POSTED ON 1/27/2023 – Industrial machining computer numerical control (CNC) programming language has evolved through many iterations since its inception in the 1950s. Standardized in the early 1960s by the Electronic Industries Alliance as RS-247-D and now known as EIA/ISO machine programming – or G-code – it has become the foundational and most widely used protocol for precision control of vertical and horizontal machining centers, lathes and additive 3D printers, detailing every movement and action necessary to produce parts ranging from the simple to the unfathomably complex.
IT ALL STARTS WITH G
At the risk of oversimplification and with no desire to understate its capabilities, EIA/ISO programming is at its core a straightforward control language that follows a logical pattern. Machines are told what to do, when and how via a sequence of codes and data, and the sequence starts with the letter G, which directs a change in geometric coordinates. The G command can be followed by additional numeric commands dictating the nature or other detail of the move. For example, G00 commands a rapid move to a specific coordinate; G01 directs a linear feed move, while G02/03 indicates a clockwise/counterclockwise circular movement or circular interpolation.
The initial G designation would be followed by additional data, such as geometric location along a particular axis on a plane. A move to -130mm along the X axis would be written as X-130, and Y-5 would indicate -5mm along the Y axis. Additional instructions would then come in a variety of function letter codes. An S command would set spindle speed. Feed rate is set with an F code, while T codes dictate tool type. All machine functions are programmed with various commands. Pallet changes, coolant on/off, spindle rotations – every minute movement is directed and controlled by a code and a value. Once a cycle starts, the program will run until it is stopped or edited.
The G-code’s blessing and bane lies in its detail. Given the fact that every possible parameter and movement is given a command and value, there is no limit to what can be programmed and manufactured using EIA/ISO code. Five-axes machining of highly contoured surfaces, complex and critical parts such as jet engine components and other high-end manufacturing require intricate programming commands. Such complex programming, however, is so involved that in many cases an advanced Computer Aided Manufacturing (CAM) program is needed. A programmer imports part geometry into the program, selects tooling and defines cutting parameters, and the CAM software produces the necessary code. Even with CAM, a sufficiently complex part can take days to program; whereas a simple component will take less time to create.
While G-code may be advantageous (and with the aid of CAM) necessary in some cases, what about those applications and situations where such labor-intensive complexity is simply not necessary or required?