How the hot-end design can evolve

Discussion in 'General' started by shadowphile, Jan 28, 2018.

  1. shadowphile

    shadowphile Member

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    I have always disliked the 'threaded-nozzle and threaded-heatbreak in a threaded-block' approach, too many pieces that all need each other just to stay firm. Loosen one and they all loosen. It seems like a cheap-and-easy design concept from the early days that never evolved!
    I would like to change nozzles between jobs without the nozzle height changing, or having to worry about breaking the heatbreak. My imagination starts with an unthreaded nozzle and works backwards from there using an approach similar to how the heater cartridge is clamped in place.
    I don't do job runs, just a series of prototypes that may have very different print requirements so quick-swapping would be high priority for me.

    Has e3d investigated a standardized design that would allow a quick low-stress way to swap nozzles with predicable positions wrt the effector? I found the shiftable heatblocks in the multi-nozzle designs interesting.
    thanks
     
  2. dc42

    dc42 Well-Known Member

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    RepRapPro had what they called a Quick Set hot end, see https://reprappro.com/documentation/huxley-duo/hot-end-assembly/. The heat break and nozzle were a single stainless steel piece (which of course didn't leak because there wasn't a join, but made it harder to change nozzle size) with a threaded end to attach it to the threaded heat block with a brass nut. The cold end of the heat break was not threaded and was clamped into an aluminium part that was attached to the heatsink. The aim was that it was very easy to get the two nozzles the same height; you just loosened the clamp screws, dropped the two nozzles on to the bed, and tightened them.
     
  3. shadowphile

    shadowphile Member

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    Isn't that a description of the Chimera (and probably Kraken)? But you have to deal with the heater and thermistor connections so less than ideal. The less the wiring is jostled the longer it will last before the inevitable breaking.
     
    #3 shadowphile, Jan 28, 2018
    Last edited: Jan 28, 2018
  4. shadowphile

    shadowphile Member

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    I had a design in my head with a more complex heater block. It would have a horizontal slit in it so an unthreaded nozzle could just be pushed in and tightened like the heater is. The heatbreak would stay the same and thread down into the block until it hits an internal ring machined into the block (or it could use the same clamping-on-a-smooth-surface approach as the nozzle.)
    The nozzle would be pushed against the opposite side of that ring. The in-facing surface of that ring would be exposed to the molten plastic so not sure if that would be a problem. Any buildup of plastic between the ring and nozzle could be cleaned off with a few twists of a little tool before putting in the nozzle. The only issue I can see at first glance is the sideways force on the heatbreak when tightening the clamp on the nozzle, and the more complex coupling of heat flow. A zero-insertion-force concept (electronics people know what I mean) for the nozzle would be ideal.
    As printers get more sophisticated and commercialized we are seeing more components that can't be made in a garage, but that is a given if we expect performance to evolve forward.
     
    #4 shadowphile, Jan 28, 2018
    Last edited: Jan 28, 2018
  5. dc42

    dc42 Well-Known Member

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    I don't see how that design would prevent leakage of molten filament from the joint between the nozzle and the heat break. The filament will find its way through any small gap. The present E3D design relies on the end faces of the nozzle and the heat break being machined flat and screwed tightly one against the other.
     
  6. shadowphile

    shadowphile Member

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    You have a point. I will ponder alternatives.
     

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