and a voice spoke out from the one lurking in the shadows. I may be just blowing smoke here - but there might be a functional compromise.
I honestly have not been under the hood of EMC (interp or trajectory planner) so I don't know if what I'm proposing is even possible with the existing code structure. A steppers weakest point is at its peak velocity, or maybe depending on the accell settings the beginning of decell/breaking from peak vel. So basically Rapid G00 moves are the Achilles heal. I am not proposing using an encoder for coordinated movement feedback like a servo would require, that would still be handled by counting the stepgen output. What I propose would be having an aux input for the encoders and a separate DRO display on the GUI like XA/YA/ZA. With the proper ini file setting an "in position check" could be done (with a acceptable tolerance factor) after each G00 or fixed cycle position move. If an out of tolerance position is detected an alarm could occur (the easy way) or a correction move could be applied (much more difficult). Normally if a G00 is issued the tool is free of the work so applying a correction should be as safe, if the tool failed to clear the work, then the damage was all ready done. I'm guessing this would be very resource intensive. So a alternative might be to use a non-modal user defined M or G code to compare and/or reset position. This option would be handy for people using Step/dir servo drives where they are unable to adjust the in-drive following error such as Gecko 320/340 drives. Geckos allow 128 count error before tripping a servo fault. This won't help a machine fighting mid-band resonance, or one overloaded in a cut. That is a hardware/software issue where the builder needs to know the weakness and limits of the machine. However these comparisons if logged could help the builder tweak accel & max vel settings to an acceptable range that will run error free 95+% of the time. I could see how a machine which ran great all summer start losing steps in a cold garage in January, Vactra #2 (Way oil) can get like honey due to age and very cold temps. Greg Bentzinger ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
