Chris Morley wrote: > > For instance if your machine could move maximally at 50 inches a minute, why > would > you allow the TP to ask it to move 52 while G33.1? Same premise as jerk > limiting. > If your machine really can run 52 then why not set the limits to 52? > Well, this is the problem. If the spindle is connected to the Z axis by a tap, and the program calls for a spindle speed such that the Z axis exceeds its limits of speed or acceleration, it will break the tap or damage the workpiece. Spindle speed can be fairly easily calculated so the Z feeds are within the machine's capability. But, if a VFD is reversing the motor by forward/reverse relays, it may produce a strong acceleration that exceeds the Z axis' acceleration limit at that particular thread pitch. I was worried about this and used a filter to slow down the rate of the deceleration and reversal. But, in a case without an analog spindle speed command to the spindle drive, this won't be possible. (Not that I'm saying such a setup is a good idea!) So, it is possible to write G-code with a G33.1 where the spindle speed or the spindle acceleration exceeds the machine's limits. LinuxCNC has no way to know this is going to happen until it is in the middle of the G33.1 cycle! (Actually, it could use commanded spindle speed times the thread pitch to compute required feed and report an error if this is greater than the velocity limit on Z.) But, it certainly has no idea how quickly the spindle will reverse at the bottom of the thread. I don't know what to do about that, except test first with no tool and Halscope.
Jon ------------------------------------------------------------------------------ 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
