I have a gantry-style CNC mill (actually, engraver) which has 2 spindles on independent Z axis but common X&Y axis. It operates as a tool-changer with one spindle doing the roughing and the other finishing. It also allows me to make parts which are longer than the official work envelope since I can take advantage of the Z1-Z2 offset. S1 has max 10000 rpm and S2 has 20000 rpm, but the setups are otherwise identical except the drive pulleys.

The current system allows operation of one spindle/Z axis combination at a time, with separate M codes switching between the 2 spindles and the 2 Z axis.
This works well, especially when programming, as S and Z commands are S and Z, regardless of combination selected.
I have had occasion where it would be handy to be able to use both combinations at the same time, and I can see this would require use of different axis names.

The machine uses a PC based control system, with a PCI card controlling 6x Mitsubishi MR-J2 servo amps (4x Axis and 2x spindles) and all I/Os. It has a proper MPG, but that is the limit of the HMI, as everything else is software controlled by keyboard and mouse.

The PCI controller card has just failed, and as it is no longer available, I need to do a retrofit.

I don't have a lot of cash to splash around for a new control, otherwise I'd probably go Beckhoff, so I am looking at cheaper options.

It seems that if I had steppers, there are any number of options in the "hobby" price range, but when you require analog outputs (+-10V) to control servos, options are limited.

After reading a lot of forums, and the odd PDF manual or two, I have identified 2 possible options.

Both options are Ethernet connection to PC, and I choose to go that way to "future proof" the machine. As internal PC connections are forever evolving, it seems Ethernet is the one constant. It will also reduces any driver related issues, and will allow me to substitute alternate PC options, eg Rasberry PI or whatever other formats may tickle my fancy, provided I can run the necessary software.

Option 1. CSMIO/IP-A with ENC, MPG, I/O expansions and using Mach4.
This is a much tidier setup, but I have concerns about dual spindle setup. As only one axis is independent, it would need be setup to operate either spindle through switching (as per current setup), but I may not be able to utilise both spindles at the same time (duplicate parts). It is also the more expensive option and I have not had any email replies regarding suitability, which tends to make me shy away from it.

Option 2. Mesa 7i97 with 7i84 I/O expansion running LinuxCNC.
This is the less expensive option, but my knowledge of Linux is zero, and this could cause significant problems when trying to configure it. Having said that, it appears that I should be able to utilise the spindles either way, if I can get it configured properly. I can't find too much information about either card, or configuration thereof, which is a real concern given my knowledge of Linux.

If anyone knows of a different analog option in the sub AU$2k price range, I'd be interested to hear about it.

I'd also like some feedback/opinions on the above options, especially anything to be aware of with these setups.

Thanks for reading.

regards, Oz