Im slightly new to the CNC world. This may be a normal situation but can anyone help me.
Ive got a basic 540 cnc router. Link for is http://en.step-four.at/hp2/index.php?action=1482
The problem i'm having is that when i increase the speeds of the motors, my motors dont run smoothly across the axis, this is for the Y and X axis. This is on Mach3 and i specifically increase the velocity. Below 100 in/min it runs smoothly. above that it appears as if the motor is becoming jammed on the way but it is going faster. Is this normal for this type of router?

Thanks