Part Programming:
A set of
instructions to carry out the machining of a work piece is called part
programming. A part programmer carries out this work. Her prepares the planning
sheet and writes the instructions in a coded form, which is acceptable to the
machine tool controller. Part programming is of two types:
i) Manual Part Programming
ii) Computer Assisted Part Programming
In
manual part programming the programmer prepares the program or punches the tape
with typewriter-like machine. In the latter, the input to the machine (tape or
program) is generated by computer.
Data
Required For Programming:
To prepare manual part program the programmer needs:
i) Machine Tool specification
ii) Specification of all tools
iii) Specification of Work Material
iv)
Speed, feed tables
Following
information are conveyed to machine control unit by tape reader:
i) Operation Number (Serial Number)
ii) Operation Code
iii) Coordinates for position /motion
iv) Tool Information
v) Speed and feed for information
vi) Miscellaneous Information like ON or OFF, Clock wise or Counter Clockwise rotation of spindle, Coolant OFF, Coolant ON
All
these information form a block
Formats
to represent block in punched tape:
1. Fixed Sequential
2. Word Address
3.
Tab Sequential
Fixed
sequential format:
In this format information is given in particular sequence that cannot be changed. If any information remains same as in the previous block then to maintain the sequence, it is necessary to repeat the information.
Let us
consider an example of such format:
(2
Digits for Sequence Number) (2
Digits for Operation Code) (Set of 6 digits for X) (Set of 6 digits for Y) (Set of 6 digits for Z) ( 4 digits for speed)
(four digits for feed) (3 digits
for tool) (2 digits for miscellaneous information)
And the block will look like (say):
31
50 345000 120000 450000 3500
2000 006
03
This
type of format is quite difficult to work on because of likelihood of mistakes
in writing the program and subsequent interpretation by the controller.
Word
Address Format:
In this format each element of information is prefixed by a alphabetical character which the controller understands for conveying it to particular register. Information is labeled by alphabet and there is no necessity to follow fixed sequence. The controller retrieves any information absent in the current block from the previous block. Thus chances of errors are eliminated and program is shortened. An example of a block in this format:
N32 G81 X0Y0Z50000 R30000 S5000 F100 M03*
N33 X100Y100*
In the
second bock only changed data are provided, rest of the parameters will be same
as mentioned in the previous block.
Tab Sequential Format:
In this format all information has to be in particular sequence but the elements of information have to be separated by the code TAB. If the information remains same as in the earlier block, then it need not be repeated but the code TAB is used in succession
For
example:
37TAB 81TAB 235000TAB 115000TAB 300000TAB 4500TAB 3000TAB 007TAB..
38TAB
100000TAB TAB………
This
means operation code 81 and all other steps in first bock are to be repeated in
second block too: only change in second block is X-coordinate.
Symbols:
In word
address format alphabet is used as prefix for each word of information. This
acts as an address that enables the data processing unit to allot to it specific
location in the control system. Following are the letter addresses used in
programming:
N : Operation Sequence Number Address
G Preparatory Function Address
X, Y, Z, A, B, C…. Dimension Address
S Spindle Speed Address
F Feed Rate Address
T Tool Address
M Miscellaneous Function Address