Offsets are making me CRAZY!!!

[CNCRob]

As for my other question about the G401 file, I am just looking for a way at home to tell my machine to reset itself so that zero is on top of the workpiece(the way my machine is setup is zero is at the top of the z axis when it is homed). Without haveing to jog it out everytime. I would like my home machine to work in the same way as my work machine at work. At work all I have to do is put in the fixture thickness, the part thickness, and put in the tool lenght in the tool directory on the machine. The machine knows how far the distance is from the bottom of the spindle to the top of the vacuum table then computes the information to reset the Z to the top of the work piece. I would just like to find someway to do this at home. Is there a calculation I can do and enter that into the G54 offset. I guess something like distance from bottom of spindle to top of vacuum table minus tool lengh minus fixture thickness minus part thickness(this probably isn't correct, but I just wanted to give an ideal of what im looking for). Would something like that work or is there a more automatic way to do it.

[turmite]

While G92 might be obselete, it does work and work well if you pay attention. A G92 can be cancelled by a G92.1, at least in Mach software, but the G92.1 needs to be at the end of a complete program. If a G92.1 is inserted inside a program disaster is about to take place!

Mike

[HuFlungDung]

Total Height = fixture height + work height + tool height

In my mind your G54 Z = fixture height + work height

Your tool offset length is always relative to the table. So if the spindle distance from spindle nose to table is 20", then the tool length (measured on a presetter) would be 20" - height of tool. If you can set the height of your presetter so that it is 20" at the bottom of its mast (raise it to 20" height then zero it), then this subtraction operation would not be necessary because it would already be taken care of.

The sign of the value you would enter is undetermined here, but it will be + or -