Welcome to the introductory guide to CNC machine machining! If you are new to the field of machining, you may be unfamiliar with the "CNC machine process". This article will start from the basic definition, step by step dismantle the principle, composition, and operation process of CNC machine tools, integrate real industry cases and practical techniques, and help you quickly establish a systematic understanding of CNC machining and easily get started with the core technology of precision manufacturing.
1. Introduction
1.1 Definition of CNC machine tool
CNC machine tool, that is, computer numerical control machine tool (Computer Numerical Control Machine)., is an automated processing equipment driven by a computer control system through a pre-written digital program. To put it simply, it gets rid of the traditional machine tool mode of relying on manual manual operation, and accurately controls the movement trajectory, rotation speed, feed rate and other parameters of the tool through program instructions, and realizes automatic cutting, milling, drilling and other processing of metals, plastics and other materials. Compared with traditional machine tools, its core advantages are high machining accuracy, strong stability, and the ability to replicate complex parts in batches.
1.2 The importance of CNC machine tools
In modern manufacturing, CNC machine tool processing process is the core support for industrial upgrading, widely used in key fields such as aerospace, automobile manufacturing, electronic equipment, and medical devices. According to industry data, more than 70% of the current global precision parts processing relies on CNC machine tools to complete the process; In the production of auto parts, the penetration rate of CNC machining has reached more than 95%. Taking automobile engine block processing as an example, traditional manual processing requires multiple technicians to work together, with an error rate of more than 0.1mm, while CNC machine tools can control the error within 0.005mm, and the production efficiency is increased by more than 3 times, fully reflecting its irreplaceability in precision manufacturing.
2. The basic principles of CNC machine tools
2.1 The concept of CNC technology
Numerical Control Technology is the core foundation of CNC machine tool machining process, which is a technology that uses digital information to control mechanical movement and machining processes. Its core logic is to convert the geometry, size, processing technology and other requirements of the machined parts into computer-recognizable numerical codes (i.e., G code, M code, etc.), and then the control system parses the code and drives the actuator to complete the processing. This digital control mode realizes the automation, precision and flexibility of the processing process, and is a core component of modern manufacturing technology.
2.2 Working principle of CNC machine tools
The core workflow of CNC machine tool processing can be summarized as three steps: "information input, data processing, and execution processing", as follows:
- Information input: write CNC programs for part processing through programming software, or directly import CAD design files to convert processing requirements into digital codes;
- Data processing: The control system parses and calculates the input digital code to generate pulse signals that drive the movement of each axis.
- Execution of machining: The drive system receives pulse signals, controls the machine tool spindle, worktable and other components to move according to the preset trajectory, and at the same time moves relative to the workpiece to complete the material cutting process.
To give a practical example: when processing the aluminum alloy parts of the middle frame of the mobile phone, first draw a three-dimensional model of the middle frame through CAD software, and then use CAM software to generate a CNC program, after the program is imported into the CNC milling machine, the system drives the X, Y, Z three-axis worktable to move precisely, and the milling cutter cuts the aluminum alloy plate according to the preset path, and finally processes the middle frame of the mobile phone that meets the size requirements.
2.3 Common types of CNC machine tools
Different types of CNC machine tools are suitable for different machining scenarios, and novices need to focus on the following 4 common types:
| Machine type | Core features: | Applicable scenarios |
|---|---|---|
| CNC milling machine | It mainly carries out milling, drilling, and boring processing, and can realize multi-axis linkage | Box parts, flat parts, complex curved parts (such as mechanical housings) |
| CNC lathe | The workpiece rotates, the tool is fixed feed, and it mainly processes shaft and disc parts | Rotary body parts such as automobile drive shafts, bearing sleeves, and bolts |
| CNC machining center | It integrates various functions such as milling, drilling, and boring, and is equipped with a tool magazine for automatic tool change | Multi-process integrated machining of complex precision parts (e.g., aerospace parts) |
| CNC wire EDM machine | The material is cut by EDM, and the processing accuracy is extremely high | Mold parts, thin precision parts (e.g., mold cavities, electronic component pins) |
3. The main components of CNC machine tools
3.1 Control system
The control system is the "brain" of CNC machine tools, responsible for receiving and parsing CNC programs and issuing control instructions. At present, the mainstream control systems on the market include Fanuc from Japan, Siemens from Germany, and Chinese CNC. For example, in precision mold processing, the program parsing speed of Fanuc 0i-MF control system can reach 1000 pieces per second, which can effectively avoid machining lag and ensure the smoothness of surface processing.
3.2 Mechanical structure
The mechanical structure is the "skeleton" of CNC machine tools, which directly affects the machining accuracy and stability, and the core components include the bed, worktable, spindle, guide rail, etc. Among them, the bed needs to have high strength and rigidity, usually made of cast iron or granite; the guide rail is divided into line rail and hard rail, which is suitable for high-speed precision machining and hard rail is suitable for heavy cutting processing. Taking a heavy-duty CNC lathe as an example, its bed is cast with integral cast iron, which is aged to eliminate internal stress, which can effectively avoid deformation during machining.
3.3 Drive system
The drive system is the "power source" of CNC machine tools, responsible for converting the pulse signal of the control system into mechanical motion, which is divided into two types: servo drive and stepper drive. The servo drive has high accuracy and fast response, making it suitable for precision machining; the stepper drive has low cost and low precision, making it suitable for simple machining scenarios. In practical applications, high-end CNC machining centers all use servo drive systems, which can achieve a positioning accuracy of 0.001mm, which can meet the machining requirements of aerospace parts.
