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When did fanuc switch to AC servos?

pmtool

Cast Iron
Joined
Jul 10, 2011
Location
Portland, OR
Just curious, Seems like mid to late 80's? I still see some old yellow cap servos out there. Did they switch all at once? Are they or I guess were they fairly reliable? Seems amazing that there are still some running 30 years later...
 
AC analog was introduced in the early 80's. I've got some service documentation dated 1982 on them. My oldest AC digital documentation is 1987 and it is revision 5 so imagine a couple years earlier than that.

DC must have still been available for a few years as I recall a working on a 1985 Kira machining center still having yellow cap DC motors (though it could have been an old stock machine).
 
Silly question, but what is the difference between the analog & digital systems? I mean fundamentally, I know the difference between analog/digital signals but hows that work in a servo motor/amplifier system?
 
Seems amazing that there are still some running 30 years later...

I have 3 machines with yellow caps. One did ferrous parts for Boeing (supplier on Boeing field) 2 shifts a day, 6 days a week from 1982 until about 2007. It had an indexer on one end of the table with a quick change pallet and pallet system on the other end of the table. One side was loaded while the other side was cutting. It made the same simple parts it's entire life. In 2007 a "rebuilt" Fanuc main board put the machine down long term. That board was bad from Fanuc. I have what I believe is the entire repair and maintenance history for the machine. There isn't a servo or servo drive repair in there.
 
Silly question, but what is the difference between the analog & digital systems? I mean fundamentally, I know the difference between analog/digital signals but hows that work in a servo motor/amplifier system?

On the analog drives, the tuning was still performed by adjusting pots on the drive board. The digital drives are tuned by servo parameters stored on the CNC. At power up, the parameters are downloaded to the drives.
 
On the analog drives, the tuning was still performed by adjusting pots on the drive board. The digital drives are tuned by servo parameters stored on the CNC. At power up, the parameters are downloaded to the drives.

Ok, so the difference is at the CNC-to-amplifier level then. The motors work like any other AC servo motor I suppose?

I know some of the older Fanuc red-cap (AC) motors had large encoders the size of the motor frame, as where modern Fanuc encoders are much smaller in size than the motor frame. Are these the older AC/Analog motors by chance? Or older incremental-encoders style? Or is that no indication of the system type, but just older designs?
 
Ok, so the difference is at the CNC-to-amplifier level then. The motors work like any other AC servo motor I suppose?

yes.

I know some of the older Fanuc red-cap (AC) motors had large encoders the size of the motor frame, as where modern Fanuc encoders are much smaller in size than the motor frame. Are these the older AC/Analog motors by chance? Or older incremental-encoders style? Or is that no indication of the system type, but just older designs?

DC motors use incremental 3 channel (A, B, and Z) encoders. Older AC motors (with either analog or digital drives) use a 3 channel encoder for position and a 4 bit binary "gray code" signal for commutation position information. Those are the larger bodied black or red encoders and would be incremental on analog drives and incremental or absolute on digital drives. Later AC motors with digital drives use a serial encoder. They are smaller and communication is by a serial data stream instead of the pulse train of the older 3 channel style.
 
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