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« on: November 24, 2008, 06:05:39 PM »
Okay, I'm back after a computer meltdown. If it isn't one thing it's another....
I have reread all the posts re: this subject several times now, and I still need some clarity. Firstly, unless I have completely misunderstood some of the posts, it seems that there is some disagreement about the Z axis and whether it is standard for the Z zero to be set at the high part of its range, and everything below that (closer to the table) is negative. Others seem to think that Z zero should be set at the work surface, and everything above that should be positive. In the case of the Z zero at the top, a soft limit above the Z zero position would be positive, but it would be negative if it is set below the low position. In the latter case (the Z zero is at the work surface), the soft limit would have to be negative if it is below the work surface. The problem as I see it with the first configuration is that you have to work with negatives, measuring down from your tool bit and then adding another negative number to that to get the cut depth you want. The problem with the second method is that if you want your tool to go home after doing a procedure, or to get ready for another procedure, it would travel at the height of, and/or end up at, the work surface, making it hard to remove the work and possibly damaging the surface of the material.
So, let's solve that first.
As to Hood's question about my machine orientation, the lower left corner of the XY axes is near the operator and on his left. As of yet, there are no limit or home switches -- this is why I want to get this soft limit thing correct.
Is it possible to avoid some of the issues mentioned above by having the soft limits be the home and positions away from home beyond which you don't want to go (that is, what I would consider the usable work surface), and the slow down 1/4 inch, say, before that? The only problem that I can see is that the machine slows down when it is working near the limits...is that a problem?
Thanks again, Bob