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Graphite Foil

Posted by corry 
Graphite Foil
March 16, 2015 07:57PM
Its a really interesting material.....I'm considering ordering a roll (since I can't find anyone selling big enough sheets at less than a 1000% markup....no exaggeration either unfortunately)

Interesting property-Highly anisotropic thermal and electrical conductivity. That is, its extremely conductive (thermally on the order of up to 1500 w/(m k), along the plane of the foil, but not so great....3 W/(m k) through the foil. To give you an idea, aluminum is about 250 W/(m k).

That's all well and good, but what has that got to do with 3D printing? I had figured to mostly block the radiational loss of heat to the insulator under the heater, I'd stick aluminum foil between the heater and the insulator. I've had great success with that in other areas. However, this time I was looking at overkill, so rather than Styrofoam or cork for insulation, I thought I'd go with ceramic fiber, which led me to graphite foil. Everything I'm doing with this 3d printer is likely overkill, but I've got a lot of time on my hands, so I'm more trying to have fun and keep my mind busy. That said, graphite foil isn't too awfully expensive if, as I said, someone sold it by the sheet. That kind of conductivity may be enough alone to remove the hot spots in beds and remove the necessity for other heat spreaders (insulation and heat spreader in one!). I'll eventually try that if I decide to go through and order a roll.

My main reason I'm posting here was to see if anyone else had tried it, and if not, gauge interest in whether or not other people would want to experiment as well. Getting rid of the heat spreader on a Cartesian printer wouldn't help a lot, but it would help. If I can part out a roll, I might just order it and try it. Even if I can't I might go through with it anyhow, but its a tougher decision. The cost should end up being less or similar to that of shipping it around USPS. Since I don't want to come too close to being a post that doesn't belong here, I won't go into the actual cost, but you can see the rolls on big "auction" sites, and get an idea. I figure I'll put some markup on there just for the hassle....and if its popular, to fund another roll and keep up until interest wanes. As I said, I'm also willing to listen to others experiences with it if anyone else has tried it. (Talk me out of it or into it smiling smiley ).

I know I've posted very little here and I'm not talking much about what I'm doing, but that's just because I don't have much to show for the whole project yet. Just some cad drawings, probably 25% of the parts I need. The entire thing may be so stupid, its pointless, but like I said, this is more about keeping my mind busy, so if its stupid, I don't want to lose interest in something that's held my interest pretty well since just after Christmas smiling smiley If everything works as planned, I've got some additional ideas for some stuff to try....doing more in more fields which I have no experience in....great for keeping the mind occupied smiling smiley

So thoughts? Anyone else want to or have tried using this stuff? Thicknesses used/wanted? Details! smiling smiley
Re: Graphite Foil
March 17, 2015 04:58AM
... the properties of the graphite material sounds good, so I'll be interested to test it out ... but pure graphene should be of much more interest winking smiley

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Re: Graphite Foil
March 17, 2015 07:37PM
Uneven heating of a print bed is a non-problem. Anything that comes on a roll is going to have to have some mechanical support, so your heat spreader insulator idea is sort of pointless. If you have to have mechanical support, just use a piece of aluminum. The slightly uneven heating of a print bed using less exotic and very cheap materials like aluminum does not affect print quality. Using much more expensive materials will not improve prints. If you have no better use for your money, have fun. But 3D printing has many bigger problems to solve than slightly uneven heating of the print bed.

