On Tuesday 15 January 2019 22:42:11 Jon Elson wrote: > On 01/15/2019 01:02 PM, John Figie wrote: > > I Also want to add that John Elson seems to be saying the opposite > > of the LinuxCNC gcode reference. Was that a mistake? Am I missing > > something? > > > > http://linuxcnc.org/docs/html/gcode/g-code.html#gcode:g2-g3 > > > > "It is not good practice to program radius format arcs that are > > nearly full circles or nearly semicircles because a small change in > > the location of the end point will produce a much larger change in > > the location of the center of the circle (and, hence, the middle of > > the arc). The magnification effect is large enough that rounding > > error in a number can produce out-of-tolerance cuts. For instance, a > > 1% displacement ....." > > Well, I've been using EMC, EMC2, and LinuxCNC since 1998. > And, I never program more than 90 degree arcs, so have not > run into this issue. It is absolutely true that full > circles CANNOT be specified with the R form. I have no idea > how any particular post processor deals with this problem, > but it seems likely (since this is NOT a LinuxCNC-specific > problem, but due to the way the G-code language is > specified) that a good post would limit R word arcs to 90 > degrees. > ISTR doing 75 and 105 degree R word arcs for the corners of a dsub hole at some time in the past and had to spec it out to 8 decimal places. But since I've learned how to use big johns arcgenm18.py correctly, have used only the IJK version much more easily. I often drill a hole by using a smaller tool to cut out a plug by setting a depth increment of .0075 or so per revolution around the hole going about 10 thou into the spoil board. Slow of course, but I get good holes w/o the drill bit grab on the punchthru. > I use a bunch of C programs I have written over the years to > write G-code for specific operations (round holes, slots, > etc.) and these all use R word arcs in quadrants. > > Now that the arc tolerance has been made easily adjustable > without recompiling source, it is a lot less of an issue.
Tell me more about this please. It is not mentioned in the pdf dox I get from master yet. But in scanning that doc for that, I noted a hal file command that might be handy: delf It sounds as if its a way to remove a setup/test stanza used during the machine calibration by removing modules in the addf list after they are no longer relevant for normal operation. So since its not mentioned anyplace else in the docs, where can I find a discusion/tut on how to properly use it? What I have been doing is just commenting that code out of the file, including its addf's. That may be doing the same thing, saving cycles in the loop threads, but I'd like to learn about its proper use. This getting rid of stuff no longer used would be a lot handier if its modules could be included to separate loadrt's, but currently a module can only be mentioned in one loadrt, so I am stuck with it in memory even if its individual addf is commented out. Then the loadrt's for this no longer used stuff could be commented out along with its addf's. Thanks all. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
