Thanks a lot for your help andy, you've really cleared my doubts. The last question is, do you think is necesary to home when i change from spindle to axis? or the index pulse itself gives me the warranty that i've never loose the real position?, because as you know the home sequence makes two movements to set the zero point.
Thanks in advance. Leonardo. 2010/5/5 Andy Pugh <a...@andypugh.fsnet.co.uk> > 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 > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
