An Alternative to Groovemount

Discussion in 'E3D-v6 and Lite6' started by Rory, Apr 3, 2017.

  1. Rory

    Rory Member
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    What’s the problem?

    Here at E3D we’ve always used groovemount on our hotends as the means of attachment. It's been the standard way to mount a hotend on a printer since the makergear standard was introduced. When introduced, it was intended for attaching a hotend to piece of laser cut wood. This is something we don’t really do anymore. It’s a method well-suited to making prototypes as it needs a minimum of skills and lathing tools, but it does have a few issues:

    • Relying on 2 parts that simply push together requires that the parts are really precisely made. Even slight variation can result in a poor fit, with heat sinks that are either hard to push into a bracket or that wobble around during printing. We do our best to avoid this by using good machinists and doing random spot checks, but it’s still an issue we’d like to eliminate completely.

    • Mounting brackets can wear down from repeated removal and replacement of the hotend, leading to a once well-fitting hotend becoming wobbly.

    While these issues don’t make groovemount unusable, we want to come up with a better fix.

    The solution
    We’ve thrown around a few ideas, but one that we’d like to take forward is kinda like a light bulb, consisting of a threaded socket and a heatsink with matching thread. The idea is that the socket would be permanently attached to the printer’s carriage. The hotend would then be screwed into it (just like screwing in a lightbulb!). One small addition is the that there is also a hole for a grub screw in the socket, the idea being that the grub screw prevents the heatsink from coming loose. It also lets you adjust the orientation of the hotend anywhere in a 360° arc - handy if you have a cooling fan very close to the heater block. It also lets you adjust your Z-height, for easy leveling if you have 2 or more hotends.


    [​IMG]


    Using threads has the benefit of not needing anywhere near as much precision as groovemount. Metal-on-metal threads will also take an incredibly long time for appreciable wear to develop, so that you can take it out and tinker as much as you like. This makes it easier to design for - capture a nut or use a heat-fit insert type, just tap the part or do something completely new altogether. Check out David Crocker’s PCB delta printer using an early prototype of this design.

    https://www.duet3d.com/forum/thread.php?pid=10669#p10669


    [​IMG]

    We need you!
    We have about 10 sets of prototype parts here, and we’d like to get your thoughts and add any suggested improvements so that we can create the most design and user-friendly solution.

    If you’ve read this far, hotend mounting is clearly something important to you and we’d like to get your input. If you are interested in testing one, message me with a shipping address and a little bit about your 3D printing experience, and if you are lucky we will send you one.


    Some data about the parts:
    • Functionally the same as the V6 1.75mm universal heatsink.

    • Uses M14x1 thread for the main thread (this could change depending on feedback)

    • Same overall height as a standard heatsink

    • Combined mass of collar and heatsink is 10g more than a standard heatsink.

    • 3x M3 holes for collar.


    [​IMG]
     
    #1 Rory, Apr 3, 2017
    Last edited: Apr 3, 2017
  2. mhackney

    mhackney Well-Known Member

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    Rory, I like this idea - especially the ability to rotate the hot end into a preferred orientation and lock it in place. Is the grub screw nylon or other non-damaging material?

    And I suppose the weight fanatics could mill/turn some excess material off to lighten the socket.

    One comment on the thread, if it were a bit courser it might be possible to 3D print the socket as part of an integrated socket/effector. Have you thought about that?

    cheers,
    Michael
     
  3. ianlee74

    ianlee74 Member

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    Love it! The sooner we can escape groove mount and get to something more sturdy the better. I like the idea of having two separate parts. Like Michael, though, I'm a bit concerned about a typical grub screw going into (and damaging) aluminum threads.

    While you're breaking the mold... Have you considered something that might be compatible with the Cyclops/Chimera mount?
     
  4. elmoret

    elmoret Administrator

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    As far as I can tell, the grub screw doesn't seat on the threads.

    Perhaps a silly question, why not drill/tap the triangular hole pattern into the top of an existing heatsink? That way a single heatsink is cross-compatible with groove mount style setups. Would be cheaper too from a machining perspective.
     
  5. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    I like the idea but as I see it it will not help much in dual setup. The heat block will twist with the heat sink when you have to adjust the height. I would go mad if one of the heat blocks was not aligned to the other :rolleyes:

    We would need to turn the top ring as well every time we need to adjust the height.
     
  6. Rory

    Rory Member
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    Michael, the plan was to use a regular black oxide / stainless grub screw, the idea being that you would screw up against the plain portion at the top and it wouldn't matter if it got slightly marked. If you were screwing against the threaded portion this would be a major concern.

    I am considering a different thread already, I picked fine thread as this gives the most rotational adjustment and M14 as it's around the right diameter. Talking with our machinist M12 would still give enough wall thickness for the Bowden coupling and standard thread pitch should still give you enough rotation. M12 standard thread should be fine for a printed socket and you can also readily find nuts in that size so should give the most options?
     
  7. Rory

    Rory Member
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    Hi Ian, I didn't make it particularly clear in my post, the grub screw would clamp against the plain section at the top, even the thought of screwing up against threads is not good.

