2014-08-24 10:31 GMT+03:00 Gregg Eshelman <[email protected]>: > I dunno why anyone would ever *want* a gantry > where the two sides aren't mechanically linked. It's so dead simple and > can't get out of whack, plus you don't need an extra motor and driver.
Well, I do know, why I *want* 2 motors on gantry: 1) I have yet to see a mechanical design of a machine, where such a mechanical linkage is so dead simple _and_ does not disturb operator to access work area _and_ allows for more than 30-50 mm Z axis travel. All the options I have seen and have thought myself, are not so dead simple. 2) gantry on my router is 3 m long; a) either the shaft has to be very thick and thus have very high rotation inertia (and require extra power from motor) or b) there will be flexible deformations in shaft that will eventually unsquare the gantry for a moment and affect precision, when torch will be on the opposite end of motor or c) the max_accel limits would be very low to avoid any of previous 2 points; 3) gantry itself is much more heavy than carriage, so I like 2 motors to share the higher load - that way the machine can run faster. Of course, one can use bigger motor to move the gantry, but then bigger motor is more expensive and needs bigger drive, which also is more expensive... So I am sure that "total cost of ownership" for 2 motors on gantry is not bigger than one motor and mechanical linkage. And I have modified Axis UI and added HAL pin that switches to world mode. I have it connected to axis.n.homed pins in HAL, so I have minimized the risk of accidentaly jogging the machine, while in joint mode. > It should be possible to remember the coordinates it stopped or was > paused at then run a simulation from the position at the line start up > to the current position *then* lower the torch, light it up and continue. On waterjet machine I added hardware "override" switch, which allowed to turn the nozzle off, when there was active M3 (motion.spindle-on and gpio pin from switch connected to and2 inputs, and2 output connected to gpio that drives the nozzle). So I would disengage that switch (nozzle would remain off, regardless of M3/M5 status), select whatever the line from beginning with "run from line" and then simply manually turn the nozzle on, when it was very close to actual position of previous stop. This approach might be little tricky with plasma as it needs some time to close the arc. Viesturs ------------------------------------------------------------------------------ Slashdot TV. Video for Nerds. Stuff that matters. http://tv.slashdot.org/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
