RTV goes bad

3D Printing
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Not really news, but I went to use a tube of RTV to finish building my new hotbed for my corexy printer, and while the tube felt very flexible, the RTV had cured inside.

I’m taking Mark Rehorst’s advice to bond the TCO to the heater so that if the heater detaches from the bed, the TCO is more likely to trip.

Fortunately, before I connected the TCO to the (neutral) power lead, I pondered, “soldering a heat-sensitive component? let me look that up…” and substituted a crimp connection. If the crimps start to fail, they will start with high resistance, heating up the TCO, which will then open, so it’s a pretty safe choice.

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The main difficulty I ran into was making sure that the RTV was fully bonded around the entire perimeter of the heater pad, including under the wires at the side. I also had to bond the TCO to the heater pad in two stages; first getting enough RTV to hold the TCO to the heater pad and letting that cure, and then a more generous helping to make it secure.

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