Okuma lathe retrofit servo help

Hi, I need a bit of information on retrofitting a okuma ls30-n flat bed CNC lathe.
 
This one is a fairly large size lathe and with two turrets which i believe linuxcnc can easily control.
   

VFD seems usable. It takes an analog input for speed control.
 


My main issue is with the servo motors.
 
this thing has okuma's own ac servos and drives. (sorry I wasn't able to take photos of the actual motors but as far as I can confirm they seems AC servos with absolute encoder) After digging on the forum I came across that these things don't really accept analog commands or step/dir commands. Instead they have a serial communication to a main board which takes the encoder inputs and command the motors accordingly. 

I plan to get rid of the old controller and the servo drives because it seems like a dead end. What I'm really curious is that can i use the old servo motors with new drives? I mean even if I can get away with replacing only the encoders of the motors that would be great. Does anyone has experiance with that.

I have successfully retrofitted my okuma ram type mill with linuxcnc but I replaced all the servos with new delta ASDA A2 servos and motors. That was expensive trying to save some if I can use the servos. Any help is appreciated.
Thanks.

 

Only real option is the mesa 8i20 drives. But I think they are too light for your motors.

I have an ongoing retrofit on a lh35-n Okuma flatbed - looks very similar to yours.
mine was brushed servos with tachos and okuma's absolute encoders.
Mine looks older (about 1980 vintage) it used +-10volt servo commands.

At first I replaced the absolute encoders with incremental encoders. - was pretty simple. I could take a pic of what i have left.

Then for reasons, I switched to an AMD drive for one axis. It would have worked fine but I didn't realize the used drive was broken.

I finally re-motored with BALDOR ac servos and STMBL drives using smartserial protocol (ie all digital)
This was a bit more difficult due to the shaft adapter required but in practice has worked fine.
I wonder if the parts are interchangable on these lathes. i am looking for an adapter plate for the splined end of spindle shaft. be nice to know what it looked like.

My original Okuma drive was great just i managed to break it (my fault-ish)
but of course there was no information on fixing them.
I wish there was info on the absolute encoder - that would have been nicer.

STMBL drives are great - just hard to get
Used (ebay) AMC analog drives are a great deal but of course a riskier purchase.
I have a couple AMC digital drives and they seem ok but i have not used one as a servo drive just a spindle drive on a small mill.

Chris

They might work but won't be getting the real performance out of the motors. these things are rated at 50A peak. Any chinese drives maybe?

• cmorley

Thanks for the reply. Is there a place where I can buy the STMBLs fully assembled? I'm happy send you any photos if you need but the lathe is not on my workshop yet. (need to find space for it. it's still at where it was. That's why I could't get to the motors)

Have you used AMC's drives with AC servos, I looked at them when I did the mill conversion but I had the get rid of that idea due to a damaged z axis motor. Then replaced all three motors with delta ASDA-A2 motors and drive. They turned out to be just great. But it cost me more than what I paid for the mill.

I am using a digital AMC drive for a small ac servo spindle motor with a resolver.
It's a bit of a fool around to tune it (windows xp program over serial)

I dabbled with a larger motor just for testing - it suffered from noise on the +-10 volt input but that was probably my fault.

I bet you don't need 50Amps continuous output.
In fact it looks like the dip switches are set for 30A (though it's a bit hard to see in your pic)

I'm thinking the 50 A is peak power rating.

Are you going to use this lathe for production/money making work?

STMBL are very hard to get particularly now (chips are high price)
It usually comes as a kit.
I've heard there are people that have units in a bit of quantity but they don't advertise - not sure what the deal is there.
There is a chat site for STMBL and people do runs on the boards and kits - you might try them if you are interested.
gitter.im/rene-dev/stmbl

STMBL are limited to about 20A @ 320 Volts dc or 2kw
They are also a pain to set up as the documentation is sparse and the settings are difficult to figure out.

On my machine (IIRC) the Z axis was about 2kw and the X 1.5kw from the factory.
The rapid speeds were 200 IPM.