Cooling requirements for 11 steppers



  • Hello,
    I am finnishing my dual IDEX carthesian build with duet2, expanded with duex5 + an extra external stepper driver. Four independant X carriages on 2 rails, dual Z, stock double Z stepper is for dual Y motors.
    As i have populated almost every connector available, and probably some stuff might even apear as optional the obvious thing that comes to mind is the processing unit might probably get a bit warmer than usual in quad printing mode.

    So do i have to put any heatsink on the processor or is the simple blow over it adequate?

    Should i be concerned about anything else maybe?

    The bed is AC so there is plenty of juice from the PSU.



  • The chips on the Duet board are engineered to transfer heat through the board and be cooled from the bottom. There are great suggestions here on how to design your mounting and cooling solution: https://duet3d.dozuki.com/Wiki/Mounting_and_cooling_the_board You can actually use the internal temperature monitoring from the chips themselves to control a cooling fan. I built a setup with this configuration, with the fan exhausting from a well-sealed enclosure and air intake holes directly underneath the stepper drivers, and the fan almost never goes above 10%.

    Especially as you're not routing a bunch of amps through the bed MOSFET, you should be in fine shape!



  • @whopping-pochard thank you. I know drivers cool through the board but i did not know that is also true for CPU. Is it really? If yes, then great.

    No worries, I am using an AC powered bed



  • @MaracMB For info I'm running 13 steppers on my CoreXYUVAB with 6 extruders on a Duet 3 with 3 expansion boards. Six of those motors are for the extruders and are small Nema 17s rated at a modest 800mA and set to 600 mA.
    The remaining motors drive the 3 XY axes and the Z axis. The moving mass of each gantry is between 2 and 3 Kgs. Four of the motors are Nema17s rated at 2.0 amps and set to 1800mA. The remaining 3 motors are Nema 23s rated at 2.8 amps and set to 2400mA. With all axes driven using travel speeds of 350mm/sec, nothing gets remotely warm, including the processor(s).

    However, the boards are open - not enclosed. So there is plenty of room for air to circulate. I did fit a fan to blow air onto the back of the main boards but I've never had a need to connect it. If the board(s) was/were enclosed then a fan blowing air onto the back of the boards(s) might be a wise thing to do.



  • @deckingman i know your machine Sir 😀 but thank you for a kind introduction. I admire that thing from when it was showed online. Deepest respect.

    The thing is, i have duet2. It is 3 times slower processor, 3 times less memmory... and it will need to calculate stuff a bunch.
    Electronics are enclosed yes..

    I’ll test run it but thought i’d ask if someone has some experience to share with potential overheating. Or if something else might show up also.


  • Moderator

    The CPU is good up to 80c or beyond. The drivers over 100c. So with reasonable motor currents you shouldn't really have to worry about overheating provided there is at least some air flow for your enclosure.

    The page on mounting and cooling should give you some ideas, but ideally you'd have the board mounted vertically with some air slots and top and bottom to facilitate convective flow. Forced air with even a single small quiet fan can help keep it all near ambient without much trouble.



  • @Phaedrux thanks. Yes I always placed my duets according to the manual, sandwiched, fan on the bottom, pwm-ed via MCU temp etc.
    This one is different as i had to adapt to existing printer box. For now. I adapted two Tenlog D3 pro’s and one has the box under the frame... so i have to get creative to get all the stuff crammed in there and also to add additional substructure.... I need this to fit in an office space when done and be... non-alien, discrete looking

    Will post pictures for you today... 😉



  • @MaracMB I also used to run Duet3 with a Duex 5 and 10 motors. In that case, the boards were in vented enclosures and I had thermostatic fans blowing air over the back of the boards. That arrangement was more than sufficient to keep everything cool.


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