> I dont think, the z position is "geared" to the counts beyond > index so locked unambiguously to spindle angle beyond index, > after initial sync is acheived. > > > Peter Wallace > Mesa Electronics
So far that makes sense. From "LinuxCNC User manual" "The tool will pause briefly for synchronization before each threading pass, so a relief groove will be required at the entry unless the beginning of the thread is past the end of the material or an entry taper is used." Following that is: "Unless using an exit taper, the exit move is not synchronized to the spindle speed and will be a rapid move. With a slow spindle,the exit move might take only a small fraction of a revolution. If the spindle speed is increased after several passes are complete, subsequent exit moves will require a larger portion of a revolution, resulting in a very heavy cut during the exit move. This can be avoided by providing a relief groove at the exit, or by not changing the spindle speed while threading." So there are side effects to changing the spindle speed but nothing that infers it can't or shouldn't be done. The implication is that at the start of the G76 based on spindle speed and Z axis acceleration along with target Z axis speed a specific spindle encoder value is used after that to determine when the axis is synchronized. Or N encoder counts before the index is used as the starting point for the Z to begin so it's up to speed, ready to engage, at the spindle index mark. Synchronizing it to the index mark for up to speed condition if you want to create multi-start threads makes sense. Move the start point by half the pitch to the right. Since the position of tool entry at speed is the index pulse regardless of spindle speed the thread should start 180 degrees from the first. So where is this calculated? In the Trajectory Planner? I'd like to look at the code but no idea where to even start looking. John Dammeyer _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
