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last step with north90 stainless hot-end

Posted by nb99 
last step with north90 stainless hot-end
February 13, 2012 06:58AM
Ready to try my stainless hot-end, last hurdle to adapt it to my groove-mount Greg's extruder,
is the gap between the top of the stainless+PTFE liner and the top of the 16mm diam hole that groove-mount hot-ends seat into.
(there's about 15mm thru the carriage and extruder to the 3mm feed hole under the hobbed bolt - filament is bendy!.)

The construction pages sorta skimp on the layout at the top of the hot-end - obviously can be various arrangements, so not unreasonable..

I guess if I had thought ahead enough I could have cut the SS tube 15mm longer so it butted up to the top of the extruder seating hole.
Thought it was worth a query here in case there was a clever solution that I can't see after midnight... Otherwise a wee rebuild tomorrow night.

(I'm pretty impressed at the temperature gradient - from 185 deg at the bottom to 60 under the heatsink, and 40 above - no fan - I had some difficulty intuiting "thermal insulation using a metal tube")

      |             +----||----+             |
      |             |          |             | Gregs extruder
      |  #          |          |          #  |
      +--#----------+          +----------#--+
 --------#------+                 +-------#----------- X carriage
 --------#------+       |\/|      +-------#-----------
    +----#--------------|  |--------------#-----+
    |    #              |  |              #     | Aluminium heatsink
    +----#--------------|  |--------------#-----+
         #              |  |              #
                        |  |
                        |  |
                        |  |  45mm stainless 6.3 od x 5.5 id
                        |  |
                        |  |
                        |  |
                  +-----   ------+
                  |              |
                  +-----   ------+
                        \  /

Re: last step with north90 stainless hot-end
February 13, 2012 08:50AM
Wouldn't it be better mounted above the carriage? That would make the gap a lot less. Otherwise you need something to bridge the gap to stop the filament buckling.

Re: last step with north90 stainless hot-end
February 13, 2012 02:11PM
Yeah - some sleep helps
I like the quick access of the groove mount, (my new J-head should be here anytime now, so I will now&then be swapping from "good H-E" to "Experimental" )

so I will fabricate a 16mm dia "plug" to go above the heatsink, and experiment with lightening the hsink (it hardly gets 'very warm' atm) until it can be comfortably supported by the groove mount instead of using the extruder securing boltholes.
Re: last step with north90 stainless hot-end
February 14, 2012 12:12AM
Great that you are trying out this design. And you make a good point about the mount.
I think the best solution is to print the 16mm dia plug, as you say.
I don't print my extruders with that hole in it, so i never thought about it.

The heatsink should be exposed to some airflow, otherwise it might overheat in a long print and when using a heated bed. My heatsinks get pretty warm, but i have the bed at 110C and only a 30mm long hot-end (from bottom x-car to printbed).

When you have found a good solution for your situation: edit the wiki pages and help others!
Re: last step with north90 stainless hot-end
February 14, 2012 02:37AM
If heatisnk is wide enough may be its worth thinking of a way to use it also as a carriage with 2 mounting points for extruder. Would be more efficient sink without anything obstructing airflow on top of it.
Re: last step with north90 stainless hot-end
February 14, 2012 04:09AM
@noobman: good idea - but for another time - this exercise was for me to check out the simplest fabrication hot-end with nothing "heavier" than my little drill-press.

@north90: I ended up using an L section piece of aluminium, which is a bit thinner but more surface area for a similar volume of metal, so it looks like it will sink the heat quite nicely.
I had one or two other variations on the basic design and methods, so yes I will add "possible alternatives" notes to the wiki.

I'll have to check out where I can get injection needles here in Auckland...

May be another day or three before I get it all done - as my new J-head has just arrived. That at least should allow me to print up my 16mm Plug with groove mount grooves and embedded nuts - which my old hot-end would not have achieved anywhere near accurately enough.

Anyway - kudos mate on a nice practical simple design and procedure!
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