axis moves in forward direction more than backward direction

[mamech]

hello I am building a 3d printer called "e-waste", it is based on steppers gotten from old floppy and cd-rom.Its electronics are based on ramps 1.4 and its firmware is based on marlin 1.02 firmware. I am trying to move manually the steppers from repetier or pronterface. I could move them successfully, but I noticed that when I move an axis from the software to move 10 and then -10 (for example) I found that motor does not return to same place. I notice that motors moves in a direction more than the opposite direction. I tried to play with pots of current limiter in stepper driver without success. any ideas about the possible cause?