    This is good for example if the motors powered down but you are at Z0, then you home it raises 4mm so the nozzle does not stretch over the plate.
    But if the box is at Z300 there is no space to do that hop. In the config of Marlin there is the a warning you should have that space.

    So I see three alternatives here:
    1. remove the raise before home
    2. do not move to 300 but only to 295 or 290
    3. after moving to dock after a print move the bed up at least 4mm
    I don't like 1 because I don't wanna scratch the nozzle over the plate. Homing if Z=0 happens often to me because when I start a print I home. If I homed before the nozzle sits at Z0 and so it would scratch if the offset is not 100% correct...

    2 would help but there is still the problem what if we printed to Z300? The bed is at max, the head is at the dock, we remove the print and then? If we home we have the problem, we have to remember to move the bed up, this will work even if we didn't home before and the do the next homing sequence.

    At the moment I prefer 3. Because this does not hurt, the head is out of the way after docking and 5mm are always there to move the bed up.
    Homing with a finished model on the plate would crash the head anyways.

    So what do you think? 1 and 2 would be change to the firmware, 3 would be a change to the end script. 1 and 2 would help everyone but with drawbacks, 3 only people who know about the problem or use (at least at the moment) my profile or hack it in their own profiles...
     
  16. R Design

    R Design Well-Known Member

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    My vote is for "2". Going to 295 is as good as going to 300 from a time saving perspective and for most maintenance tasks makes no difference.

    The utility of using "go to z max" is to get there quickly and only an idiot would use it when it's already at 250 (once they understand by experience it launches an autohome first).
     
  17. mike01hu

    mike01hu Well-Known Member

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    3, for the reasons you say but near the bottom is good enough as it is no effort to tweak it down a bit further if required.
     
  18. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    Maybe I don't get it. But lowering bed to the bottom should first do a full auto home. Then go as low as possible. If you do not home Z before lowering it will crash. And if you do not home X/Y before Z then the bed will crash in the nozzles. I did this in OctoPrint.

    As long as we do not have endstops at the bottom I think moving to bottom should include a full auto home.

    PS. A bit of topic but I'm considering adding dual Z endstops for dual Z stepper on RUMBA. Should have two on the bottom as well :) Maybe a pressure sensor strip along all axis where there is no endstop and wire it to the emergency stop pins :D
     
  19. Alex9779

    Alex9779 Moderator
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    I built that in, if the box is homed aka the machine knows the current position of every axis then I do NOT home, it not then I home before moving to the bottom. The function I added is safe. I also mentioned that in the commit message...

    The problem I was talking about is related to the raise of the Z of 4mm when you home and the machine does not know the current position. This is a safety feature active in my firmwares, the official ones don't have this activated, but as I described above I find it useful...

    Here is what the config help says:
    Code:
    #define MIN_Z_HEIGHT_FOR_HOMING 4 // (in mm) Minimal z height before homing (G28) for Z clearance above the bed, clamps, ...
                                        // Be sure you have this distance over your Z_MAX_POS in case.
    So if you are at the max then you should have that height additionally because if it happens that the firmware does not know the coordinates anymore, that happens when the motors power down, the bed is dropped by 4mm before the homeing is done. And in our case we do not have those 4mm...
     
  20. Alex9779

    Alex9779 Moderator
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    BTW I am for 3, that is three votes, @R Design looses... ;)
     

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