ok if i go 400 steps on the distance 3'' or 76.2mm machine can not overcome this distance, missing distance is 0.18 mm I have to change the step to 401 then it is slightly more than 76.2mm . but if I increases the distance to 152.4 is 6'' is again a problem, step 401 is not enough I have to give 402 step and again the machine goes a little more