Hi Kirk, Every big windstorm we have has me wondering which tree will fall across our powerline or house. But I like the trees too much to remove them.
The problem I find when looking for " START_SPEED_FEED_SYNCH " is they are all either printf functions or null as in they don't appear to do anything: void START_SPEED_FEED_SYNCH(int spindle, double feed_per_revolution, bool velocity_mode) {} After that function (wherever it is and whatever it does) returns the actual threading pass to the target_z position is done: STRAIGHT_FEED(block->line_number, boring? safe_x + depth: safe_x - depth, start_y, target_z - zoff, AABBCC); //over The carriage is brought to the correct Z + offset location where the offset is the tan of the X distance and angle to follow the slope of the thread angle. Like setting the compound to 29.5 degrees. Then we wait for some sort of sync. It appears the Z may well be stopped at this point and the tool is at the depth for cutting the next pass. I guess it depends on how slow the spindle is moving. But that parameter "feed_per_revolution" probably is probably used along with the Z axis "MAX_ACCELERATION" in the INI and HAL files to count out a specific index position so the START_SPEED_FEED_SYNCH function returns not at the index position but where it would be given Z axis acceleration at the current angular velocity of the spindle. Have I got that right? And if so where is the real code for START_SPEED_FEED_SYNCH? John Dammeyer > -----Original Message----- > From: Kirk Wallace [mailto:kwall...@wallacecompany.com] > Sent: January-20-21 8:07 AM > To: emc-users@lists.sourceforge.net > Subject: Re: [Emc-users] Spindle speed changes with threading. > > (bottom posted this one) > > On 1/19/21 9:42 PM, John Dammeyer wrote: > >> 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 > > > > snip ... > > I left the trail here: > > > https://github.com/LinuxCNC/linuxcnc/blob/master/src/emc/rs274ngc/interp_convert.cc#L4881-L5028 > > I think this is my next stop: > > > https://github.com/LinuxCNC/linuxcnc/tree/master/src/emc/motion > > (but after a day of 50 mph winds, there are a few chores to attend to) > > Kirk Wallace > > > _______________________________________________ > 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