AB Aux Encoder Mystery

[TimothyMoulder]

Hi all,

Working on a system with a CompactLogix 43 processor, Kinetix 6000 servo drives, and a sercos interface between them.

The 6000 is using the aux encoder port to read an encoder that measures the material being fed through the machine. The problem is, it runs amuck and feeds material at a high rate of speed. So naturally the encoder is my suspect.

Replaced encoder and cable - same problem. Replaced drive - same problem. The only clue I've found in logic is that the aux encoder actual position keeps getting reset to 0 whenever it is moved, and there is no active logic to prompt that. It happens during homing, then doesn't happen again.

Anybody seen anything like this before? Looking for a direction to follow.

Thanks!

 

[Ken Roach]

It is typical for an axis position to be set to zero, or a specified position, after a Home command completes. That's the essential function of Homing, after all.

Are the Auxiliary Encoder axes and the feed servo axis tied together with a Motion Axis Gear instruction ?

I admit I don't have much experience homing axes that are geared together. I would expect to decouple them while doing homing, then re-gear them after everything's at the expected positions.

How often does the malfunction occur ? How does it end or resolve ?

It would be useful to run a Trend on the .ActualVelocity of the auxiliary encoder to see what the system thinks it's getting when the feed axis malfunctions.