Main processing applications of the hottest ultra-

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The main processing application of ultra-high speed spindle machining center

Mr. Suzuki fan of Kuroda Seiko Co., Ltd. published an article on the problems of tool system in high speed machining in the Journal of mechanical technology 10 years ago. At that time, he defined the high speed of machining center as more than 10000 revolutions. Now, machine tools with spindle speeds of 30000 ~ 40000 revolutions have been sold on the market as standard machine tools. If the tool system is defined again as an object, and the definition of high speed remains unchanged, the spindle speed above 30000 RPM can be defined as ultra-high speed. The reason is that when the spindle speed is above 30000 rpm, the original tool system is not applicable. Machining centers with ultra-high speed spindles are mainly used for processing small precision molds of high hardness materials. The manufacturing of high-precision molds for small civil products, connectors, etc. requires high technology and skills. In the fierce competitive environment, enterprises must promote high precision and reduce processing costs in order to seek high added value

the superiority of ultra-high speed spindle is mainly reflected in the realization of efficient cutting. Especially in the finishing of the mold, the diameter is about φ The high-speed milling with 1mm end milling cutter can save the subsequent grinding process, and the grinding process is a manual operation that is difficult to realize automation, which is mainly reflected in the "cold winter and hot summer", which is a major problem to realize the automation of mold manufacturing. In high-speed finish milling, the machining accuracy can reach 2 ~ 3 μ m. To make the machining accuracy reach 2 μ m. Then the runout accuracy of the tool tip should be controlled at least 2 μ Below M. Therefore, the tool system for ultra-high speed cutting must meet the following requirements: ① excellent rotation balance; ② Excellent handle repeatability; ③ Excellent tool clamping repeatability; ④ Good radial jump accuracy

the following introduces the tool system products suitable for ultra-high speed and high precision cutting manufactured by Kuroda Seiko Co., Ltd

hot mount tool handle for ultra-high speed cutting

the mainstream tools for milling small high hardness steel precision molds are φ End mills below 6mm are used uniformly φ 3、 φ 4 and φ 6mm three specifications of hot fitting tool handle. This kind of tool holder has simple structure and is very suitable for ultra-high speed milling. As long as the reasonable process is adopted, the tool handle with high diameter jump accuracy can be manufactured, and the repetition accuracy of the tool handle installation is excellent

the recently developed high-performance electromagnetic induction heating knife loading equipment can complete the heating in only a few seconds, but it takes 5 minutes to complete the forced cooling. In addition, slight negligence in hot charging operation is prone to burn accidents. Therefore, from the perspective of on-site safety, we hope to develop spring collets that can meet the requirements of ultra-high speed

spring collets suitable for ultra-high speed cutting

spring collets suitable for ultra-high speed cutting must meet the above requirements. For this reason, Kuroda Seiko Co., Ltd. has made the following improvements and developed CMG series products: ① the groove structure used for wrenches in the shape of nuts has been canceled; ② Make the main body of the spring collet shortest, and try not to use milling processing; ③ The dust-proof sealing design of the front and rear ends of the nuts is added; ④ Special wrenches have been developed

through the above improved design, the possibility of imbalance is reduced; Considering that it is close to the workpiece and not easy to interfere during milling, the shape of the nut is reduced, and it has both high rigidity to adapt to efficient milling; The radial jump accuracy of the spring collet is controlled within 3 at the end of the standard test bar 4D μ Within m; The handle is marked with hske32. 1. If the viscosity of buffer oil is too large or the oil quality is too dirty, choose to manufacture hske25 handle

because the groove for wrench on collet nut is canceled, a special one-way overrunning clutch wrench is required. In the development of spring collet, in order to maintain good clamping performance, the wrench with torque limiter is taken as the development standard. Although the purchase price of this wrench is higher, it is also cost-effective to be more expensive in order to ensure the good and stable performance of the spring collet. The improved spring collet can work normally at the speed of 40000 R/min. However, according to the quality (thickness) of the machine tool spindle, it is necessary to correct the imbalance

diametral jump accuracy compensation toolholder

even though the machine tool spindle, toolholder and tool are high-precision products, after they are combined and installed on the spindle, the diametral jump at the front end of the tool sometimes reaches 6 due to the accumulation of the diametral jump of the three μ M above. In this case, if the radial jump accuracy of the front end of the tool can be adjusted to 1 μ Within m, it has a significant effect on improving the service life of the tool tip and the quality of the machined surface. Although this tool holder is not for ultra-high speed cutting, it is suitable for high-precision milling

the structural feature of the diametral jump accuracy compensation tool handle developed by Kuroda Seiko Co., Ltd. is that the straight cylindrical part of the spring collet body is equipped with a diametral jump compensation ring with an empty groove in the middle of the inner hole wall. When the diametral jump compensation screw in the middle of the compensation ring is tightened, the collet body can be changed into a "zigzag" shape and its end can be concentric with the center line. Its advantage is that the diametral jump compensation ring can be installed at the end of the assembly. When compensation is not required, The radial jump compensation ring can be removed and used as an ordinary spring collet. The method of use is to install the spring collet installed with the tool on the spindle of the machine tool, and use the radial jump measuring instrument to measure the radial jump of the tool tip. If it is difficult to measure the tool tip, you can also measure the radial jump of the cylinder at the front end of the tool handle

the specific method of diametral jump compensation is: first find out the rotation position of the maximum negative value of diametral jump, so that the oil discharge of the oil pump is uneven, and then turn the compensation ring to this position to align it with the diametral jump compensation screw. While observing the diametral jump value displayed by the diametral jump measuring instrument, adjust the tightening degree of the diametral jump compensation screw, so that the tool tip is close to the positive side, and then the diametral jump accuracy can be compensated to 1 μ M or so. This process is not complicated, and compensation can be easily completed even for the first operation

because the tool holder of radial jump accuracy compensation is to make the tool holder produce elastic deformation to correct the position of the tool tip, so as to improve the radial jump accuracy, the tool balance will be destroyed after the radial jump accuracy compensation. In order to determine its influence, the radial jump changes of the rotation center before and after the radial jump accuracy compensation are detected respectively. In the test, the super BT tool holder (a new type of BT tool holder with two side positioning and clamping) bts40-cmahh is used and clamped with a spring collet φ 12.5 standard test bar, detect Lissajous waveform at 82mm overhang. Because the diameter jump of ordinary spring collets is very small, spring collets with poor accuracy and relatively large diameter jump value are specially prepared. During the test, slowly increase the speed, and observe the change of radial jump value at 50r/min and 10000r/min. The result is increased by 9.6 before radial jump accuracy compensation μ m. Added 3.3 after radial jump accuracy compensation μ m。 Because the standard test bar is thick and has a large overhang length, the displacement of the center of gravity caused by the radial jump accuracy compensation is larger than that of the spring collet. By changing the speed at which there is a certain corresponding relationship between the tolerance level and the surface roughness value of the rotation, the subtle change process of the spindle diameter jump of the machine tool can be observed. Therefore, under the condition of ultra-high speed, not only the evaluation of static radial jump accuracy is very important, but also the analysis of dynamic radial jump accuracy can not be ignored

recently, among the products of micro ball end mills, micro cutters such as cemented carbide end mills and CBN integral end mills with a tool tip radius less than 0.05mm have been developed. When these products are processed at a reasonable cutting speed, it is required to further improve the speed and rotation accuracy. Therefore, the requirements for the service conditions of the tool system will be more and more stringent. In the future, it is still necessary to further promote the research and development to meet the market demand

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