Especially if you care about upgrades and ease of maintenance, rip 'er out.
I started the process this afternoon. Opened up the electrical cabinet and looked at the wiring and compared to the electrical documentation. I actually have the original electrical documentation. The documentation is very good and is accurate per the machine. This machine is a perfect candidate for a DMC-4060, but am thinking about using a Dynomotion Kflop board. Haven't decided yet.
The panel is well laid out and is wired to European standards, typical ISO 9000.
Closeup of the original computer box. This has an actual off-the-shelf micro PC in it, but interestly, no hard drive or memory. Has a proprietary PCI board that appariently has the firmware and memory onboard. That PCI board is ported out to the connectnections you see here.
X, Y, Z stepper drive and spindle VFD. The stepper drives are 3 phase output. Haven't seen that before. But they take a standard step & direction signal so no reason to change them.
I'm thinking about doing something like this. I grabbed this example picture from Ebay, this DMC-4080 has a proprietary interface board attached that just plugs into the standard Galil D-sub connectors. It would be pretty easy to design a similar interface board to be compatible with connections on the computer box above. I may just buy this DMC-4080, still thinking about it.
The reason for building a compatible interface board is to not disturb the original wiring and thus allow easy return to the original computer system in case a future buyer wants the stock system, that way the value of the machine is maintained.
Then I need to decide what computer to use. I'm thinking a micro PC so it will fit in the existing enclosure. It is deep enough that I can stack a micro PC and a Galil or a Kflop and put it all in the same footprint as the original unit. Then just bring out the monitor and USB connections and hang a keyboard/monitor mount on the side of the machine. Would be a nice compact unit. I just need to find a micro PC that will run Fusion 360 so I can have that on the machine computer.
So at the moment the real decision is Dynomotion Kflop or Galil DMC-4080. My software will work with either and both are good equipment, but there would be a learning curve with the Kflop, where the Galil is almost plug & play for me. The Kflop is a lot less money, $249, vs. a used Galil >$1000. Is the difference worth the couple hundred hours of learning/programming time?
One other option is to use hardware I already have on the shelf and use Galil PCI cards. I have several 4 axis cards around and could use 2 of them to run everything. The down side of that is the wiring is going to get messy, and they require a full tower PC to stuff them into. So I lose the nice compact system.
Decisions decisions.
I may worry about this project after I finish up the the C axis upgrade on my lathe, just finishing up the software for that one, but still need to buy a servo motor and build the clutch hardware. Then there is the CNC surface grinder project that I have been putting off for the last 2 years. I have all of the parts on the shelf for that one also.