View Full Version : Best Drive for Fanuc AC servos

01-02-2018, 11:52 PM
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?

02-02-2018, 12:16 AM
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.

02-02-2018, 12:26 AM
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?

02-02-2018, 12:35 AM
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.

02-02-2018, 12:40 AM
Yes they are definatly red top AC servos and feed 3phase 415v 23703

I will try and get the numbers tommorow, cheers

02-02-2018, 11:42 AM
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.

02-02-2018, 03:33 PM
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
02-02-2018, 04:10 PM
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:thumsup:

02-02-2018, 10:28 PM
So a big plus for Granite devices then :eagerness:

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

03-02-2018, 09:22 PM
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.

03-02-2018, 11:37 PM
I'd price the different options up.

How much are a pair of drives suitable for those motors?
How much would it cost if one of those motors died (the actual motor is unlikely, but the encoder might)?

How much is a set of new servos/drives?
How much would ou get selling the Fanuc system/motors?

Personally I'd replace with new, so I've got a known quantity, and know where to get spares, but then I'm looking at things from a commercial point, where if something breaks, I want to know what's needed and where to get it, to fix it ASAP.

04-02-2018, 12:08 AM
My main aim is to keep the accuracy of the machine. I keep seeing posts that say the Fanuc set up is the best and its mad to replace with steppers.

I was also trying to keep the work load down and get it running Asap by just a rewire and not have to mess with pullies and belts.

Any idea on the value of a Fanuc OT system?

I know how much the Granite drives units are to run the Fanuc motors but there is such a variety of replacement servos and drives I have no idea what is the best option.

What nema 34 servo motors and drives would you recomend?

04-02-2018, 12:40 AM
I can understand keeping things simple.

I have no idea about Fanuc values, but I know there are people who buy machines just to get the control, then scrap the machine.

Nema34 is 69.58 square distance between mounting holes, and 86 overall square.
Those servos are not actually that powerful. 112V and 1A puts them at 120W continuous (there will likely be an instantaneous rating 2-3x this).

Kinco from Zapp, you could go for SMH60 400W servos which are 264 along with a CD422 drive at 240 makes it 504 per axis (those prices are including VAT).
If you go for a Chinese option, 200W servo and drive combos can be had $264 per set (https://www.aliexpress.com/item/New-Chinese-Servo-motor-set-0-637N-M-200W-220V-60ST-AC-Servo-Motor-60ST-M00630/760383887.html) or 400W for a similar price (https://www.aliexpress.com/store/product/New-Servo-motor-and-driver-1-27N-M-0-4KW-3000RPM-80ST-AC-Servo-Motor-80ST/314742_760376015.html with an 80 frame motor, or https://www.aliexpress.com/store/product/New-Chinese-High-Performance-Servo-motor-set-1pcs-1-27N-M-400W-220V-60ST-M01330-AC/314742_760394727.html with 60 frame motor)

Or I've just remembered CNCdrive do servos and drives. They do AC servos in 156 and 400W versions at €156 and €198 respectively, although I can't find their corresponding drive in their web shop. They also do DC brushed servos, but I'd personally pay the extra for AC servos.

04-02-2018, 11:59 PM
I had a dig around today and found the kolmorgen Goldline XT servo motors on another project and they are nema 34. If they work then they would get me started and maybe replace later.

That said Granite devices sell motors so If the Fanucs did pack up.

Are the ones from Ali express good quality?

05-02-2018, 12:49 PM
I just had a search and the Goldline XT are shown as discontinued.

The Granite drives do look quite versatile, so using another motor shouldn't be too much of a problem.

DaveK used the Chinese drives on his Bridgeport conversion, and I'm pretty sure Jazz has used them.