[Dancy]

In the operators manual of my Hitachi Seiki VK-45 there is a reference to the 'ladder' and how to access it. So OK, I went and looked at it. Looks something like a electrical schematic with a bunch of contacts. What is this? What is it trying to show me and how is it used?

Dan

[Al_The_Man]

The ladder is the machine tool controller that processes the machine inputs and outputs M,S,T codes and Tool changers etc.
It is called ladder because of the N American custom of displaying the logic with the two power rails on either side of the page and the logic rungs shown between them.
A typical rung consists individual bits, which can either be Physical inputs or outputs or communication back and forth the the CNC side, these are programmed in a form of Boolean logic, ( And/Nand Or/Nor etc).
It is a very usefull maintenance tool, that will indicate where a problem is when a machine malfunctions due to mis-operation of switches or solenoids etc.
Al.

[single phase]

Does it include g-code too?

[Al_The_Man]

No G code, part program and Servo control is customarily the duty of the CNC processor, The Ladder is usually the function of the 'miscellaneous machine control processor'
Al.