Quote Originally Posted by depronman View Post
Seconded on the 3 phase motor and vfd
Holy thread revival, Batman! :-)

You've described pretty much what I ended up doing, and it's worked... to a fashion. My biggest problem resulting from the above is getting closed-loop control back into LinuxCNC, and (recognising after the event) tuning the PID in LinuxCNC with the VFD PID. I always ended up with either oscillation or slow ramp rate when changing spindle speed that took seconds (or tens of seconds) to stabilise. I did try tweaking many times but never got to where I wanted it. Coupled with the clumsiness of the countershaft etc, and my desire to remove that, and the third-party spindle encoder has sent me down a different path with light-at-the-end-of-the-tunnel, which involves removing much of the original lathe and replacing the spindle motor with a 2kW servo. That's working quite well at the moment but this weekend's job is re-boring a new timing pulley to fit the servo shaft (the reamer went for a wander on the first one). Pics may follow.