Hi wisconsinjimmy,
are you a country person? I am and am therefore comfortable with rural analogies.
Lets say you have an automatic tractor and you wish for it to plow a rectangular paddock. You could build 'limit switches' on to the tractor so it knows when it
hits the fence but really its too late, its hit the fence, the switches may stop it from wrecking it but the switches haven't helped it navigate around the paddock
to do its job.
Imagine that somewhere in the paddock there is one rock which pokes out of the ground. If you manually drive the tractor to the rock and then program the tractor
'you are at the rock', and the boundaries of the paddock are 210 yards to the North, 65 yard to the South ...etc. Now the tractor knows where it is and if you let it go to
work it will know where it is based on the distance and direction its travelled since it was 'at the rock'.
If you had mistakenly programmed the tractor to plow out to 250 yards North of the rock the tractor 'soft limits' will say NO, the boundary is 210 yard North, I can't
go where you want me to go so I'll stop.
That is the essential meaning of soft limits. It absolutely relies on a place 'at the rock'. That place must be exactly the same everytime the tractor is required to plow
that paddock because only then do the boundaries make sense.
For this reason I always argue that home switches ('the rock') are more important than limit switches. It seems that a lot of people disagree with me but I happen
to know some very experienced CNCers who do agree and don't even bother with limit switches. Good reliable home switches and soft limits are the way to go.
Craig