Hello,

From the details you described what I understood is as below.

1. You are applying tool change command.

2. Spindle start orientation so that spindle can be positioned at predefined position.

3. Spindle rotates but could not detect its orientation position.

4. Your controller displays alarm/fault as spindle not at zero speed.

If above is true, please check below points.

1. Is there BERO signal, (proxy or dog) which will activate detection of orientation or spindle position predefine signal.

2. Why you replaced encoder? Is encoder you replaced is exactly same?

3. Is spindle drive control card OK?

 It seems you know the basic of how adjust spindle. I think your use 3rd party CNC, I am not sure how they send commader to make spindle positioning --I attached manual, 

please read  HS/2-31  "Positioning spindle "

you can seperat 56/14 or 24/8 from CNC to see you can make spindle positioning --stop --then adjust angle , finally connect back to CNC--you need read that manual help you self

BD Rob

   I have 6sn1121-0ba11-0aa1 control card showing no errors. p133 showing 63,926 - 63929 tics per home pulse.  The belts have been replaced and swapped out the control card. I recently replaced the encoder to resolve a prior issue. I have checked the cables from the spindle and double-checked shielding is grounded.

  when given a tool change command the spindle goes to search speed (-200) after 2 revs it seems to slow. then speeds back up and never stops. The Boston Digital controls will error out with a " Spindle not at zero speed " Then the spindle stops.