Thank you for all the help above.

Thanks Boyan for doing the workings out I will definitely be saving them both and follow your instruction.

Clive, it most certainly feels like I'm conducting a mechanical orchestra when I start running the machine. I've taken it back to its original configuration as the previous owner had his stepper motors clinging to the outside. But I still can't find where the resonance is coming from slower speeds seem to make it worse.

It has a 5tpi screw and the x & y are on belts.