Increasingly high performance of the hottest Japan

2022-08-24
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The increasingly high-performance cutting tools in Japan

at present, with the expansion of the field of cutting, the cutting tools are also constantly improved. It is not only aimed at achieving more efficient machining improvements, but also to support the development of new cutting materials such as composite materials used in aircraft

high efficiency turning and cutting tools

machine tools used for turning (mainly rotating materials and cutting with fixed tools) are gradually transitioning from previous CNC lathes to CNC composite machine tools. Therefore, the tool shown in Figure 1 is being developed. This tool has a taper handle that can be installed on the spindle of the CNC compound machine tool, and the rotation function of the spindle can be used to arbitrarily change the guide angle of the tool head and multiple blades. The compression of turning tool types and the high cutting efficiency are expected to be realized

Figure 1: turning tool (Mitsubishi material tool) for CNC composite machine with dividing head function

CNC composite machine tool has a spindle that rotates the tool, which can realize "vertical turning and milling" by using the rotation of materials at the same time. In turning, the tool always rests on the material to be cut (continuous cutting), but in vertical turning and milling, the cutting edge of the tool rests on the material to be cut intermittently (intermittent cutting), which is more beneficial in chip treatment and reducing thermal effect

as shown in Figure 2, it is a tool that can improve turning efficiency. Although the cutter head used for outer diameter turning that can carry out high-speed feed cutting is adopted, the average feed per revolution can be as high as about 2.5mm

Figure 2: high speed feed cutting outer diameter turning head (Toshiba tycolo)

high performance end milling cutter and cutting technology

since the establishment of high-speed milling technology, the cutting of high hardness steel has been popularized, and now the final finishing can be carried out through cutting. As a result, while the end milling cutter is required to achieve high efficiency, it is also required to achieve 1 μ High machining accuracy in new fields below m, and such diversified development is currently under way. By using this kind of cutting tool, it is expected to achieve new high-efficiency cutting

taking Figure 3 as an example, this is an end mill with arc radius designed to realize high-speed feed cutting. The material to be cut from cast iron to prehardened steel (hrc40 degree) can be processed in a high-speed feed cutting mode of 0.5 ~ 0.8 (mm/edge: tool diameter of 40 ~ 125mm, feed rate of 2 ~ 3mm). The rigidity of the edge of the cutting edge is high. Even the end face of the flange structure can be cut stably. It has the multi-directional cutting function of inclined and spiral tool path cutting

Figure 3: high speed feed cutting end milling cutter (Japan OSG)

for different product categories of machining objects, the best tool scheme is also proposed. For example, tools that can carry out high-speed milling of grooves and holes commonly seen on mold parts (Fig. 4), tools of cast iron materials suitable for cylinder blocks in automotive parts (Fig. 5), etc. Figure 5 shows a milling cutter with an octagonal blade of CBN sintered body, which can perform 16 angle cutting with the help of a negative angle cutting edge (the knife edge angle is an obtuse angle). The above two tools are expected to achieve high-speed cutting and machining under long service life

Figure 4: the high-4 ball friction and wear experimental machine is mainly a high-precision wall cutting of hard steel in the form of sliding friction (Japan OSG)

Figure 5: milling cutter with octagonal CBN sintered body blade (Mitsubishi material tool)

in terms of the cutting of curved surface shape commonly seen in the forming part of the mold, the use of ball end milling cutter is a common practice, common fault 3: the pendulum position is abnormal, but now it is required to further achieve high efficiency High precision and long service life, multi blade tools with more than two edges have been on sale. For example, Figure 6 shows a ball end mill with 3 edges. If the number of blades is large, when the average feed rate of each blade is the same, the feed rate will inevitably increase, which is more beneficial in shortening the processing time, and it is expected to achieve the effect of small tool wear (flank wear) (Fig. 7)

figure 6:3-edge coated superhard alloy ball end milling cutter (Rijin tool)

Figure 7: comparison between 3-edge and double-edge through cutting examples (Rijin tool)

previous ball end milling cutters have a central part of the cutting edge, which has become a weakness. Because the central part is the center of the tool rotation, there is no movement of the cutting edge, which has no effect on cutting. Therefore, it will cause the roughness of finish machined surface and the decline of tool life to avoid damage. The Japanese Institute of physics and chemistry has developed a CBN sintered ball end mill without a central edge, which has been confirmed to be more advantageous in terms of cutting accuracy. Figure 8 shows the commercial 4-edge coated superhard alloy ball end milling cutter without center edge. An example of using this kind of end milling cutter to realize high-precision finish machining is shown in Figure 9. In the future, it is expected that 5-axis control machining centers, CNC compound machining machines, etc. will be popularized, and the cutting that deliberately does not use the central part of the end mill and uses more peripheral edges will become the main way. Therefore, it can be imagined that this kind of end mill will become the mainstream

figure 8: 4-edge ball end milling cutter with center edge removed (Union tool in Japan)

