TABLE OF CONTENTS Each line of a CNC program is called a block. In the terminology established earlier, a block was simply defined as a single instruction processed by the CNC system.
A sequence block, a program block - or simply a block - is normally one hand written line of the program listing, or a line typed in a text editor and terminated by the Enter key. This line can contain one or more program words - words that result in the definition of a single instruction to the CNC system. Such a program instruction typically contains combinations of preparatory commands, coordinate words, tool functions and commands, coolant function, speeds and feeds commands, position registration, offsets of different kinds, etc. In plain English, the contents of one block will be processed as a single unit before the control processes any following block of instruction. While a CNC program is being processed, the control system will evaluate individual instructions (blocks) as one complete machine operation step. Each part program consists of a series of blocks necessary to complete a certain machining process. The overall program length will always depend on the total number of blocks and their size.
A single block allows as many program words as necessary. Some controls impose a limit on the number of characters in one block. There is only a theoretical maximum for Fanuc and similar controls, irrelevant in practice. The only restriction is that two or
