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Research on the Milling Performance and Parameters Optimization with Large Parts of Heavy Machine

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Tutor: GuoXuHong
School: Suzhou University
Course: Mechanical Manufacturing and Automation
Keywords: grey cast iron,milling mechanism,Genetic Algorithm,parameters optimization,large
CLC: TG54
Type: Master's thesis
Year:  2011
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Abstract:
During the process planning, it is important to choose the proper cutting parameters. The reasonable selection of the parameters is beneficial for improving the product quality and the productivity, reducing the production cost, as well as improving the equipment utilization. The traditional way of choosing by workers¡¯experience data or by the handbooks leads to low processing efficiency and high manufacturing costs. Therefore, acquiring optimization process parameters by introducing advanced optimization algorithms based on the machinability of materials would have an important guiding significance on the enterprise processing.This thesis aims at studying the cutting parameters optimization of the finish milling of large parts in heavy machine, coating carbide cutting tools GC3220 and GC1010 were used to dry finish milling the grey cast iron material and the surface hardening cast iron material which widespreadly used in the parts of heavy machine. The cutting force, tool wear condition and surface roughness were recorded to analysis the cutting performance and tool wear mechanisms when the samples were cutted with smaller cut depth, larger cutting speed and feed rate per tooth. Additionally, the mathematical regression models of the cutting force and surface roughness with the cutting parameters were established, and the evaluation model of tool life was built. According to the optimizing design method and the actual machining status, the common milling parameters optimization models were established, and the practical applicability of genetic algorithm in MATLAB was verified by the optimization examples of selected objective functions. By comparing the production, process cost and the surface quality of a single process with the actual and optimization parameters, improvement schemes for the production of the enterprise were proposed, which can provide guidance for practical production. The main results of this thesis are summarized as follows:1. When dry finish milling gray cast iron HT300 using with smaller depth of cut by coating carbide cutting tools GC3220, the cutting speed should be not higher than 475m/min, and the feed rate per tooth should be not higher than 0.54mm/z. The increase of cutting speed will make the surface roughness value reduced, as well the cutting force increasing and tool wear intensifying. The increase of feed rate per tooth will cause the surface roughness value increased continuously, with impacting little on the cutting force. At the same time, the cutting time when the tool wear up to some set value will reduce, while the total cutting area will increase. The tool wear mechanisms is mainly adhesion wear, diffusion wear and coating spalling. And the tool wear will be faster with the cutting speed increasing.2. When dry finish milling surface hardening cast iron with coating carbide cutting tools GC1010, the cutting speed should be not higher than 110m/min, and the feed rate per tooth should not higher than 0.26mm/z. The influence of the cutting speed on cutting force and surface roughness is of the most significant, and we can get the surface roughness less than 0.8¦Ìm which meets the precision requirement when the cutting speed is greater than 90m/min.3. Combining with the theory of optimal design method, genetic algorithm, and the method to solve the multi-objective nonlinear constraints problem by genetic algorithm in MATLAB, the common optimization target problems and constraints were described from the perspective of the actual production requirements, and the solutions of some selected problems were done by genetic algorithm. The results show that the genetic algorithm can solve complex non-linear optimization problems rapidly and effectively.4. With the study above, the finish milling of selected face in common machine tool box were optimized basing on the current production situation of Huading heavy machine tool factory. The optimization results show that good surface roughness, about 20 times of area removal rate, 5% of cutting time and 15% of production cost can be obtained by comparing with the practical ones while they were optimized at the targets of the most area removal rate, the shortest processing time and the lowest production cost with a limited amount life of the cutter.5. A technology improvement scheme of¡°milling replaces planning, milling replaces grinding¡±for the process of guide rails was proposed with combined the current production situation, so that the production time can be reduced and the production lead time can be shorten greatly, and the competitiveness of the enterprise in the market can be promoted.
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