[UKRobotics]

A few months ago I purchased a 20 year old Bridgeport Series 2 Interact 4 in perfect mechanical order but blown controls for the purpose of retrofitting.

My plan (if possible) is to leave all the axis motors + encoders intact but replace the computer and drives with a pc based rutex combo.

Originally my plan was to get a single to 3phase VFD and run the spindle motor off that as doing so would make it very simple to connect to the computer and give proportional speed control. Unfortunatly things are never that simple. Though there is no markings visible on the motor, I have been informed by numerous sources that the motor is a 5hp 200volt DC motor! most likley shunt or series wound.

The question is, where to go from here. I have never seen a AD - DC VFD for a motor of that size for a sensible price, but i still really do want computer controlled speed adjustment.

Using the current spindle drive (Contravis) is not really viable because I beliefe it is already faulty (and would be too damn expensive to repair) and also it requires a 3 phase input and I really want to keep this machine single phase for simplicity.

It seems like my options are, try to find a cheaper VFD which will run the current motor as is, or to replace the DC motor with a 3 phase AC motor of the same sort of size and power rating and then get a 'normal' vfd to run that.

Just wondering what peoples advice would be regarding what to do here. Swapping the motor over seems like a relativly simple option in theory but perhaps i'm missing somting ? Has anyone on here ever done what i am trying to attempt and succeeded ? If i did go down that route, what sort of price would i be expecting to pay for a 3 - 5hp 3 phase motor ? I quick google search didnt throw up anything useful for me.

[Karl_T]

Replacing the motor with a three phase one is your best route. I had a DC unit just like yours on my Hardinge CHNC. I know of four places that are salvage yards for industrial equipment. On my third stop I found found two motors that would mount up with modfication, so I bought both for $120. (one spare)Had to move up to 7 1/2 horse from the original 2 horse. Now I got lots more power, Scotty(Grin for star trekkies)

Seriously, try to get a larger three phase motor, if you can. Here's your chance to never be limited by spindle hp.

Good Luck

Karl