Are there compact stepper motors without axial play and backlash?
CuriousOne
Posts: 931
Hello.
Need a compact stepper for an application, where motion should be precisely controlled. These cheap steppers from ebay have about 5-6 degrees of "free play" which is a disaster for me. Anyone knows servo without such problems?
P.S. I do have two steppers removed from 5.25 floppy drives, without that problem, but they are too huge for my application. I was thinking about lens drive steppers from cd-rom drives, but they all have long and non standard shaft.
Need a compact stepper for an application, where motion should be precisely controlled. These cheap steppers from ebay have about 5-6 degrees of "free play" which is a disaster for me. Anyone knows servo without such problems?
P.S. I do have two steppers removed from 5.25 floppy drives, without that problem, but they are too huge for my application. I was thinking about lens drive steppers from cd-rom drives, but they all have long and non standard shaft.
Comments
You need to be explicit about your requirements - everything has play and backlash, its what limits are
acceptable, and how many steps/revolution and torque and speed are you needed? The numbers...
The ball screw portion of the shaft can be cut off with a small diamond cutting wheel, and a 3.5" floppy drive head stepper might also be an option.
leadscrew, not ball screw, surely?
LOL, yes, lead screw. So much of what I work with has ball screws I'm auto-typing ball screw now.
As far as end play, it's possible to add a little 'preload' to whatever bearing is on the other end of your rotating assembly. caveat though, most steppers can't stand much axial load, and most have no real thrust bearings. The proper way is to pre load bearings for your rotating assembly for 'zero' end play without a motor, and then install the motor with it's rotor centeredin it's axial play.
As far as radial play, this is more a function of the driving circuitry than the motor. (Unless it's plain old broken..)
as far as size,is somethin like this:
http://www.allelectronics.com/make-a-store/item/SMT-356/24V-STEPPER-MOTOR/1.html
in the ballpark? The 7 degree step angle is not free play, and the microstepping drivers like this:
http://www.allegromicro.com/en/Products/Motor-Driver-And-Interface-ICs/Bipolar-Stepper-Motor-Drivers/A3977.aspx
can cut that to under a degree.
The steppers from late model automotive instrument panels (that drive the indicators for fuel, temp, speed, etc..) are tiny and have gearboxes to increase their resolution. Just check your local junkyard.. (New Egg carries these for about 8 bucks.)
http://forums.parallax.com/showthread.php/141149-3-Stepper-Motor-amp-Board?p=1216953&viewfull=1#post1216953
I used two from a junkyard panel, with pointers, to make CPU load and temp gauges for my modded case.. I stepped 'em from an SX 28 through an L293. Surprisingly strong, but certainly not going to move anything big.