Don't count on those 270 ozin steppers to spin any faster than 1000 RPM, if you even get that much. If they do spin faster, the torque they do have will be all but useless.
I suggest 20 pitch, 20 degree p/a rack, and 20 tooth spur gears. That is what I run, and it works for me. One revolution of the spur gear gives 3.14 inches of movement.
I would either get gearboxes or run chain/sprockets or timing belts and pulleys to get a more effective gear ratio, and increase resolution. You should never rely on microstepping to better your resolution. Make sure the mechanics allow for the accuracy you want.
I would suggest a 1:5 ratio for starters, give or take. Check with the manufacturer of the motor for a torque chart, find out at what speed your motor makes the most torque, and gear your machine to that. If the motor does not make sufficient torque at that speed, or you need the torque at a different RPM than that motor allows for, get a different motor.
If you are not that picky, try the belts and pulleys approach, and change out the drive pulleys to suit the best balance of torque-speed.
At a 1:5 ratio, when your motor spins 5 times, the spur gear will rotate once.
This gives you 3.14 inches of travel for every 5 revolutions of the motor.
At 500 RPM, you now have 314 IPM. This is more than fast enough for a hobby machine, and cutting speeds will probably be half of that or less. My bet being less, as the 269 ozin motors just simply do not have enough torque to push a router through hardwood or even MDF at 150-200 In/min.
I think you will find your options limited with that size of motor, at least for routing. You can increase the torque by going up in ratio of your gearbox,as well as gain accuracy (resolution) but then you lose speed.
As far as figuring out your resolution, take the number of motor steps (200 or 400, most these days are 200) and the number of teeth on your pulleys or sprockets (I will use a 10 tooth and a 50 tooth here, for the 1:5), etc. or the ratio of your gearbox and the final diametrical pitch of your spur gear (I will use 3.14 for example, what I have.) and
200 x (50/10) / 3.14 = 318 steps per inch. That is without microstepping.
Basically, your motor will turn 1.59 full revolutions to move one inch.
Figure out your microstepping amount on the drivers, and do the math from there.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
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