On May 25, 2013, at 12:40 AM, Jon Elson <el...@pico-systems.com> wrote: > But, the first side to find the index marker will stop there, the second > side will > have to travel to the index mark, thereby racking the gantry. that is > unacceptable. > So, the two encoders MUST have the index marks aligned. Depending on how > the machine is built, it may not be that hard. It may be possible to > lift the > pinion off the rack to get close. if the motor drives a gearbox or > timing belt > drive, the couplings or pulleys can be readjusted on the shafts. if the > encoder > has servo mount, it can be rotated to adjust the timing.
We have a painted mark on our pinion tooth and rack tooth on both sides that get the encoders close, but not exact. It is probably within a 0.1 or less. If, for some reason, the pinions have slipped, we lower the motors (they are on turnbuckles and springs) and move the pinion gear until the painted marks line up. By the way, this has happened only twice in one year. Once when we moved the whole machine across town and once when someone had lowered the motors because they didn't know what they were doing. In practice you will rarely have to realign the encoder indexes. Anyway, we then carefully measured the squareness of the gantry to the X axis and set an offset to one side only. That offset is very small (equal or less than the 0.1" mentioned above). So the whole system homes to hard stop, moves back to indexes on both sides and then one side moves the tiny amount (configured in the hal file) to the offset. Homing complete. Tom ------------------------------------------------------------------------------ Try New Relic Now & We'll Send You this Cool Shirt New Relic is the only SaaS-based application performance monitoring service that delivers powerful full stack analytics. Optimize and monitor your browser, app, & servers with just a few lines of code. Try New Relic and get this awesome Nerd Life shirt! http://p.sf.net/sfu/newrelic_d2d_may _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
