Steve, what I was talking about is the capability of my drives to use the incremental encoders as, I suppose, you would an absolute encoder.
I have a gearbox on my turrets motor that is actually 25:1 reduction (not 20:1 previously mentioned) and my encoder on the motor is 2000 (8000ppr) so I tell the drive that it should roll-over at 200.000 pulses (25 x 8000).
The motor turns 25 times but the turret turns once and the count in the drive goes from 0 to 200,000 then starts again. That means as far as the drive is concerned 360 degrees is 200,000 pulses. Because I can set things up this way then I can index to any position on the turret and the drive knows exactly where to go, doesn’t matter if the turret has rotated 30 full turns or not as the count would roll-over at one rev (200,000 pulses). In reality that never happens as there is another nice feature, the drive can be set to take the shortest route between index positions and thus it can go both forward and backwards depending on the index you call, this makes it ideal for a turret or an ATC.
The tricky part was the ladder, it took me a while to get my head round how to accomplish it but it worked out well in the end.
I keep the logic side of the drive alive so I never have to home it unless switch off at the mains or there is a power cut. Even if the drive faults for some reason, say for example some stupid person pushes a boring bar too far into the holder such that it sticks out the back and then when indexing it jams against the saddle and faults the drive (Don’t know who would ever be so stupid to do such a thing

) Anyway even if the drive faults it just needs a reset and it still knows exactly where it is as it has been keeping track of the encoder counts.
If I lose power then all I need to do is home the turret, I have it homing to a low current value so I have it clamped when homing and thus it doesn’t move. To home after a power failure I just unclamp, manually rotate to tool 1 and then clamp then home and that’s it set.
Hood