Cutting Parameters Optimization Based On Physical Model Of Cutting Process And Database Application

With the developing of modern manufacturing technology, high speed cutting, high efficiency cutting and high performance of work material have been the characteristics of metal cutting. In order to satisfy the situation, it puts forward rigorous demands for cutting performance of tool. So, the developing of tool are high precision, high efficiency, high reliability and specification. Thus, Cutting technology has faced much unprecedented opportunities and challenges nowdays. By now, cutting parameters optimization has been a bottleneck of cutting technology in order to exploit the maximal potentials of machine tool and cutting tool. Under this new situation, cutting parameters have shorter timeliness than ever before, but the essences of cutting process are invariable such as cutting force and cutting temperature. On the basis of this, parameter optimization based on physical models is performed here.Firstly, three essential elements of cutting parameters optimization have been analyzed: optimization variables, objective functions and constrain conditions. Optimization variables include cutting speed and feed rate. Objective functions refer to surface quality, material removal rate and tool life. Constraint conditions include forces, heat and vibration constraint. With the constraint conditions, cutting tool would be performed efficiency in a certain range of cutting parameters. In this dissertation, according to several typical working conditions the study of cutting parameters optimization would be expanded as three respects as follows: force and heat constraint, intelligent methods and chatter stability.Cutting forces and heat, the basic physical qualities in cutting process, is also the prominent features when difficult-to-cut material is machined. The formation of cutting forces and heat in oblique cutting is analyzed firstly. Then Mises flow stress in the primary deformation zone is studied by JC constitutive model. Stress characters and its computational methods on tool edge are studied. At the same time, the influence of alternate milling forces on cutting edge strength is discussed here. It indicates that the optimization of feed per tooth is depended on fatigue strength of tool edge. In order to reduce work hardening of workpiece and tool wear in high temperature, the cutting temperature in the secondary deformation zone is used as the thermal constraint. It indicates that cutting temperature is controlled by the range of recrystallized temperature of work material and service temperature of tool or coating. That is to say, cutting speed is limited by cutting temperature in a feasible zone. Besides, the impacts of surface quality, power consumption, and tool life to cutting parameters optimization are also studied. It shows that the result of cutting parameters optimization is not a specified value, but a range that includes several suboptimum solutions. Based on the above research, taking the difficult-to-cut material TC4 for example, the milling speed and feed per tooth are optimized in a certain range.As for common material, neuro-fuzzy optimization method is put forward based on multiple objectives optimization when cutting force and heat are not serious. Surface residual stress in pre-stretched aluminum milling is forecasted by an established ANFIS model. When small sample is used in ANFIS training, its forecasting effect can be improved by input selection in order to reduce the dimensions of input data. Besides, multiple objective functions are optimized by fuzzy synthetic evaluation based on different weight vectors. It shows that different sorting results can be obtained by use of different operators. An optimized result is obtained under the specified weight vector. Thus the corresponding cutting parameters can be solved by BP network with Bayesian regularization.When there are weak rigidity components in cutting process such as thin wall part, chatter stability verification to the whole system is absolutely necessary. The cutting system consists of machine tool, cutting tool, workpiece and chucks. According to conventional regenerative chatter theory, fuzzy chatter stability theory is put forward based on grade of stability (GOS). Cutting chatter stability grade represents the ability and grade of stability. In fact, the transition of cutting chatter from unstable to stable condition actually is a gradual process, that is to say, the grade of stability is in a range of a closed interval [0,1] not 0 or 1. Deeper studies on Lobes curves show that there should be different width of transition belt in different order Lobe curve because of the different Lobe slope. Thus, the method to calculate the transition belt width is defined according to Sigmoid function. Therefore, stability verification to milling parameters of die steel has been done based on the modified fuzzy stability Lobes.At last, according to specific engineering applications, a tool selection database and cutting parameters optimization decision-making system have been developed based on Web browser. In this way, it could service practical application directly.