    I like the idea of having the same mounting pattern as the Cyclops / Chimera, I'll look into it. First thoughts are that you'd lose rotational symmetry i.e it would only fit in 1 orientation instead of 3, it may also make it more difficult to machine with an irregular hole pattern. Anyway, its still something I'll look at.
     
  8. Rory

    Rory Member
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    Hi Tim, I love the idea of integrating flange mounting and groovemount for an all in one solution. That said I would like to explore having thread on the top of the heatsink and being able to attach that way, eg. through a plate as per David Crocker's Delta printer.
     
  9. Spoon Unit

    Spoon Unit Well-Known Member

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    Just to echo the sentiment about grub screw wear, whatever is selected here should work well and have no chance of losing shape. The grubs used in the Titan to connect the hobbed bolt to the shaft are too small, or the metal is too soft which ultimately leads to a poor feel and potentially needing to acquire new parts. This thing looks chunky enough to use a large grub, which probably won't suffer the same problem. Is one grub sufficient here?
     
  10. Rory

    Rory Member
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    Hi Stian, I can see your pain, you could rotate the heater block by itself and screw it a little more or less along the heatbreak (you can get about +-45 deg before you get any issues), although this is really a dirty hack and I can't officially recommend it.
     
  11. Rory

    Rory Member
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    Spoon, I don't have enough info yet on wear as the only way to ascertain this is from testing (hopefully by giving out samples for testing, you guys will have good input on this). Currently this would use an M3 grub, like Titan. However the difference here is that the M14 main thread should be taking all the force, the grub screw is just for retention and doesn't have to handle any rotation loading like Titan, so really doesn't need to be that tight.
     
  12. Spoon Unit

    Spoon Unit Well-Known Member

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    This problem is crying out for a solution with a cylindrical heatblock.
     
    Stian Indal Haugseth likes this.
  13. A Dragon In A Pie Costume

    A Dragon In A Pie Costume Well-Known Member

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    the idea sounds good, but I can see issues with x in 1 out hotends, especially like the diamond where the inputs are in different angles to each other

    but for idex or single nozzle this looks good
     
  14. mhackney

    mhackney Well-Known Member

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    All, I think the idea here is to come up with a much better mounting alternative for the V6 and its successors and not to develop an all-in-one generic mount for every hot end. As it is today, Diamond, Cyclops/Chimera, Kraken and others all have unique mounts (Diamond being the most difficult of the lot to mount). The issues with the Groove Mount are two-fold in my experience:
    1. The hot end often is not held securely enough and can wobble and twist. Some of this is due to variations in the slot height on other hot ends that claim "Groove Mount" but are off and some is due to aftermarket aluminum mounts that also are not the standard thickness. I put a small dab of medium CA on ALL my groove mounts to ensure they stay put.
    2. It is surprisingly time consuming to remove a groove mounted hot end in some configurations (especially on deltas that raise the hot end to reclaim Z height).
    It was trivial to design and print or machine adapters for my top-screw-mounted hot end like Kraken, Cyclops and other 3rd party hot ends. This idea takes this one step forward by using a "socket adapter" to allow the hot end itself to be easy removed and positioned. I really like this idea and look forward to actually trying it out.
     
    Rory likes this.
  15. bvandiepenbos

    bvandiepenbos Member

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    I like this idea.
    Making the thread M12 vs. M14 is a better choice, M12 would be backward compatible with existing groove mounts on many delta printers. You could simply slide threaded section into groove mount and secure down with nut on top. Or use proposed collar as a nut. Although it seems rather bulky.

    I am curious about the outside diameter of collar and what is the bolt circle diameter of the (3) M3 screws?
     
  16. bvandiepenbos

    bvandiepenbos Member

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    I would hope the M12 thread would be continued all the way up to top. This would provide better mounting options.
     
  17. Rory

    Rory Member
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    In terms of dims for the M14 prototypes I've had made up, the collar is 26mm OD and the hole PCD is 20mm. I've started redesign for M12 and the collar is now 24mm OD with a PCD of 18mm.

    I'm not sure I follow what better options continuing the M12 all the way to the top allows you to achieve, that having the plain section prevents you from doing?
     
  18. bvandiepenbos

    bvandiepenbos Member

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    With M12 thread all the way to top you could slide hot end into 12 mm hole in effector plate and put a nut on top to retain. Simple... no threaded collar with 3 tapped holes and grub screw needed.

    The more I think about this, a collar is overly complicated and not really needed in some instances? ...at least for delta printers or bowden tube configuration.
    That said, I do see the value in the collar/socket for direct drive mounts.
    Seems like running thread all the way off the top would neatly address both situations.

    How will M12 threaded hot end fit into direct mounting into Titan extruder, threaded insert I suppose could work.
    Like the bowden insert does now.?
    But that od is 16 mm correct?
     
  19. William Cook

    William Cook New Member

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    Shut up and take my money.
     
  20. Ryan Carlyle

    Ryan Carlyle Member

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    How about a jam nut instead of a set screw? It'll be a lot more robust, and allow for some additional mounting options (like clamping onto a simple plate hole).

    Basically you would extend the M12 thread on the heatsink a bit longer (eliminate the setscrew flat section) and put the jam nut on the lower side of the flange collar.
     

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