Lathe threading with GRBL (testing)

I started adding a spindle synchronisation mode to GRBL, to enable threading on the lathe. First I added the G95 mode (feedrate per revolution), which measures the actual spindle speed with an encoder (on this lathe, a 4 tick/rev magnetic encoder), and adjusts the feedrate continuously in real-time. This works pretty well, but does not synchronise to the absolute spindle position, so repeat passes will not line up.
To remedy this, while keeping things simple for now, I extended the "dwell" command (G4). If G95 mode is active, the dwell command also waits for the spindle to pass the zero position. For threading, it is now possible to issue a G4 to sync at the start of the thread, just before executing the actual threading command.
The code is on github: https://github.com/fschill/grbl-Mega
(spindle_sync branch at the time of writing this).
Further discussion on the main grbl repository:
https://github.com/gnea/grbl-Mega/issues/26

Видео Lathe threading with GRBL (testing) канала codemakeshare