Dual spindle router

Hi,
I have a moving gantry router with two spindles configured as a Z and W axis. Only one spindle operates at a time as they share one VFD that switches between the spindles using a contactor. Ultimately I would like to use the second spindle on the w-axis with a different tool to reduce tool changes. Currently I think the best way of achieving this would be using M6 somehow ? Get the post processor to recognise a tool change and then swap Z to W-axis and have linuxcnc activate the contactor and apply an offset for the tool.
Any thoughts and guidance would be much appreciated,
Guy

Hi, so presumably I could get the post processor to put the G54 and G55 in which should work well. Yes the Z and W axis are independent but move together in the X and Y.

Also what is the best way of going about getting linuxcnc to operate the contactor at the tool change? Should I look towards classic ladder or sub routines etc?
Cheers

Cheers JT, great help! The last thing concerning me with this router was that it is only designed to operate within a certain work area, essentially so the spindles may overlap and work the same area. However this does mean if erroneous G-Code was written instructing a spindle to lower and work outside of this area the spindle could hit the frame of the router. Is there anything in Linuxcnc to prevent it following certain G-Code unless the relevant spindle is retracted ? Maybe this needs to be a new topic in itself.

Hi Andy, your HAL ideas sound good if it means I don't have to play around with the post processors! What are the thoughts on Linuxcnc recognising bad G-Code ie. at X0 only one spindle may travel as the other would collide with the gantry support? Or would it be standard practice just to verify the G-Code before hand?