With the rapid development of science, technology and social production, mechanical products are becoming more and more complex, and the requirements for the quality and productivity of mechanical products are higher and higher. In industries such as aerospace, military and IT, parts have high precision, complex shapes, small batches, frequent modification, difficult processing, low production efficiency, labor intensity high and a quality difficult to guarantee.
Automation and intelligence of the machining process is the most important way to adapt to the above development characteristics. In order to solve the above problems, a flexible, versatile, high-precision and efficient automated production equipment-CNC machine tool has emerged in this situation. At present, CNC technology has gradually become popular, and CNC machine tools have been widely used in industrial production and become an important development direction of machine tool automation.
1.CNC
1) The meaning of CNC:
CNC is numerical control (NUMERICALCONTROL), which is the abbreviation of numerical sequential control.
The essence of CNC is to automatically control the movement of mechanical equipment via digital information (digital quantities that do not change internally) according to a specific processing method. It has exactly the same nature as sequential control (i.e. sequential control) via continuously changing analog quantities. . Since the control information in CNC is inseparable from computers, the automatic control technology through computers is called CNC. The CNC mentioned here specifically refers to the CNC used in machine tool processing (i.e. machine tool CNC). In addition, CNC is also widely used in fields such as measurement, physical and chemical experiments and analysis, material and information transmission, construction and scientific management.
2) Classification of CNCs:
The NC device of early CNC machine tools was composed of various logic components and memory components to form random logic circuits. It was a hardware structure with fixed wiring. CNC functions were implemented by hardware, called a hardware CNC machine tool. with this technology are generally called numerically controlled machine tools.
Computer numerical control (COMPUTERNUMERICALCONTROL), called CNC. A modern CNC system is a CNC system that uses a dedicated microprocessor or microcomputer. The system program (software) stored in memory in advance realizes control logic, performs partial or partial CNC functions, and connects to peripheral devices through interfaces. is called For CNC systems, these machine tools are generally called CNC machine tools.
2. CNC machine tools and CNC machine tools
1) CNC machine tool
Machine tool CNC refers to a discipline that automatically controls the sequence, displacement and speed of various movements of the machine tool by programming the machining sequence, recording its control instructions on the information carrier as digital signals and processing them through the output. computer. Its control objects are specifically aimed at machine tools and machine tool machining. The machine tools mentioned here do not only refer to machine tools for metal machining (machine tools such as slide turning, milling, planing, drilling, grinding, boring, etc. ).
2) CNC machine tools
CNC machine tools are a new type of integrated electromechanical processing equipment that uses digital information to control machine tools to perform active processing according to given static rules.
CNC machine tools are the product of a combination of numerical control technology and machine tools. CNC machine tool technology is carried out through machine tool processing technology such as CNC gantry milling machines. The key to using CNC technology is to properly learn and use CNC machine tools. .
The CNC rate of a country’s machine tools reflects the level of the country’s machine tool industry and machine manufacturing industry. It is also one of the important indicators to measure the technological progress of a country. This is of great importance to realize the automation of the production process, promote scientific and technological progress and accelerate modernization. Developed countries regard CNC technology as the strategic direction of development of the machinery industry, and vigorously promote and develop CNC machine tools.
3. Application of CNC machine tools
Features of CNC machine tools:
Compared with traditional machine tools, control machine tools have the following characteristics.
1) Very flexible
The processing of parts on CNC machine tools mainly depends on the processing sequence. Unlike ordinary machine tools, it does not require the manufacture or replacement of many molds and accessories, and there is no need to frequently readjust the machine tool. Therefore, CNC machine tools are suitable for situations where the processed parts are frequently changed, that is, they are suitable for the production of single parts, small batches of products and the development of new products, thereby extending the production preparation cycle and saving the cost of a large amount of processing equipment.
