Well, I have a full 4'X8' vacuum table with 5 zones on it. From time to time I would like to zero my Z axis on the bed of the machine, but I have work covering the entire surface. What am I to do? Well...... here is what I did today and it works great.
I got a 1.5" aluminum rod about 9" long. I used the laser to cut a sturdy bracket to mount this rod to the end of the machines table. I wrote a file to move the spindle over the rod, zero the cuter on top of the rod, move away a bit and start the spindle. Then it will lower 0.005 below the surface of the rod and surface it. Then the spindles speed is changed to a speed to cut the Ultralite I use for a bleeder. The cutter is moved to 0,0 and plunged 0.005, to the same height it just cut the aluminum rod to. Then the surface of my table is cut the same height of the aluminum rod.
Now I have a smooth table and a contact point off of the table that I can use to automate the z zero process, as long as I am happy to zero at the machine surface. Next I will add some code to allow me to measure the exact thickness of the material on the table and calculate cut depths from that.
Fun and useful for me all wrapped up in one project.
Here is a quick picture of it.