Thanks for the suggestions but I'm confused. Does G1 in polar coordinates produce an arc or a straight line?
> -----Original Message----- > From: andy pugh [mailto:[email protected]] > Sent: Wednesday, March 21, 2018 11:49 AM > To: Enhanced Machine Controller (EMC) > Subject: Re: [Emc-users] Tapered Helix > > On 21 March 2018 at 14:47, Ken Strauss <[email protected]> wrote: > > I need to thread mill some tapered threads (similar to normal pipe > > threads -- NPT). I am considering using polar coordinates in > > incremental mode to approximate a tapered helix. Is that reasonable? > > Is there a better way? Will cumulative errors bite me after hundreds of > incremental moves? > > Why use incremental mode? It is probably just as easy to use variables and a > loop > > Polar coordinates ought to work, but you can approximate a spiral with arcs > too. (I would guess that 8 per rev would be better than 4 per > rev) > > In polar, and not using incremental, something like this, assuming you are > already at X0 Y0 > > #<Z> = -1 > #<pitch> = [1 / 13] ; 13TPI > #<minor> = [1 / 2] ; radius of 1" thread > F10 > G0 Z #<Z> > G1 ^0 @#<minor> > O100 DO > G1 ^90 @[#<minor> + #<pitch> /64] Z[#<Z> + #<pitch> * 0.25] > G1 ^180 @[#<minor> + #<pitch> / 32] Z[#<Z> + #<pitch> * 0.5] > G1 ^ 270 @[#<minor> + #<pitch> / 21.33] Z[#<Z> + #<pitch> * 0.75] > G1 ^ 360 @[#<minor> + #<pitch> / 16] Z[#<Z> + #<pitch> * 1.0] > #<Z> = [#<Z> + #<pitch>] > O100 WHILE [#<Z> LT #<pitch>] > > This uses 4 arcs. It could be done exactly the same with more, for a closer > approximation to a true spiral. > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is designed > for the especial use of mechanical geniuses, daredevils and lunatics." > - George Fitch, Atlanta Constitution Newspaper, 1916 > > ------------------------------------------------------------------------------ > Check out the vibrant tech community on one of the world's most engaging > tech sites, Slashdot.org! http://sdm.link/slashdot > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
