A new boring bar designed by computer simulation

2022-08-11
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In the process of cutting, if the process system vibrates, the normal movement in processing will be disturbed, and the correct position relationship between the machine tool, workpiece and tool will be destroyed, which will make the machined surface vibrate and surface wavy, deteriorate the quality of the machined surface, reduce the durability of the tool, and even shorten the service life of the machine tool

in order to solve the problem of cutting vibration, Mitsubishi Corporation of Japan launched a new product - damping boring bar. The design of damping boring bar changes the original vibration reduction method. The boring bar designed by computer simulation method reduces the quality of boring head and adopts a special structure. The damping boring bar has good damping effect, which can quickly attenuate and eliminate the vibration, and can ensure good machining surface quality

1 structural characteristics of damping impact bar

the damping boring bar adopts the reasonable structure of high rigid boring bar and light cutter head designed by computer simulation analysis. Due to the prevention of deflection, the damping effect is increased, and the purpose of restraining system vibration is achieved. The damping boring bar has the following structural characteristics:

1) large concave head, light overall weight, which is conducive to suppressing vibration

2) there are chip holding grooves in both directions, and chip removal is good

3) the diameter of boring bar is smaller than the minimum machining diameter specified in ISO standard

4) there are laser engraved scales on the side of the cutter bar, which is convenient for processing and positioning

5) it can be equipped with ultra-high pressure sintered body blades with good wear resistance. The blades have f and FS chip breaking grooves that are conducive to improving processing quality, MV chip breaking grooves that are conducive to chip processing, and SV chip breaking grooves that are suitable for light cutting

as shown in Figure 1, the groove on the damping boring bar makes the boring bar have a unique section shape that meets the requirements of the green development period, which can well balance the cutting force and reduce the deflection by 17%; The head weight of the damping impact bar is only 49.7g, which is 20.4g less than that of the anti vibration boring bar, reducing the vibration during cutting, giving full play to the damping effect, and the vibration stop time is only 15.8ms. There are two kinds of rod body materials of damping boring bar: steel and cemented carbide. The cemented carbide rod body has large elastic modulus and good rigidity, and can process holes with large length diameter ratio

Figure 1

2 characteristics of indexable blades for damping boring bar to ensure experimental concentricity

2.1 blade materials

as shown in Table 1, when processing different materials under different cutting conditions, blades of different materials and chip breaking grooves can be selected

the nx2525 recommended in Table 1 is a particulate cermet with good adhesion resistance, which is suitable for high-speed cutting of materials with soft hardness; Us7020 is suitable for high-speed cutting of stainless steel and boring of iron castings; Hti10 is suitable for processing aluminum alloy and cast iron; Diamond md220 is used for precision high-speed machining of aluminum alloy; Mb825 (CBN material) is recommended for precision boring of quenched steel. Ue6020 and vp15tf recommended in Table 1 are two new materials: ue6020 coating is the preferred coating for cutting steel. It adopts the newly developed even deposition technology, which is wear-resistant and damage resistant, and can prevent adhesion damage and adhesion peeling; Vp15tf is a new blade material based on ultra-fine cemented carbide TF15 and using the miracle coating technology developed by Mitsubishi Kobe Steel. Its chip breaking groove is grinded, with stable cutting and high machining surface quality

selecting different blade chip breaking grooves can effectively break and treat chips, and the cutting depth and feed rate range are shown in Figure 2

Figure 2 applicable cutting range of various blade chip breaking grooves

2.2 structural characteristics of blade chip breaking grooves

the structure of SV and MV chip breaking grooves suitable for boring processing is shown in figures 3a and 3b. S4. After the sample is broken, the V chip breaking groove is composed of a peninsula boss and two chip breaking grooves, which are tightened in time when processing softer materials; Excellent cutting performance when cutting materials or workpieces with cutting depth less than 1mm; MV chip breaking groove is used for medium cutting, and its structure is composed of spherical boss and two chip breaking grooves. It can cut a variety of materials, and satisfactory cutting and chip breaking effects can be obtained within a wide range of cutting conditions (see Figure 2a)

figure 3

2.3 blade shape

there are many models of damping boring bar, which can use triangular (T-type), 80 ° diamond (C-type), 55 ° diamond (D-type), 35 ° diamond (V-type) and hexagonal (W-type) blades respectively. Table 2 lists the cutting stability, blade strength, economy and the ability to adapt to profiling processing of various blades, which can be used as a reference for selection. Generally speaking, the blade with a large number of effective blades is economical; The larger the tip angle of the blade, the higher the strength, and the more dispersed the cutting temperature. In addition to increasing the normal force, it is generally beneficial to cutting; The blade with small top angle is suitable for profiling processing. The shape of the blade is usually selected according to the shape and size of the workpiece to be processed

3 recommended cutting conditions for damping boring bar

the recommended cutting conditions for machining different materials with steel damping boring bar are shown in Table 3, and the recommended cutting conditions for cutting different materials with cemented carbide damping boring bar are shown in Table 4

4 damping boring bar processing examples

steel damping boring bar and carbide damping boring bar processing examples are shown in Table 5

(end)

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