Many years ago, when I worked in the automotive industry, we used something called “Copaslip” for high temperature lubrication/anti-seize purposes. Then a couple of years ago, before I started this blog, I had the idea that, if it has a high copper content, then it might make a good high temperature thermal transfer compound for heater cartridges. One possible issue that someone pointed out was that the carrier grease would boil off at 240 deg C. On the basis that this might not matter as long as the copper was left behind, I tested it any way (up to 400 deg C) and posted my results on the re-rap forums, which you can see here https://reprap.org/forum/read.php?1,683821,684391#msg-684391.
The results showed a definite improvement in heat up time, despite the fact that after the first run the carrier grease did indeed burn off and made a bit of smoke.
More recently, I have been doing some research into heater cartridges for something else that I’m working on. As part of this research, I came across a few articles and manufactures recommendations as to how cartridges should be installed. In summary, most manufacturers who give installation instructions, state that they should be a very snug fit in the housing and ideally, that hole should have a fine polished surface with no ridges or grooves. This makes perfect sense as any air gap will lead to poor heat transfer. Also, the casing of the cartridge can oxidise over time which can make them difficult to remove should they fail.
Most 3D printer hot ends that I have seen don’t seem to have this snug fit for the heater cartridge but instead use an over sized hole and maybe some sort of clamping arrangement. This may still lead to air gaps and potentially reduce the efficiency of the heater. Indeed, the Diamond hot ends that I use, just have an over sized hole with no clamping arrangement and the heater cartridge is quite a loose fit. It seems to work OK so it’s not a huge problem but it could be better.
Anyway, one UK manufacturer actually recommends using a product called Loctite LB 8065 when installing heater cartridges. They don’t really give a reason why but I assume that it’s to prevent oxidisation and make it easier to remove a cartridge if and when it fails. The product is after all marketed as a lubricant but it is claimed to be “temperature resistant up to 980deg C” (that is what it says on the tube).
Remembering the earlier work that I had done with “Copaslip”, I decided to get some of this Loctite LB8065 and try it, to see if it works as a thermal transfer compound. It is more expensive that the more usual copper greases that one can find but it’s a completely different consistency – much more solid. I paid £6.99 and bought it off of Ebay. It comes in a tube very similar to glue sticks such as “Pritt Stick”.
Starting at ambient, I heated the hot end to 240 deg C and noted the temperature every 10 seconds. The next day, I removed the heater cartridge, coated it with Loctite LB 8065 and repeated the test.
Here are the results – I can make the spread sheet available to anyone who wants it.
On my machine, it reduces the warm up to normal print temperature by about 15 seconds which is a reasonably significant saving in time. That was with a used heater which was showing signs of oxidisation. So, with a new heater and if it prevents oxidisation of the cartridge case, the improvements over time might be greater. For me, every time I home my printer, the first thing I do is start heating the nozzle because I use the nozzle tip as a probe so want any “oozed” plastic to be soft. Then I home X Y U and V but still have to wait a while before the nozzle is hot enough (about 140 deg C ) before Z will home. So reducing the warm up time is beneficial and that tube will likely last me forever so the cost is negligible.
In summary, Loctite LB 8065 is marketed as a high temperature lubricant but I believe that it is also useful as a high temperature thermal transfer compound. I just use a normal bead thermistor but if I used and E3D cartridge type temperature sensor, it might be interesting to try some on that too. Do to the high copper content, I would imagine that it is highly electrically conductive.
So if you think a small but significant reduction in hot end warm up time will be beneficial, give it a try. It should also help with future removal if the cartridge is a snug fit in the housing.
As ever, hope someone finds this helpful.