Not letting go...

Discussion in 'Getting Started' started by Brian Peterson, Jan 22, 2020.

  1. Brian Peterson

    Joined:
    Jun 26, 2018
    Messages:
    7
    Likes Received:
    1
    Hey everyone,

    I had the toolchanger working well (note...had) and it failed halfway through the kraken print. It turns out now my toolchanger can pick up a tool but wont put it down. It goes through the motions of putting the head back and turning the tbar but when it backs up the toolhead is still partially attached and this lead to some crashes. I have tracked it back to the t-bar doesn't reset back to perfectly parallel with the bed. I also found that the tbar can manually be turned by hand with the motor enabled by a few mm. I confirmed this by taking the back cover off and exposing the gears aren't moving, but the screw holding the t-bar to the gear is slipping. Is this normal behavior or did I find the root cause?

    Any ideas how to keep it from sliding? I have some star lock, m3 lock washer coming to try to keep the bar from slipping.
     
  2. Brian Peterson

    Joined:
    Jun 26, 2018
    Messages:
    7
    Likes Received:
    1
    Figured it out. The grub screw on the gear came loose.
     
  3. Paul Meyer

    Paul Meyer Well-Known Member

    Joined:
    Dec 18, 2019
    Messages:
    49
    Likes Received:
    8
    One note here:

    The build instructions say to have the big m6 grub screw in the tool "flush with the surface" (https://e3d-online.dozuki.com/Guide/03+-+V6+Bowden+Tool+Assembly./103?lang=en step 5).

    This worked fine for my v6 tool. For my direct drive Hemera tool (quite a bit heavier) this didn't work as well. Because the dock magnet is recessed into the dock by a few mm, there is a gap between the flush grub screw and the magnet, weakening the grip. To get my Hemera tool to stick to the dock (and not slide back off when the unlocked TC backed away), I needed to screw the grub screw out a bit more so it fit in the recess around the magnet and got closer to the magnet. Fortunately, I had ignored the instructions and not superglued it.

    YMMV.
     
    Nibbels likes this.
  4. Nibbels

    Nibbels Well-Known Member

    Joined:
    Dec 12, 2019
    Messages:
    165
    Likes Received:
    32
    I had some magnets having the same diameter but another height. Both of them combined kind of fit into the dock parts hole length and I added one little piece of paper to have them both completely locked in. I didnt want to glue anything until I am sure that it works.

    So I have two magnets connected in a serial row. In theory they both are not stronger but should have a force which stays strong within a longer distance - a bit. Am I right here?

    ( Those diagrams suggest longer magnets are a bit stronger and the strenght persists within a longer distance, but I am confused about that rightnow. What would a physisist say?
    https://www.supermagnete.de/eng/adh...n/result?paramset=i/d/42/5/2/Pure Iron/10/250 vs.
    https://www.supermagnete.de/eng/adh...n/result?paramset=i/d/42/5/5/Pure Iron/10/250)
     
  5. Paul Meyer

    Paul Meyer Well-Known Member

    Joined:
    Dec 18, 2019
    Messages:
    49
    Likes Received:
    8
    It’s been a *long* while since college physics, but I think each magnet is generating a certain “strength” of magnetic field, looping around from one end out through space to the other. When you put two of them together, the fields of each channel through the other, out the ends and around. The total strength coming out each end would therefore be 2x for two magnets.

    Not sure how much practical impact that has.
     
  6. Brian Peterson

    Joined:
    Jun 26, 2018
    Messages:
    7
    Likes Received:
    1
    Interesting idea but I followed instructions and glued everything. Anyone know of any STL for the docking part? My newest problem is T2 keeps falling. It definitely looks like the magnet isn't grabbing the grub screw enough.
     
  7. Nibbels

    Nibbels Well-Known Member

    Joined:
    Dec 12, 2019
    Messages:
    165
    Likes Received:
    32
    There are CAD files somewhere on thingiverse. And on other places.

    I tried to print the docking part. And I turned the round dock "nail" parts out of a cheap M5 threaded rod.
    Screenshot_4.jpg
    But I was much happier when the original parts arrived. I have been ordering them seperatly using secret links within the e3d-online shop.

    My experience is, that you might want to have a close look at the dock position to have it in sync with the tool grabber.
    There should be some play to adjust the dock.
    When my printer got that Z-angle orelse the x-coordinate in config.g out of specs it pulled down the tool as well. My problem was a slightly wrong angle and I adjusted the x-coordinate atop of that. But I first had to fix the angle, then find the right x-coordinate.

    I read one post in which the author adjusted all x-coordinates for a tool but forgot one line. That might drop your tool as well.
     
    #7 Nibbels, Jan 24, 2020
    Last edited: Jan 24, 2020
  8. Brian Peterson

    Joined:
    Jun 26, 2018
    Messages:
    7
    Likes Received:
    1
    You post pointed me in the right direction I think. I noticed the tool was not pushed all the way back and had a 2-3mm gap with the back. That really isn't bad but I noticed when the tool would pick up a new hotend and clean it forward and back it vibrated some of the idle heads towards the magnet. I also noticed some of the gaps got slightly wider. I am going to try adjusting and see if that resolves the issue.
     

Share This Page