2400rpm Servor motors that is compatible with Duet2

  • Hi
    I have started a project for myself to build an extremely reliable 3d printer using ball screws for XY axis.

    Knowledge wise im meeting a wall when it comes to finding steppers/servo motors.

    I have chosen 1610 ballscrews (10mm per full rotation) and to print at 300mm/s I cant use regular stepper motors as the RPM is too low. My nema17 and 23 motors are useable to around 5-600rpm without losing steps or too much torque.

    I need motors with very high accuracy at 2400rpm.

    q1: How would I go about and find servo motors?
    Q2: Does a servo motor need a controll board or can the Duet run it?
    Q3: is "closed loop stepper" a servo motor?

    Hoping for some help, or some pointing direction as this is mostly greek to me at the momemt.

    Best regards
    John Bergene

  • No, a closed loop stepper is not the same thing as an AC servomotor.

    I used servomotors in my sand table. Take a look at the iHSV series of motors from China if you're on a budget, but be aware there's not a lot of information about configuring them out there. I tried them in the XY stage of my printer and got poor results because they don't seem to be able to position accurately over small distances (maybe I'm not configuring them well). I may try again one day, but for now the servos are going back into the sand table.

    The iHSV motors have drivers built in, so a Duet expansion board makes connections to them very easy- just step/dir/enable wired from the expansion header to the motors. I don't know how long your lead screw is, but that's a lot of mass to spin- that's going to take some power .Make sure you use adequate power supplies for the servos. I used separate supplies- 150 and 200W for the 78W servos. If I crank acceleration/jerk too high the 150W power supply shuts down.

    I think you're going to find that with 10mm lead screws, you won't get adequate resolution for printing using either steppers or servos.

    I put all the info I could find on the iHSV servos here.

  • @mrehorstdmd that looks like an excellent blog post I have to read after work.

    Why do you say that screws wont provide good enough resolution?
    I have a ball screws and they are super tight and accurate, not regular Lead screws. There is only 0.05mm play over a 300mm length (theorical). Practically I cant feel any play whatsoever. Much much less than what I can with a belt.

    The top speed, and acceleration is also very high. Much higher than 3000mm/s and theroically I Could run theese at 500mm/s. But I think a 300mm/s goal would be good enough for now.

  • @jbergene 300 mm/sec implies 30 revs per sec, 500: 50 revs per sec. You're spinning a ball screw- that's a lot of mass to start and stop quickly, in addition to whatever you're moving with the screw.

    Are you planning to move the bed in Y? How long is the ball screw?

  • @mrehorstdmd yes, X and y.

    Roughly 400mm on Y and 500mm on X. The bed is 400x300mm

  • Moderator

    I would definitely re-evaluate your design goals. If you really want 300mm/s speeds and high accelerations then ball screws really aren't ideal.

    You've already realized this and are seeking out exotic motors as a possible solution, but that's really just a new problem.

    I would suggest you take a pause, re-evaluate what your end goals are, and then start working backwards from there to find the simplest solutions that get you there. Maybe that's ball screws and servos, but I think a more traditional approach is more appropriate.

    That being said, to better answer your question on servos, you can use them as any other external motor driver that accepts a step and direction signal.

    @mrehorstdmd adventure in servos would be very informative.

Log in to reply