anyone know a good formula for calculating steps per revolution.  im trying to "fine tune" my a axis.(rotating table)

thanks

dave

Personal message sent to you through the Mach forum.  I dont want my half baked knowledge logged on here forever. 

-Nick

That's not on, all my craps on here 

Graham.

its been a couple of years since I set mine up , but if memory serves heres how I calulated mine , 8" rotary table with servo motor, was to detirmine the ratio of the worm gear that drives it, in my case its 30 to one. 30 revolutions of the input shaft results in one full rotation of the table. I then have a timing belt (gatesXL .2 pitch) reduction  of 3 to 1. at this point it takes 90 revolutions of the motor shaft to turn the table 360 degrees I cant remember the encoder count but lets guess its a 500 cpr qaud encoder and takes 2000 pulses to move the motor shaft one revolution  . this works out to 180,000 pulse for one 360 degree revolution , 180k devided by  360 eqauls 500 steps per degree . In motor setup I just entered 500 steps per unit .

Here is how you do the math. I will give you mine as an example. What we need to know is, How many pulses from Mach will it take to move the machine 1 of your units? (inch,mm,deg.) Mine is in inches. 1 inch = 10,000 pulses on mine. This is how I came up with the number.
My steppers have 200 pulses per revolution. ( 360 degrees divided by 1.8 degrees = 200 )
Micro stepping = 10. So 200 X 10=2,000
Motor to screw gearing is 1-1. So 2,000 X 1=2,000
Screw lead is .200 of an inch. My screw will have to turn 5 rounds to move the nut 1". 1.0 divided by 0.200=5. So 2,000 X 5=10,000.

Brett