Viesturs Lācis wrote: > 2012/1/7 Jon Elson <el...@pico-systems.com>: > >> There are two options, I suppose. >> Provide a different mode, where this >> restriction is ignored, and the CAM is trusted to not ever exceed the >> machine acceleration limits. >> Or, develop an N-block look-ahead, and I know that can be QUITE >> complex. >> > > Could You, please, expand on how what could CAM do differently? If EMC had a setting to trust the G-code file and just obey the requested velocity, this might be desirable. What I believe is the current behavior is if the G-code has a long string of very short, nearly-colinear moves, it will not allow the axis to run faster than it can stop at the end of each segment. A CAM program could specify a slowdown at the end of such a series of moves, by bringing the tool up off the work, slowing down, turning around and then getting back up to speed before entering the work for the next pass. This would make it possible for EMC to run contouring programs at higher speed, but it would be at the mercy of the CAM program to never ask for more acceleration than the machine could perform.
> Do You > mean that CAM would insert commands in g-code telling the controller: > "next n moves (or all moves until told differently) can be done at > full speed" or "now beware and get ready to stop at the end of move". > What if there are arcs, described with many small straight lines and > there is very sharp corner between two arcs? Each machine has > different acceleration/deceleration limits. How will CAM know, when to > tell "go at full speed" and when to tell "start braking"? > The CAM would HAVE to be given this info. It would then just put Fxxx words into the G-code as appropriate. > IMHO the second option is the only viable way to go, but I have no idea, how > :)) > And maybe it should not look up a certain number of rows, but certain > distance - if the next move is very long, there is no need to rush. If > a certain number of lines for look-ahead is done, what happens, if > small lines are so small, that it takes more than predefined number of > them for a full stop? > This makes it a general n-segment lookahead, which I realize is pretty complicated, and REALLY hard to do in real-time. A CAM program can do it in a more leisurely manner, and also has the overall view of the machining operation required. I have no idea if there are CAM programs that do this kind of thing. Jon ------------------------------------------------------------------------------ Ridiculously easy VDI. With Citrix VDI-in-a-Box, you don't need a complex infrastructure or vast IT resources to deliver seamless, secure access to virtual desktops. With this all-in-one solution, easily deploy virtual desktops for less than the cost of PCs and save 60% on VDI infrastructure costs. Try it free! http://p.sf.net/sfu/Citrix-VDIinabox _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
