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What is the optimum resolution for a stepper driven axis?
In other words, turns per inch.
I have a stepper driven screw drive that is 1 revolution per inch.
Is that resolution good enough or should I plan on gearing it down with a pulley/belt ?
Also ... I'm working on another project that is toothed belt driven on a 48" axis.
What is the optimum stepper turns per inch that I should shoot for?
I will be cutting and engraving wood and foam not machining mill parts, if that makes a difference.
1 turn per inch is not too handy. 5 turns per inch on a standard 200 step stepper gives you .001" resolution. That's a good goal. For small steppers (~100 oz.) which will probably turn a little faster 10 turns per inch is a good bet.
Eric
If your steppers are Not directly coupled to your axis then you must also take into account the gear ratio of the drive mechanism to determine actual resolution.
Dear Sir:
You might consider microstepping. Although the increments are not precise divisions of the basic step, the system operates MUCH more smoothly. I use 10x microstepping with 2" circumference pinions, resulting in .001"/step. In your case, 10x microstepping would give you .0005"/step. (200 x 10 steps). I like direct coupling if the numbers (torque, speed, etc) come out right. My stepper drivers are Gecko Systems, and I am quite happy with them.
Regards,
Jack C.
With the typical stepper motor (400 steps, half stepped) you would get 1/400 = 0.0025" resolution or 24.4/400 = 0.0635mm resolution. So ask yourself is that enough for what you want to make?
With a 1" lead the leadscrew will give you less force for a given torque, for that reason you might want to add a little gearing or go for the proven 5 TPI screws.
See the FAQ section, there is now a good description of those things by Arvid.
Graham
Micro stepping will only give you enhanced resolution if you motors have much more torque than required, which is unlikely with a 1 tpi lead screw. At their rated torque stepper motors will be lagging 1/2 a full step from the commanded position. Microstepping will of course give you much smoother motion.