Gcode

G-code is a numerical control programming language used to instruct CNC machines and 3D printers. It controls tool movement, speeds, feeds, and various auxiliary operations, enabling automated manufacturing and fabrication across a range of technologies.

Programs consist of G-codes and M-codes. G-codes are preparatory commands that define motion and machine state (for example, G0 for rapid positioning, G1 for linear interpolation, G2/G3 for circular interpolation). Other settings include unit selection (G20 inches, G21 millimeters) and coordinate mode (G90 absolute, G91 incremental). M-codes handle miscellaneous functions such as spindle on/off, coolant, or program end. Codes are largely modal, meaning a command remains in effect until changed.

Standards and dialects: The core concepts are standardized internationally as ISO 6983 (formerly RS-274). In practice, machines and CAM tools implement dialects or machine-specific post-processors, so programs may require tailoring to a particular controller. Common firmware and controllers that interpret G-code include Grbl, LinuxCNC, Mach3/4, Marlin, and various proprietary CNC controllers.

Applications: G-code drives motion for CNC milling, turning, routing, and other subtractive or subtractive/additive processes. In 3D printing, G-code sequences moves and extrusion, along with temperature control, bed leveling, and other printer functions. Typical commands reference coordinates (X, Y, Z), extrusion or feed (E, F), tool numbers (T), and offsets. Programs may also include tool changes, subroutines, and dwell commands (G4).

Safety and workflow: Verification through simulation or dry runs is common before running on real hardware. Using appropriate post-processors, validating tool paths, and maintaining version control are standard practice to prevent collisions and insure manufacturability.