Our gantry uses feature in the Granite Devices drives that lowers torque, homes to a hard stop (until a configurable ferror is reached) and then backs to the encoder index. It is described here: http://wiki.linuxcnc.org/cgi-bin/wiki.pl?GantryPlasmaMachine#Homing_Controller. This system has worked great.
Seems like you could implement something like this even without using Granites though you would need to be able to lower the torque while you do the homing... Tom On May 22, 2013, at 9:43 PM, Jon Elson <el...@pico-systems.com> wrote: > So, the issue of homing a dual-motor gantry comes up, again. > > This one is a stiff structure, and the customer says if the motors get > seriously out of synch, it will bend the slide rails. Well, at power-on, > the motors will be pretty well synched by mechanical forces. So, > there would be two ways to home it. One is to kill one servo amp > and allow just one of the servo amps to drive to the home position. > Then, enable the 2nd amp and home it. The machine builder would > need to be sure the home positions were such that with both at home > the gantry was not under stress. > > The other scheme would be some kind of simultaneous homing that > kept both encoders at the same relative offset during the whole > process. If the home switch was only on one side of the gantry, then > maybe there is a way to have both encoders home to their own index > pulses at the same time. (When properly set up, the two encoders > should arrive at their index positions nearly simultaneously.) > > Anybody have any ideas or especially experience with a system like > this? > > Jon ------------------------------------------------------------------------------ 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-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
