A machine (in my oppinion) would have a home switch (where it would home
consistently). Starting from that position you have software limits (you
are allowed to travel up to the soft limits, and never beyond).
Outside of the soft limits bounds, you have the hardware limits. Usually
these are wired as tripping faults which disable the motor amplifiers,
so crashing them is a serious problem. (One would need to move the axis
by hand back off the limit switch).
On some machines the hardware limits aren't as extreme, and are used
only as a fault input to the controller (emc2 in our case), so if it
trips emc2 errors out. You still have the option to push override limits
then, and jog the axis in the other direction back off the limit switch.

But yeah, I agree with no home switch (homing by eye) software limits
move according to where you homed. Having limit switches but no home
switch seems like an odd setup to me. I would use one of the limit
switches as the home switch and properly define HOME position and HOME
OFFSET (this scenario is supported by emc2, and described in the docs).

Regards,
Alex



On Wed, 2008-04-30 at 13:20 -0700, Kirk Wallace wrote:
> The soft limit callout in the .ini file is a puzzle to me. It seems to
> be based on the home location, so if your home location changes, the
> limit setting may be inappropriate. Unless you home your machine to the
> same location every time you start EMC2, the soft limit setting is of no
> value. If you have hardware limit switches, again the soft limit seems
> to have no value. It seems I always end up disabling the soft limits by
> setting it out of the way. 
> 
> Home itself seems to have limited value. It comes in handy with a G28,
> but that seems to be it.
> 
> Am I missing anything? I think I need to do more using than building.
> 


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