Millpwr Retrofit-Retrofit on Bridgeport
There have been a couple of threads from people who have a mill with a Millpwr retrofit, minus the console, looking for solutions. I'm have the same situation with a Bridgeport mill. It came from a secure government facility, so they removed the console for security reasons. I thought I would share my solution.
I want to take advantage of what remains of the nice Millpwr package. There seems to be a few revisions of the Millpwr. In my case, the 3-axis Millpwr has the power supply and amplifier co-located with the 140VDC SEM motors in a really nice aluminum casting and environmentally tight fittings and cables along with glass scales. So I wanted to take advantage of that package. I know nothing about CNC or machining. I'm setting up a CNC mill just for fun.
It turns out that the units can be used as-is, cables and all, without fear that it will be costly to support (a concern that one person here has mentioned, and rightfully so). That’s because the amp is Servo Dynamics, the power supply is generic and easy to repair if needed, and the other functions (a PIC processor doing some minor control) can be bypassed with two jumper-wires on the board. I was able to figure out the pin definitions of all the connections and I will use the cables as-is without hacking anything up.
I'm going to connect the units to a Vital Systems DSPMC with Mach 3. I've chosen this after also considering Camsoft with Galil. The choice was obvious for an amateur. Camsoft and Galil's documentation gave me a headache. It was clear I would spend a long time trying to figure out what they are trying to tell me and how to use them. Perhaps they are too sophisticated for my taste. The DSPMC does what I need and spells things out in clear and simple language, with nice start up tools to test and configure the system. It looks like it comes up quite easily.
The motor units are the same except the z-axis has 3 limit switches while the x and y do not. I guess they depend upon the glass scales to do the job. I’m not quite sure what the sequence is to find home as the glass scales have a home reference mark. But if you power up and don’t know what side of the home mark you’re on, then what is the homing sequence? You could go too far in either direction to seek home since there are no limit switches. Sure you can do it manually, but it would be nice for the computer to automatically seek home without crashing from side to side. I can add limit switches to do the job. I’m just curious how Millpwr does it as they brag on how they can pick up a job where it left off after power is lost. The only thing I can think of is that position is constantly stored in FLASH, but that would burn up FLASH in a hurry...does it have a hard drive?; or they have more than one reference mark on the glass that indicates each limit and center. I’ll be checking that with a scope later on.
The other thing this solution provides is the ability to add a 4th axis in the future.
I’ve got the power supplies, amps and motors running. The only thing I need now is to figure out what the AC voltage is coming into the motor units. I assumed it was straight 120VAC from the wall, but if it is, then that would be converted to 170VDC at the motors, which are rated for 140VDC maximum. So I’ve asked Millpwr users to measure that voltage to see what it is on another thread. No response so far.
Next is to wire up a box with the cables and then buy the DSPMC. It’s a lot of fun doing this discovery and learning all about CNC and machining.
