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Posted by HanClinto 
December 17, 2008 11:17AM
As I was reading yet another conversation about the troubles with heaters melting the rest of the plastic extruder, I started wondering if we could use more ceramic insulators. "But where to acquire ceramic parts?" I wondered, and then thought about the possibility of extruding straight clay ( [www.diynetwork.com] ) -- either traditional fired clay or some sort of air-dried clay polymer.

I searched the forums and didn't see any references beyond the metallic (bronze / silver) clay discussions.

Has this been brought up before? I know the torque and pressure issues for extrusion would be significant, but the possibility of it as a material intrigues me. The price is certainly right -- as they say, "clay is dirt cheap".

* Very heat tolerant and ideal for working with high-temperature materials
* Cheap and plentiful source material, from 1st to 3rd world

* Likely need to be fired after extrusion
* Parts can be brittle, and while harder, it wouldn't be nearly as strong as HDPE or ABS
* Shrinkage would need to be taken into account when scaling models to aim for desired post-firing final size.
* Getting the water / clay ratio correct for every clay / humidity could be tricky. Even a single batch of clay could dry out during a single printing if not properly sealed / hydrated.
* Potentially higher torque requirements for extrusion

Still, for making things like heater assemblies, the idea of clay intrigues me a bit. I'll keep pondering, but wanted to throw that out there. If there's a previous discussion that I'm missing, please enlighten me.



Edited 1 time(s). Last edit at 12/17/2008 03:04PM by HanClinto.
Clay and/or other ceramics?
December 17, 2008 04:15PM

I recall there being some forum discussions on ceramics (specifically machinable ceramics like Macor) as well as soapstone. The cost of Macor (and similar) discouraged me, as did the need for carbide tools to work it. I think somebody had a blog post about a soapstone barrel that didn't live up to hopes.

I've been thinking about ceramic/insulated standoffs for the Nichrome connections -- the flying leads make me nervous. Keystone makes these. For example part # 7710, 1/4 inch diameter, 1/4 inch long, with a 6-32 tapped hole.) These are a bit bulky (and costly {2.73/each at digikey} for bits of fired clay), but might serve.
FYI: [search.digikey.com]

I'm working on another moldable ceramic, but haven't fully tested it out. I hope to have enough results to post this weekend. (Fingers crossed.)

One think I can report is that adding either glass fiber (or other short ceramic fiber staples) significantly increases the strength/decreases the brittleness of my ceramics. I suspect this would work for most (water based, at least) ceramics. So, the brittleness issue may not be fatal to these approaches.

Best Regards,

Re: Clay?
December 17, 2008 05:26PM
Hi Clint,

i made some tests with glass-dust mixed with waterglass - this was not so good dispensable because of the friction between the dust-particles and the tube ...

The i tried with solid glass-spheres around 100 microns diameter from 'glass-pearl-sanding' what runs better, but the glass-spheres were to big to pass free through a 200micron dispenser-needle.

Actually i've got a probe of hollow micro-glass-spheres with diameters around 10 microns what should result in a better dispensable paste (as the particles are perfect uniform spheres) and with the foamy micro-structure this could be a very good heat-isolation.

When mixing with other materials you should avoid any acidic stuff as the waterglass would solidify at once (especially some gypsum powders) - it's a bit better with talcum-powder, but for higher rigidity you should mix with some glass-fibres (or even better not specified/selected carbon nanotubes - the selected grades are very expensive)

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