CNC machining requirements for tools
1. Overview
With the vigorous development of modern digital manufacturing technology, the application of high-efficiency equipment such as CNC machine tools and machining centers characterized by "high precision, high efficiency, high reliability and specialization" is becoming more and more popular, driven by the unprecedented development of aerospace, automobiles, high-speed trains, wind power, electronics, energy, molds and other equipment manufacturing industries, cutting has entered a new era of high-speed processing development marked by high speed, high efficiency and environmental protection. High-speed cutting, dry cutting and hard cutting are important development directions of current cutting technology, and their important position and role are becoming increasingly prominent. The application of these advanced cutting technologies not only multiplies the machining efficiency, but also promotes the development of tool technology. With the emergence of various new material tools, such as poly diamond tools (PCD), poly cubic boron ammonia tools (PCBN), CVD diamond tools, nano composite tools, nanolayer tools, pinsu toughened ceramic tools, ultra-fine grain cemented carbide tools, TC (N) based cemented carbide tools, powder metallurgy high-speed steel tools, etc., the advanced CNC machine tool processing equipment has played a great role in matching with high-performance CNC tools, and has achieved good economic benefits. CNC tool refers to the general term of various tools used with CNC machine tools (such as machining centers, CNC lathes, CNC boring and milling machines, CNC drilling machines, automatic lines and flexible manufacturing systems, etc.), which is an indispensable key supporting product of CNC machine tools. Table 1-1 shows the comparison between traditional tools and modern CNC tools.
2. CNC machining requirements for tools
CNC machining has the characteristics of high speed, high efficiency and high degree of automation, and CNC tools are one of the key technologies to achieve CNC machining. In order to meet the needs of CNC machining technology and ensure the high-quality and efficient completion of CNC machining tasks, the CNC machining tools put forward higher requirements than the traditional processing tools, which not only require the tool to be wear-resistant, long life, good reliability, high precision, good rigidity, but also require the tool size stability, easy installation and adjustment, etc. The specific requirements of CNC machining for tools are as follows:
(1) The tool material should have high reliability CNC machining has a high cutting speed and degree of automation on CNC machine tools or machining centers, which requires the tool to have high reliability, and requires the tool to have a long life, stable cutting performance, good quality consistency and high repeatability. Solving the reliability problem of tools has become one of the key technologies for the successful application of CNC machining. When choosing CNC machining tools, in addition to the reliability of the tool material itself, the structure and clamp of the tool should also be considered
solid reliability. (2) The tool material should have high heat resistance, thermal shock resistance and high temperature mechanical properties In order to improve production efficiency, the current CNC machine tool is developing towards high speed, high rigidity and high power, and the increase of cutting speed often leads to a sharp increase in cutting temperature. Therefore, the tool material is required to have a high melting point, high oxidation temperature, good heat resistance, strong thermal shock resistance, and high high temperature mechanics of the tool material
energy, such as high temperature strength, high temperature hardness, high temperature toughness, etc. (3) CNC tools should have high precision In CNC machining production, the processed parts are required to complete their machining accuracy after the second clamping. Therefore, the tool is required to be adjusted to the required dimensional accuracy with the help of a special tool setting device or tool setting instrument, and then installed on the machine tool for application. This requires a high level of precision in the manufacture of the tool. Especially when using tools with indexable structure, there are strict precision requirements for the dimensional tolerance of the insert and the repeatability of the spatial position of the tool tip after the insert is indexed.
(4) CNC tools should be able to achieve rapid replacement CNC tools should be able to quickly and accurately engage and disconnect with CNC machine tools, and can adapt to the operation of manipulators and robots, and require good tool interchangeability, rapid replacement, convenient size adjustment, and reliable installation, so as to reduce the downtime caused by the replacement of tools. The size of the tool should be able to be pre-set off-machine with the help of the tool setter to reduce downtime for tool change adjustments. Today's CNC machining centers mostly use automatic tool change devices.
(5) CNC tools should be serialized, standardized and generalized to minimize tool specifications, in order to facilitate CNC programming and convenient tool management, reduce processing costs, improve production efficiency, establish tool preparation units, centralized management, responsible for the storage, maintenance, pre-adjustment, configuration and other work of valuable tools.
(6) CNC tools use a large number of machine clamp indexable tools, because the machine clamp indexable tools can meet the requirements of durability, stability, easy adjustment and replacement, at present, in CNC machine tools and machining centers and other equipment, widely use machine clamp indexable tool structure. The number of indexable tools in the machine clamp has reached 30%~40% of the entire CNC tool. Figure 1-1 shows the head of an indexable turning tool.
(7) CNC tools use a large number of multi-functional composite tools and special tools In order to give full play to the technical advantages of CNC machine tools and improve processing efficiency, the processing of complex parts requires the centralized processing of multiple processes in a clamping, and dilutes the boundaries of different cutting processes such as traditional turning, milling, boring, and threading, which is an effective way to improve the efficiency of CNC machine tools and accelerate product development. To this end, the new requirements of multi-function (composite tool) are put forward for CNC tools, requiring a tool to complete the processing of different processes of parts, reducing the number of tool changes, saving tool change time, reducing the number of tools and inventory, and facilitating tool management. Such as boring and milling cutters, drilling and milling cutters, etc., so that the original need for multiple processes, several tools to complete the process, in a process by a knife to complete, not only improve the production efficiency, ensure the machining accuracy, but also significantly reduce the number of tools. Figure 1-2 shows the indexable compound boring cutter for semi-fine boring, fine boring oil pump bore and orifice chamfering.
(8) CNC tools should be able to reliably break eyebrows or roll chips In order to ensure the stability of automatic production, CNC machining has higher requirements for chip processing. When cutting plastic materials, the breaking and curling of chips is often an important factor in determining whether CNC machining can be carried out normally. Therefore, CNC tools must have very good chip breaking, chip coiling and chip evacuation performance. It is required that the chips cannot be wound on the tool or workpiece, and the chips do not affect the machined surface of the workpiece and do not hinder the subsequent process. CNC tools generally take certain chip breaking measures (such as reliable chip breaking geometry, chip breaking table and chip breaker, etc.) in order to reliably break chips or roll chips.
(9) CNC tool materials should be able to adapt to the needs of difficult-to-machine materials and new materials With the development of science and technology, higher and higher requirements have been put forward for engineering materials, and various engineering materials with high strength, high hardness, corrosion resistance and high temperature resistance are increasingly adopted. Most of them are difficult-to-machine materials, which now account for more than 40% of workpieces. Therefore, CNC machining tools should be able to adapt to the needs of difficult-to-machine materials and new material processing.
