G‐Code (preparatory code)

The use of preparatory functions G‐Code in the programming of CNC machines has evolved over several decades since the advent of computer numerical control (CNC) technology in the 1950s. CNC machines use software to control the movement of cutting tools and other equipment, enabling precise and efficient manufacturing processes.

In the early days of CNC technology, programming was done manually, using simple codes to control machine movements. As the technology advanced, more complex codes were developed to enable more sophisticated machining operations. The G‐Code language, which uses preparatory functions to specify machine movements, was developed in the late 1960s and became widely adopted in the 1970s.

The first version of the G‐Code language, known as G0, was used to specify rapid positioning movements, where the cutting tool moves quickly to a new location without machining. The next version, G1, added the ability to specify linear interpolation movements, where the tool moves along a straight line between two points. Subsequent versions of the G‐Code language added more complex movements, such as circular interpolation (G2 and G3), helical interpolation (G2 and G3), and fixed cycle machining (G81 and G83).

As CNC technology became more advanced, the G code language was augmented with additional codes to enable more sophisticated machining operations. For example, the M code language was developed to specify machine functions such as turning coolant on and off, changing cutting tools, and stopping the machine.

Today, CNC programming has become highly automated, with advanced software systems that can generate G code automatically from CAD models and other design data. These systems can also simulate machining operations to identify potential problems and optimize cutting tool paths for maximum efficiency.

In summary, the use of preparatory functions G in the programming of CNC machines has evolved over several decades, from simple codes used to control basic machine movements to complex languages that enable highly sophisticated machining operations. With the continued advancement of CNC technology, the use of G code and other programming languages is likely to continue to evolve and expand, enabling even more precise and efficient manufacturing processes in the future.

Effectiveness of G‐Code commands

Commands are either modal or non-modal:
● Modal
Modal commands retain their validity with the programmed value (in all following blocks)
– A new value is programmed under the same command
– A command is programmed that revokes the effect of the previously valid command
● Non-modal
Non-modal commands only apply for the block in which they were programmed.

Example of G‐Code for turning

Example of G‐Code for milling

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