On 5 May 2010 15:03, Leonardo Marsaglia <leonardomarsagli...@gmail.com> wrote:
> I can use the same spindle servo motor as an positioning axis to make > millings controlling it with analog voltage closing the loop in emc and then > when required as a spindle motor Yes, assuming that the mechanical specification (torque at low speed etc) of the motor is sufficient for milling operations. > i was asking this because some servo > drives as you know come with pulse/dir and analog input, but these servos > have only analog input. I think that the use of pulse/direction is not preferred with EMC anyway, as it is better to close the positioning loop in EMC where you can see (and tune) the PID values. > Another thing is.. what happens when i change from axis to spindle, the > encoder will read the position everytime the spindle turns because i don't > want to loose the home reference for the axis, but if the spindle turns > several times per minute the position in the axis will be enormous, Yes. Though this is less of a problem than you might think. You could spin at full speed for months before the encoder counter would not be able to track accurately. > so i was > needing to reset the position units to 0 everytime i reach the index pulse, > this way the axis always has to make less than a turn to return to 0 when > the spindle stops. Do you think this is possible? Not only possible, but easy. The encoder.index-enable pin does exactly that. quoting from http://linuxcnc.org/docs/2.4/html/man/man9/hostmot2.9.html "(bit in/out) index-enable: When this pin is set to True, the count (and therefore also position) are reset to zero on the next Index (Phase-Z) pulse. At the same time, index-enable is reset to zero to indicate that the pulse has occurred." This is quoting from the Hostmot2 (Mesa card) page, but the software encoders have the same function. > I'm trying to clear my doubts before i start to spend money on servos and > encoders.. I have been meaning to experiment with exactly this sort of setup with my lathe (to see if a standard AC motor an VFD can be used for crude positioning for diameter probing). I haven't tried it yet, so can't give you an absolutely definitive "Yes it can be done" and I would definitely wait for some second opinions before placing the order, but I don't forsee any difficulty. -- atp ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
