On 03/21/2018 07:47 AM, Ken Strauss 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?
It has been a while since I looked at this sort of thing, but off-hand I think the G2/3 code is able to do a tapered helix with the proper parameter settings:
http://linuxcnc.org/docs/2.7/html/gcode/g-code.html#gcode:g2-g3
The current location is the start XYZ position of the helical thread mill path (allow for lead-in and out, if needed). The XYZ parameters set the path end location. The XY values set the end of the path which should have the taper included. The Z and P set the thread length and number of turns. I seem to recall having to calculate the last bit of an additional arc to finish the thread if it doesn't end in a full turn. I also seem to recall that P and the real number of turns is not intuitive, so cut air until you get what you need. I may be all wet on the above so check out the documentation and test for yourself. There are a lot of features and calculations between the control point path and the thread form -- tool diameter, tip truncation, thread pitch cone dimensions, etcetera.
Or not. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/ ------------------------------------------------------------------------------ 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
