Another Master Desay xp 380p issue - Velocity Control

For as long as i've had this plotter...the velocity control on the plotter itself does not do anything...I can set it to 1cm/sec or 30cm/sec runs the same speed no matter the setting.

I contacted the software company WinPCSign that came with the plotter to see if it was controlled on the software side, but they said its controlled on the plotter side...

Any ideas anyone? How can i control the speed of it?