printer movement resolution

hello everybody

i am trying to make a delta 3d printer out of recycled parts

the printer uses 200 steps per revolution steppers at 1/2 step mode with xl belts (5mm pitch size) with 10 teeth pulleys

so the steps per mm for this setup will be 2*200=400 steps per revolution

and 5*10 =50 mm per revolution

this mean the steps per mm will be 400 /50 =8 steps per mm

so the resolution for each axis will be 0.125 mm and this is the minimum distance each axis can move

the problem is that i can't let my printer move 0.2 mm i am trying to use the 0.1 key in the host but what's happening is that i only can move 0.7 mm as minimum distance and that will happen only if i pressed the 0.1 button 7 times

so any body can tell me what is the problem please

sorry for my english

With a delta, the motor axes only move roughly the same distance as the tool head if you're moving directly in Z. How far the motors move to move .1mm in X or Y will depend on where over the build platform the effector is at the given time as well as the machine geometry and the results of the latest bed auto-level, if you're using that. The electronics are doing far more complex math than they do for a Cartesian bot.

Even if it's not your problem, it would likely be good to use a lot more microstepping (or, failing that, change mechanics to get more resolution). My delta runs 80 steps/mm on 1/8 microstepping and I'd still go to 1/16 if my electronics would support it, for both noise and resolution reasons.

Thanks for your help
So there is a place over the bed where the printer can't move less than a specific distance and to make it all the sam the printer limited the minimum movement to that distance in all places right??