模具高速铣削加工技术及其数控编程（High speed milling technology of die and NC programming）

1、模具高速铣削加工技术及其数控编程（High speed milling technology of die and NC programming）High speed milling technology of die and NC programmingHigh speed machining can not only greatly improve the production efficiency, but also can improve the machining precision and surface quality, efficient processing, some sp

2、ecial materials to solve some of the conventional processing in the high speed machining technology has attracted great attention in the world. In this paper, the key technologies of high speed machining are expounded from the aspects of machine tools, cutting tools, materials and CAM NC programming

3、. Finally, two examples of high speed machining are given.I. PrefaceAs the key tooling of mould pressing products, the design and production cycle of mould become the decisive factor to decide the development cycle of new product. At present industry of developed countries in aerospace, automobile a

4、nd machinery, mold, machine first thanks to the new technology, the industry to improve product quality, reduce cost, gain competitive advantage in the market. In the automotive industry, the development cycle of new cars in the past is generally 10 years, now shortened to 23 years. Ford, general mo

5、tors, TOYOTA and other companies of the new car type development cycle is only 1 and a half years, all of which benefit from the enterprise mold design and manufacturing means of modernization. High speed cutting technology has been gradually applied to the processing of cast iron and aluminum alloy

6、, especially the processing of large stamping die, die, die casting mould and injection mould, in order to reduce the processing time and development time and improve the dimensional tolerances and surface consistency. The high speed machining technology is mainly used in the automotive industry, mo

7、ld industry, aerospace industry, especially in the field of complex surface machining, the workpiece itself tool system or rigid requirements of higher processing areas, shows strong function. The research and application of high-speed machining technology began in 1990s, is mainly used in mould, av

8、iation, aerospace and automobile industry, but the high speed cutting machine, CNC adopts high speed cutting tool and CAD/CAM software mainly imported.Two 、 key technologies of high speed cuttingAs one of the most important advanced manufacturing technology in the die manufacturing, NC High-speed ma

9、chining is an advanced manufacturing technology with high efficiency, high quality and low consumption. In the conventional machining, a series of problems which have been plagued by high speed machining have been solved. The cutting speed and feed rate are improved in series with respect to the tra

10、ditional cutting process, and the cutting mechanism has also changed fundamentally. Compared with the traditional cutting processing, the nature of the leap of machining, the unit power metal removal rate increased from 30% to 40%, the cutting force is reduced by 30%, the cutting tool life increased

11、 by 70%, cutting heat greatly left in the workpiece is reduced, low order vibration cutting almost disappeared. With the increase of cutting speed, the removal rate of rough material in unit time is increased, the cutting time is reduced, and the machining efficiency is improved, thus shortening the

12、 product manufacturing cycle and improving the market competitiveness of products. At the same time, a small amount of high-speed machining, fast forward to reduce the cutting force, chip high-speed exclusion, reducing the workpiece cutting force and thermal stress deformation, and improve the possi

13、bility of poor rigidity and thin-walled parts cutting. Because of the reduction of cutting force and the increase of speed, the working frequency of cutting system is far away from the low order natural frequency of the machine tool, and the surface roughness of the workpiece is most sensitive to th

14、e lower order frequency, thus reducing the surface roughness. In the high hardened steel mold (HRC45 65) during processing, the high-speed cutting can replace machining and grinding and polishing process, avoid the electrode manufacture and machining time consuming, greatly reduce the amount of grin

15、ding and polishing fitter. Some of the more and more market demand for thin-walled die workpiece, high-speed milling can be successfully completed. Moreover, in the high-speed milling CNC machining center, the mold can be completed by clamping at one time. These advantages in the capital revolving r

16、equirements, delivery time urgent, product competition fierce mold and other industries is very appropriate.1. high speed machiningHigh speed cutting tool can meet the system is mainly composed of high-speed machining center, high speed cutting clamping system and high-speed cutting tools, safe and

17、reliable high-speed cutting CAM software system, therefore, high speed machining is essentially a large system engineering. With the development of cutting tool technology, high-speed machining has been applied to the processing of alloy steel (HRC30). It is widely used in the stamping die, injectio

18、n mold and other parts of automotive and electronic component products. The definition of high speed machining depends on the type of workpiece material being processed. Fig. 1 is a cutting speed widely applied to different materials by high-speed machining. For example, high speed machining of allo

19、y steel uses a cutting speed of 500m/min, and this speed is used in the processing of aluminum alloy conventional milling speed.With the rapid expansion of the scope of application of processing,The research of new cutting tools, the improvement of tool design, the improvement of the new cutting too

20、l path and the improvement of cutting condition have also been improved. In addition, the computer aided simulation of cutting process has also appeared. This technique is significant for predicting tool temperature, stress and prolonging tool life. The application of casting, dies, hot pressing mou

21、lds and injection moulds represents the enlargement of the application range of high speed cutting of cast iron, cast steel and alloy steel. Industrial leading countries, in the manufacture of dies and moulds, most of the development time is spent on machining and polishing processes, as shown in fi

