Experimental study on the most popular multifuncti

2022-08-08
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Experimental research on multi-functional turning tool

0 preface

cutting is a very important part of machining. Many important parts of steam turbine, such as steam seal ring, steam seal ring piston and bearing, are cut. However, due to the single turning method, different turning processes need different tools to complete, the tool change and clamping assistance time is long, and the chip clamping is serious and the chip removal is difficult in the process of cutting off the groove. In order to improve the efficiency and reduce the cost, a multi-functional turning tool is developed to enable it to turn the left and right outer circles and end faces while cutting grooves and cutting, so that one tool can be used for multiple purposes

1 determination of the structure of the multi-functional turning tool

the structure of the multi-functional turning tool is improved on the basis of the structure of the upper pressing cutting tool. It solves the shortcomings of the original upper pressing cutting tool and the cutting tool clamped by the cutting force. It is composed of knife body, blade, pressing plate, screw, etc., as shown in Figure 1. There are two difficulties to be solved in determining the structure of the cutter body. One is the determination of the material of the cutter body and the processing of the cutter plate. In use, the cutter plate is required to be thin and have good rigidity and strength. The other is the determination of the positioning mode, so that it can bear both radial force and large axial force

1. Pressing plate 2 Screw 3 Cutter plate 4 Blade; 5. cutter body

figure 1

1) determination of cutter plate

because the multi-functional turning tool is mainly used for grooving and cutting, the cutter plate must first be very thin and have high strength in the cutting process, because the distance between the place where the blade is clamped on the cutter plate and the top of the cutter plate is very small, so it is easy to break and the blade is easy to fall off, and the hardness at this point is required to be higher than that at other places during heat treatment. Because it needs to turn the outer circle and end face at the same time, it also requires that the cutter plate has good rigidity and toughness, so that the cutter plate can be as stable as possible during turning, reduce vibration, and produce a small deformation without breaking. After repeated tests, the cutter plate material is determined to be spring steel, and the hardness hrc43, such as the fracture of the tensile sample of aluminum plate, should show an angle of 45 ° to 48 °

since the double V-groove arc-shaped blade is adopted, it is required that the blade clamping position of the cutter plate must also be arc-shaped. At the same time, since the cutter plate clamps the blade by elastic force, the elastic hole is required to be very close to the upper wall of the cutter plate, so it is difficult to process it with a general milling machine. Finally, after programming, it is processed by wire cutting machine. The cutter board structure is shown in Figure 2

Figure 2 Schematic diagram of cutter plate structure

2) determination of blade positioning mode

there are two main positioning modes for ordinary cutting knives: one is single V-groove positioning, which can withstand large radial force, but has poor ability to withstand axial force; the other is double V-groove positioning, which has strong ability to withstand radial and axial force

the multi-functional turning tool adopts double V-groove positioning. At the same time, due to the small size of the blade, in order to increase the contact area between the blade and the tool plate, the upper and lower sides of the blade are arc-shaped, as shown in Figure 3, so as to enhance the reliability of clamping and make it more capable of bearing axial force

figure 3

3) working principle

here, the working principle of the multi-functional turning tool is illustrated by taking the left turning outer circle as an example. As shown in Figure 4, when the turning tool is feeding the excircle to the left, the tool plate will produce a small deformation under the action of the feed force, so that a secondary main deflection angle kr'is formed between the top edge of the blade and the machined surface, which ensures that the machined surface is not scratched by the blade, and solves the problem that the cutting edge of the general cutting tool fully contacts the workpiece

figure 4

4) determination of pressing plate structure

as shown in Figure 5, the pressing plate has two spring openings and four screw holes, the middle two screw holes play the role of fixing the blade, and the two screw holes and elastic openings on both sides are designed for easy blade replacement. When replacing the blade, as long as the screw 1 is loosened, the front of the blade plate can be loosened and the blade can be taken out freely due to the elastic effect of the elastic opening. After replacing the blade, tighten the screw 1, and the blade can be clamped firmly. Therefore, this structure is very easy to replace the blade

figure 5

2 determination of blade groove type

during the cutting process, the chip discharge mode and chip breaking condition have a great impact on the machined surface quality. Therefore, it is necessary to select an appropriate groove type to obtain a better chip shape and ensure the machining accuracy of the turning tool. At present, various advanced groove types in foreign countries mainly include the following: This is a permanent topic in front of us, including p-type and F-type blades of is "car company, and T-type and U-type blades of Sandvik company in Sweden. The common feature of these grooves is that the edge of the blade is higher than the inside, which makes the chips narrower and thicker, and can not scrape the machined surface, so as to ensure the accuracy of the machined surface

3 use of multi-functional turning tool

the multi-functional turning tool has been tested on many workpieces. Now, taking the machining of steam seal ring and steam seal piston as an example, the cutting parameters are explained. The relevant data columns are used to measure the experimental force; See Table 1 for the built-in displacement measurement system of the exchange servo motor. Table 1

name material diameter

mm outer circle vc

m/minf

mm/rap

mm steam seal ring 15crmoa- Ⅱ 422 steam seal piston 2cr12nimowv- Ⅱ 41

during grooving and cutting, the cutting speed can be doubled compared with the original due to the light cutting, and the surface roughness can reach ra3.2 or more

according to different processing materials, tic, tin, Al2O3 and tic tin composite coatings can be applied to the blade surface respectively, so that the hardness, wear resistance and wear resistance of the blade can be improved, and the application range of the multi-functional turning tool can be widened, so that it can not only be applied to difficult processing materials, but also be applied under the adverse conditions of intermittent cutting and uneven cutting depth

4 conclusion

· the multi-functional turning tool has successfully realized the multi-purpose of one tool. One tool can replace 3 ~ 4 ordinary turning tools, greatly saving the clamping time and improving the production efficiency

· due to the advanced groove type, the problems of serious chip clamping and difficult chip removal existing in the conventional cutting tool are solved, so that the surface roughness can reach above ra3.2, and the durability of the tool is improved

· compared with ordinary cutting knife, it has the characteristics of reliable mounting clip and easy blade replacement

· because the multi-functional turning tool has a small body and a small blade, it is applicable to some small and medium-sized parts processing and small machine tools, with certain limitations, and it can not feed a large amount during transverse cutting. This problem needs to be solved. (end)

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