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codemaven

Thermocouple destroyed during V2 upgrade

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Hi All,

Just wanted to report that I attempted to update my machine to the V2 hot-end today, but ran into a problem when removing the old one. I had a bit of difficulty unscrewing the peek, as the threads really seemed to have latched on to the brass tube... but I eventually got that apart. I left the heater and thermocouple to last because I wanted to make sure I got the peek off while the machine was warm. So I removed the set screw and the heater cartridge slit right out easily, but thermocouple did not cooperate as much... It had basically welded itself into the aluminium block. I tried to push it out from the far end with a allen-key, and tugged and pulled with pliers... after about 30 minutes of fiddling with it the wires just came off. On close inspection the thermocouple is permanently inside the aluminum block, there's no way it would ever come out The metal sleeve that it's in has pretty much been welded to the aluminium block itself...

I've emailed UM support for a replacement, I hope to get that soon... It took a whole week from ordering of this new hot-end before it was even shipped, so with that kind of turn around who knows how long I will be out of commssion.. if it was a standard published part I could order one from Farnell and have it by tomorrow, but this seems to be a specialty item. :x

Cheers,

Troy.

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I cannot help you with this problem, but for anyone reading (and for when you re-assemble) I would

recommend the following.

1) The thermocouple body is probably stainless steel (or it certainly OUGHT to be), so will expand less

than the aluminium block. Try to remove the thermocouple when the assembly is hot.

2) When installing, (as well as a bit of aluminium foil if you have a rattley problem), I would put on

a tiny dab of Copper grease. This will smoke and generally smell a bit for the first while of use, but

is designed as a high temperature grease specifically with the property that it will prevent things

fusing together when locked together for long periods. When it gets hot the soap carrier agent will

slowly evaporate, leaving basically just copper powder in your joint. This will prevent anything from

becoming locked together over time, and also ought not to provide any problems with thermal conductivity.

However I expect that the presence of the grease carrier agent could initially slightly behave as a bit of a

thermal barrier, so until its evapourated your readings might be a fraction off.

The usual trade name for this would be COPASLIP

Anyway thats what Id do !

C.

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The body of the thermocouple did not seem like stainless steel.. It felt like Aluminium to me, but I cannot be sure.

I was thinking of putting a light coating of silicon heatsink grease on it next time. I will look into your copaslip suggestion as well, that might be better than standard silcon heatsink compound.

Cheers,

Troy.

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