Gene Heskett wrote: > Greetings; > > Yesterday I pretty well wrecked the 2nd copy of the bottom of the floor plate > I was tracing a couple of weeks ago, with the g2 command. I thought I was > tracing just under a 180 degree half circle, but it turns out that a very > minor .001" change in the r number made it go from just reaching the > endpoint, to a gouge a nice .010 deep notch in the part over 180, and also > moved the midpoint diameter of the cut such that a nearly .050" change in the > x at start-stop was required. I was using g2, cutting from the back to front > around the right end of a boss, or again, g2, cutting from the front around > the left end to the rear stopping point. I was under the impression that a > larger r would result in a less than 180 degree arc, but it appears in the > results that a larger r effectively starts at 180 degrees and goes up. > > My intention was to cut maybe 175 degrees as the part is less critical about > that, and esthetically pretty ugly if it went over 180 degrees and gouged the > side. My understanding is that a larger r will result in fewer degrees being > traversed, but such didn't appear to be the case. Humm, now that I think > about that, it was a no-no overcut too as the bit was turning clockwise, so I > should have reversed that and used a g3 move so the bit was always > cutting 'up' against the works motion. Is/was that my problem?
Radius's in corners must be tangent to get a smooth corner. Are you using cutter comp, G41 and G42? Cutter comp and the tool table are your friends. Once you get it in your head on how cutter comp works in corners life gets MUCH easier. The site that helped me most is http://www.nfrpartners.com/nfrg2g3.htm , pay attention on the use of negative R numbers in certain situations. Ever since I figured out cutter comp life is easier,I use it all the time. Part a little oversize? Change the tool diameter and run it again > > I *think* I now know how this happened, because my r number wasn't exactly > half the y motion, but when I tried that to only 3 decimal point precision, > it was rejected by emc because it couldn't reach the endpoint. And more r > moved the center locus of the cut at a much larger rate than was mentally > apparent. I cut a lot of air above the part working it out but didn't notice > the y motor reversals near the ends of the arc that would have given it away > before the bit was lowered to make the real cut due to a shop towel laying > over it to help control flying swarf. > > I think my calculations on my ti-34 didn't always jib with the bit diameter > adjustments I was doing in my head. Senior moment I think they call that. :) > > Now, I know emc has 'tool'.tbl file, and that one can somehow change the D > word in that command to switch it from the left side of the bit to the right, > but it doesn't seem to elaborate how well this works when cutting arcs where > the back of the bit gradually becomes the front of the bit, and vice-versa. > > Is there a better tutorial than the users manual on how to best use this tool > comp feature, or am I just not getting it? It seems to me that with the bit > diameter being properly compensated for, I ought to be able to just mike the > old part and plug in the results without all this experimentation. > ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
