Hemera Docking

Discussion in 'Tool heads & ToolChanger' started by Paul Arden, Aug 10, 2020.

  1. Paul Arden

    Paul Arden Well-Known Member

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    There is a similar thread on this topic but it seems that was a different issue that was solved by the poster so I’m starting a new thread for the issues I have.

    I’ve upgraded to four Hemera tools using the design here. Things mostly went smoothly, though I had to route the thermistor cable around the coupler side of the tool rather than the docking size since the Micro-fit 3.0 connector would otherwise hit the acrylic panel.

    My main problem is the alignment of the tool on the dock. With the fan shroud from the original design the shroud hits the acrylic before the top of the tool can fully dock where the magnet is and the weight of the tool then keeps it from fully docking.

    To get around that I reduced the flat section of the fan duck that hits the acrylic after which the tool docks and is held by the magnet. However after attempting commissioning I realised the tools a sagging somewhat, even though they are right up against the magnet.

    This seem to be be mostly from the weight of the Hemera. I suspect the fan duct hitting the acrylic was actually intentional and designed to keep the tool from sagging. However it looks like it really needs to be somewhere between my reduced size and the designed size.

    To test that I used my reduced sized duct and put some layers of tape on the acrylic behind it. I layered up the tape until the tool no longer fully docked and then took one layer off. It seems very touchy, one either way and it either doesn’t dock fully or sags.

    My concern is the sag is enough that the docking is pretty rough and I could definitely see there being some issues down the road where it might drop a tool or fail to pick one up (I already had a case where the coupler wouldn’t lock).

    So two questions for @Greg Holloway on the design.

    1. Is it the intension that the fan duct sits flush against the acrylic to keep the tool vertically straighter?
    2. What is the equivalent Y value during commissioning (for the V6 tools it was 243) for seating the docks? In my case right now I’m at 227 which seems to work.

    There doesn’t seem to be as much play in the docks when seated on top of the printed dock adapters as there was with the V6 tools where they were directly on the metal frame.

    Has anyone else who upgraded to Hemera struggled with this part?
     
  2. Greg Holloway

    Greg Holloway Administrator
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    Yes, make sure you have the latest fan duct on thingiverse as there is a change which tackles the vertical alignment.

    The number depends on your setup, but 227 seems about right.

    Due to the square nuts in the Hemeras there is a lot of 'adjustment' in the position of the Hemera. It can take a bit of time to find the best position for the tool plate and dock receiver.
     
  3. Paul Arden

    Paul Arden Well-Known Member

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    Originally I had the old one but I had already re-downloaded and reprinted. The latest one seems to have 6mm thick struts on the acrylic side of the fan duct. With that size I haven’t been able to get any do fully seat, at 4.5mm it doesn’t hit the acrylic and at 5.5mm one of my tools works well, though all can at least fully seat, where as none will at 6mm.

    This definitely seems to be the case. I realised staring at the printer that the top of the docking plates should be flush with the top of the top plate of the machine. Only one of my tools is really close enough even when pushed fully up manually against the dock so it seems they need some shifting on the Hemera. I guess I will loosen everything up and play with that.
     
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  4. dc42

    dc42 Well-Known Member

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    Interesting! On my two Hemera tools (built with Duet 3 Tool Boards) I found that in order to get secure docking, I had to ensure that nothing on the tool contacted the acrylic sheet, and I extended the docks forwards a little to achieve that. However, I also found that I needed to put a little grease on the docking pins (including the undersides) to achieve secure docking.
     
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  5. Paul Arden

    Paul Arden Well-Known Member

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    I’m still trying to get mine right and I have definitely found some latitude by just loosening the screws for the backplate and other parts and shifting them before retightening. However I’d say the hole for the coupler still sits a touch too low.

    The problem I find is that as with yours to get secure docking I can’t have the tool fully engage against the acrylic. In my case I did that by reducing the size of the fan duct structs rather than extending the dock but I suspect the effect would be identical. However if it doesn’t hit the acrylic it sags so the hole for the coupler ends up too low and the coupler doesn’t go in without clunking the tool.

    If I use the full size duct and it hits the acrylic fully then the tool doesn’t dock (same problem as you had). I’m still fiddling with it all trying to find the best approach.

    Once I realised that really the top of the toolplates should be flush with the top of the top plate though I was at least able to gauge how close I am to getting it right without having to run the printer.
     
  6. dc42

    dc42 Well-Known Member

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    It's odd that mine are OK then, they don't sag sufficiently to cause a problem when coupling. Perhaps the printed dock extender parts I am using raise the dock a little more than yours. Or maybe I tightened the screws a little differently and that has raised the coupling plate a little.
     
  7. Paul Arden

    Paul Arden Well-Known Member

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    I did download your dock extender and they are both 15mm high, however based on all of of the changes I have been trying screw tightening and positioning of parts within the amount of play they give seems critical. I think I could loosen and tighten things 5 times and get 5 different results.

    What I did find yesterday was that if I reduce the height of the receiver support piece (the part that ‘holds up’ the receiver and connects to the top bolts of the dock side of the Hemera) then I was able to get the first tool to fully and reliably dock. I reduced its height by 0.5mm and that seems to have helped with the angles. With that change I was able to use the original full size fan shroud.

    On the second tool I wasn’t as lucky, however I think I need to tune it a bit further. It’s definitely pretty fiddly. The reason I ended up changing the size of that top support was because I found when I removed it all together (obviously not to be done for actual use) everting started to dock properly.
     
  8. Paul Arden

    Paul Arden Well-Known Member

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    I did a lot more fiddling today and printed all 0.5mm shorter receiver supports, loosened all the screws and then switched between the many fan duct thicknesses I now have to get each dock working and aligned. I’m not really happy that I am using different size fan ducts on each tool to do this but in the end it seemed to be the simplest way. They are all resting against the acrylic at this point as well, so they don’t sag but I can still lift them by hand a little. I’ll commission it now I think and see how I go.
     
  9. dc42

    dc42 Well-Known Member

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    I'm glad you got it working. I found that when the tool board connectors were resting against the acrylic, I couldn't get the magnets to engage properly. Maybe there's something about using a tool board that changes things?
     
  10. Paul Arden

    Paul Arden Well-Known Member

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    Given how sensitive my success was to the amount of stick out on the fan ducts I’d say that could definitely make a difference. From the pictures in your blog the toolboard sits on top of the fan duct so I imagine you already had to hang it out further to give clearance for that?
     
  11. dc42

    dc42 Well-Known Member

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    Yes, even with the feet of the plastic printed part made thinner, the tool board sticks out more than the fan duct, so I had to extend the dock.
     

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