# Thread: is step per unit right

1. ## is step per unit right

can some please check my math i don't think i did it right i need the number to put in the step per unit in motor tuning. i have

1/2 10 TPI at 5 start

this is a #25 chain right on the motor shaft with 9 teeth gear, gear pitch .25and moves 2.25in on full turn or (.44 a for 1in of travel)

motor are 200 step (1.8)

kevin

2. Originally Posted by electric2u
can some please check my math i don't think i did it right i need the number to put in the step per unit in motor tuning. i have

1/2 10 TPI at 5 start

this is a #25 chain right on the motor shaft with 9 teeth gear, gear pitch .25and moves 2.25in on full turn or (.44 a for 1in of travel)

motor are 200 step (1.8)

kevin
I'll try - I presume you are using Mach 3, and I also presume you have set your native units to inches.

1. I am not clear on what you are driving with the chain - is it the feed screw? Your chain drive is hooked up to the motor shaft...and on the motor shaft you have a 9 tooth gear (sprocket) driving a #25 chain with a pitch of .25 inches. So when the motor turns one rev, the gear (sprocket) moves the chain 2.25 inches. You did not say what the chain was driving - is it driving the feed screw? If so, what is the gear(sprocket) on your feed screw? So you need to explain your drive setup more clearly for anyone to help.

2. Does your drive do microstepping? For example, the Gecko 540 breaks up every step into 10 microsteps. If this is true for your drive, what is the microstepping rate - this will be needed in the calculation.

3. Keep in mind, you can have Mach3 do the calculations for you. You take a shot at the motor tuning steps per unit, and input it on the motor tuning screen. Then you click the settings screen, and click set steps/unit. This allows you to tell an axis to move 2 inches (let's say), and measure the actual distance moved. You then input that to Mach 3 and it will calculate the steps per unit for you.

Hope this helps. If still not clear, answer questions 1 and 2 and I will take another stab at helping you.