I just got some interesting Info from Permatex

[Flateric]

I just got a email from the marker of Ultra-Copper.

They tell me that their product is much more of a thermal insulator than conductor. They do not recommend it for us in a application where heat transfer is preferred over heat insulated.

In short perhaps we should find a better heat transfer paste/glue for our hot ends?

[jesse]

Please post alternatives if you find any.

[Flateric]

I seem to remember that arctic silver made a 2 part thermal epoxy variation at one point many years ago. I wonder if they still do.

[geneb]

Keep in mind that the RTV is used to hold things in place and its thermal properties are only important in that it doesn't degrade at high temperature.

The tiny amount that forms a barrier between the thermistor and the hot-end material isn't enough to cause significantly inaccurate temperature readings.

g.

[Flateric]

No this is not related to my little disaster situation. I actually had written them inquiring simply because I had a feeling that some people think it is a good thermal transfer compound. Ideally a paste/substance that is able to take the heat and transfer the heat would be ideal. This thread is my attempt to find such a material.

There are also those little rubbery pads the put under some cheaper CPU's in the past but they do not offer any type of adhesive effect.

[Flateric]

BINGO!
http://www.arcticsilver.com/arctic_silv ... hesive.htm

[geneb]

I'm confused then. I know of no point on a Rostock MAX where thermal paste would be of any benefit whatsoever.

g.

[mhackney]

One option that I do is put a little speck of thermal paste on the thermistor and push it into the hole. Clean up the surrounding area with alcohol and then lock it in place with the copper permatex. I don't do this on the heat resistors since they are wrapped in aluminum foil and are a snug fit. I've been experimenting with cartridge heaters and I also put a thin layer of compound on those.

cheers,
Michael

[Flateric]

This is not a thermal paste, it is a thermal adhesive. So it would replace the use of ultracopper and provide a thermally conductive bond between the thermistors and the hotend for more efficient transfer of heat. Yet it solidifies hard like any two part epoxy resin.

[mhackney]

See the warning on electrical conductivity:

Arctic Silver Thermal Adhesive was formulated to conduct heat, not electricity. NOTE: Even though Arctic Silver Thermal Adhesive is specifically engineered for high electrical resistance, it should be kept away from electrical traces, pins, and leads. The cured adhesive is slightly capacitive and could potentially cause problems if it bridged two close-proximity electrical paths.

That's why I use the thermal paste and ultracopper to lock in.

[Flateric]

Thermal paste also has the same warning.

[mhackney]

I use this stuff: http://www.omega.com/pptst/OT-201.html

It explicitly calls out use for temperature sensors. Rather than use tape to hold in place (I presume they mean Kapton) I use permatex copper.

[cambo3d]

I'm thinking i might use this in my build. http://www.jbweld.com/product/j-b-highheat/ its a little less messy to work with. wrap the resistors in tin foil for a tight fit in the hotend. Then epoxy them in with this stuff.

[geneb]

You will never, ever get them out if you use JB Weld. It's one of the best epoxies I've ever used and unless you've got a chisel, it's _forever_.

g.

[cambo3d]

You will never, ever get them out if you use JB Weld. It's one of the best epoxies I've ever used and unless you've got a chisel, it's _forever_.

g.

yea, hopefully the resistors dont go bad anytime soon.

[Godspeed]

There is a better more appropriate product if anyone chooses to use a thermal paste rather than aluminum foil for this application. It is call Red Ice 611HTC and it is rated to be used up to 360°C. None of the off the shelf thermal pastes like Arctic Silver are rated above about 150°C. I have a sample of this stuff sitting in my office and plan to use it in my hotend when I have time to finish my build. I did talk to an engineer of theirs before deciding to use this product. I think it would last a long time as long as it is capped with the Ultra Copper RTV. Another advantage of Red Ice is very high dielectric effect (basically non-conductive).

Here is the link if you are interested.

http://www.timtronics.com/PDF/hightemp/ ... 611HTC.pdf

Here is also a link to some interesting and VERY heat resistant adhesives that may worth considering.

http://www.cotronics.com/vo/cotr/ca_ele ... istant.htm

[cambo3d]

looks like that could be a good alternative. I just glanced over the data sheets.

Seems like the resbond 920 would be an all in one solution for adhesive and thermal conductivity but It doesn't state how long it takes to cure?

[foshon]

BINGO!
http://www.arcticsilver.com/arctic_silv ... hesive.htm

That one conducts electricity and acts as a capacitor, this one does the same thing without harmful side effects.

http://www.arcticsilver.com/arctic_alum ... hesive.htm

[Godspeed]

Arctic silver is still not rated above 150 degrees C. It is NOT appropriate for a hotend. It may work for a short time, but will vaporize over a few uses. Stick to one of the products rated for higher temps.

[foshon]

Arctic silver is still not rated above 150 degrees C. It is NOT appropriate for a hotend. It may work for a short time, but will vaporize over a few uses. Stick to one of the products rated for higher temps.

Temperature range:
- 40C to >150C (Bond strength is slightly weakened at temperatures below 0C due to crystallization.)

Is that not meant to be read as greater than 150? My technical verbage ain't all that great.

[magicmushroom666]

Well I used a cheap ebay version of the arctic silver adhesive. It was a two part epoxy type thing that sets hard (ie permanent).

