Siemens S5 Encoder

You say you have two encoders on th X axis?

Only thing that triggers (in my head), when taken with your symptom, is that one or both are incremental encoders (rather than absolute) - with one for fine measurements, and one for coarse.

If the coarse measurement encoder was faulty, you could prob'ly move to any position within the range of the fine encoder before things went wrong.

My big problem with this is that I'd've expected the fine encoder (the one I think's working) to be connected directly to the leadscrew (assuming it's leadscrew drive!), so it would only move one screw turn (~5mm?) before faulting.

I'm prob'ly completely off the mark here - but I'd suggest that if there are two encoders, then one of them isn't doing its job.

But hey! You mention a glass scale encoder. Haven't met one of them (yet) - maybe I should look into it.

Hi John,

Thanks for the very quick reply! you are correct as to the lead screw. As well as they are both incremental. However the lead screw (motor) encoder is the course encoder and the glass scale is the fine encoder. I thought about what you are saying and I agree that possible the course encoder could be the problem due to the "Z" position pulse. the strange thing is, both encoders watch one another if you will. I am not getting any faults in comparison values. I am still stuck on how it is that the same value gets loaded in different positions.

As I understand it a reference coded glass scale encoder has distinctive reference points along it's path and each point can be assigned a particular value. I could be way off here but this is how it was explained to me.

Dave

Best I can come up with (after sleeping on it) is that the counter attached to one or other of the encoders is faulty.

Hope I don't get my knuckles rapped by CR4 Admin here, but have you tried http://www.cnczone.com/ ? I've had some useful info. from them in the past.

I am going to post there as well, Today. Thanks again

By referencing do you mean teaching the home position?

If you do it is possible that your system drives to a known position such as a hard limit switch and then moves to an electric home position or zero offset. If this is the case the hard limit switch may be stuck on and the machine then moves to what it measures as the zero offset position value, regardless of its real world position. Check the Home limit switch for proper operation.

You wouldn't have this problem if absolute encoders were used.