Tweaking G-code to cool bed
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Hello
I am currently working on a 3D printer to be used in medical research. It uses standard high end component used in 3D print in general. I have chosen to use the Duet 2 Wifi board for the application because of the quality and smooth stepping.The only difference from a normal 3D printer is that the bed has to be cooled to about 4°C instead of being heated. For that I am using a 12V peltier element beneath the bed and a buck converter to go from 24V to 12V.
This is not supported by the current G-code, but I am wondering if it is possible to tweak the G-code to hit the lower temperature using PID regulation.Any ideas may help
/Frederik
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The M307 I (invert) parameter may do what you want. However, RRF normally considers any temperature below 40C as off/don't care, so I suspect that firmware changes would be needed too. Caution: using this parameter might cause the element to be on at full power when you don't expect it, so test it with care.
Note, peltier elements do not work efficiently with raw PWM. To work well, they need smoothed PWM, which requires a reasonably high PWM frequency, flyback diode, inductor and optionally a capacitor. OTOH, if you need to run the element in bang-bang mode, or at or close to full PWM most of the time, that may not matter.
