On 4/19/2012 1:53 PM, Jon Elson wrote: > Viesturs Lācis wrote: >> 2012/4/19 Stephen Dubovsky<smdubov...@gmail.com>: >> >>> Around tight curves, that requires lots of short sections w/ >>> high changes in velocity. But you have to go slow within the limits of the >>> machine around those anyway. >>> >> Just like Andy said - if there is curve in the part, then that is why >> there are G2 and G3 commands in g-code. Period. Doing arcs with linear >> moves is _wrong_ approach by definition. >> > But, LinuxCNC does not do arbitrary arcs, but only arcs in one of the three > orthogonal planes. Also, if your arc is not a segment of a circle but > some other > curve, it has to be broken into multiple arcs anyway to approximate the > desired > curve. > > Jon I think the real issue is that the CAM programs are breaking the target shape into a sequence of short arcs so as to stay within some error band. Instead, the program could break the target shape into a sequence of arcs with common exit and entry tangents. The program could maintain the same error limits.
By doing that, linuxcnc would never have to come to a full stop. The approximation as a sequence of arcs would generally (always?) have fewer (or the same number of) lines of gcode than the approximation as a sequence of line segments. Others have stated that arcs must be in one of three orthogonal planes. Since linuxcnc can do helices, that isn't precisely true. Is anyone here interested in writing a filter that takes as input a tolerance (error band) and a sequence of motions (arcs and line segments) and generates a new sequence of motions that duplicates the original within the error band? It sounds like that would be one way to address the problem. Regards, Ken Ken > > ------------------------------------------------------------------------------ > For Developers, A Lot Can Happen In A Second. > Boundary is the first to Know...and Tell You. > Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! > http://p.sf.net/sfu/Boundary-d2dvs2 > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ For Developers, A Lot Can Happen In A Second. Boundary is the first to Know...and Tell You. Monitor Your Applications in Ultra-Fine Resolution. Try it FREE! http://p.sf.net/sfu/Boundary-d2dvs2 _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