How about reliability? THAT's a REAL problem to solve, and a much better use of time, effort, and money.
Re: Graphite Foil
March 17, 2015 10:34PM
Well, I may have been premature, turns out it's some of the more "special" graphite foils with those extreme properties (Ones made by sintering polyimide). May actually be a good thing though since it looks like they may be cheaper, they're certainly more flexible (making shipping much less hazardous). Only real issue is the availability. Can't just pick up a roll on an online marketplace. I still think its an interesting curiosity. Sure its solving a problem already solved by an aluminum heat spreader, however, you're failing to understand the material, and the cost, well, for a 3d printer, it should be only a few dollars. It maybe as high as $20, but I think that's a fairly pessimistic estimate. My guess is it will be cheaper than the aluminum heat spreaders most are using. The big difference here is because of the anisotropic nature, it goes under the heater, not above like the aluminum heat spreader. So you go carriage, graphite foil, kapton heater, borosilicate glass. This works because the stuff is so thermally conductive, and thin. I really don't think it will work well with silicone heaters, but its certainly possible. Kapton heaters are quite thin, so its easy to see that the heat spreading capability will even things out. Again, being anisotropic, its not going to conduct heat well through the foil. Its not as insulating as cork, ceramic fiber board, etc. Its around 3 W, and ceramic fiber board is more like 0.8 IIRC. The fact that its "shiny" will mean all radiation is reflected, not absorbed, and pressed right up against the heater, we can be pretty sure there won't be any convection, so yes, it will work pretty well as an insulator. People running no insulation will definitely see benefit, those with cork, ceramic fiber, fiberglass, foam, or whatever will certainly see some benefit as this will effectively block one form of losses entirely (radiational), and its not hurting the insulating capability of those other materials.

So sure, there are other problems. This one has been "solved", but its been solved with more mass. Prints could be faster, some who can't print ABS might be able to. Sure it may not be the "biggest" problem, but it is still a "problem". I didn't say, but this is basically all useless to me entirely since I'm not building a Cartesian printer. As I said though, I like overengineering things. (Definition of engineer). And its not like better efficiency doesn't help either. My heater is 560W. I'd like to run that as little as possible!

As for your specific mention of reliability, that's a new one to me, maybe its just so accepted I don't see complaints on mailing lists about it, but I'm sure I'll run into it eventually if its really as big, widespread, unsolved problem as you indicate. If/when I do, I'll see if theres anything I can contribute then. There's already a lot of smart people working on all aspects of 3D printing though. That's why I searched for this issue before posting. Had I seen it passed over, reasons not to look at it, etc, I'd have dropped it. Since I didn't, I'm looking into it. Worst case, I may just purchase some for myself, depending on costs, and report results. Id rather distribute the cost of research, since I'm pretty certain there will be at least some benefit, not a total waste of money smiling smiley
Re: Graphite Foil
July 26, 2015 01:14PM
Well, I gave up trying to source it from China. Too much drama there + a lack of interest. While looking for something completely different, however, I found some not quite as conductive, but still conductive as hell (240 W/mk XY, anisotropicly in the Z direction is 5 W/mk) on mouser, and its expensive for foil, but not that expensive. [www.mouser.com] $17 for an 18x24 sheet. Smaller sheets are likely available. They also have some 0.1" thickness sheets available, that link is for a 0.02" thick sheet.

At this point I do have my printer printing, and the 550W mains powered heated bed heats the thick aluminum plate and glass up pretty quickly and evenly, so using this is going to be overkill, but then, everything I've done on this printer has been overkill thanks to boredom! (its kept me busy which is a good thing!) I ordered a couple sheets. I may create a second insulator, remove the aluminum from the stack, and try just the graphite foil as I said, counter-intuitively underneath the heater, and see if I get even heating across the bed. I've got a lot of experiments going on with this thing already with the ultimate (totally attainable, and certainly not the first to do it) goal of printing high temp polymers. Still have a ways to go, but get closer every day smiling smiley As I said, I went off the beaten path so this wouldn't entertain me for a few weeks, but rather months since I've had way too much free time forced upon me! (I know, most wouldn't consider that a problem, but its deathly boring, and I don't recommend following the path to attain it as it was the result of some serious pain, and continued disability!)
Re: Graphite Foil
July 27, 2015 03:11AM
If you could use the electric conductivity to combine the heater and insulator in one part, I´m in smiling smiley

I suggested more than once to use carbon fibre boards as printbed/heater combo, since carbon is nothing else than conductive graphite in a very strong and light package, but the idea to put the graphite foil (- heater ) under the glass would also be worth a try.
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