On Monday 18 January 2021 22:21:00 Peter C. Wallace wrote: > On Mon, 18 Jan 2021, Gene Heskett wrote: > > But because once locked, its not a big deal if the cutting load > > slows the spindle 25%, its still locked at that phase angle and it > > will stay that way until the end of THAT cut stroke. But if YOU > > change the spindle speed, then YOU have changed the synch delay at > > the start of the next stroke and that changes the cutter position as > > it tracks the next stroke, cutting a wider groove with that next > > stroke. If you speed it up, the extra cut is the back edge of the > > tool because it synched later in the spindles rotation. > > I dont think thats true, the initial delays do not affect the thread > past any initial issues when the thread starts. > This is because once synchronized, the Z is effectively in a > _position_ locked loop with spindle rotation relative to the > accumulated angle past the index. Changing the speed may change the > start of the threads due to the lock-in time but not that main > threading pass. You can verify this by turning the spindle by hand and > doing multiple threading passses. > This is true of both G76 and G33.1, with G33.1 maintaining sync until the tap has been totally withdrawn, while G76 releases the synch during the Z retrace, so it can move at G0 speed, then both checks spindle-at-speed and if true, starts the next pass on the index if you've written a peck loop, exactly the same as for a single pass if your spindle has the hueavos to do it in one pass.
Hidden in this is the fact that either resyncs the spindle to z phaseing at the starting/resting place for either a G76 or a g33.1 for every stroke it makes. And a change in spindle speed will change that phasing, screwing up the thread. So the spindle does not stay synced with Z during the entirety of a G76, each of the pass cuts is a fresh sync. And If you have to write a peck loop for tappping because you don't have a 20 horse spindle it is also freshly resynced at the top of each g33.1. I usually stretch that top stop long enough to blow most of the swarf off the spinning tap, and to give it a drink of rapid tap or buttercut. It Helps to keep the tap from packing full. > Peter Wallace > Mesa Electronics > > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
