Help requested for Fanuc A06B DC servo system problem

[ERIC14779]

Have an old 1987 machine with Fanuc A06B DC Servo system on it. the motors have Tachs as far as I can determine.

 

the motor P/N is A06B-0652-B005 the velocity Control is P/N A06B-6047-H003

 

I am trying to identify how this system works so I can troubleshoot.

 

On the motor under the yellow end cap is what I think is the Tachometer, looks like a motor armature with (from memory) 6 little tiny brushes around the commutator, then there is a aluminum plate, and the rest of the motor...

 

the endmost cable connector is attached to the Tach and the other has many large pins and at least 4 smaller pins (again from memory)

 

the "velocity Control" in the electrical cabinet has the incoming power, output power to motor and 2 connectors a blue one with many wires and a white one with 5 or 6 wires.

 

I have been trying to find diagrams and/or manuals on this Fanuc system to no avail...

 

the CNC control does not report any errors.... (Sharnoa Tiger 6)

 

any help to resolve this is appreciated.

[Guest CNC Apps Guy 1]

Do you know when the last time the brushes were replaced?

 

Diagnostic No. 0800 is the X Axis Position Deviation

Diagnostic No. 0801 is the Y Axis Position Deviation

Diagnostic No. 0802 is the Z Axis Position Deviation

 

I only have an OMA Operators manual, no maintenance. May be tough to find that stuff. You could try calling FANUC. They are usually pretty helpful for me.

 

Sorry I could not be of more help.

[ERIC14779]

CNC Apps Guy

 

Are you talking about the motor or Tach brushes ??

[Guest CNC Apps Guy 1]

There's no mention of "Tach" brushes in my book. You sure it's a "Tach"?

[ERIC14779]

CNC Apps Guy 1,

 

be sure to read all my posts this morning....

 

 

To be clear,

this is a 1987 machine

the motor P/N is A06B-0652-B005 motor MFG date 9/86

I believe that the only Fanuc components are the drives --> X,Y,Z,spindle P/N A20B-xxxx-xxxx

and it has a PC based control (running Win98) Industrial PC w/Motion card and a Resolver to encoder converter ?? before the signals from the resolvers plug into the motion card.

 

I think that the tach and/or resolvers in the motors only go back to the Motor drives. and the PC motion Card instructs the drives to move axis...

 

So I am not getting any Fanuc error codes on the control (Sharnoa Tiger 6)

 

A repair place I found on the internet indicated that the -B005 denotes a Tach.... ?? IDK..

 

 

also I found a picture that said it was showing a tach on an old Gettys Fanuc DC servo motor, and what I saw on mine looked the same. See attached pic.

 

I am checking the motor brushes this AM.

 

UPDATE 0822 EST:

 

Z axis Servo motor brushes look good... still have about 3/8" of spring compression on all 4

 

Now what about the tach ??? how do I know if they are worn out ??

[ERIC14779]

I am continuing my research.....

 

Again there is an additional resolver mounted above the Z axis ballscrew, I believe that it is coupled to it (the ballscrew).

 

and the cable from this device is connected to what I believe is a Resolver to Encoder converter then to the PC motion Card.

 

It looks like the resolver may have slip rings, and if bad, would this allow for progressive position deviation. and I would not get any error because the system is not set up to detect this deviation ??

 

UPDATE 0919 EST:

 

additional feedback is NOT a Resolver.

 

figured out that the "box" before the PC motion card is to supply the attached ENCODERS with 5 VDC from the PC power supply as there is a connector from the computer power supply plugged into it as well.

 

So it looks like there are encoders on X,Y,& Z connected to the PC Motion Card and then some connections to the Fanuc servo drives... But why then does Z drift farther and farther out of position ??? :-(

[Guest CNC Apps Guy 1]

I was not able to dig up squat on this control. I'm only good from about the mid-90's on manuals.

 

Sorry. Have you tried calling FANUC? They are usually pretty helpful.

[ERIC14779]

Well I do not think this Sharnoa Mill has a Fanuc Control I think it is all Sharnoa.

 

Only the Motors/drives are Fanuc, including the Spindle..

 

See the pics.

 

 

 

[Guest CNC Apps Guy 1]

FANUC still supports their hardware, (Drives, Boards, PLC's, Motors, etc...)

[ERIC14779]

YES... But I think that the Position feed back goes to the 3rd party Motion Control board.

 

how can I narrow down where the problem is when the machine is moved with 2 separate vendors equipment, embedded together ???

 

This issue is very low priority right now but when the next large part job comes in it will get important in a hurry !!

[ERIC14779]

Update:

 

Ok I started looking at the encoder input "chain" and here is what I have found:

 

The Z axis encoder is Heidenhan ROD type. It is connected to a terminal strip at the encoder and then a 4 pair cable brings the signals down into the control cabinet.

 

The cable has shielding but it is not being used.

 

The signal is then ran into a box that has a line driver (digital amp) for each axis, and also brings in the 5VDC from the Computer power supply for the encoder(s) and the digital amp circuits.

 

The signal then comes out of the box and is fed into the motion card in the PC, again with unshielded cable (I believe that it is twisted pair (4) wire)

 

I do not know how old this setup is but, I am wondering if the problem could be with the Digital amp on the Z axis feed ???

 

I also do not like that there is no signal shielding, I would like to fix that as well.

 

Anybody think I may be on the right track ??