Parametric Programming?


Parametric programming is not the most  commonly  used  programming tool but it is a very powerful technique which  will greatly  enhance a program’s capacity  to  include complex routines.   

Parametric programming combines manual programming  with computer programming techniques similar to those found  in  BASIC,
‘C’  or  PASCAL.

 Computer-related features  such as  variables, arithmetic expressions,  and looping are all  made available.
 One of the  most popular  implementations  of parametric programming is Custom Macro B (used by Fanuc and Fanuc-compatible controls) . The  Advanced Programming Language [APL]  is another.

There are many applications for  this type of programming which  range from  the simple inclusion  of a variable,  to the creation  of
 routines which deliver complex motions.
If  a number of  similar  parts are being manufactured by  constantly  editing the same  CNC program  then , using  the techniques provided  by parametric programming , a single program  can  be created which  suits all.  
Built-in  canned cycles don’t always  provide  the  precise functions you  require.  Parametric programming allows  you to develop special  purpose routines for operations like thread milling and  contour pocketing  etc.  In essence you can  design  your own  canned cycles.
Parametric programming  can also be used to create complex motion.  Unfortunately  most CNC machines do not include spiral interpolation  but  this can be generated using parametric functions as can any other form  of  interpolation  you might need to initiate.      

Parametric programming puts a new dimension on part programming  giving  creative and innovative programmers a tool  to make the best use of  the machine’s capabilities.


Example:
To stress what can be done with parametric programming, here is a simple example  for a machining centre  application. It will machine a  hole of any size at any location. Notice how similar this program is to a program written in BASIC.

 
   V01=0.5     ;  Cutter rad
   V02=3.0   ;  X position of hole
   V03=1.5   ;  Y position of hole
   V04=.5     ;  Depth of counterbored hole
   V07=2.5   ; Diameter of counterbored hole
   
   F150                       ;  Feedrate 150 in/min
  X (V02)  Y (V03)    ;  Rapid to hole centre   X3.0  Y1.5
  Z0                          ;  Move tool to top of work
  F4                          ; cutting feedrate
  Z  (0-(V04))                 ;
  X  ( (V02+(V07/2)) -V01)             ; move to edge of hole ( (3 + (2.5/2))-0.5) = 3.75
   I                                                    ; incremental mode
  G02 X0 Y0 I (0-((V07/2)-V01)) J0   ; machine c’bore
  A                                                    ;  absolute mode
  G01 X (V02) Y (V03)                      ; move back to hole centre
  F150                                               ; rapid feed
  Z.1                                                  ; Z clearance height
  X0 Y0                                              ;
  E                                                     ; program end