Best Drive for Fanuc AC servos

[Ross77]

Ive just bought a Boxford 250F that is running 3ph Fanuc OT system. I had planned to runn it off a converter but I understand that the OT system is quite old and cant handle large programmes.

I could reto fit with steppers but it seems crazy to loss the fanuc servos for steppers.

If I convert to 240v single phase I would like to retain the motors and run from linux cnc with mesa cards.

Ive seen The pico system and granite devices do a compatable drives but the pico is standalone and the GD is pricey.

Are there any other drives available or anyone done a similar project?

[m_c]

If the existing servo drives work (technically they're Servo Amplifiers, and a search should turn up more options) , keep them. You'll just need to figure out what they are, and what signals they need to run (they'll be +/-10V analogue drives, but you'll need to find enable/fault signals).

Other option is you convert to something like the CNC Drive DC servo drives, which will accept a step/dir signal, removing the need for an analogue controller.

[Ross77]

Unfortunally the lathe is at a freinds workshop at the moment so I cant check model numbers ect. I just assumed that the Fanuc drives cant be used as I couldnt find any examlples of people doing it. Also they are 3 phase so I would still need a rotary converter.

in the documents it looks like the spindle VFD has already been changed for a Mitubishi 240v one, if so that takes care of the spindle so its only the servo drives that need to be changed to get it all on 240v.

Can I use DC servo drives on an AC motor?

[m_c]

Are you sure they're AC servos?

From what I'm aware, most machines of that era used DC servos. The 3 phase will go through a transformer, before being rectified to provide DC for the amps.

You really need to get model numbers of everything.

[Ross77]

Yes they are definatly red top AC servos and feed 3phase 415v

I will try and get the numbers tommorow, cheers

[m_c]

Oh.
Selling them and buying some new servos and drives is likely to be the far easier option, if you do want to change the control.

Lack of program memory on a lathe isn't that big a problem, as most lathe programmes aren't that big anyway.
But it all depends on where you want to spend time and money, between running the existing system, or fitting a new system.

I'd be seeing how much a working Fanuc system is worth, and making a decision from there.