I've been working on an issue with a friend's cnc plasma setup that he bought new. One of the cables to the X axis got damaged. All the shielded cables are very long, like probable 30 feet. So i repaired this cable by removing most of this length, maybe 20 feet and it's still plenty long. However, the motor works fine but the cable gets very. Was the idea of long cable to add resistance into the circuit? The cable is a 4 conductor, shielded with maybe a 22 AWG wire size. Can I replace it with AWG 18? The driver amps is set at lowest value. I'm an industrial electrician but totally new to this CNC stuff.
Any help greatly appreciated.

AWG22 sounds very small for Motor cable, there is no reason why not replacing them to bigger ones.