C not homing after unlocking

Discussion in 'Getting Started' started by Andy Cohen, Sep 20, 2019.

  1. Andy Cohen

    Andy Cohen Well-Known Member

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    I recall seeing a post here on this topic on this forum before but now I cannot find it. For T2 and T3 on my machine C does not fully return to home on tool unlock. It does not get completely horizontal and as such does not fully release or will not full engage on lock.
    My bet is it is going out of it's register due to friction between the tool plate and the T lock since the docks cannot be adjusted. The senseless homing is too sensitive maybe?
    I recall a post where it was suggested ithat ncreasing the voltage to the C stepper could solve it and I recall it did. It's currently set to 400 mA in the config.

    Can whomever wrote that post point to it please...
     
  2. Andy Cohen

    Andy Cohen Well-Known Member

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  3. Amr

    Amr Well-Known Member

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    HI Andy

    I was having this issue when I first built the machine, the solution was to raise the current percentage while homing c in homec.g file, but this was already added to the GitHub files on the 16th of august so it should be there if you built your machine after that date.
     
  4. Andy Cohen

    Andy Cohen Well-Known Member

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    OK but did you solve it? Seems to me the setup assumes the dock is within a level of tolerance which we cannot adjust to.

    Is "homec.g" used within FW based commands such as T-1?
     
  5. Amr

    Amr Well-Known Member

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    Yes this did solve my issue, but if this is the setting you have already then I think you might be having a different problem. One other issue was in the Tprex.g and Tfreex.g gcode files where the location of pickup and drop of needed a to be adjusted specifically the Y value needs to be 243 not 242.5 I checked the github files now and it is still 242.5 so maybe try this change.

    PS: I would do a manual Move to the pickup location slowly while making sure it will not crash and note the final coordinates just to make sure you are not causing any crashes with the changes you can do this by putting in the commands in the tprex.g into the gcode console one by one..and do this for all tools
     
  6. Andy Cohen

    Andy Cohen Well-Known Member

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    I think the intention of 242.5 is to get it close enough to the magnet so it gets pulled into the dock.
    My experience tells me that moving a homed Tbar manually into the docked tool must go through the Thole without touching. I adjusted accordingly and now every thing seems to work ok until I run the test file. It's tricky to see what's actually happening but it seems to me that it's going out of register in either y or c... too hard to tell. If I run T0-3 commands manually into the console it works reliably. When it runs fast with the test file it misses at T3.
     
  7. Spoon Unit

    Spoon Unit Well-Known Member

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    This is the only way to truly be sure and own your own machine and settings. I had mine tweaked well but when i fitted the physical endstops I had to move everything a spot, so I just redid them all again. It's really worth doing this carefully as you can then be sure you'll never have a problem, but it is nerve wracking at times.

    This is key. Using the console, I used something like this to home in slowly

    G53 G1 X-5.5 Y200 F5000

    Then real slow to test your docking

    G53 G1 Y230 F250
    G53 G1 Y235 F250
    G53 G1 Y240 F250

    This is really slow and you can nudge X at any time to perfect the dock alignment. When you have it all sorted adjust your tpre and tfree.

    You can simplify Tpre and Tfre so there's not so much to change also. X is repeated multiple times in the original scripts:

    https://github.com/e3donline/RepRapFirmware-SD/blob/master/sys/tpre0.g

    e.g.

    https://github.com/e3donline/RepRapFirmware-SD/blob/master/sys/tpre0.g#L11
    https://github.com/e3donline/RepRapFirmware-SD/blob/master/sys/tpre0.g#L14
    https://github.com/e3donline/RepRapFirmware-SD/blob/master/sys/tpre0.g#L17
    https://github.com/e3donline/RepRapFirmware-SD/blob/master/sys/tpre0.g#L29

    I removed X on all but the first line to reduce the work on any future changes.

    My current tpre0.x looks like this now:

    Code:
    ; tpre0.g
    ; called before tool 0 is selected
    
    ;Ensure no tool is selected
    ;T-1
    
    ;Unlock Coupler
    M98 P/macros/Coupler - Unlock
    M400
    
    ;Move to location
    G53 G1 X-6 Y200 F50000
    
    ;Move in
    G53 G1 Y239 F50000
    
    ;Collect
    G53 G1 Y243.5 F500
    
    ;Close Coupler
    M98 P/macros/Coupler - Lock
    
    ;WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!
    ;if you are using non-standard length hotends ensure the bed is lowered enough BEFORE undocking the tool!
    G91
    G1 Z10 F1000
    G90
    
    ;Move Out
    G53 G1 Y165 F4000
     
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  8. Andy Cohen

    Andy Cohen Well-Known Member

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    Yup! For sure you need to adjust per your machine. I have it working OK, but every now and then it misses a lock such as when I manually select a hotend to heat... I assume it is a different setting in a different config file.
     
  9. Spoon Unit

    Spoon Unit Well-Known Member

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    When you say, manually select a hot end to heat, do you mean that you press T0 on the DWC? I don't believe it's a different file if so, I think it will still run tpre0 and tpost0.

    One thing that did catch me out when tweaking all this is the when you switch from tool coordinates to absolute coordinates, the machine actually physically moves before moving in absolute coords, which is a bit strange and can lead to a nasty head crash. I think it's worse than that actually, something like, when T0 is dropped, it at some point feels it necessary to move by the tool offset before taking the next step. In any case, what I observe is that if I don't move back to something like Y=150 after dropping a tool, I can get a smash of the tool head into a tool.

    I missed lock is most likely the result of not being quite far enough in, or perhaps a missed step in X or Y. To get my Y absolutely maxed before locking the coupler I moved to 240, then slowly move forward 0.5 until you hear it fail. Then look at your Y and set the pick up/drops to that number. I think 240 is probably safe to move to at high speed for all setups, but then push in slow to the final position.

    Early on I had drops that wouldn't engage the magnet as they were slightly out. That extra 0.5 can ensure it connects.
     

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