User friendly heating chamber control

  • I have an isolated chamber (550x470x400) inside my corexy printer that I want to heat up to 180°C.

    I have these components:

    • Finned heater, 230V, 1kW, controlled via SSR? via PWM? via bang-bang?
    • A cross flow fan will suck air through the finned heater and out through a flat but wide air nozzle so that the air flows directly across the currently printing layer. Driven by a 24V brushed motor.

    The air circulation is a closed system, the same air will be reheated.
    Where should the temperature probe be? Directly in front of the air nozzle? Somewhere else in the chamber? Both?

    If possible, I want to control the chamber just via the Cura slicer (maybe setting up cura profiles for different materials and their according chamber temperature, like PEEK 180°C or ABS 60°C).
    Upon starting a print, the chamber should first heat up to the specific temperature and then proceed with the actual printing.

    Additionially I want to use the cross flow fan as a cooling fan when printing PLA.

    What would be the smartest way to implement all this? Is something like this possible?
    I would really appreciate your ideas!

    0_1561631410748_Air circulation.JPG

  • Where you place the sensor depends mostly on how you want to deal with the temperature gradient inside the chamber. It will take time (and/or some) thinking to get the whole chamber to an even temperature. The closer to the heat source you place the sensor the less overshoot you will have in parts of the system, but it will take longer to get the whole chamber to the desired temperature. I'd start by placing it the furthest away from the heater where any excess temperature won't cause a problem.

    For the PLA cooling with the same fan you would need some sort of baffle actuated by a servo or solenoid to direct your airflow, unless you want the air flow to cool the part with any material, which sounds unlikely.

    Presumably the fan motor is outside the chamber? 180C might be a bit hot for the motor to operate in.

  • I'm not sure if I got your thought on PLA cooling right...
    Since my print nozzle stays on the same height and the (300x300) bed moves down, I always blow air on the nozzle tips. The air nozzle and thus also the airstream is 300mm wide (and maybe 5mm high, depending on how far away from the air nozzle) and moves parallel across the whole bed.

  • @sharctic said in User friendly heating chamber control:

    I always blow air on the nozzle tips

    That means you're effectively also cooling PEEK and ABS when printing those, albeit with hotter air. If that is what you're after then its not an issue in the first place?

  • Yes, I mainly wanted to know, from a firmware perspective, if it is possible to use the same fan for two different roles. One being a chamber heater, the other being a part cooler run by fan control G-codes from the slicer.
    (On a sidenote: I only now got into printing PEEK and don't know too much about it, but would you consider blowing 180°C air on a PEEK print cooling?)

  • The fan has to be configured for thermostatic control with the chamber heater or a part cooling fan; which is why if you want it on at all times then you don't need to make a distinction. If you want to vary the speed for different layers on the other hand you'll run into problems with the heater being tuned for one airflow and used for another.

    And yes, 180C hot air would cool the PEEK which is printed at more than twice the temperature. Same with 60C hot air for ABS.

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