Dans la fabrication de précision, CNC (Commande numérique par ordinateur) les machines sont l’épine dorsale d’une production efficace et précise. Cependant, de nombreux ingénieurs, programmeurs, and manufacturers struggle with understanding and using CNC machining formats correctly—leading to errors in program execution, problèmes de compatibilité avec les fichiers CAO, et des retards dans la production. This article breaks down the core components of CNC machining formats, providing practical solutions to common problems and helping you master the skills needed for smooth CNC operations.
1. Core CNC Machining Program Formats: The Building Blocks of Machine Instructions
A CNC program is more than just a list of commands; it follows a strict structure to ensure the machine interprets instructions accurately. Let’s break down the key elements, starting with the overall program structure.
1.1 Program Structure: What Makes a Valid CNC Program?
Every CNC program has three essential parts: program name, program body, et program terminator. Missing or incorrect elements here can cause the machine to fail to load or run the program.
| Component | But | Requirements & Exemples |
| Program Name | Identifies the program; located after the initiator and before the body | Uses letters (A-Z) + numbers; par ex., O0012 (for Fanuc systems) |
| Program Body | Contains movement/operation commands (par ex., G-codes, M-codes) | Must follow segment format rules; par ex., G01 X10 Y20 F500 |
| Program Terminator | Marks the end of the program and resets the machine | Common codes: M02 (stops machine) or M30 (stops + resets to start) |
Why does this matter? Imagine a manufacturer trying to run a program without a terminator (M02/M30). The CNC machine would keep waiting for more instructions, leading to unplanned downtime and potential material waste. By following the structure, you avoid such costly mistakes.
1.2 Program Format: Starting and Closing the Program Correctly
Before the program body begins, you need a starter symbol to signal the start of instructions. Similarly, un closing mark ends the program file. These symbols vary by coding standard.
- ISO Code (Global Standard): Utilisations % as both the starter and closing symbol. Exemple:
%
O0012 (Program Name)
G00 X0 Y0 (Body Segment)
M30
%
- EIA Code (Older U.S. Standard): Uses ER as the starter symbol and no separate closing mark.
Common Problem Solved: If you use an EIA starter (ER) for a machine set to ISO, the program won’t load. Always check your machine’s code standard (ISO/EIA) before creating the program.
1.3 Segment Format: How to Organize Commands in Each Line
UN program segment is a single line of instructions (par ex., moving the tool to a specific coordinate). The most widely used type is the variable program segment format—flexible and easy to adapt.
Key Features of Variable Segment Format:
- Variable Word Length: No fixed number of characters per command (par ex., X5 vs. X12.345 are both allowed).
- Variable Word Count: Include only the commands you need (par ex., omit Y if moving only in the X-axis).
- Flexible Word Order: Commands can be arranged in any order (par ex., G01 F500 X10 works the same as G01 X10 F500).
Exemple: A segment to mill a 10mm x 20mm rectangle at 500mm/min feed rate:
G01 X10 Y20 F500 (includes G-code for linear interpolation, X/Y coordinates, et vitesse d'avance).
1.4 Main Program vs. Subprogram: Streamlining Repeated Tasks
For parts with repeated features (par ex., forage 10 identical holes), subprograms save time and reduce code duplication. Think of them as “reusable templates” that the main program can call.
How They Work: A Step-by-Step Breakdown
- Define the Subprogram: Write a set of instructions for the repeated task (par ex., drilling a hole).
Example Subprogram (O9001 for drilling a 5mm hole):
O9001
G00 Z5 (Rapid move to 5mm above part)
G81 Z-10 R2 F100 (Drill 10mm deep at 100mm/min)
G00 Z20 (Retract tool)
M99 (Return to main program)
- Call the Subprogram from the Main Program: Use a call command (par ex., M98 P9001 L10 for Fanuc systems) to run the subprogram 10 times.
- Subprogram Nesting: Subprograms can call other subprograms (par ex., Subprogram A calls Subprogram B). Most CNC systems support 3-5 nesting layers.
Avantage: Instead of writing 10 identical drilling segments in the main program, you write one subprogram and call it 10 times—reducing code length by 80% and minimizing typos.
2. CAD File Formats for CNC Machining: Avoiding Compatibility Issues
CNC machines rely on CAD (Conception Assistée par Ordinateur) files to understand part geometry. Choosing the wrong format leads to quality degradation (par ex., rough surfaces) ou file corruption (par ex., missing features). Below is a comparison of the most common formats, with recommendations for CNC use.
| Format | Taper | Compatibilité | Use Case for CNC Machining | Avantages | Inconvénients |
| ÉTAPE | Neutral | All major CAD software (SolidWorks, AutoCAD) | Best for 3D parts; preserves geometry and dimensions | No vendor lock-in; haute précision | Slightly larger file size |
| IGES | Neutral | Most CAD software (older and new) | 2D/3D parts; legacy projects | Widely supported; works with old systems | Risk of data loss for complex 3D parts |
| STL | 3D Mesh | 3D printing software; not for CNC | 3D printing only | Simple; small file size | Loses geometric data (par ex., exact dimensions); poor for CNC precision |
| DXF | 2D Vector | Découpe laser; 2D CNC (par ex., milling flat parts) | 2Pièces D (par ex., signes, joints) | Ideal for 2D geometry; easy to edit | Not suitable for 3D parts |
| DWG | Proprietary | AutoCAD and compatible software | Avoid for CNC file sharing | High detail for AutoCAD users | Compatibility issues across software; risk of corruption |
Critical Recommendation: Utiliser STEP format for 3D CNC parts (par ex., composants du moteur) et DXF format for 2D parts (par ex., flat metal brackets). Avoid STL (for 3D printing only) and DWG (compatibility risks) when sharing files with CNC shops.
Yigu Technology’s Perspective
Chez Yigu Technologie, we see CNC machining formats as the foundation of precision manufacturing. Many clients struggle with program errors or incompatible CAD files—costing them time and money. Our solutions prioritize STEP/DXF for CAD files and variable segment formats for programs, simplifying workflows. We also train teams on subprograms to cut code duplication by 50%+ for repeated tasks. As CNC tech evolves, we’ll keep updating tools to make format mastery easier, helping manufacturers boost efficiency and reduce waste.
FAQ
1. Can I use STL files for CNC machining?
Non. STL files are mesh-based and lose exact geometric data (par ex., hole diameters, surface finish specs) critical for CNC precision. They work for 3D printing but will cause errors or poor part quality in CNC machining. Use STEP instead.
2. How many subprogram layers can I nest?
Most CNC systems (par ex., Fanuc, Siemens) soutien 3-5 nesting layers. Par exemple: Main Program → Subprogram A → Subprogram B (2 layers). Check your machine’s manual—exceeding the limit will trigger a “nesting error” and stop the program.
3. What’s the difference between M02 and M30 (program terminators)?
M02 stops the spindle, liquide de refroidissement, and feed but keeps the program at the end. You need to manually reset the machine to run the program again. M30 stops the machine AND resets it to the start of the program—ideal for repeating production runs without manual intervention.