1) Please clean the axes and smear the lubricating oil evenly.

2) The deformation of machine framework caused by external force during the  transportation. 

3) The cable connection of X.Y motor is loose.  Please open the machine base, check and re-connect the cable. 

4). The fixing screw of the timing pulley is loose.  Please check the fixing screw of XY axis, find out the loose one, and tighten it with  screwdriver. 

5). Synchronous belt drops or breaks. Please change a new synchronous belt.