Using simulation methods to obtain basic data and variation rules of process systems

The simulation method is used to obtain the basic data and variation rules of the process system, and provide the necessary basic data for the optimization of cutting parameters and the construction of the database. The milling force modeling is discussed as an example of the most common cylindrical end mill in actual milling. The contact between the cylindrical end mill and the workpiece during the milling process is shown. Milling is different from turning. The instantaneous milling thickness h varies periodically with time during milling. It can be approximated as the cutting force component acting in the Cartesian coordinate system. The number of teeth participating in the cutting process depends on the number of cutter teeth and Radial cutting depth. Set the number of teeth, the inter-tooth angle of the milling cutter is: When the cutting angle is larger than the inter-tooth angle, more than one tooth will participate in the cutting at the same time. When multiple cutters are simultaneously cut, the total cutting force can be expressed as effective when the milling force is between. The instantaneous cutting force is: the instantaneous cutting torque acting on the spindle. Due to the existence of the helix angle of the milling cutter, the point on the cutting edge will lag behind the tool tip point. Relationship between the lag angle at the axial cutting depth z and the helix angle When the contact angle of the bottom of the spiral groove is , the contact angle of the point on the cutting edge at the axial distance z is -. In the simulation calculation, the cutting edge in the machining area is discretized in the tool rotation angle direction and the axial cutting depth direction, and the discretized micro-element is integrated to obtain the total cutting force. One method for identifying the cutting force coefficient is to calculate the cutting force coefficient of the bevel cutting according to the geometric model of different tools based on the existing right angle cutting parameters. The cutting force coefficient in Armarego's bevel cutting model can be expressed as a function of shear angle, average friction angle, shear yield strength, right angle cut, and chip flow angle. For milling cutters, the helix angle is used as the angle of the end mill (ie i=). The cutting force coefficient is: another method is determined by the full-tooth milling (milling) experiment. In this case, the angle is cut and the angle is cut. According to the conditions of full contact milling, the average milling force per tooth in one cycle will be simplified to the average cutting force which can be expressed as the linear function of the feed rate c and the sum of the cutting forces. : The average force at each feed rate can be measured, and the component of the cutting edge force will be obtained by linear regression of these data. This process can be applied repeatedly to milling cutters of various geometries, so it is impossible to predict the milling force coefficient before cutting experiments with mechanical models with newly designed milling cutters. However, using the basic right-angle cutting parameters, the cutting force coefficient can be predicted by the bevel cutting transformation before the milling cutter is manufactured.

The milling cutter and its constrained form can be simplified into two mutually perpendicular spring damping systems. The mathematical model is: the dynamic cutting thickness of the machine tool/tool ​​system dynamics model changes as shown. Analysis of the influence of modal parameters on the flutter stability domain In the milling modal system, the parameters affecting the flutter stability domain are mainly the stiffness, natural frequency and damping ratio of the workpiece. Since the machining system is a multi-modal system, There are problems in modal identification when modal identification is performed. Too much modal order will make the identification process and stability domain simulation too complicated, and the modal order is too small and will affect the simulation accuracy. Through the author's series of experimental results in the subject, the actual system modal simplification method can be obtained. The product of the damping ratio and the stiffness determines the stability of the system. The least of the damping ratio and the stiffness product is the main mode, which determines the basic pattern of the system flutter stability domain. According to the natural frequency and damping ratio of the main mode, the maximum peak-to-valley ratio of the first stable lobe of the main mode is calculated, and then the rightmost lobe is the first stable lobe according to the flutter stability domain graph, thereby calculating The actual maximum peak-to-valley ratio of the main mode can be ignored if the ratio of the mode to the main mode of the mode is greater than the maximum peak-to-valley ratio of the main mode. Experimental modal technology is an effective method to obtain modal parameters of milling process, and modal parameter identification technology is one of the key technologies. The identification methods of modal parameters mainly include frequency domain method, time domain method, time-frequency method and simulation evolution based method. Among them, frequency domain method is divided into single mode identification method, multi-modal identification method and partition. Modal synthesis method and frequency domain overall identification method. Considering the characteristics of the research object and more convenient estimation of modal parameters, orthogonal multi-fitting can be used to identify modal parameters. Conclusion The dynamics simulation study of the milling process is difficult to select the process parameters that are common in the field of CNC machining in China. Through the research on the dynamics modeling and simulation of the milling process, not only the dynamic simulation theory is innovative, but also It is also possible to research and develop a complete dynamic simulation system for the milling process according to the actual situation of the project. The work has achieved the expected goals, mainly solving the following problems: a. Using the instantaneous rigid force model, the average milling The force is expressed as a function of the cutting area and the length of the cutting edge contact. Based on this, the milling process is discretized, and the simulation calculation of milling force for different types of milling cutters is realized.

The intelligent electric actuator is a new type of terminal control instrument. It directly controls the opening degree of the valve, online calibration, self-diagnosis and other control functions. It is the development direction of modern electric actuators. For over-torque protection in traditional valve electric actuators, most domestic and foreign manufacturers use software control, that is, during the energization of the valve, the valve is detected. If it is found that it is stuck for a period of time, the MCU issues a shutdown command to cut off the power supply. .

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