Devoloping Post Processor for Fanuc 3M mill

We have a 1982 Yuasa Accumill equipped with a Fanuc 3M control. Being that this control is this vintage, there are several modern g-code standards that the control does not recognize (G54, notes, etc.) I have successfully programmed this machine manually but we want to use CAD/CAM with it. I have been experimenting with CAMBAM as the software is much easier for me to wrap my head around than F360, and it's more intuitive when it comes to making the post processor. I would like to start with making simple 2D tool paths on the XY-plane and move on from there. I have been drawing some simple shapes and checking the output g-code to examine any errors. So far these are the errors with our post processor:

-G 92 offset still not set up(cannot use G54)
-Control does not recognize something in the line “G20 G90 G64 G40“
-The code for arcs (G02/G03) does not format correctly, using i and j codes instead of r/radius value.
-Program ends with M30 causing the machine to go into a loop instead of ending the program
-Z axis outputs in wrong direction (machine reads tool advance towards table as negative, CamBam outputs it as positive.

Any insight on this issue/issues is much appreciated.

—Justin

Justin-
Modifying a post is a tedious, but satisfying project. Cambam was my gateway drug to cnc and is an excellent program for what it is. If you haven't found this already:
CamBam 0.9.8 documentation - Post Processor
The basics for modifying a post are:
1. Always save a copy of the existing/ best working one! It's really easy to break a post processor due to some kind of syntax error, or other hard to find mistake. Never edit the working post!
2. Try to fix one issue at a time. For example, edit the header block to eliminate one of the "G20 G90 G64 G40" at a time. This will let you know which one your control disagrees with.
3. Try to find documentation for the controller. There is a programming manual somewhere that will tell you what the controller is expecting.
4. Find an existing program and look at how it is formatted! This is an easy way to see what works. Is there a program already loaded into the machine? If not try to find one from someone who is using the same control.
Good luck with that dinosaur!
Hahn Rossman
Hahn

Suggestion ... use a standard post for output than use an application like our KipwareXC to convert that output G code to the format you require.
Convert G54 to G92 ... remove G codes ... separate G codes ... many options available and very easy to set-up.
Have a look here : KipwareXC - G Code Conversion / Post Processor Software - Kentech Inc.