Describe how parametric programming can be used to create a single CNC program capable of machining parts of varying sizes and shapes.

Parametric programming allows a single CNC program to machine parts of varying sizes and shapes by using variables to represent key dimensions and parameters of the part. Instead of hard-coding specific numerical values for each dimension, the program uses symbolic names (variables) that can be assigned different values at runtime. These variables are then used in calculations and G-code commands to define the toolpath and machining operations. By changing the values assigned to these variables, the program can adapt to different part sizes and shapes without requiring manual editing of the G-code. For example, if machining a rectangular pocket, variables could be defined for the length, width, and depth of the pocket. The CNC program would then use these variables in the G-code commands to define the toolpath for milling the pocket. To machine a different size pocket, only the values assigned to the length, width, and depth variables need to be changed; the rest of the program remains the same. This is achieved using custom macros or subprograms that accept these variables as input. Often, conditional statements (IF/THEN) are used to handle variations in part geometry. If a certain parameter exceeds a threshold, a different machining strategy or toolpath might be selected. Parametric programming significantly increases programming efficiency and reduces the risk of errors when machining families of parts with similar features but different dimensions.