Five major directions and three major gaps in CNC machine tool technology
In the 1990s, countries such as Europe, the United States and Japan began to study and formulate architecture specifications for open CNC devices (OMAC, OSACA, OSEC), developed open CNC devices as a development strategy. Our country also began to study and formulate a regulatory framework for open CNC devices in 2000, but it is still far from complete.
4.2 Networking
Networking is conducive to information sharing and improving production efficiency. According to some data, in multi-variety and small-batch production, the cutting time of a CNC machine tool only accounts for 25% to 35% of the maneuvering time. After being connected into a network, it can be increased to 60% to 65%.
The network technology of CNC mainly refers to the network connection and network control between the control system and other external control systems or host computers. The CNC system first faces the enterprise's internal LAN, and then transmits it to the outside of the enterprise via the Internet. This is called Internet/Intranet. The network enables cross-regional collaborative design, collaborative manufacturing, information sharing, remote monitoring, remote diagnosis and services between enterprises. The network can provide complete production data information for manufacturing. Processing programs can be transmitted to remote machine tools for processing through the network, and remote diagnosis and instruction adjustment can also be issued. The network connects scattered CNC machine tools in various places, coordinates with each other, and makes unified optimization and adjustment, so that product processing is not limited to one factory and realizes socialized production.
The information integration of my country's machinery manufacturing enterprises has also developed relatively quickly, achieving workshop-level and enterprise-level information network integration. The network development of CNC has broad prospects, but there is still a long way to go to truly realize cross-enterprise and cross-regional information networks.
5 Optimize process parameters to improve efficiency
Whether the process parameters used in CNC machining are reasonable is very important for improving production efficiency and ensuring processing quality. It must be gradually optimized and a process database established.
There are two methods for optimizing process parameters. One is to select reasonable process parameters through actual trial cutting, which is time-consuming, labor-intensive, and material-consuming; the other method is to apply the mechanical dynamic optimization simulation method, which saves time, effort, and materials than the first method, and can also obtain more results. Reasonable process parameters. In production practice, these parameters can also be reasonably adjusted.
The aviation industry is a large user of CNC machine tools and has an urgent need to optimize process parameters, establish process databases, and apply them in production practice. Therefore, Beijing University of Aeronautics and Astronautics and AVIC Beijing Aviation Manufacturing Engineering Research Institute were organized by the government to carry out technical research on optimizing process parameters. The above units have developed a complete set of process parameter mechanics dynamic optimization simulation, prediction and digital software and hardware systems, established an optimized process parameter database, and formed an optimized high-speed cutting process parameter manual, which fundamentally realizes the process parameter selection from trial cutting to simulation. across, improving processing efficiency and quality. This is significant and far-reaching work.
Shaanxi Aircraft Manufacturing Company has applied optimized process parameters in the processing of nearly 100 parts, and the average processing efficiency has increased by more than 2 times; Wangjiang Industrial Co., Ltd. has adopted optimized process parameters in the processing of artillery parts, and the efficiency It has increased by more than 4 times; Changhe Aircraft Industry (Group) Company uses optimized process parameters to process aluminum alloy parts, and the efficiency has increased by more than 2.8 times.
The Siemens 828D CNC system has a dynamic process package (Dynmics), which contains a new "precision surface" function, which can achieve efficient processing and obtain the best surface quality.
my country’s CNC equipment manufacturers should also provide technology and services in this area. The use of process optimization parameters can not only improve production efficiency and processing quality, but is also of great significance to saving materials, energy saving and emission reduction, and realizing green manufacturing.
Pursue high precision and high quality
Pursue high precision and high quality of workpieces processed by CNC machine tools. First of all, the CNC machine tool itself must have such performance.
To this end, the structure and layout of CNC machine tools, and the selection of materials must take into account the improvement of rigidity and load-bearing capacity to ensure high precision; at the same time, CNC systems, servo drive systems, transmission systems, and measurement sensors must also have high resolution. , High-precision performance can meet the high-precision and high-quality requirements of processed workpieces.
1 Structural layout
In order to realize functions and improve rigidity, CNC lathes, turning centers, vertical machining centers, horizontal machining centers, gantry machining centers, turning and milling composite machining centers, etc. There were profound changes in the structural layout.
For example, in the vertical machining centers and horizontal machining centers produced by some domestic manufacturers, the lateral coordinates are moved by columns, which reduces the number of worktables (the traditional structure is a double-layer cross worktable) and improves the machining center. The rigidity and load-bearing capacity of the workbench; the gantry machining center has developed from a fixed workbench and two moving columns to a bridge structure, that is, the workbench is fixed, two columns are made into a fixed wall, and guide rails and cross beams are installed on the wall. Make longitudinal movement on the guide rail. This structure reduces the mass and motion inertia of moving parts, facilitates accurate positioning, and reduces the floor space.
The GMC2590? bridge-type five-axis machining center produced by Shenyang Machine Tool, the `XHV2525?60 elevated five-axis linkage high-speed boring and milling machining center produced by Jinan No. 2 Machine Tool, and the Cross-rail high-speed gantry machining centers all adopt a bridge-type gantry frame structure. The structure has reasonable layout, good rigidity, strong load-bearing capacity, uniform stress, good thermal balance, stable accuracy and small footprint. The typical structural layout is shown in Figure 3.
2 Use new materials to improve rigidity
The development and application of high-quality new materials for CNC machine tools will help improve the overall rigidity and accuracy of CNC machine tools, which is very important.
For example, Ningbo Haitian Precision Machinery Co., Ltd. uses a bed made of 90% granite polymerized casting in the HTM-V120L CNC vertical turning and milling machining center. According to the factory, the seismic strength of the lathe made of this material is 10 times higher than that of ordinary cast iron lathes.
For another example, the base of the TG-45 six-axis (or five-axis) linkage CNC tool grinder produced by Dalian Kede Company uses artificial stone.
It is said that the above two companies have applied these two new materials. Because of their good shock absorption, good stability, wear resistance and other characteristics, they provide a guarantee for improving and maintaining the accuracy of machine tools.
In addition, there are data showing that honeycomb materials, cement materials, natural granite stones, etc. are also used in CNC equipment. Paying attention to the development and application of new materials will inevitably lead to changes in the structural design and performance of machine tools.
3 High-precision interpolation CNC system
The application of high-digit CPU (64-bit) in CNC devices, high-speed nano-level interpolation operations, high-resolution servo and other functions are to improve Make an important contribution to the accuracy of CNC machine tools.
The CPU used in CNC machine tools has developed from 16-bit in the 1980s to the current 64-bit, and its frequency has also increased from the original 5MHZ and 10MHZ to thousands of MHZ. The development of CPU has further improved the computing speed and resolution (0.1?m, 0.01?m). Domestic CNC systems have begun to use 64-bit CPUs, which can achieve micron-level precision interpolation, but there is still a gap compared with foreign advanced CNC systems.
For example, FANUC 30i/31i/32i/35iB series CNC systems, Mitsubishi M700V CNC systems, and Siemens 828D CNC systems all have nanometer-level interpolation or nanometer-level calculation accuracy.
To achieve nano-level precision interpolation, the control resolution and response capabilities of the servo drive system are very critical. To this end, a high-precision sensor (16?106 lines/revolution) is installed on the servo motor shaft in the drive unit, and a high-resolution (1?m) grating ruler is used in the closed-loop system to make the moving parts of small CNC machine tools The positioning accuracy reaches 2~3?m. Under normal circumstances, domestic small CNC machine tools cannot reach this level.