Chapter 6. Post Processor

Table of Contents

General terms
General rules

Abstract

This section explains how to customize the system's output to match the programming languages of various milling machines. The system expresses coordinates and machining conditions in terms of binary files. Most machines need an ASCII file input for axis movement commands, spindle, feedrates and other machining cycles. The post-processor that converts the marked tool path groups into the machine special language – known as G-Code – translates from the internal geometry base to the machine special language. The post-processor is an ASCII file with a .PPC extension. The post-processor includes sets of predefined commands and procedures that specify the output G-Code file.

General terms

Variable - Identifier that marks a value that can change. There are two kinds of variables: number and string.

Expressions - Composed of operators and operands. Most operators are binary: they take two operands. The rest take only one operand. Binary operators use the usual algebraic form (for example, A + B).

Table 6.1. Arithmetic and equalization operators

<<	Less than
>>	Greater than
<>	Not equal
==	Equal to
<=	Less than or equal to
>=	Greater than or equal to
+	Add
-	Subtract
*	Multiply
/	Divide
{xxx}	Get ASCII value of XXX
=	Assignment
\n	New line

Statements - Describe algorithmic actions that can be executed.
Block - Composed of declarations which are written and combined in any order, and statements.
Procedures - Allows nesting of additional blocks in the main program block. Each procedure or function declaration has a heading followed by a block. A procedure is activated by a procedure statement. A procedure is a set of commands to be carried out in sequence. There are two kinds of procedures: pre-defined and user-defined.
Script - A collection of procedures that can be read by the program to commit certain actions (in this case: generate G-Code).


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