Gear reduction

[DragnsBane]

When one uses a gear reduction to increase torque, wouldn't you in essence also get a microstepping effect too? For example if one uses a 4:1 reduction the drive gear would have to move four times for the driven gear to complete one revolution. A 1/4 step. So if this is true then one could use a half stepping driver, add a 4:1 reduction and get a 1/8 step machine. Am I right on this?

[ynneb]

As you say " In essence" this is true.

You need to work out how much axis travel a stepper step will tranlate into. If the end of the travel is small enough, (acceptable tolerance) then use it.

Because most computer software can only drive at certain top speeds (PPS), it would be wrong to gear down your drive too much, because that would reduce the top speed that your axis can travel at.

[ger21]

Originally Posted by DragnsBane When one uses a gear reduction to increase torque, wouldn't you in essence also get a microstepping effect too? For example if one uses a 4:1 reduction the drive gear would have to move four times for the driven gear to complete one revolution. A 1/4 step. So if this is true then one could use a half stepping driver, add a 4:1 reduction and get a 1/8 step machine. Am I right on this?

Sort of but not really. The main benefit of microstepping is smoothness, and minimizing stepper resonance. Not added resolution. The reason for this is that the more microsteps you have, the less torque each one will have, as microstepping drives basically split the full step torque into the smaller steps. because of this, the torque for say a 1/8 step may not be enought o maove your machine, but the torque will accumulate with each succesive microstep until the motor can turn, then it will basically move all those microsteps up to that point.

A microstepping driver will usually run much smoother than a half step driver. Half and full step drivers can suffer from resonances which can cause lost steps. Microstepping can help to minimize or eliminate this resonance.

Another problem with gearing down steppers, is that steppers have there highest torque when they are not spinning. By gearing them to spin faster, you end up with less torque. But the gearing would cancel that out, leaving you with probably the same amount of power at the same speed if you didn't have the gearing.

Having said all that, all machines are different, and what you're proposing may work well for what you are doing. Give it a try and let us know if it works.

[ger21]

You might want to read this for more info on what I said above.

http://www.machinedesign.com/ASP/vie...strSite=MDSite