It smoked quite a bit when first heated up, but once it ran for around 30mins, its settled down and is working great now. It has lost some of its strength after being so hot and is a bit flaky if picked at but still holds everything together nicely and gives good readings and thermal response to the hot end.

I've run the machine for the last few weeks on it without issues.

I'm sure i could drill it all out if needed, although it'd just be easier to try out another hot end if this one dies.

[foshon]

Arctic silver is still not rated above 150 degrees C. It is NOT appropriate for a hotend. It may work for a short time, but will vaporize over a few uses. Stick to one of the products rated for higher temps.

Temperature range:
- 40C to >150C (Bond strength is slightly weakened at temperatures below 0C due to crystallization.)

Is that not meant to be read as greater than 150? My technical verbage ain't all that great.

I ended up using this to mount my heater cartridges and thermistor. It stunk for a few hours, but seems to be holding up just fine. I will update again if it fails.

[oeginc]

I'm still not sure I understand what the point is. If you wrap your resistors in aluminum foil to the point that they fit snuggly into the hot-end, you don't need anything that can thermally transfer heat - you only need something to help hold them in place, right?

Same for the thermistor. Insert the thermistor all the way in the hole, they put a couple dabs of RTV to hold it in place...

I understand the desire to have something thermally transfer the heat, but in reality I don't think it's necessary and when you are talking about losing the ability to remove your resistors or thermistors, I don't think that's a great trade off for the (very) little benefit you might get.

[foshon]

I'm still not sure I understand what the point is. If you wrap your resistors in aluminum foil to the point that they fit snuggly into the hot-end, you don't need anything that can thermally transfer heat - you only need something to help hold them in place, right?

Same for the thermistor. Insert the thermistor all the way in the hole, they put a couple dabs of RTV to hold it in place...

I understand the desire to have something thermally transfer the heat, but in reality I don't think it's necessary and when you are talking about losing the ability to remove your resistors or thermistors, I don't think that's a great trade off for the (very) little benefit you might get.

Well, since you asked. Power resistors are not heaters. They are resistors, a by product of their day job is that they produce heat. I have heard (not experienced) that these will break apart shortly after they begin cycling.

If you wrap the resistor in foil and put it in the hole there are air gaps. Air is a thermal insulator, not exactly the best thing in the world when you want to transfer heat. Rather than glue a device not meant for the job into a hole that is not sized to fit it, and covering it in gasket maker; resulting in a sammich of air gaps and stuff that isn't meant to transfer heat (the heat transfer of copper permatex is a advertising bonus, its job is to seal to machined mating surfaces) I went another direction. I now have a hot end with a thermistor mounted in thermal adhesive (the products main intent is thermal transfer) and a heater cartridge that slides perfectly (so much so I think that they may have intended it) into the hot end also attached with thermal epoxy.

I have yet to have a thermistor or heater cartridge fail (in all fairness I have not had a power resistor fail either) so I am going to assume that this setup is going to chug along long after other parts fail. I also have two heater leads that are made out of heat resistant silicon insulated wire. Oh, and if the heater does fail, I have another one, (exactly the same as the first) ready to go on the other side.

I am willing to bet (not a lot) that PartDaddy either used what he had on hand, or made a decision based on his experience; I assume the method works well enough as I don't see a shed load of failure posts. I used what I had on hand, I had the thermal adhesive left over from attaching heat sinks on eletronics for printers. I made choices based on my experience. If you don't like my installation method, don't use it. There was a debate here on whether or not it would work, it does. Quite well actually.

[oeginc]

I'm still not sure I understand what the point is. If you wrap your resistors in aluminum foil to the point that they fit snuggly into the hot-end, you don't need anything that can thermally transfer heat - you only need something to help hold them in place, right?

Same for the thermistor. Insert the thermistor all the way in the hole, they put a couple dabs of RTV to hold it in place...

I understand the desire to have something thermally transfer the heat, but in reality I don't think it's necessary and when you are talking about losing the ability to remove your resistors or thermistors, I don't think that's a great trade off for the (very) little benefit you might get.

Well, since you asked. Power resistors are not heaters. They are resistors, a by product of their day job is that they produce heat. I have heard (not experienced) that these will break apart shortly after they begin cycling.
...
If you don't like my installation method, don't use it. There was a debate here on whether or not it would work, it does. Quite well actually.

I have only been using my power resistors for a couple weeks now and took my hot end apart to rebuild it. In doing so, I did notice that they had started to crumble - I was not aware that this was "normal" behavior, thanks for pointing that out.

On a side note, I apologize - I think you misunderstood me, or perhaps I should have worded my reply differently. I meant no disrespect by it, I was honestly asking why you did it because I was under the impression there would be little to no gain from it. I am still not convinced it's the best way to go, but it's funny because even before reading your post I was think "there HAS to be a better way than wrapping these up in tin foil" and I was thinking something along the lines of artic silver around the resistor, and then using the RTV still to hold it in so it could be removed easily.

Thank you for taking the time to respond, I definitely understand the point about the air pockets that may be in between the resistor/tin foil and/or the tin foil/hot end. That makes sense. I tried to wrap mine as tight as possible, and I tried to make it fit as snug as possible, but I'm sure there are still gaps...