Peltier Cooled Heated bed
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Running an automated 3D printer that uses a heat differential to release parts, much time is spent waiting for the bed to cool down. Right now I am looking at setting up a heated bed that uses peltiers.
In order to remove the complication of reversing the voltage, I plan to have 2 series of 10X 50w peltier coolers on a 350mm square bed of a voron. Under the peltiers I plan on having a set of waterblocks. The reservoir will have an emersion heater in order to raise the temperature of the water block side to 60-70C so that the heated bed can easily hit 90-100C.
Theoretically, at this point we are talking about 3 circuits to control the temperature of the bed. Heating peltiers 500W 12VDC, Cooling peltiers 500W 12VDC, emersion heater 1500W 120VAC.
I can figure out the hardware side of enabling the three circuits. However the software side has me puzzled. It seems to me that the duet firmware fundamentally only supports active circuits for heating circuits, not cooling circuits. From where I stand it looks like I would have to configure a servo channel, activate it when I want cooling, use a wait for temp command, remove the part with the gantry, then disable the servo channel.
Any ideas?
One I came up with was that I would be better served using a traditional heating method and connecting the water block directly to the heated bed. Turning the pump on when I wanted to cool it off.
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@sphyloid said in Peltier Cooled Heated bed:
using a traditional heating method and connecting the water block directly to the heated bed.
You might risk boiling water in the idle water blocks.Re: the original idea
What's beyond me is, why do you actively heat the cooling side to 60-70°C? I thought the Peltiers work better, the cooler the cold side is?
The surface of the cold side will reach these temps on it's own even with cold water blocks. -
Peltier modules are bidirectional.
Can you switch the water flow between heated and cold via valves, and reverse the peltier supply polarity for heating / cooling?
It would save the mass of the second set of peltier modules and allow the one set to be distributed more evenly under the bed.
If you used a second heating channel with an appropriate PTC (rather than the normal NTC) thermistor for the cooling control, the board would read the temperature in reverse and should allow it to drive the cooling control?
The displayed temperature would be wrong, but it should allow regulation?
