On Wednesday 20 March 2013 02:59:22 Igor Chudov did opine: > I have a vertical mill with a fourth axis A. > > My buddy wants me to write a subroutine that would let me mill thread > on round parts, that are held in the fourth axis, and the thread would > be milled using a 60 degree chamfer end mill, rotating the part around > the A axis. > > I have some questions about the odds and ends of this. > > 1. I would like to be able to say to the machine, in G code, that > "wherever we are on the A axis, call it zero degrees position". In > other words, I want to change the coordinate system in G code for one A > axis only. How do I do it. > > 2. Is that correct that feedrate F in a G1 statement that changes both > X, as well as A, only refers to the change of X? I can live with that, > I just want to know.
I think the canned routine g33? might be the first place I'd check in the docs. I started to say G76, but one would have to cobble up some sort of an index pulse from the combo of A=0 + Z=0 in hal, and dummy up encoder quad signals from the step count going to the A table in order to lock the A/Z timing together on the multipass loopback g76 uses. I have one of those milling bits, but I've now cnc'd my lathe so I do all that on the lathe with the G76, at any tpi, and any diameter my spindle motor has the power to cut, perhaps an inch in diameter max. But in the mill, using that bit in the mill, the thread could be cut full depth in one pass, with the speed of the A table being the speed limit, on my 4" toy table, about 1800 degrees/minute. However, resharpening a cutoff blade to be the single tooth on the lathe is certainly a heck of a lot cheaper than resharpening such a mill, another reason my mill has only been out of the box to admire it 2 or 3 times. A very $pen$ive little milling bit. Another item to consider in writing your own routine is that the A table needs to be tilted on the X axis according to the thread pitch so the tooth arc effectively matches the threads pitch. That in turn brings in a need to drive the Y slowly in time with Z to maintain the X to part contact point at exactly along the X axis. Otherwise the thread diameter over its length will be in error according to the sine? of that X angle miss-match. That part I handle on the lathe by tilting the blade slightly in the grip of the 3 jaw on my table while driving the table to the proper angles. There are as many ways to skin this cat. :) Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> Would you care to view the ruins of my good intentions? I was taught to respect my elders, but its getting harder and harder to find any... ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_mar _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
