CNC PROGRAMMING INTRODUCTION

CNC programming is the language  which is understand by the cnc machines. If you want talk  to the machine you need to learn the language of  the CNC machines . If you want to move the machine in left, right, up & down you need to give the command to the machine in the language of the machine so that it will be under stand.

PROGRAM :
To machine a component on a CNC machine, information like co-ordinate values and other
technical data which indicate, how, a tool should be moved in relation to a work piece to
achieve a desired machining form, is to be given in the form of coded instructions to the
control unit. These information are called a “PART PROGRAM”.

AXIS NOMENCLATURE :



Standard right hand Cartesian co-ordinate system is used. Always cutting tool moves with
respect to the work piece. ( Lathe machine )

X-AXIS : Always parallel to the work-holding surface or perpendicular to main axis.

Z-AXIS : It is always the main spindle axis.

C-AXIS : It is rotating axis about Z -AXIS.

PROGRAM STRUCTURE :

Part program comprises of a string of blocks written one after the other. When writing a program,
a particular syntax is to be followed.
As per part program structure :

                    A. Program starts with program number.

                    B. Consists of series of blocks – dimensional and non-dimensional data like feed,                                         speed,auxiliary functions etc.,

                    C. Program ends with program end code.

Character for program start, precedes the first block in the part program.
Character for main program start is given by “O”
To start program 1 – O 0001
To start program 2 – O 0002
Program start can also be called as program numbering. The program number is useful in
identification of a program and calling a program.

PROGRAM BLOCKS :

Program blocks contain data required to execute an operation. It is possible to write the program
blocks with or without a sequence number. Sequence number is given at the block head. It need
not be consecutive. It is used for the convenience of the operator. Sequence number is of 4 digits.

Examples :
              * N0005 G00X20.Z5. ; Program block written with block number.
                  G00X20.Z5. ; Program block written without block number.

All the blocks end with block end character ; or ✫
If no block number is given or same block number is given to several blocks, then there cannot be
a defined program jump or block search.

PROGRAMMING WORD :

A program is made up a number of blocks. Similarly a block is made up a number of words.
A word consists of an address character and a string of digits (alphanumeric character).
An address character is normally an alphabet.
X,Z,S,F ….. are all address characters.

N         Address of block number
G         Preparatory function
X         Axes address
Z          Axes address
F         Feed rate
S         Spindle speed
T         Tool number
M        Miscellaneous function
;           Block end character