On Mon, Sep 21, 2009 at 11:59 AM, Jon Elson <[email protected]> wrote:
> Stuart Stevenson wrote:
> > During this I learned something. I have been trying to "fix" the servo
> > amps so when I hit a hard limit they just disable the direction the table
> > was moving when the limit switch was contacted. I found the servo amps
> are
> > working correct. It is EMC2 that is shutting the servos off when I hit
> the
> > limit switches.
> Are you using the individual amp enables? I think if you use the E-stop
> relay to enable the
> amps, they will stay on after a limit switch is hit. A limit switch
> normally does the same as hitting
> F2, which goes from "Machine On" to "Machine Off", but it doesn't cause
> an E-stop.
> > I much prefer the servos to remain on. This is not a problem
> > on the X, Y or Z axes. The problem is the A and B axes. Given the weight
> of
> > the head and the reality that there are no brakes on the motors:
> > if the head is tilted enough to hit the limit
> > switch
> > and
> > the servos turn off
> > then
> > the weight of the head will cause the head to
> > coast (fall) until the pinion gear disengages from the rack.
> > This is not a huge problem and should be almost nonexistent. I will
> know
> > and do not feel comfortable with this as a possibility.
> > I have disengaged the limit feedback for each axis. I am just using
> one
> > limit hooked to the home feedback. This allows homing.
> > My question is this (and maybe I have just overlooked it in the
> manual).
> > Is there a pin out of EMC2 that will disable
> the
> > motion in the direction of motion instead of shutting down all the
> servos?
> >
> Well, EMC by default doesn't produce separate amp enables for + and -
> direction. it depends on
> additional limit switches to control those direction enable inputs on
> the amps. But, of course,
> you could rig the regular limit inputs in HAL directly to digital
> outputs to drive the amp's
> limit inputs. Given enough digitial outputs, that would be no biggie,
> and you shouldn't even
> need any hal component for it. Just use the invert parameter of the
> output pin to select the
> desired polarity. Of course, on a 5-axis machine, this will eat up 10
> more digital outputs.
>
> I hope this helps.
>
> Jon
>
>
> Yes, I have individual amp enables.
The current as configured (prior to homing) action is as follows:
motion toward axis end of travel
cam on slide hits the limit switch
axis following error (the limit switch disable motion in
that direction of travel but EMC2 does not stop it's motion output).
The desired action would be for EMC2 to stop motion output in that
direction of travel also.
thanks
Stuart
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