Len Shelton wrote: > Anyone care to describe their experiences on the accuracy of their home > switches, and the type, and relate that to the jigs they were using? For best repeatability, you want to use the index pulse from an optical encoder to refine the home position. Some people claim to get .0002" repeatability just from a mechanical switch, but a speck of swarf on the switch actuator will mess that up. If you are not using servos with an index channel, then you might be able to cobble up a substitute by making a disc with a narrow slot and one of those U-shaped optical sensors from a floppy drive.
I have used encoders with index pulses, and the machine will home to far greater repeatability than I can produce with an edge finder. Presumably, it is homing to a precisely repeatable encoder count, which on my Bridgeport is .00005" (50 u-inch). I can barely attempt to measure that with a Federal Maxxum electronic indicator, but the various flexes and stictions in the machone's ways produce more un-repeatability than that. So, presumably, I could re-index to a fixture on the machine the next day, but I never trusted it enough to do it without at least checking with an edge finder or coax indicator. Jon ------------------------------------------------------------------------- This SF.Net email is sponsored by the Moblin Your Move Developer's challenge Build the coolest Linux based applications with Moblin SDK & win great prizes Grand prize is a trip for two to an Open Source event anywhere in the world http://moblin-contest.org/redirect.php?banner_id=100&url=/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