Figure 9: comparison of cutting surface with center edge and without center edge (Union tool in Japan)

new materials and cutting technology: aircraft parts

IMTS2008 (international production technology exhibition in the United States, commonly known as Chicago exhibition) Boeing introduced the processing technology, including many aircraft parts and tools And aircraft related information. With the growth of global demand, aircraft, whose component production is expected to expand, has more components and more integrated components with complex shapes than automobiles. The main body parts are thin and long, and the cutting from blank to specific shape accounts for most of the processing task

in order to ensure qualified products leave the factory, not only aluminum alloy and titanium alloy are widely used, but also fiber-reinforced composites are being introduced to achieve the effect of lightweight, high reinforcement and high rigidity of the body. For example, the main wing, tail and body of B787 are all made of CFRP (carbon fiber reinforced composite), and the processing methods are mainly trimming and hole drilling. CFRP is a structure with hard texture and superimposed layers with different machinability, so it is key to suppress internal peeling and burr caused by cutting. On the other hand, the cutting tools and cutting conditions applicable to the processing of aircraft components have been predetermined, and the adoption and change of this must be approved

for example, figure 11 shows the state and cutting conditions when cutting titanium alloy with cutting edge exchange multi edge end mills. It is required to process under the conditions of 5-axis control machining center with high speed and high power, end mills and cutting conditions that support high efficiency and long tool life. Figure 12 shows the cutting edge exchange end milling cutter for aluminum alloy. It is an integrated tool handle, and has a blade shape with long cutting edge, which can cope with the tightening method of two closely matched bolts under centrifugal force during high-speed rotation, and has many originality. By adopting the appearance design that pays attention to high speed and high chip discharge, the cutting speed of 2800m per minute and the chip discharge of about 10000 ml per minute can be achieved

Figure 11: cutting scenario of aircraft parts (titanium alloy) (Makino milling cutter manufacturing Institute)

Figure 12: cutting edge exchange milling cutter (Mitsubishi material tool) for aluminum alloy parts

Figure 13 shows an example of cutting CFRP with end mills with diamond sintered body cutting edges. No burr is found after cutting 254m. This end milling cutter is installed on the split hot sleeve support, and the part of the hot sleeve on the shank cannot be disassembled. Through regrinding, the deflection accuracy and edge arrangement accuracy of the cutting edge can be controlled within a few μ Within M

Figure 13: diamond sintered end mills for CFRP cutting (megadiamond, USA)

new materials and cutting technology: new graphite electrode

with the development of high-speed milling technology, high hardness steel can also be cut, and the scope of application of EDM becomes narrower. In recent years, CNC discharge machining machines equipped with new discharge power supplies supporting graphite electrodes have been developed, and at the same time, CNC discharge machining machines with μ Graphite electrode for discharge of M-class ultrafine particle tissue. In this way, it is possible to cut thin-walled and sharp edge shapes that are difficult to achieve under the previous conditions of graphite electrode materials, and it is also expected to reduce electrode consumption and improve the accuracy of EDM surfaces

the latest graphite material is the sintered body of abrasive materials, and its high hardness is expected to cause rapid tool wear. For example, Figure 14 shows the ratio of ultra-fine crystalline diamond coating to coated superhard alloy. Ordinary coated superhard alloy end mills can see the rapid deepening of wear. For diamond coated superhard alloy end mills, it was difficult to realize the microminiaturization of diamond particle size at first, so diamond grinding wheels were used for grinding after coating. Therefore, the manufacturing cost increases. Although the performance is excellent, the application in the production line is slow. At this time, the coating technology of micro diamond layer was developed, and the cost of diamond coated superhard alloy end mills was greatly reduced and began to be rapidly promoted

Fig. 14: comparison between ultramicro crystalline diamond coating and coated superhard alloy (Japan OSG)

the cutting edge of the ultrahard alloy end mill made of the new ultramicro crystalline diamond coating is extremely sharp (FIG. 15). Compared with the previous diamond coated superhard alloy, the difference is obvious. It is applicable to the processing of discharge electrodes with a thin wall shape with a wall thickness of 0.3mm as shown in Figure 16

Figure 15: comparison of ultra-fine crystalline diamond coating with the cutting edge of previous diamond coating (Japan OSG)

Figure 16: example of electrode with 0.3mm thin wall (Rijin tool)

in addition, end mills with diamond cutting edges are also of great concern, which makes ultra-fine machining of small parts possible. (end)

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