Stepper motor with no backlash?

Hey, I'm looking for a stepper motor that will have no backlash at all(is there even anything like that for a decent price?)

I'd like to use a stepper motor to control an automated focusing system, so I'm first trying to see if I can achieve anything without backlash.

I have a NEMA17, but as far as I understood it still has slight amount of backlash, I could use the stepper motor as direct drive, or I could maybe use belt drive and gear reduction. I think belt drive should slightly increase the torque, and lower the speed and backlash, but will it make the backlash 0? I have no idea....

I currently use A4988, but I plan on switching to TMC2209 which as far as I know should be better, but once again I don't know how much that would improve in terms of backlash.

There's also encoders, but I'm not all that familiar with that, if you think it could be useful and fits in the budget that could be an option.

I don't intend to spend so much into it, Looking for something around the ~$30 max.
Obviously, the cheaper the better, and if there is nothing in the $30 budget, what would be the cheapest option beyond that?

Any help would be much appreciated, if there is any further information needed please let me know.

Thanks :slight_smile:

I have good news for you!
Stepper motors do not have backlash. None whatsoever.

Now if there are gears involved, like a stepper motor that has a gearbox, then the gears can have backlash.

Timing belts don't have backlash, assuming the belt is tensioned properly.

+1 for toothed belts. If they had backlash, many 3D printers would not work very well.

And I agree, steppers, themselves, do not have backlash.

mayyortom:
I have good news for you!
Stepper motors do not have backlash. None whatsoever.

Now if there are gears involved, like a stepper motor that has a gearbox, then the gears can have backlash.

Timing belts don’t have backlash, assuming the belt is tensioned properly.

groundFungus:
+1 for toothed belts. If they had backlash, many 3D printers would not work very well.

And I agree, steppers, themselves, do not have backlash.

Hmm that’s interesting, I always thought that more gears = lower ratio = lower backlash/more torque/less speed.

So…in my case for NEMA 17, is there any gears in it? It’s a standard 1.8 step angle stepper motor.
I actually thought of like getting a NEMA with planetary gearbox or something ^^

So I have 2 questions:

  1. If the NEMA 17 doesn’t have backlash I can just connect it as direct drive and there shouldn’t be any backlash?

  2. If that’s not the case, does timing belts really have 0 backlash? And is there any kit that will allow me to ‘play’ with the tension? My parts are static and it needs to be ‘spot on’ I guess…

Thank you! :slight_smile:

Each gear step adds X° of backlash. You can use zero backlash gears (spring loaded split gears), but less backlash needs more power.

zwieblum:
Each gear step adds X° of backlash. You can use zero backlash gears (spring loaded split gears), but less backlash needs more power.

Very interesting.
So going back, does the NEMA17 by itself have any backlash? If it has no backlash, then I’d just correct it as direct drive to the shaft. Or do I still need timing belt?
Thanks :slight_smile:

msacco4:
So going back, does the NEMA17 by itself have any backlash?

No.

Provided, of course, that the load does not overwhelm the magnetic forces. If it does then you need a motor with more torque. "Nema 17" only defines the size of the front face (1.7 inches) and there are dozens or hundreds of different Nema 17 motors with different torque specifications.

...R
Stepper Motor Basics
Simple Stepper Code

Robin2:
No.

...R
Stepper Motor Basics
Simple Stepper Code

Funny...So in that case I don't really need to worry about timing belt and just connect it as direct drive? Anything else I should check?

While steppers have no backlash, they still do not have absolute invariant positions. Timing belts, too, are soft. Check the datasheets if it concerns you. Most likely you will not be able to measure the effect.

msacco4:
Funny...So in that case I don't really need to worry about timing belt and just connect it as direct drive? Anything else I should check?

You need to do some experiments to see if the system works in the way you require.

...R

Robin2:
You need to do some experiments to see if the system works in the way you require.

...R

By that you mean check for backlash in the system itself?
Thanks!

msacco4:
By that you mean check for backlash in the system itself?
Thanks!

Not just "backlash", but flexing of your entire system when the stepper motor rotates. Doe it flex and then react to stepper rotation. Remember the stepper torque is equally applied to the shaft and the motor housing.
Paul

Backlash is mechanical slack in the system, but the problem with steppers is compliance - they
do not hold rigidly fixed, but have an elastic response to torque until overwhelmed and they skip.

This means they will show what looks like backlash if the load torque reverses direction, since the
change in the torque creates a small change in angle.

This means that you can't expect much greater position accuracy than a single step - you can't
expect microstepping to improve this, it just reduces vibration and gives smoother operation
and for a stable load torque gives more precision.

If you drive a system with significant solid friction with a stepper using a high microstepping factor, it will
appear to display classic backlash symptoms if you look at the movement closely.

Every standard transmission and also the Timig strap has a backlash in the opposite direction. The reason that accurate printers with such a backlash is - they only work in one direction. It is possible to measure this and perform a correction in the software - that is, the measured value to add steps in each direction reversal.

uriyank:
Every standard transmission and also the Timig strap has a backlash in the opposite direction. The reason that accurate printers with such a backlash is - they only work in one direction. It is possible to measure this and perform a correction in the software - that is, the measured value to add steps in each direction reversal.

All the HP printers I have had always measure the backlash in each direction when they do the alignment phase with new ink cartridges. And they always print both directions.
Paul