Ray/ Jon, Thanks for your comments. I should try and clear up a few things: Machine is a minimill with home brew L297/L298 stepper driver boards + stepper motors. Signals come from parallel port to drive cards via a home brew opto-isolator card. All hardware has been running without fault for some time with various versions of EMC and some fairly large GCODE files.
DRO's are mounted to the axes (cheap Chinese scales + PIC ucontroller to read them) and totally separate from EMC and the drives. Normally agreement between the scales and EMC is to within 0.0005". When I say HOME I mean just setting the axis reading to zero at the start point of my GCODE - I'm not performing homing with limit switches etc. Interesting point Jon made re. a counter getting reset, this would generate the observed effect. So whats changed? I've used EMC without problems for quite sometime now from DBI4.38 to current 2.1.7 and have confidence in its stability. Ubuntu is totally up to date. No hardware changes. On both occasions that the "jump" has occurred I've been running GCODE generated by a small windows based Excel utility written in VBA - it creates simple facing and slotting tool paths. Could this be the source of the problem? Odd characters in the text files coming over from Windows? Jumps dont occur at consistent points though, Hmm more head scratching. Regards Andy -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Ray Henry Sent: 10 September 2007 02:23 To: Enhanced Machine Controller (EMC) Subject: Re: [Emc-users] Change of Home Position Hi Andy I don't remember the details of your machine but if it's servo with encoders you might look at the location of the index pulse with respect to the angular position where the home switch closes or opens. In the old days we called this stuff a grid and if the switch closure was right close to the index it could jump a full rotation, or in the case of a resolver 1/4 of a rotation. IMO it's a good idea to put the index pulse a half rotation away from the switch change. Rayh On Sun, 2007-09-09 at 21:46 +0100, Andy Ibbotson wrote: > Hello Everyone, > > Over the last few nights Ive experienced a coupled of odd events > with EMC 2.1.7 normally runs flawlessly. Running AXIS Ive homed > all axes to zero and then commenced running my Gcode. Last night the > Y axis home position appeared to jump by 0.400 (as seen on the DRO), > axis still reported Y home at 0.0000. Tonight a similar thing > happened with the Z axis. Initially DRO Z and AXIS Z were zeroed and > followed one another to within ½ thou (which is okay for me) then > following a return to Z = 0.0000, the DRO read +0.0250 and AXIS still > reported Z=0.0000. The cutter was obviously offset from the workpiece > so I stopped the programme, rehomed everything and started again, > this time with no problem. Has anyone else experienced similar > behaviour Im guessing not since I havent seen any posts. > > Regards > > Andy > > > ------------------------------------------------------------------------ - > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2005. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------ - This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
