On Jul 7 2013 12:00 PM, Jon Elson wrote: > Matt Shaver wrote: >> >> >> Here's what I think Jon is talking about: When in a rigid tapping >> cycle, the Z axis is "slaved" to the rotational position of the >> spindle. The spindle will have its own characteristics of motion, >> but >> we don't always have tight servo control over them. For example, at >> the >> bottom of a tapped hole, the spindle must reverse, but it may come >> to a >> stop with a jerk due to high friction (you've probably experienced a >> tapping operation where the tap wants to move in small jerks rather >> than smoothly cutting). At this point the Z axis should probably be >> controlled with no limit on jerk (and maybe no acceleration limit >> either) so as to maintain the spindle-to-Z-axis position >> relationship >> which is critical since they are now _mechanically_ interlocked >> through >> the tap and it's threads in the workpiece. >> >> > Yes, that was my concern. Although the tap may jerk a bit, the > torsional > flex in the tap and mass of the spindle assembly will already > somewhat > damp these sharp movements, making what the Z has to follow a bit > less drastic. But, you certainly want the Z to follow the spindle > encoder > as closely as possible, introducing the minimum amount of smoothing > and delay as you possibly can.
when minimizing jerk across all axes (including the spindle since its position is also tracked), then in the above case you would basically be minimizing jerk on the spindle, and z would follow. This would likely induce a slight delay near the normal acceleration bounderies, but IIRC it was trivial. Unfortunately, the only way to know is to test it. EBo -- ------------------------------------------------------------------------------ This SF.net email is sponsored by Windows: Build for Windows Store. http://p.sf.net/sfu/windows-dev2dev _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
