[whateg01]

I haven't seen much feedback in other threads about this, so I'll start a new thread dedicated to it.

Other than needing to be mechanically synchronized, what complications are there with ganging multiple stepper motors together mechanically? I am contemplating using multiple motors on one axis to get more torque. I would probably use a short belt or chain to connect them. The reason for this is that several less powerful motors can be purchased for much less money than an equivalent single motor. So, if I can use two motors together on a single axis, it might be worth a try.

Assuming the driver can handle the current, could the motors be electrically connected, as well?

One side effect that might be nice is that by putting two motors in parallel, the inductive reactance is cut in half reducing it's effect on the time constant, so a lower voltage could be used to achieve the same time constant, or a shorter time constant (faster max speed) could be had with the same voltage. (at least in theory)

Comments?

Dave

[ViperTX]

...the resistance is also 1/2 so the current is doubled......try it let us know what happens.......

[joecnc2006]

I have asked a question twice but i guess people did not see it, But what if you slave two motors one on each end of a leadscrew in the center on the long axis (slave Y and A) but on the A reverse it in software so they both turn with each other.. Any comments ?

[whateg01]

I have asked a question twice but i guess people did not see it, But what if you slave two motors one on each end of a leadscrew in the center on the long axis (slave Y and A) but on the A reverse it in software so they both turn with each other.. Any comments ?

Another thought I had. Good idea (I think)

It might be simpler. The only thing that I think might make it more difficult is that you would have to have all of this outside of the bearing. I guess, though, that this isn't any different than having supporting bearings at both ends. Hmmm...


Dave

[whateg01]

Actually, I don't even think you would have to reverse it in the software. You could connect it electrically backwards so that it ran opposite the motor at the other end.

Dave

[ESjaavik]

One side effect that might be nice is that by putting two motors in parallel, the inductive reactance is cut in half reducing it's effect on the time constant, so a lower voltage could be used to achieve the same time constant, or a shorter time constant (faster max speed) could be had with the same voltage. (at least in theory)

Is it? Time constant is L/R, and you will be cutting both L and R in half, so .....
And you will have doubled the inertia, so no gain there either.

[ger21]

I have asked a question twice but i guess people did not see it, But what if you slave two motors one on each end of a leadscrew in the center on the long axis (slave Y and A) but on the A reverse it in software so they both turn with each other.. Any comments ?

When you apply power to the motors, if they are not exactly synchronized (to the microstep), they'll be fighting each other.

IMO, if you're using Gecko drives, the cost of a bigger motor wouldn't be that much more, and that's the route I'd go. If your using something like a HobbyCNC, and would need to upgrade the drives to use a bigger motor, then give it a try and see if it works, and be sure to let everyone know your results.

[CJL5585]

When you apply power to the motors, if they are not exactly synchronized (to the microstep), they'll be fighting each other.

IMO, if you're using Gecko drives, the cost of a bigger motor wouldn't be that much more, and that's the route I'd go. If your using something like a HobbyCNC, and would need to upgrade the drives to use a bigger motor, then give it a try and see if it works, and be sure to let everyone know your results.

I agree with Gerry's post.

I think the easiest route would be to find a stepper manufacturer who has some technical literature on, or even recommends running steppers in parallel. I would then purchase his product. (I HAVE NEVER SEEN ANY, AND I HAVE LOOKED AT LOTS OF STEPPER TECHNICAL MANUALS AND LITERATURE.) Until then, I would personally follow the accepted practice of using one stepper with the torque required for the application.

Jerry

[daedalus]

you wont find much by way of literature on running multiple steppers in parallel, most people would just buy a proper sized stepper for the job. I have done some work with bldc motors in parallel, and trust me getting the motors / steppers syncronised is a pain in the ass. If you are going to do this then get double shaft steppers and connect the shafts together with low backlash couplers at the same end of the screw, as any flex between the two motor shafts and you will start to loose allignment, making the motors fight each other.

IMO its not worth the grief to do this unless you have a very good reason to have two motors.

[CJL5585]

you wont find much by way of literature on running multiple steppers in parallel, most people would just buy a proper sized stepper for the job. I have done some work with bldc motors in parallel, and trust me getting the motors / steppers syncronised is a pain in the ass. If you are going to do this then get double shaft steppers and connect the shafts together with low backlash couplers at the same end of the screw, as any flex between the two motor shafts and you will start to loose allignment, making the motors fight each other.

IMO its not worth the grief to do this unless you have a very good reason to have two motors.

That is the point I was trying to make. I don't think that you will find a MANUFACTURER who is willing to recommend it due to the fact that it is not a recommended application. One might see info on the internet by some hobbiest, but NONE from the people who build the steppers.

Jerry

[ger21]

One might see info on the internet by some hobbiest, but NONE from the people who build the steppers and drives.

Jerry

Mariss from Gecko has sid that you can run two steppers from one drive, and get decent results at speeds up to 3-5 revs/sec. At faster speeds you'll get resonance issues. But I'd still go with the one bigger motor approach.

[CJL5585]

Mariss from Gecko has sid that you can run two steppers from one drive, and get decent results at speeds up to 3-5 revs/sec. At faster speeds you'll get resonance issues. But I'd still go with the one bigger motor approach.

That is true, but after calculating the leadscrew turns per inch and even any microstepping, (even half-stepping) your max speed is down to around 3 to 15+ inches per minute max, which is not a reasonable max speed for a CNC unit which I would consider using.

Also, I think the resonance might occur at any point in time according to the many factors of speed, acceleration, and possibly de-acceleration which would be calculated from the g-code running at the time. I do not think that it could be pre-determined when or where the resonance might take place. This in itself is a good reason not to parallel steppers.

Just my 2 cents.
Jerry