On Monday 18 January 2021 18:05:56 John Dammeyer wrote: > Quick question about threading with LinuxCNC. If you do a feed hold > between passes for cutting a thread and during that feed hold change > the spindle speed what will happen? > > From a start it takes a certain amount of time to accelerate up to the > required speed. If the spindle is turning twice as fast as the > previous pass it then turns twice as far. That doesn't line up the > cutter with the previous thread. > > The observation comment assumes a standard acceleration rate for the Z > axis. > > However, the system could also be configured to accelerate up to > arrive at a specific spindle position once it reaches threading speed. > > For example. The system knows using the fastest Z axis > acceleration+speed and spindle speed means it can arrive at threading > speed in 30 degrees of spindle rotation. At slower spindle speeds it > would not accelerate so fast that it might be there at 5 degrees of > spindle rotation. Instead it would ramp up much slower so that when > it reaches the much slower Z axis speed it also has reached the 30 > degree spindle position. > > At that point it doesn't matter anymore as long as the Z axis tracks > the spindle speed the tool bit will follow the previous thread. > > So what does LinuxCNC do? Is the thread mucked up if spindle speed is > changed during a feed hold and then start? > Feed hold has nothing to do with it John, you can't change the spindle speed in mid thread. Full stop. Period. I think it could do what is needed. But its like Yogi Berra once said about theory and practice. Which in this case means machine balistics are hard to do. > Thanks > John Dammeyer > > "ELS! Nothing else works as well for your Lathe" > Automation Artisans Inc. > www dot autoartisans dot com > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users
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