NC Part Programming
Google Books Link
• NC Part programming: Manual Programming-
Concepts tape form atstab sequential fixed block
word address and variable block formats - Part
Programming examples- Point to point
programming and simple contour programming-
• Computer aided programming Concepts – Post
• programming languages - APT programming- Part
• NC part programming comprises the collection
of all data required to produce the part, the
calculation of a tool path along which the
machine operations will be performed, and
the arrangement of those given and calculated
in standard format, which could be converted
to an acceptable form for a particular MCU.
• Necessary data for producing a part may be
– Information directly taken from a drawing. tool path is
– Machining parameters which depends on surface
quality , required tolerance, and type of work piece
and drilling tool
– Data determined by the part programmer such as
cutting direction and changing of tools.
– Information depending on particular NC system , such
as acceleration or deceleration intervals.
• All data is fed into NC system in such a form
that it can be read and processed by the MCU.
• Two types of data processing techniques
employed to produce the punched tape.
– Manual (with use of calculator )
– Computer assisted preparation of tapes
• In manual programming the data required for
machining a part is written in a standard
format on a special manuscript.
• The manuscript is planning chart or list of
instructions which describes the operations
necessary to produce the part.
• The manuscript is typed with teletype or flexo
• Part programming of simple parts can be
performed manually with calculators.
• Its suitable for point to point machines.
• Computers are used as an aid in NC
programming by applying special purpose
• It consist of series of statement which are
punched on cards and are used as the input to
Manual Programming - Basic Concepts
• Manual tape preparation is executed by part
• Determine machining parameters and optimal
sequence of operation to be performed
• Calculate tool path and write a manuscript.
• Each line is block,
• Should be in standard format eg_ RS273-A
• eg for 1 block
– N102 g04 x-52000 y09100 f315 s717 t 65432 m03
– The letter and number referred to a word
– The first letter of word is word address
– EB- end of block is not printed , but only
punched. The EB indicates to the MCU that the
present reading is completed and the axes of
motion have to start up. When motion is
accomplished the next block is read.
• Word address
– N sequential number
– G – preparatory function
– X & Y – dimensional word
– F – federate code
– S – spindle speed code
– T – tool code
– M - Miscellaneous function
• Tab sequential format, a tab character is inserted
between two words in the block.
• The + sign dimension words may be ignored in
most systems, where no sign means that a
positive coordinate or positive increment would
• RWS rewind stop code – usually placed as the
first character on the tape. This code stops the
tape reader when it is automatically rewinding
while executing the m30 function.
• Perforated tape as input medium
• Electronic Industry Alliance (EIA) has prepared
standard RS-273A ,RS 274-B (may 1967)
• Each line of the manuscript is equivalent to
Sequence number - n
• Sequence number word n consist of three digits.
• First in block
• The major purpose is to identify specific
machining operations through the block number.
• When tape is read, each sequence number is
displayed at the operator console while the block
commands are performed.
• Operator can compare the actual performance
with the programmed commnds.
Preparatory function- g
• Preparatory function- g consist of two digit.
• Preparatory functions are used to set up the
mode in which the rest of the operation is to
• G codes
• x,y,z primary motion dimension in the X,Y,Z
• u,v,w secondary motion parallel to X,Y,Z
• p,q,r tertiary motion parallel to X,Y,Z
• I ,j,k distance to the arc center
• a,b,c angular dimensions around the X,Y,Z
• Distance expressed by incremental or
• Circular words always incremental.
• Decimal points are not used dimensional
words are programmed in BLU.
• An algebraic sign (+or -) precedes the first
• Circular arc are machined only in the main
• Four dimensional words per block are required.
• Two distance dimension words are used to
provide distance, 2 circular dimension give the
distance to arc center.
• The preparatory functions
– To select plane g17 XY ,g18 ZX ,g19 YZ
– Direction of tool g02,g03
Feed word f
• The f word is generally used in contouring or
• Constant maximum feedrate for point to point
Expressed asinches per minute,millimeter per
minute rather than inches per revolution
Spindle speed word s
• The spindle speed word is programmed in
revolution per minute and is expressed by a
three digit coded number .
• Speed is rounded to 2 digit accuracy, (2nd & 3rd
• Speed is written in the form of biggest decimal
fraction multiplied by the power of 10.
• First digit code has value of 3 greater than
power of 10 ( power + 3)
• 1645 rpm
• Rounded to 1600
• 0.16 X 10 ^ 4
Tool word t
• Tool word may consist of a max of five digits in
a coded number.
• The tool is automatically selected by the
automatic tool changer when its code number
is programmed in a block
Miscellaneous function m
• Consist of two digit
• It contains auxiliary information