K8400 doesn't print the whole area of the section

My printer does homing well, although the X axis is a little bit tough and hard to move by hand. So, we adjusted the power of drivers and as I said it does the Autohome well, the problem is when it starts printing, the first layer is very small and every section that completes then the section increases just for a side of the part. It is better to see some pictures for a better understanding.

PS: The part to be printed in pictures is a CELTIC SKULL.

Thank you.

Hi,

Sorry there was no picture.
You should look at this page.
http://www.k8xxx-3dprinters.crimed.be/w/index.php/XY-Carriage_Alignment