Moray yes I think that you're on to something there. I have long thought that there MUST be some way to set up the relative rotational positions of the Index pulse and the two pairs of Curvic Couplings.
The index position is sensed by a proximity sensor looking for a notch. When the turret is initialised the SMCC card seeks the index position and homes on it - you can see the drive dog for the powered tooling rotate, then finding the position go off it and back on for accuracy.
Now it's rather difficult to see what is attached to what within the turret, but certainly at the point that it is seeking Index the front curvic is fully engaged and the rear one dis-engaged. The listing of the SMCC program that I have shows that there are 2000 encoder points between tool positions so when it is asked to change tools it seeks Tn x 2000 pulses.
But what sets the relative rotational positions of the Index to the other bits I am not clear. The Index proximity sensor is in a tapping in the turret casing so not rotationally adjustable.
This morning with the machine cold it resolutely refused to run the Turret Exerciser program without failing. It was OK on anti-clockwise moves but failed to seat the curvic on clockwise moves.
There is a setting ('Offset') on the servo card that so far I have failed to adjust by the book - it requires that certain wires be removed and links made, but the terminal numbers in the book don't all correspond to the printed numbers on the card. Basically you enable the drive, and also it's 'inch' mode and apply 0v to the analogue input, and tweak the multi-turn offset pot until the servo motor stops turning. Now just using the system rather than links, for 0v input the servo motor IS stationary.
However this morning with the program failing every time, I thought - what the heck - tweak it. I gave it 5 turns anti-clockwise (I think that it's a 20 turn pot) and guess what, the program instantly started working. So somehow I need to bottom out the wiring and get the offset accurately set.
It is very difficult to see if the clockwise last minute rotation that Moray noticed is still as consistent as it was - the camera angle is such that the tool disk is moving away at an angle anyway as it seats so it looks to rotate anyway - I shot another video so I'll let you decide as it's easier to see in the video than in real life.
I've also included the Turret cross section for reference.