Does anyone in the aftermarket offer a good quality MPG that will work with most any CNC equipment? A lot of the MPGs I see offered with control upgrades seem to be in the $300-600 range. I'm not terribly clear on what is inside one of them, but that seems like a lot for what appears to be a pretty simple device.
Every now and then there will be a used Fanuc MPG on eBay. Are MPGs sufficiently generic that they can be swapped between controls, or do they need to be designed specifically for each control?