Trinamic QSH4218 Motors with Duet 2



  • I've spent the last few months specifying and building my ideal cartesian printer. It currently has some placeholder motors for X & Y which I don't even know the full specs on. My design intent is to have a very quiet and reliable printer capable of speeds up to 200mm/s (for travel).

    I'm looking at:

    • Trinamic QSH4218-51-10-049 49Ncm 1.00A
    • Trinamic QSH4218-47-28-040 40Ncm 2.80A

    Datasheet including both motors https://www.trinamic.com/fileadmin/assets/Products/Motors_Documents/QSH4218_manual.pdf

    I don't know which motor best suits the Duet 2 and my requirements?

    I have a 12V PSU, operate my motors at 16x microstepping with interpolation, i use sensorless homing and stall detection. My stall detection seems quiet challenging to tune on my current motors and i think its made worse by using IGUS drylin bearings and IGUS rails with higher friction than steel balls on steel rails.

    Can anyone advise on the best motor for me to match well with the drivers on the Duet 2? Cost isn't really a concern.





  • out of those 2 the first is very high inductance and the second is about the lowest I have ever seen so that is the one I would go with personally but the current is a bit on the high side.but if run at 75-80& then it should be pithing the spec of the Duet2 drivers



  • .............But the very best thing of all would be to ditch the 12V PSU and use 24V, especially as the goal seems to be the capability to run at highish speeds.



  • Thanks for the input so far guys! I wish I started out building a 24V system, bit too much effort to change now.

    Will I still be able to use sensorless homing with such a low inductance motor?



  • @nbgu said in Trinamic QSH4218 Motors with Duet 2:

    Will I still be able to use sensorless homing with such a low inductance motor?

    I have to ask, why do you want to use sensor less homing ? Even if you manage to get it working, it'll never be as reliable or accurate as a simple micro-switch which can be bought for next to nothing. I can almost see the logic as far as Mr Prusa is concerned because saving a few cents per printer, multiplied by a lot of printers, is maybe a worthwhile addition to his profit margins. But for a one off printer that you are building from scratch, why go through the hassle of trying to get sensor less homing working and still up sacrificing consistancy and reliability when a simple micro-switch will perform better?

    Edit. and if you want to change to 24V, you can still runs fans from 12v by using a DC to DC converter. Heaters too for that matter but they tend to be so cheap that it's hardly worthwhile. Unless you are using a 12V bed heater - but then again, you shouldn't be.



  • @deckingman

    I suppose the only real reason I'm using sensorless homing is because it was easier to set up than it would have been to design limit switch brackets and install them... pure laziness!

    I do have switches in my spares kit so it wouldn't be the end of the world if I couldn't get it working with the new motors. It's nice to have less wires to route though.

    The 2.8A motors are only 1.4V so even at 12V supply these motors should perform well.

    I'm going to pull the trigger and get them, will see if they're worth the rather high cost!



  • I would also not recommend sensorless homing. It's not guaranteed that ramming the axes against the wall requires the same force every time to trigger it. If you change the characteristics of the move (microsteps, current, speed, weight, damping), then you change the characteristics of the detection. For a tiny printer like the Prusa it'll be okay, but for a bigger and faster axis it's a rough ride.



  • As an update I installed the very low inductance motors on X and Y axis of my P3 steel. They are great! Sensorless homing was easy to tune and thanks to the flattest torque/speed curve I've ever seen on any stepper motor I'm able to achieve the 200mm/s for travel moves despite my IGUS RJUM bushings on IGUS rails having rather a lot of friction because of poor parallelism of the rails on the laser cut frame.

    I'm running the motors at 2.1A, they barely get warm and I have good cooling on the underside of the Duet 2.

    I think I will replace the igus setup with some quality LM8UU bearings and smooth rods though and save the polymer set up for a more tightly toleranced
    frame build.


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