Sir 

How Axis external encoder bypass in 828d controller 

------------------------------------------------------------------------------------------
Split from Siemens 840 DSL- Spindle Motor Encoder Bypass procedure.

Hello, Santlal Kumia!

Bypassing of secondary feedback is quite easy, but in same time is quite tricky task.

The most difficult task is to change active measuring system in PLC, you're need to change state of PLC interface signals "Position measuring system 2 (PMS2)" DB3xDBX1.6 to "0", and "Position measuring system 1 (PMS1)" DB3xDBX1.5 to "1", where "x" is number of your axis.

As you have 828d system you are quite lucky, because often HMI of this system is equipped with LAD redactor. If my memory says me right, to access LAD redactor you need to choose "Diagnostic” menu (I can mistake, I haven't dealt with 828d for last year).

When you have entered LAD redactor, try to find Network with name "Measuring system" or "Meas system". For each axis it will be separate network. You need to find circuit that affects interface signals DB3xDBX1.5/1.6. Usually circuit that activates  DB3xDBX1.5 is shunted with NC/NO contact (depending on programmed logic) linked with bit of word MD14512 $MD_USER_DATA_HEX. For deactivating interface signal  DB3xDBX1.6 there is series NO/NC contact in circuit. For example Spinner uses on its lathes setting to "1" bit 1 of MD14512[31] for X axis, MD14512[32] for axis Z to changeover interface signals DB3xDBX1.6/1.5. Any way if there is no such contacts you can add them by redacting LAD diagram.

And now the procedure for bypassing secondary feedback:

1. Enable (set to "1") DB3xDBX1.5 signal and disable  DB3xDBX1.6 signal by one of methods that have been mentioned above (by editing LAD diagram, or by changing bit of MD14512 word.

2. Change Axis Data MA30200 $MA_ENC_NUMS from 2 to 1.

4. Machine OFF/ON. After check the Axis on which you have disabled secondary feedback. If necessary, new reference the axis. That's why REMEMBER ACTUAL POSITION OF AXIS, before doing any manipulations.