How would I go about creating a passively heated build chamber?



  • On my new printer build, I am planning on having it be 100% enclosed. My plan was to set up a temperature as the "heated chamber" temperature, and when the internal temperature reaches that, turn on a cooling fan, that'll draw out hot air, until it reaches the temperature again.

    I know there is a page on the Duet Documentation on setting up an actively heated chamber, but I can't seem to find one on passives. Does anyone have any information or links that would help me with this?



  • This is a great thought. It would be nice to control chambers with cooling as well as heating on the same PID loop.



  • I'm using what I call "passively heated chamber".. I've simply closed all sides except the top - using acrylic sides with magnets, so easy to remove.

    The chamber is "passively" heated using my heated bed and it works great with minimal fuss.

    I know it's not a controlled environment as such, but the temperature is constant, and I can even have an open door/window next to the printer.

    I have fans on my XY motors, which are inside the chamber, they are fed air from the bottom through ducts (Ultimaker style)

    Regarding a real heated chamber:
    https://duet3d.com/wiki/G-code#M141:Set_Chamber_Temperature.28Fast.29
    Fan for temperature controlled fans
    https://duet3d.com/wiki/G-code#M106:_Fan_On



  • If you used E1 thermistor to monitor your chamber and then heater 1 output to drive the fan then in theory you could control the chamber temp using PID. The only issue I can see if you want higher PWM on this heater output channel (more fan speed) as the temperature rises rather than as it falls, so you need to invert the logic in some way.


  • administrators

    You could use one of the fan outputs set to thermostatic mode.



  • Would it not be possible to implement heating and cooling on the same pid loop?

    I'm designing a printer with multiple "chambers" that need to be regulated in temp. It would be nicer to have heaters and coolers working together rather than against each other. For now, I plan on either getting external commercial PID controllers or implementing multiple PID loops (via the expansion board) that control either a fan or a heater, but they'd all be working "against" each other in some respects.


  • administrators

    You could use a 4-wire PWM fan with the PWM control wire connected via a diode to the heater output (cathode to heater output, anode to fan PWM input). That way, the higher the heater output, the slower the fan will run.



  • I think that might work quite well, actually. But, I'm not sure if it would work exactly like I'd imagine. Would it be hard to implement this kind of thing?

    The problem I encounter with long prints is that the ambient temperature can vary wildly from hot to cold, during night and day cycles. This causes the aluminum parts of my printer to fluctuate in temp, and therefor grow and shrink. Even if I had an inner build chamber, the outer portions of the printer that are exposed will still vary in temp. I want to have an inner chamber, set to about 50C, and the outer chamber more like 20C. The outer chamber would ideally have the capacity to heat the outer chamber to 20C when it's cold, and cool it when it goes above 20C. Since the expansion board has so many heater and fan outputs, I figured it might be good to integrate it into the printer itself.


  • administrators

    Here's another idea. Configure a chamber temperature heater as normal using M141. Also configure a spare fan channel as a thermostatic fan controlled by the chamber temperature, set to turn on at a temperature a little higher than you have the chamber temperature set in normal use.


 

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