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Hot-end lining film idea

Posted by anwe79 
Hot-end lining film idea
January 26, 2015 07:36PM
I think I've stumbled over a possible solution looking for a problem winking smiley

I've been thinking for a long while about hot-end construction and how to improve on current designs.
So far it's all arm-chair engineering though.
Anyway, my mind is hooked on using a ceramic insulator.
I've seen the "Chess" one by hp_ but I haven't tried one yet, though I really like the design.
Maybe it could be improved upon by making it out of a more porous material, but what do I know, I've never seen one IRL...

Anyway, I may have found the perfect solution to the (possibly) high friction in the ceramic insulator bore:

Collodial graphite coating.

(also known as aquadag, but that's just a trademark)

It has a low coeffcient of friction (0.22) and high service temperature (316 ℃, peak 1204 ℃).

Does anyone have some collodial graphite and ceramic hot-end handy to try? (I seriously doubt it...)
In lack of aquadag maybe just polishing the bore with a graphite coated Q-tip could make for an interesting experiment.
Possbily one could use a pulverised pencil "lead"... I know pencil lead works well for lubricating guitar bridges.
Stove black is also mostly graphite, but I'm not so sure I would want those solvents inside a hot end...

Anyhow, all I have personally right now is a J-head, so I can't really try this myself at the moment.
The graphite will probably just increase the friction over PTFE.
That's why i'm just throwing this out there.

Let me know if you try it, in a ceramic hot-end or otherwise.
Meanwhile i'm going to search for some aquadag and a ceramic hot-end.
(The Chess piece seems to be out of stock, in Europe at least)

I suppose this could fail horribly somehow, maybe if it rubs off too quickly, or it contaminates the plastic.
Needless to say, i'm not going to be responsible if you ruin your hot end, do this at your peril.

Re: Hot-end lining film idea
January 27, 2015 05:20AM
... someone can try mixing graphite into sodium silicate and impregnate the bore - it's fixing the graphite and seal the porosities of the ceramic or soaptstone (if one has the old prototypes) ...

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Re: Hot-end lining film idea
January 27, 2015 12:48PM
Ahh, waterglass?
I hadn't thought of that but it sounds like a good combination.
In the name of caution maybe try plain graphite first.
Waterglass may be a bitch to remove (i don't know, maybe it's not that hard with heat?)
I have a feeling plain graphite may be enough, if it's rubbed with suffcient force.
Sort of like a pencil strike but rubbed onto the whole surface. It all comes down to surface though. I tried stove black on a spare piece of pcb last night and it seems to stick ok with some rubbing. That does contain solvents though, so plain graphite may be a whole different story.

Re: Hot-end lining film idea
January 27, 2015 04:37PM
I'm not convinced heat-break insulation is currently a limiting factor in hot-end designs.
No matter what exotic material you choose, there will always be a comparatively massive volume of regular plastic right in the middle.

The coating may be effective in traditional all metal designs though. Right now it seems friction and surface finish is very important for reliability.
Re: Hot-end lining film idea
January 28, 2015 03:10AM
Yep, the plastic is a fairly good thermal conductor, you're right. I originally stumbled over aquadag when i was investigating means to do diy through hole plating of pcbs. Graphite is a common base coat for plating non conductive surfaces. Revisiting that alley, I was thinking that one could possibly electroplate the internal bore to make an internal heatsink surface, that would connect to a traditional heatsink at the top. All very contrived contrived I know, but it's just an idea...

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