In precision manufacturing, CNC (Controllo numerico del computer) machines are the backbone of efficient and accurate production. Tuttavia, many engineers, programmers, and manufacturers struggle with understanding and using CNC machining formats correctly—leading to errors in program execution, compatibility issues with CAD files, and delays in 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, E program terminator. Missing or incorrect elements here can cause the machine to fail to load or run the program.
| Componente | Scopo | Requisiti & Esempi |
| Program Name | Identifies the program; located after the initiator and before the body | Uses letters (A-Z) + numbers; PER ESEMPIO., O0012 (for Fanuc systems) |
| Program Body | Contains movement/operation commands (PER ESEMPIO., G-codes, M-codes) | Must follow segment format rules; PER ESEMPIO., 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) |
Perché questo è importante? 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, hai bisogno di un 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): Usi % as both the starter and closing symbol. Esempio:
%
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.
Problema comune risolto: 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 (PER ESEMPIO., 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 (PER ESEMPIO., X5 vs. X12.345 are both allowed).
- Variable Word Count: Include only the commands you need (PER ESEMPIO., omit Y if moving only in the X-axis).
- Flexible Word Order: Commands can be arranged in any order (PER ESEMPIO., G01 F500 X10 works the same as G01 X10 F500).
Esempio: 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, e velocità di alimentazione).
1.4 Main Program vs. Subprogram: Streamlining Repeated Tasks
For parts with repeated features (PER ESEMPIO., perforazione 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: Una rottura passo-passo
- Define the Subprogram: Write a set of instructions for the repeated task (PER ESEMPIO., 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 (PER ESEMPIO., M98 P9001 L10 for Fanuc systems) to run the subprogram 10 volte.
- Subprogram Nesting: Subprograms can call other subprograms (PER ESEMPIO., Subprogram A calls Subprogram B). Most CNC systems support 3-5 nesting layers.
Beneficio: 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 (Design assistito da computer) files to understand part geometry. Choosing the wrong format leads to quality degradation (PER ESEMPIO., superfici ruvide) O file corruption (PER ESEMPIO., missing features). Di seguito è riportato un confronto dei formati più comuni, with recommendations for CNC use.
| Formato | Tipo | Compatibilità | Use Case for CNC Machining | Professionisti | Contro |
| FARE UN PASSO | Neutral | All major CAD software (Solidworks, AutoCAD) | Best for 3D parts; preserves geometry and dimensions | No vendor lock-in; alta precisione | Slightly larger file size |
| Iges | Neutral | La maggior parte del software CAD (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 | Semplice; small file size | Loses geometric data (PER ESEMPIO., exact dimensions); poor for CNC precision |
| Dxf | 2D Vector | Taglio laser; 2D CNC (PER ESEMPIO., milling flat parts) | 2D parts (PER ESEMPIO., segni, guarnizioni) | 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: Utilizzo STEP format for 3D CNC parts (PER ESEMPIO., Componenti del motore) E DXF format for 2D parts (PER ESEMPIO., flat metal brackets). Avoid STL (for 3D printing only) and DWG (compatibility risks) when sharing files with CNC shops.
La prospettiva della tecnologia Yigu
Alla tecnologia Yigu, vediamo 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.
Domande frequenti
1. Can I use STL files for CNC machining?
NO. STL files are mesh-based and lose exact geometric data (PER ESEMPIO., diametri del foro, 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 (PER ESEMPIO., Fanuc, Siemens) supporto 3-5 nesting layers. Per esempio: Main Program → Subprogram A → Subprogram B (2 strati). 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, refrigerante, 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.