3.4 Tools and fixtures
Tools and fixtures are critical components in CNC machining that directly touch the workpiece, and their selection directly affects machining quality and efficiency. Tools need to be selected according to the processing material and process, such as carbide tools for steel and diamond-coated tools for aluminum alloys. The clamp is used to fix the workpiece to ensure the stable position of the workpiece during the processing process, and the common clamp has a three-jaw chuck, vise, customized tooling, etc. Case: When machining stainless steel flanges, a cemented carbide end mill is used, and a three-jaw chuck is used to fix the workpiece, which can effectively avoid the vibration of the workpiece and ensure the flatness of the processing plane.
4. The operation process of CNC machine tools
4.1 Design and Programming
This is the preparatory part of CNC machining, where the core is to convert part requirements into CNC programs. First, the 3D model of the part is drawn through CAD software (such as AutoCAD and SolidWorks), and then the CAM software (such as Mastercam, UG) is used for process planning, and the tool path, rotation speed, feed rate and other parameters are set, and finally the G-code program is generated. Note to novices: When programming, you need to avoid the problem of tool interference, and you can preview the machining process through the simulation function of CAM software to troubleshoot errors in advance.
4.2 Machine Setup and Calibration
After the program is written, the machine tool needs to be set up and calibrated to ensure the machining accuracy. The steps include: importing the CNC program into the machine control system, installing the appropriate tool and fixture, tool setting operation (determining the position of the tool relative to the origin of the workpiece), calibrating the machine spindle speed and feed volume. Among them, tool setting is a key step, if the tool setting error is too large, it will directly lead to the deviation of the processing size of the part. In actual operation, manual tool setting or automatic tool setting instrument can be used, and the tool setting accuracy of the automatic tool setting machine can reach 0.0005mm, which is suitable for precision machining.
4.3 Machining process monitoring
During the machining process, it is necessary to monitor the operating status of the machine tool in real time to avoid problems such as tool damage, loose workpieces, and overheating of processing. The cutting status can be observed through the monitoring system of the machine tool, and the sound of the machine tool operation can be monitored (the sound is stable during normal operation, and abnormal noise will occur when it is abnormal), and the supply of cutting fluid can be paid attention to (the cutting fluid can be cooled and lubricated to avoid tool wear). Case: When processing aluminum alloy parts, if the cutting fluid is found to be insufficient, it will lead to an increase in the tool temperature and the phenomenon of sticking the tool.
4.4 Post-processing and quality inspection
After the processing is completed, the workpiece is post-processed, including removing burrs, cleaning oil stains, heat treatment, etc.; Then conduct quality inspection, using calipers, micrometers, coordinate measuring instruments and other tools to detect the size and shape and position tolerance of parts. If the dimensional deviation is found during the inspection, the cause (it may be a program error, tool setting deviation, decrease in machine tool accuracy, etc.), adjust and reprocess. For example, if the aperture of the part is found to be 0.02mm smaller, it is found that it is caused by tool wear, and it can be reprocessed after replacing it with a new tool, which can meet the size requirements.
5. Conclusion
The CNC machine tool processing process is a systematic precision manufacturing system, from the basic definition, principle composition, to the specific operation process, each link directly affects the quality and efficiency of processing. For novices, they can quickly get started with CNC machining by first establishing an overall understanding of core concepts and processes, and then accumulating experience through practical operations, gradually mastering key skills such as programming, tool setting, and process monitoring. With the development of the manufacturing industry towards intelligence and high precision, mastering CNC machine tool processing technology will become an important professional competitiveness.
As an enterprise deeply involved in the field of precision manufacturing, we believe that the core value of CNC machine tool machining process lies in the "balance between precision and efficiency". When beginners get started, they should prioritize the basic principles and operating specifications, rather than blindly pursuing processing speed. In the future, with the integration of Industry 4.0 technology, CNC machining will be further upgraded in the direction of intelligence and automation, and CNC equipment with functions such as data collection, remote monitoring, and intelligent diagnosis will become the mainstream. For enterprises, choosing suitable CNC equipment and optimizing the processing process is the key to enhancing core competitiveness; For practitioners, only by continuously learning new technologies and improving their practical skills can they adapt to the development needs of the industry.
FAQ
1. What core skills should novices master first when learning CNC machine tool machining? Novices should give priority to mastering three core skills: first, the basic knowledge of CAD/CAM programming, which can independently complete the modeling and programming of simple parts; second, machine tool operation specifications, including tool installation, tool setting, machine tool calibration and other basic operations; The third is the basis of quality inspection, which can use common measuring tools to judge whether the parts are qualified.
2. What are the common reasons for errors in CNC machine tool machining? There are four main types of common error reasons: first, program errors, such as unreasonable tool path planning and incorrect parameter settings; second, the deviation of the knife setting, and the position of the origin was not accurately determined when the knife was matched; third, the accuracy of machine tools, such as guide rail wear and spindle runout; Fourth, there are problems with tools and fixtures, such as worn tools and loose fixtures.
3. How to choose the right CNC machine type for different material processing? For processing rigid materials (such as steel and stainless steel), you can choose CNC milling machines, machining centers, and carbide tools; For processing rotary body parts (such as shafts and discs), CNC lathes are preferred; For processing precision thin parts and mold parts, you can choose CNC wire cutting machine tools; For processing lightweight materials such as aluminum alloy, CNC milling machines and machining centers can be adapted, so you need to pay attention to choosing the appropriate cutting speed.
4. What is the role of cutting fluid in the CNC machine tool machining process? The cutting fluid has three main functions: one is to cool down and avoid damage or deformation of tools and workpieces due to overheating during the machining process; the second is lubrication, which reduces the friction between the tool and the workpiece, reduces tool wear, and improves the quality of the machining surface; The third is chip removal, which takes away the chips generated by processing in time to avoid chip accumulation affecting the processing accuracy.
