Tooling plate heated bed, where to place sensor?

Hi,

after two years of printing on an unheated bed, I decided it is time to upgrade, to print bigger parts out of PLA and also print PETG. Now I have a bed of 420x420x8 mm tooling plate, which will require quite some heat. I bought a 1400W 220V silicone heater and isolation foam. The heater comes with the sensor, but I feel it won't measure the plate surface temp correctly. I think I need to drill a small 3mm hole in the side of the plate at fit a sensor similar to the one in the hotend. Does that make sense or am I worrying about something I shouldn't bother with?

Cheers,

Hugo

Edited 1 time(s). Last edit at 10/24/2019 03:13PM by HugoW.

Definitely place it in the center as most prints will not be at the edges of the plate but at the center. I'm not sure if you can use multiple sensors. If using one sensor the center of the plate would be the most logical. Also, indeed, put it into the plate. What I would do myself is drill a 7mm deep hole to get the sensor closest to the print surface. I don't know if that is the best way to do it since I have not done much research into it but I'm just thinking along what would be logical to do.

My own sensor is mounted with kapton tape onto the bottom of the printbed and is very close to the heater and I notice the sensor reaches the 60ºC too fast because the mass of the heater gets up to temp really fast and the aluminium printbed doesn't reach the desired temp that fast.

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http://www.marinusdebeer.nl/

I wouldn't worry too much about it. Aluminum is a good thermal conductor and there will be minimal temperature difference regardless of where you put the thermistor. The edges of the plate will be a few degrees cooler than the center, but not enough to matter. With 1400W, the bed plate will heat faster than the hot end.

Edited 1 time(s). Last edit at 10/24/2019 06:08PM by the_digital_dentist.

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Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]

My printer has a 330mm diameter x 5mm thick aluminium bed with a 350W silicone heater underneath. I use the sensor built in to the heater. It's not ideal, in particular the temperature of the bed surface lags the thermistor temperature during heating, but it works well enough for me. By the time the hot end is up to temperature, the bed surface temperature has stabilised.

Edited 1 time(s). Last edit at 10/25/2019 02:15AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

yup with insulation and using a thick sheet of aluminum i think you'll be fine putting it about anywhere. there will be variance across the plate. prob best position would be center underneath, prob no need to drill since heat is coming from the silicon pad.but if you need to to mount it so it wont fall out about anywhere inside the aluminum should pretty much be at about temp equilibrium if it is 8mm thick, and heated evenly from underneath.


with such a powerful heater did you also build it a thermal cut off switch in case of software glitch as a redundancy failsafe?