Hi all,
I have a belt drive on my y axis.
Trying to calculate steps per mm.
Heres what i have got :-
Stepper motor with 18 tooth sprocket
driving a 45 tooth sprocket - which is fitted with a 20 tooth socket that drives the gantry along the belt.
So have started to try and work it out -
45/18 = 1:2.5 ratio
45/20 = 1:2.25 ratio
How do i realise a ratio i can use to calculate my steps per?

Done a little sketch (no laughing - i know, at least i didnt do it in crayon!) attached.

To calculate the distance per step you need to also state the steps per stepper revolution, micro stepping value and gantry belt pitch.
You may want to consider the error from chordal action from the pulleys. It's probably insignificant, depending on your requirements.
http://chain-guide.com/basics/2-2-1-chordal-action.html

Thanks for that, I have got the info for the steps per stepper revolution, micro stepping value.
Was wondering how to come to the factor that I multiply the pulse/rev.
Hadn't considered the gantry belt pitch - where in the calculations would that apply?