22、gure 1. The mechanical processing and polishing of dies or moulds make up about 2/3 of the whole processing cost, while the high speed milling can be used to shorten the development cycle and reduce the processing cost.2. high speed milling machine toolsUltra high speed cutting technology is the dev

23、elopment direction of cutting, and also the product of the development of the times. High speed cutting technology is one of the main development directions of cutting technology. With the development of CNC technology, micro electronics technology, new material and new structure, high speed cutting

24、 technology has stepped onto a higher level. However, the high speed cutting technology itself also has some problems, such as monitoring technology of cutting mechanism, high hardness materials when the load changes in the process of damage, the establishment of high-speed cutting database and appl

25、y to the development of high speed machining state and green manufacturing technology. CNC machine tools, cutting tools and CAD/CAM software used in high speed cutting have high technical content and high price, which make the investment of high speed machining very large, which restricts the popula

26、rization and application of high speed cutting technology to a certain extent. The high efficiency application of high speed cutting requires that the parts in the machine tool system must be advanced, mainly in the following aspects:(1) rigidity of machine tool structure;A drive requiring high spee

27、d feed (fast forward speed of about 40m/min, 3D contouring speed of 10m/min), capable of providing 0.4m/s2 to 10m/s2 acceleration and deceleration.(2) rigidity of spindle and handle;Required to meet the 10000r/min to 50000r/min speed, through the spindle compressed air or cooling system control, han

28、dle and spindle between the axial gap is not more than 0.0002 inches.(3) control unitRequires 32 or 64 bit parallel processor, with high data rate, automatic acceleration and deceleration.(4) reliability and processing technologyIn order to improve the utilization ratio of machine tools (6000h/y) an

29、d the reliability of unmanned operations, process models are helpful to understand the relationship between cutting conditions and tool life.The representative of the high-speed machining centers at home and abroad is shown in table 1. Compared with ordinary CNC machine tools, the machine tool struc

30、ture, processing speed and performance more excellent performance, such as DMC85 high speed machining center in Germany, with the linear motor and electric spindle, the spindle speed reaches 30000r/min, the feed speed of 120m/min, acceleration over 1g (gravity acceleration). The requirement of high

31、performance of high speed machine tool spindle unit and cooling system, high rigidity of the machine structure, safety device and control system and excellent static and dynamic characteristics, has the characteristics of high technical content, the difficulty of machine tool manufacturing etc. At p

32、resent, the domestic high-speed machine tools, its performance compared with foreign countries, there is still a gap.3. tool shanks and cutters for high speed machiningBecause of the influence of centrifugal force and vibration in high speed machining, it is required that the tool has high geometric

33、 accuracy and clamping repeatability, and it has high stiffness and high dynamic balance safety reliability. Due to the high speed machining of large centrifugal force and vibration characteristics, the traditional 7:24 taper shank system in high-speed cutting showed obvious lack of rigidity and rep

34、eated positioning accuracy is not high, the axial dimension is not stable, the deviation caused by the tool spindle expansion and clamping mechanism of the heart of the matter, affect the dynamic balance ability of tool. At present, more and more HSK high-speed knife handle and abroad are now popula

35、r thermal expansion cold contraction fastening type handle. The heating system of the heat expansion and cold contraction fastening type knife handle has better rigidity, but the tool has poor interchangeability, and a knife tool which can be connected with a diameter can be installed on a knife han

36、dle. Since such heating systems are expensive, the HSK class cutter system can be used in the early days. When the number of high-speed machine tools is more than 3 units, it is suitable to use expansion, cold contraction and fastening type.Cutting tool is one of the most active and important factor

37、s in high speed machining. It directly affects machining efficiency, manufacturing cost and machining accuracy. The cutting tool in high speed machining process to withstand high temperature and high pressure, friction, shock and vibration load, so the basic properties of the hardness and wear resis

38、tance, strength and toughness, heat resistance, technology and economic performance is one of the key factors to realize high speed machining. At the same time, the high speed cutting of materials with different materials should pay attention to the matching of the material and the workpiece,Table 2

39、 is the adaptability of various high speed cutters to cutting of different workpiece materials. High speed cutting tool technology development is very fast, more applications such as diamond and cubic boron nitride (PCD) (CBN), ceramic cutting tools, coated carbide, titanium carbide nitride (carbon)

40、 TIC (N) etc. At present, because of the high price of high speed machine tools and tool materials, it is one of the important reasons that affect the popularity of high-speed machining in china. Among them, coating carbide is the most widely used in high speed machining. It can be used for high spe

41、ed cutting of heat-resistant alloy, titanium alloy, high temperature alloy, cast iron, pure steel, aluminum alloy and composite material.Carbide is the most commonly used cutting tool in cutting iron and alloy steels. Carbide cutting tools have good wear resistance, but they are lower in hardness than CBN and ceramics. I