Fuzzy comprehensive evaluation of cutting performa

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Fuzzy comprehensive evaluation of cutting performance of cutting tools in insert milling process of titanium alloy

titanium alloy has been more and more widely used in aviation, aerospace, navigation and other industrial departments because of its high specific strength, good thermal strength, corrosion resistance, rich resources and a series of advantages. However, due to its low thermal conductivity, high chemical activity and low cutting deformation coefficient, titanium alloy has become a difficult material to machine. Insert milling method, also known as z-axis milling method, has a cutting efficiency of 4 ~ 5 times higher than general milling, especially in the large removal rate of difficult cutting materials. It is one of the most effective machining methods to achieve high removal rate metal cutting. The insert milling object is shown in Figure 1

Tianjin University has measured and analyzed the cutting force in the process of aluminum alloy and titanium alloy slotting milling, established the exponential empirical formula of cutting force in three directions by using the regression method, and studied the mathematical modeling of cutting force in the process of titanium alloy slotting milling. It is found that the simulation results of single tooth and multi tooth are in good agreement with the experimental results. Jeong Hoon Ko and others analyzed the dynamic characteristics and stability of the insert milling process, and established a cutting force model based on the rapid movement of the tool. The simulation model can predict the cutting force, torque and vibration according to the cutting error and time variable parameters of the tool. Shunsuke wakaoka et al. Studied the machining accuracy, thermal hardness and machining efficiency in the process of insert milling with titanium precision of 0.1. This provides an important reference for the in-depth study of the characteristics of titanium alloy insert milling. This topic takes the NC milling cutter used in insert milling titanium alloy (Ti-6Al-4V) as the research object, and evaluates the tool performance through experiments based on the fuzzy comprehensive evaluation theory

evaluation object performance index

comprehensive evaluation is also called multi-objective decision-making, which refers to the overall evaluation of things or phenomena affected by many factors. If this evaluation process involves fuzzy factors, it is called fuzzy comprehensive evaluation. Fuzzy comprehensive evaluation applies the method of fuzzy mathematics to 3 After the equipment installation and debugging, the objects and things are evaluated in general, so as to achieve the optimization purpose of multiple schemes of fuzzy concept and under various evaluation standards. The factors that affect the quality of cutting tools are very complex, and they affect each other. It is difficult to use a single factor to evaluate the quality of cutting tools, so this problem is suitable for the application of fuzzy comprehensive evaluation

1 evaluation object

in the test data of cutting force, cutting heat, wear and vibration, representative test data are selected as the performance index for the evaluation of cutting performance of insert milling cutter. In this paper, the cutting performance of a certain type of indexable cemented carbide inserts provided by four different manufacturers is compared and studied. The geometric parameters of the tool are shown in Table 1

2cutting force

the size of the cutting force determines the power in the cutting process and the deformation of the processing system, and directly affects the generation of cutting heat, making the tool blunt and lose cutting ability. Therefore, the size of cutting force can be used as one of the symbols to measure the cutting performance of cutting tools

the cutting parameters selected from the test data of four kinds of blades include: the cutting speed VC is 35m/min, 45m/min, 55m/min, the feed FZ of each tooth is 0.04mm, the cutting width AE is 8mm, and the cutting depth AP is 10mm. Analyze the cutting force in the main direction, that is, the Z-direction force, as shown in Table 2

3 cutting heat

cutting heat is one of the important physical phenomena in the process of metal cutting. A large amount of cutting heat increases the temperature of the cutting area, which directly affects the wear of tools. Therefore, cutting heat is also an important factor to evaluate the quality of tools. Through the cutting heat test, four groups of blades are cut under different conditions, and the cutting temperature is compared, as shown in Table 3

4 vibration

vibration in the process of metal cutting often causes problems such as the increase of machined surface roughness, the reduction of part accuracy, the intensification of tool wear, the limitation of the ultimate machining capacity of machine tools, and the noise pollution of the working environment. In addition, vibration is also a serious obstacle to the automation of machining process. Therefore, the vibration of the tool in the cutting process is an important index to evaluate the cutting performance of the tool. Through the cutting test, the vibration of four kinds of blades are compared, and the results are shown in Table 4. From the amplitude in the main direction of vibration in Figure 2, it can be concluded that the order of stability from good to bad is: blade 1, blade 2, blade 3, blade 4

5 tool wear

the cutting part of the tool bears great cutting force and high cutting temperature in the cutting process, and also has strong friction with chips and machined surfaces, which makes the tool gradually dull and invalid. Wear can be used to measure the cutting performance of tools, and it is an important factor, such as force value automatic shift, reset and data query. The cutting tests of four groups of cutting tools show that the main wear forms of cutting tools are bonding wear and mechanical wear, among which bonding wear is more serious

it can be seen from Figure 3 that the chip buildup on the rake face near the tool tip of the main cutting edge is obvious; The sticking of the tip is serious; The part of the auxiliary cutting edge close to the tool tip is not seriously bonded and worn; There is slight bonding wear on the back surface of the main cutting edge. Tool wear is concentrated on the rake face of the main cutting edge and the tip of the main cutting edge and the auxiliary cutting edge. The wear conditions of four groups of blades were compared by scanning electron microscope. Among them, blade 3 had the least wear, blade 2 had the most serious wear, and blade 4 and blade 1 had similar wear conditions

fuzzy comprehensive evaluation model of tool performance

fuzzy comprehensive evaluation can be divided into two steps from the main steps: one is to evaluate separately by single factor, that is, the first level of fuzzy comprehensive evaluation; Second, comprehensive evaluation according to all factors, that is, two-level fuzzy comprehensive evaluation. Through the first level fuzzy comprehensive evaluation, the single factor evaluation matrix of cutting force, cutting heat, vibration and wear is obtained. After normalization, it is as follows

cutting force: b1={0.341, 0.189, 0.102, 0.368}

cutting heat: b2={0.418, 0.385, 0.180, 0.017}

vibration: b3={0.458, 0.364, 0.178, 0}

wear: b4={0.238, 0.143, 0.381, 0.238}

make judgment according to the investigation and statistics of tool selection in actual production. The wear resistance of the tool is directly reflected in the durability of the tool, which has the greatest impact on the performance of the tool. The influence of cutting heat, vibration and cutting force on the cutting performance of the tool decreases in turn. The weights of each factor are: cutting force is 0.1, cutting heat is 0.3, vibration is 0.2, wear is 0.4, that is, the weight matrix:

a= {0.1, 0.3, 0.2, 0.4}

The evaluation matrix of the second level comprehensive evaluation is:

the result of the second level comprehensive evaluation is:

the result of the second level comprehensive evaluation shows that the cutting performance of blade 1 is the best, followed by blade 2 and blade 3, and blade 4 is poor. The application on the production site proves that the above evaluation is correct that some foreign peers have made new and obvious progress in the research and development of deformation measurement technology, which is consistent with the conclusion of fuzzy comprehensive evaluation of milling experimental research

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