Vericut Post-Processor Help¶
Introduction to the Vericut Post-Processor¶
A CAM system generates NC programs that are largely independent of the machines that will be used to manufacture a design. The syntax, or language, of these NC programs is typically a variant of APT CL. The machine controllers require files with a different syntax, often referred to as machine code or G-Code. The purpose of an NC post-processor is to convert the machine independent NC programs to G-Code files.
An early strategy for creating post-processors was to have a tailored program for each machine/control combination needed. Such a program required no input from the user other than the machine independent NC program files. But development of these post-processors was time consuming and maintenance of a full suite of them quickly became a nightmare in large organizations.
The next step in the evolution of post-processors was the "generalized post". With this approach a single program would access a file of parameters for a given machine/control combination, then process machine independent NC programs according to the values and settings of the parameters. As machines became more complex and controllers correspondingly more capable, the parameter files grew rapidly from a few flags and limit values to a very complex set of inter-related choices. Effectively the parameter files were required to express some logic handling abilities.
So the next required evolutionary step became clear. The machine/control parameter files were enhanced with the syntax of their own language, so that they could express the complex logic required for modern machines and controls. The post-processor program became simpler as the language got more powerful, so that now the principal role of the post-processor is to interpret the language.
Unfortunately post-processor technology has not matured to the point that there is just one language for describing how to convert machine independent NC programs to G-Code. Each post-processor vendor requires a different syntax and language. The language of the Vericut Post-Processor borrows heavily from the syntax of BASIC (Beginner's All-purpose Symbolic Instruction Code).
Why BASIC? The CAD/CAM world doesn't need another new language, so why not BASIC? There is an inherent danger in borrowing the syntax of an established general-purpose language for a specific task. Users who are familiar with the language can be irritated by minor departures from the "standard". On the other hand, the fact that there are users who don't have to learn the language from scratch is a big plus. We have attempted to minimize departures from BASIC syntax as much as possible. Where there are extensions, we have borrowed from Visual-Basic's syntax.
The post-processor reads a machine independent NC program, usually in some flavor of APT CL, and processes one statement at a time. A statement can span several lines of the input file. For each statement it invokes a "Sub" or subroutine which is a section of a nominated machine/control dependent language file. Which "Sub" gets called depends on the statement's major word. If there is no "Sub" for a particular major word, nothing happens and no error message is generated. More typically the "Sub" will format a G-Code line or lines, for output to a machine dependent NC program and a log.
If you are new to the Vericut Post-Processor, it is suggested that you browse the Post-Processor Language topics in the order they are presented. If you are already familiar with the Post-Processor Language and only need to apply it to one of Vericut's applications, you could jump directly to one of the following application specific sections.
Inspection Programming capabilities:
Vericut Composite Programming: