Control system for Harrison M250 CNC

[AdrianW]

if there are four index pulses per spindle revolution, odds are not good for success.

Yeah - I had been assuming that the rotations would be counted by a running pulse total i.e. (pulses/pulses per rev) but as you say it's entirely possible that the index is used to reset the position - this could have odd effects!

[m_c]

Yeah - I had been assuming that the rotations would be counted by a running pulse total i.e. (pulses/pulses per rev) but as you say it's entirely possible that the index is used to reset the position - this could have odd effects!

It's something that the designers will know, but they don't always release the information, as it's not something you really need to know for implementation. You just need to know if an index pulse is needed or not.

I know the KFlop continually counts the pulses and you don't need an index pulse, but it has a lot of the internal workings exposed so you can customise exactly what it does. If you don't have an index pulse, it relies on using wherever the encoder count started as the index point for spindle orientation. Even if you do add an index pulse, all it can do is reset the zero point to the index pulse location (or any offset you'd like).
On my lathe, although I have the encoder index wired up, I only ever used it for confirming the encoder count when I was setting things up, it's never been used since.