I have been giving some additional thought to converting one of our mills to a more modern controller platform. Based on some research, it seems to me the best current option will be to convert it using EMC2. Another reasonable choice would be to use Mach3, but as Mach3 relies on external hardware to track motor position, whereas EMC2 runs in a real-time Linux kernel and does the motor control directly in hardware, I think an EMC2-based solution will ultimately be more flexible and better suit what we have. For instance, you can do rigid tapping with EMC2 but not Mach3. The hardware costs will be a bit lower with EMC2 as a secondary benefit. As a tertiary benefit, EMC2 is open source.
I believe doing this properly will require a dedicated PC with the following interface hardware as one potential (prices from http://www.mesanet.com/
* Mesa 5i20 : general purpose PCI interface with Xilinx FPGAs. There are already proven EMC2 drivers for this hardware $199
* Mesa 7i33 4-axis servo controller daughter board $69
* Mesa 7i37 general purpose IO daughter boards $69
Both of the daughter boards hook into the 5i20 via 50 pin cables, and there is a third 50 pin header available on the 5i20 for additional future flexibility (driving steppers, for example).
This approach would get us a fairly sophisticated solution for under $400 (counting the PC as free).
These posts detail some folks that have successfully take this path:http://www.cnczone.com/forums/emc_linux ... ories.html
So we wouldn't be blazing too much new ground.
This site details a generic Arduino interface to EMC:http://axis.unpy.net/01198594294
To illustrate the kind of flexibility a solution like that would ultimately have to consider driving an extruder head.
This is certainly only in the formative stages, but I'm looking for feedback and to touch base with anyone else that has experience or interest in these things.