I under stand the analogy, but I wonder if Linuxcnc is erroneously behaving as if the "leadscrew" were multiple start, with the number of starts equal to the encoder's counts/rev. Resulting in the syncing of the axis to the spindle is inconsistent if the syncing move isn't always the same? (Not saying this is how it is, just proposing a possible reason if the problem is real.)
I don't do any threading or have any machines with a spindle encoder. But I have observed this debate on whether this problem exists in Linuxcnc for years now here on this list. Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: Peter C. Wallace <p...@mesanet.com> Sent: Tuesday, January 19, 2021 3:10 PM To: Enhanced Machine Controller (EMC) <emc-users@lists.sourceforge.net> Subject: Re: [Emc-users] Spindle speed changes with threading. On Tue, 19 Jan 2021, Gene Heskett wrote: > It wasn't the last time I tested it Jon, and most of the recent > conversations here are ignoreing the fact that every new stroke, > starting from its resting position, regardless of whether its a G76 or > you are "pecking" a G33.1 for rigid tapping, is a NEW sync action, and > its here that diddling the the spindle speed affects both the accel > time to get Z up to sync speed, so in addition to the spindle turning > further at a higher speed, it also takes Z longer to get up to that > higher speed and become phase locked. This combined change in the > delay from 0 to locked is changing the phasing between the spindle and > the tool at about 2x the change in spindle speed. And screwing up your thread. > As long as the sync can happen before the tool hits the metal that will be no error in the created thread (no phase error) regardless of when the speed change occurs. The only change will be where the thread starts. Once synced, this is basically identical to a mechanical lathe (when the half nut is engaged). Peter Wallace Mesa Electronics _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