2) High processing precision
The processing precision of CNC machine tools can generally reach 0.05-0.1mm. CNC machine tools are controlled in the form of digital signals. Each time the CNC device outputs a pulse signal, the moving parts of the machine tool move by an equivalent pulse (usually 0.001 mm), and the machine tool moves forward. The backlash of the transmission chain and the uniformity error of the screw pitch can be compensated by the CNC installation process. Therefore, the positioning accuracy of the CNC machine tool is relatively high.
3) Processing quality is stable and reliable
When processing the same batch of parts on the same machine tool, under the same processing conditions, using the same tools and processing sequences, the toolpaths will be exactly the same and the parts will have good consistency and smoothness. stable quality.
4) High consumption rate
CNC machine tools can effectively reduce the processing time and auxiliary time of parts. The wide range of spindle sound speed and feed quantity of CNC machine tools allows the machine tools to perform powerful cutting with large cutting quantities. CNC machine tools are currently entering the era of high-speed processing. The rapid movement and positioning of moving parts of CNC machine tools and high-speed cutting processing have greatly improved productivity. Additionally, when used in conjunction with the machining center’s tool magazine, multiple processes can be processed continuously on a single machine tool, reducing turnaround time between semi-finished product processes and improves productivity.
5) Improve rest conditions
After the CNC machine tool is adjusted before processing, the sequence is entered and started, and the machine tool can process automatically and continuously until the processing is completed. All the operator needs to do is program entry, editing, loading and unloading parts, preparing tools, observing the machining status, testing parts and others tasks. The labor intensity is greatly reduced, and the machine tool operator’s work tends to be intellectual work. Additionally, machine tools are usually combined to make them clean and safe.
6) Apply modernization of consumption management
The processing time of CNC machine tools can be accurately predicted in advance, the tools and accessories used can be standardized and upgraded, and it is easy to standardize the processing information. It was organically combined with computer-aided design and manufacturing (CAD/CAM). ) Together they form the basis of modern integrated production techniques.
4. Development of CNC technology
1) High speed
The CNC system adopts more than 32-bit microprocessor, so that the input, decoding, synthesis, output and other aspects of the CNC system are all realized at high speed. It can also improve the resolution of the CNC system and achieve high performance. speed and high-speed operation of continuous finishing of small sequence segments.
The new CNC system currently under development using a 64-bit central processing unit (CPU) has enhanced interpolation calculation functions and fast feed functions to achieve high-speed processing and multi-control functions. axes. The number of individual control axes is 3 to 15 axes, up to 24 axes, and the number of axes controlled at the same time can reach 3 to 6 axes.
2) multifunction
The CNC system has various monitoring, detection and compensation functions. Such as tool wear detection, system accuracy and thermal change detection, etc. It also has functions such as tool life management, tool length offset, tool radius compensation, tool tip compensation and pitch compensation. Most modern CNC machine tools adopt CRT screen, which can display the trajectory of two-dimensional graphics, and some can also realize three-dimensional black static graphics display. With the help of the CRT, functions such as entering, editing, modifying and deleting programs can be performed using the keyboard. Modern CNC systems have hardware, software and fault self-diagnosis functions.
3) Smart
In modern CNC systems, adaptive mastering techniques are introduced. Adaptive control technology is a technology that can adjust the characteristics of the working conditions measured during the machining process and enable the cutting process to achieve and maintain the best state.
The development of intelligence in modern CNC systems is currently mainly reflected in the following aspects:
①The part is actively detected and centered.
② Detect tool damage and automatically replace spare tools.
Management of tool life and tool storage status.
④Load monitoring, data management and maintenance management.
⑤Use feedforward control to compensate for the vector function in real time.
⑥The real-time compensation function for the expansion and contraction of ball rods, etc., based on thermal deformation during processing.
5. Composition of CNC machine tools
Modern CNC machine tools are composed of programs, input and output equipment, CNC devices, servo systems and machine tool bodies.
Daguang focuses on providing solutions such as precision CNC machining services (3-axis, 4-axis, 5-axis machining), CNC milling, 3D printing and rapid prototyping services.
