I’m trying to make a hotbed for my delta printer. I have two circular mirrors (dollar store), an MK2a hotbed and thermistor and some cork as insulation.
The plan is to make a sandwich like so : mirror | Cork | MK2a | mirror.
Does this make sense? What kind of wires do I need for the thermistor (and where to put it) so the wires don’t melt? If I run the thermistor wires under the cork, would that be enough insulation to prevent them to melt ? Any thoughts or comments are welcome. Thanks.
Teflon/PTFE coated wire is pretty common for high temp applications, and able to be easily found. IIRC, the MK2a heat bed actually has a center hole in it for the thermistor, so I would sandwich it in there.
Silicone insulated wire is also pretty common for R/C applications and heatproof up to about 250C.
Using a round piece of glass is probably a bad choice on top of a square heated bed - the non-heated parts of the glass won’t get enough heat conducted to them to have plastic stick properly, but they will act as cooling fins to some extent. If i only heat up one half of my double-wide bed (with a continuous glass sheet), the heated half will have its usable heated area reduced by as much 50mm into the build area.
EDIT: Here’s a quick and dirty simulation to show what i mean: https://www.dropbox.com/s/w2vupsl21qrovd9/roundSquare.PNG
The heated bed (at 120C) is set below a 3mm glass sheet that has its top surface affected by a 10W/m²K convection. No fluid dynamics simulations used, which would probably enhance the effects seen.
@Thomas_Sanladerer understood, but I’ll have to live with it for now. Large circular hotbeds are expensive. thanks for the nice simulation 
