> For the complete documentation index, see [llms.txt](https://infosys.selmotech.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://infosys.selmotech.com/selmo-solution/selmo-solution-en/engineering-through-the-ages/nc-and-g-code-the-language-of-movement.md). # NC and G-Code – The language of movement With the first **NC machines (Numerical Control)** in the 1950s, the need arose for a language for **machine movements**. * Solution: **G-code** (DIN 66025, ISO), from the 1960s onward. * Standardized commands (G00, G01, M03 …) clearly describe movements, tools, and processes. * From drawings and later 3D models comes **machine-readable code**. πŸ‘‰ G-code is a success model: a **formal language**, which to this day forms the basis for CNC manufacturing.
Historical development * **1949–1952**: MIT develops the first numerical control (US Air Force) * **1960s**: Standardization β†’ G-code (DIN 66025) * **1970s–80s**: CNC machines, extensions (cycles, macros) * **1990s**: CAD/CAM integration β†’ automatic generation of G-code * **Today**: G-code global standard, basis of all CNC manufacturing
## Numeric Control (NC) and G-code #### 1. Origin * First **numerical controls (NC)** emerged in the late **1940s / early 1950s** in the USA (MIT, funded by the US Air Force). * Goal: make machine tools **programmable** – instead of cams, templates, or manual operation. * The first controls ran with **punched cards or punched tape**, which contained position data. *** #### 2. Development of G-code * From the **1960s onward**: introduction of a standardized language β†’ **G-code** (DIN 66025 in Germany). * G-code describes: * **geometry** (Movements: G00 = rapid traverse, G01 = linear interpolation, G02/G03 = circular arcs) * **technology** (M-commands: spindle on/off, coolant, tool change) * This made G-code a **formal language of manufacturing**, comparable to: * Technical drawing (geometry β†’ target image) * Circuit diagram (electrics β†’ function) *** #### 3. Significance * G-code is **universally readable** for every CNC technician. * A program is **was standardized** and represents the machining unambiguously. * Advantage: **precise, formal language** for machine movements. * Disadvantage: **very detail-oriented** – little abstraction, highly error-prone for complex processes. *** #### 4. Comparison to PLC programming * **G-code** is for CNC machines what the **Technical drawing** is for components: a **clear description of target movements**. * In contrast, PLC programming has never been **uniformly formalized** – even though it describes the β€œlogic.” * This means: * For movements (NC) β†’ **formal language available** (G-code). * For mechanics (drawing) β†’ **formal language available**. * For electrics (circuit diagram) β†’ **formal language available**. * For **logic of machines** (PLC) β†’ **no globally uniform language**. *** ### Conclusion: Role of G-code * **Numeric Control / G-code** is a **clear, standardized language for machine movements** – established since the 1960s. * This meant mechanics (via CNC) gained a β€œprogramming aspect” early on that was standardized. * **The great paradox:** * While the logic (PLC) **became flexible but unclear** , * motion control (NC/G-code) **developed clearly and in a standardized way** . πŸ‘‰ This shows: It is **possible**, to create a formal language for machine logic as well – just as G-code has done for movements. ## Development of NC/CNC programming (G-code) ### 1. The beginnings (1950s–1960s) – **Numerical Control (NC)** * First NC machines (punched tape, punched cards) β†’ control via **pure sequences of numbers** (coordinates, feed rates). * Everything was **direct and formal**: positions, paths, speeds. * Advantage: machine movements became **exactly describable**. * Disadvantage: extremely **inflexible**, tedious to program, no variables/logic. *** ### 2. Standardization & G-code (1960s–1970s) * Introduction of **G-code** (e.g., DIN 66025 in Germany). * Clearly structured commands: * G00 = rapid traverse, G01 = linear interpolation, G02/G03 = circular arcs * M-codes = machine functions (spindle, coolant, tool change) * Machine movements were **formalized and internationally standardized**. * Advantage: **Readable and universally understandable** – similar to a drawing. * Disadvantage: programming depth still very detail-oriented. *** ### 3. CNC and macro programming (1980s–1990s) * Introduction of **CNC control** (Computerized NC). * Extensions: * variables and parametric programming * subprograms and macros * cycles (drilling, milling, thread cutting) β†’ predefined routines * Advantage: more **flexibility and reusability**. * Disadvantage: programs became more complex, harder to oversee. *** ### 4. CAM integration (2000s) * Introduction of **CAM systems** (Computer Aided Manufacturing): * design (CAD) β†’ automatic generation of G-code. * Simulation and collision checking in advance. * Advantage: **Automation** of programming, high efficiency. * Disadvantage: operator loses direct understanding of the G-code β†’ **black-box effect**. *** ### 5. Today (2010s–2020s) – hybrid world * **G-code lives on**, is still the standard for almost all CNC machines. * At the same time: * **CAM-first**: programs are generated 90% automatically. * **high-level languages**: some manufacturers (e.g., Siemens ShopMill, Heidenhain Klartext) offer simplified programming languages. * **digital twins**: simulation replaces classical programming. * Advantage: enormous **productivity** and **error minimization**. * Disadvantage: * **loss of clarity** – G-code is hardly read directly anymore. * **dependence on software tools** and manufacturer dialects. *** ## Pros and cons at a glance | Era | Advantages | Disadvantages | | ------------------------------- | -------------------------------------- | ----------------------------------------------------- | | **NC (’50s–’60s)** | Formal, clear, direct | Very inflexible, cumbersome | | **G-code standard (’60s–’70s)** | Clear, internationally valid, readable | Detail-oriented work, complex for large parts | | **CNC & macros (’80s–’90s)** | More flexible, structured, cycles | Increasing complexity, harder overview | | **CAM integration (2000s)** | Automated, efficient, safe | Black box, loss of G-code competence | | **Today (2010s–2020s)** | Simulation, automation, digital twin | Little transparency, dependence on CAM & manufacturer | *** ## Placement in the big picture * **Mechanics:** Drawing β†’ CAD β†’ simulation (clarity decreased, flexibility increased). * **Electrics:** Circuit diagram remained stable and clear. * **Logic:** Previously visible in the circuit diagram β†’ made flexible by PLC, but intransparent. * **Movements (NC/G-code):** Standardized language was created, but through automation **disappeared from users’ view**. πŸ‘‰ **Today we are here:** * G-code still exists as a **formal base language**. * But most programmers now work only indirectly (CAM, cycles, simulation). * This means that here too the **original transparency** a **has made way for a higher level of automation** . *** ### Conclusion G-code is proof that **formal programming languages for machines work** – it revolutionized manufacturing and standardized it over decades.\ Today it is still a foundation, but in everyday life it is **hidden behind CAM systems**.\ This shows: **A formal base language is indispensable – but without modeling and abstraction, things become confusing.** --- # Agent Instructions This documentation is published with GitBook. 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