The concept of using macros in CNC programming revolves around code reuse and job repetition. Macros provide a way to create reusable blocks of code that can be called multiple times within a program. This eliminates the need to rewrite the same instructions for similar tasks, improving programming efficiency. One key aspect of macros is the use of variables. Variables in CNC programming allow for the dynamic storage and manipulation of data during program execution. By incorporating variables into macros, we can create flexible and adaptable code that can handle varying input values and perform calculations based on them. This enhances the versatility and power of macros, enabling them to handle a wide range of tasks in CNC machining.

In summary, variables are a fundamental component of macros, replacing actual data within the program. Programmers assign values to variables based on the specific application at hand. The use of variables enhances the flexibility of macro programming, allowing for adaptable and dynamic code. Additionally, variables benefit from features such as input data integrity and range checking, ensuring the accuracy and reliability of the program. By leveraging variables, macro programming becomes more versatile and capable of handling diverse scenarios and input data.

Variable Declaration

Before using variables in macros, they need to be defined through a process known as variable declaration. This step is similar to entering data into a calculator's memory. In macro programming, the # symbol (often called the pound sign or sharp sign) is used to signify variable definitions. The declaration of a variable involves assigning it a specific value or data. This allows variables to add flexibility to macro programs, enabling input data integrity checks and adherence to allowable value ranges.

#i = assigned current value

Example:

#19 = 1200 

#9 = 150.0 

Variable as an Expression 

Variables in macros can be defined using expressions, which can include mathematical formulas or calculations. The simplest form is assigning a direct value to a variable within the macro body. 

Example: 

#9 = 250.0 assigns a value of 250.0 mm to variable #9. 

This assigned value can be used in place of the variable in the macro, such as in the cutting feedrate statement. Variables can also use complex expressions, involving previously defined variables and mathematical operations. When using expressions, square brackets [expression] are used to enclose the calculations. These expressions allow for nested calculations, following the standard mathematical hierarchy.

G01    X375.0    F#9 

The F#9 macro statement will be interpreted as F250.0 (mm/min) actual statement. Re definition of the variable, for example #9=300.0, will pass on the new definition to the macro body, so 

G01 X375.0 F#9 will mean G01 X375.0 F300.0. 

When ex pres sions are used in a macro, they always evaluate a multiple mathematical or logical operation. Expressions must be enclosed in square brackets [expression]:

#i = #i * [#j + #k]

Local Variables

Local variables in macro programs serve to transfer user-supplied data to the macro body. They are limited to the macro they are defined in and cannot be transferred between macros. Each local variable is associated with a letter of the English alphabet. There are two options for assignment lists: Assignment List 1 with 21 available local variables and Assignment List 2 with 33 available local variables. These assignment lists allow for detailed management of local variables in macro programming.

Set a value:

#1 = 135.0

Use variable #1

G00 X#1

Set #1 variable to null

#1 = #0