On Monday 22 July 2019 13:06:34 John Dammeyer wrote: > I've run into a situation with the CAM file generated by MECSOFT > AlibreCAM appears to have a problem. I've asked this on the support > group for AlibreCAM but I think it's a more general question involving > simultaneous 4 axis milling where I write the G-Code myself. > > > N1 G17 G20 G40 G90 > (4th Axis Create Cylinder/Round) > N2 T2 M06 > N3 S20000 M3 > N4 G0 X-2.2788 Y0. Z1.664 A46.8 F0. > N5 G1 Z1.45 A46.8 F11. > N6 X-2.4983 Z1.4113 A46.8 > N7 X-2.5389 Z1.404 A46.3 > N8 Z1.4 A45. > N9 X-2.5388 A43.7 F14.7 > N10 X-2.4959 A43.2 > N11 X-0.0018 A43.2 > > > Effectively the feed rate on the X,Y and Z is 11 IPM or 14.7 IPM. But > the rotary axis is angular under LinuxCNC and measured in degrees per > minute. I believe that makes sense because the diameter of the part > being rotated determines the actual feed rate. So if the circumference > was 14.7" and the cutting speed is set at 14.7 IPM then the rotary > axis should turn 360 degrees per minute. > > But as shown in line N9 we have simultaneous motion on X and A but at > F14.7. > > Clearly if the diameter was such that the circumference was 29.4" then > the feed rate of the A axis would have to be half or 180 > degrees/minute. > > Running the G-Code above sees the Z or X axis moving at the expected > speed. Watching paint dry is more interesting than watching the A > axis turn. But if I just do a G1 A360 F360 the motion of the A axis > at 4.68 diameter appears to be about the same speed as the X or Z > horizontally. It also takes exactly 1 minute to move 360 degrees at > 360 degrees/minute. > > So how is this solved? How would the A axis know the diameter and be > able to translate that a request of F14.7 should really be F360 when Z > is being moved at the same time? Odds are I've configured the CAM > software wrong but if I was going to just manually write some G-Code > that involved simultaneous motion what would I do? > > The AXIS display shows 14.7 for speed. The Z is known. Is there > something missing so that the A axis actually gets a much faster rate? > See, in LinuxCNC_Documentation.pdf, the G93-94-95 versions of how a feed rate in interpreted. You probably want G93, with a < 1.0 feed rate for starters. A F0.25 would take 4 minutes for the A move, with any other axises in that _same command line_ slaved to the A progress. F0.5 would take 2 minutes. Note that is effective only for the line it begins, and reverts to normal motion then line is completed.
I haven't used it enough to be a spurt. let alone an expert so fire up your favorite pdf viewer and read it starting at G93 to make sure. Any conversions of degrees to linear speed, similar to CSS, will have to be done in the gcode, I think... I've carved drill bits for wood working that way by making the spiral with a round nosed bit. Didn't work like a $25 bit, but it did get the job done. I was planting short (16") 4x4's on the front deck, dropping/driving the 4x4 post to hold a plastic fence on one side of the wheelchair ramp I built when the missus fell & broke a hip. Came out a heck of a lot more rigid than I thought it was going to be. > Thanks > John > > > > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users 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) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene> _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
