John Kasunich wrote: > > At the beginning of each G33 pass, LinuxCNC uses the spindle > speed and the machine limits to calculate how long it will > take Z to accelerate, and determines how many degrees the > spindle will rotate during that time. It then adds that > angle to the index position and computes the Z position > using the corrected spindle angle. That means that Z will > reach the correct position just as it finishes accelerating > to the proper speed, and can immediately begin cutting a > good thread. Z will never have to move faster than you > would expect given the spindle speed and thread pitch. > > The downside of this fix is that the offset is different > if the spindle speed is different. I was worried about > that at the time, and argued with Chris about it. But > I couldn't come up with a better way to solve the problem. > It has been at three or four years now (maybe longer?), > and this is the first time someone has been bitten by > this particular behavior, so I think Chris was right. > Thanks very much for describing how this is accomplished. I remember some of the discussion of damped oscillations of the Z axis at the start of a thread. Ingenious fix, for the most part. I suspect there is someone out there, somewhere, who needs to know exactly where a thread starts on a particular part. But, that is sure a special use. Anyway, this RPM-dependent offset really needs to be documented in the user guide, so the average user doesn't get surprised by this.
Jon ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
