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.

[hanermo2]

The mesa stuff is known to drive motors/servos well.
Granite D. is actually cheap ..

Getting any of the commercial/fanuc servos running well has been an adventure, in general, for others.

It will be very cheap to try with a granite d. system, vs anything else ..
and about 3x easier, imho.

There are endless caveats, most are unlikely.
So it might be it wont work .. but this is 5-10% probability.

Using the granite d. stuff makes you 10x more likely to succeed - imho.

[Clive S]

Ross here is the link to the drives https://granitedevices.com/products/

and a page that might be able to walk you through http://www.wiki.eusurplus.com/index.php?title=Main_Page

as you know I am following this

[Ross77]

So a big plus for Granite devices then

Not sure I class £420 a drive as cheap though, Would the IONI series be powerfully enough? Modular so I could build up the system as I need it.

Thanks Clive, hadnt found that wiki but looks promising, I could even use my current mesa cards as the GD's accept step direction signals as well as 0-10v

[Ross77]

Had a look today and the motors are Type 3-OS, A06B 0533-B001#7000 and dated 90 04 so guesing April 1990

6 pole, 112v, 0.5Nm and 1 amp, google seems to indicate a 2000ppr incremental encoder.

Are they worth saving or just replace with a all new drives.