When you say it does not work do you mean it is still taking no notice of the F commands in the gcode?
Does the gcode you are using have F commands in it? I ask this because the gcode sample that was given with the machine I used had no F commands.
Perhaps the software that comes with it (ucancam??) does not issue F commands in the gcode it produces.
If you are not sure then try running this gcode,
G1 X100 F500
G1 X200 F100
G1 X300 F1000
Or if using imperial,
G1 X4 F20
G1 X8 F4
G1 X12 F40
Greg |