On the Advantages of Modern Design Methods in Mechanical Design

The Present Situation and Prospect Analysis of China's Machinery Manufacturing Industry

The design of mechanical products has undergone more than a hundred years of change and development since the development of technological design in the middle of the 19th century. The history of any product production is also the history of people's pursuit of innovative design of advanced products and services, and their theory, methods, and tools. And mankind has also experienced a long process of innovation and design and manufacturing.

In recent years, with the development of science and technology and the globalization of the economy, mechanical technology and various disciplines have continued to intersect and integrate, and the manufacturing industry has continued to develop in the direction of high-speed, lightweight, and virtualization. Users 'demand for products has become more and more personalized and diversified.. The design method of mechanical products tends to be more scientific and perfect, with higher calculation accuracy and faster calculation speed. The mechanical design tends to the application of modern design methods on the basis of traditional design.

2, traditional mechanical design methods

Traditional mechanical design is a conventional design method based on intuitive design, empirical design, and static design. It is mainly divided into the following stages[ 1] Intuitive design stage

Ancient design is an intuitive design. At that time, people either received direct inspiration from natural phenomena, or they designed and produced tools based on people's intuitive feelings. The design scheme exists in the mind of a craftsman and can not record expressions. The product is also relatively simple. The intuitive design stage has gone through a long period in human history. Before the 17th century, it basically belonged to this stage. (2) Experience Design Phase

With the development of production, the experience of a single craftsman or the ideas in his mind have been difficult to meet these requirements. As a result, craftsmen unite and collaborate with each other. Some experienced artisans express their experience or ideas in drawings and organize production according to the drawings. The appearance of drawings can enable craftsmen with rich experience to record their experience or ideas through drawings, pass them on to others, facilitate the analysis, improvement and improvement of products with drawings, and promote the development of design work. More people can also participate in the production of the same product at the same time, meeting the demand for products and increasing productivity. Therefore, using the drawings to design, the human design activities from the intuitive design stage to the experience design stage. (3) Semi-theoretical and semi-empirical design stage Since the 20th century, due to the development and advancement of science and technology, the research and experimental research on the basic theory of design have been strengthened, and with the deepening of theoretical research, experimental data, and the accumulation of design experience, A set of semi-empirical and semi-theoretical design methods has been formed. This method is based on the experience, formulas, charts, and design manuals formed by theoretical calculations and long-term design practices. It is designed by means of empirical formulas, approximate coefficients, or analogies. There are three main design methods for this phase[ 2] 1: Theoretical design The design based on long-term summarized design theory and experimental data is called theoretical design. For example, the design of the strength of a simple pull rod: the design strength calculation formula σ ≤ σ lim/s or F/A ≤ σ Lim F: External load acting on the rod; A: cross-sectional area of the pull rod; Σ Lim: limit stress of pull rod material; S: The safety factor can use the above formula to directly solve the necessary cross-sectional area of the rod part, or it can be used to initially design the cross section size of the rod part according to other methods, and then use the strength calculation formula to check. Due to the complicated and changeable actual situation, if the safety factor is selected too large, The product is stupid, large, and thick. If the safety factor is too small, it is difficult to guarantee safety[ 3] And ... Experience design is called experience design based on the existing design methods and experience relationships of certain types of parts, or based on the designer's personal work experience. As the design of the product's technical system becomes more and more complex. The technological content has been continuously improved, the speed of product renewal and development has accelerated, and the design method of empirical analogy has not been able to meet the needs of the market. In order to improve the design quality, model experimental design method can be adopted. That is, the preliminary design of the parts or machines into a small model or small size prototype, through the means of experiments to test its characteristics in all aspects, according to the experimental results to gradually modify the design, so as to achieve perfection. This design process is called model experimental design.

3, modern design methods

The modern design method is an emerging comprehensive and cross-cutting discipline, developed in the study of design competition laws and design activities in a distributed resource environment, and is a method of applying scientific ideas and methods to create products with advanced performance and reasonable structure. It is a dynamic, scientific, computerized method. It applies all the scientific methodologies applied in the scientific field to mechanical design, and passively repeats the process of analyzing the performance of the product as an active design of product parameters. Transform static, empirical, manual methods into scientific, dynamic, computerized methods[ 4] And ... Modern design methods have the following applications in mechanical design:(1) Computer-Aided Design Computer-Aided Design, which uses computers for information processing, and uses computers to have features such as fast and accurate operation, large storage capacity, and strong logic judgment functions. Through human-computer interaction to complete the design work. Compared with the traditional design method, it has the following advantages: 1. It significantly improves the design efficiency and shortens the design cycle; It quickens the upgrading of mechanical parts and mechanical products and enhances the market competitiveness of products; 2 can store a lot of design information and design experience, so that the lack of design experience can also successfully complete the design task; 3 can give a lot of design solutions in a short time, and analyze and compare, so as to obtain the best design plan; 4 Make the mechanical designer free from the heavy repetitive work, and concentrate more time and energy on creative work; 5 Combined with computer-aided manufacturing and computer management automation to form a computer integrated manufacturing system; Starting from the highest overall benefit of the enterprise, a series of tasks such as market forecasting, product design, production planning, manufacturing and sales are comprehensively carried out, thus realizing the effective use of various resources such as manpower, material resources, and time[ 5] And ... (2) Mechanical reliability design Mechanical reliability design is a comprehensive design technology that combines probability theory, mathematical statistics, failed material resources, and mechanics. Its main feature is that the design variables involved in the conventional design method, such as load, stress, strength, life, etc., have a multi-valued phenomenon as a random variable that obeys a certain distribution law. The main parameters and structural dimensions of parts and whole machine which meet the requirements of reliability index of mechanical products are designed by means of probability statistics. (3) Mechanical system and its optimal design, mechanical system design is an application system point of view for the design of mechanical products. The process generally includes four stages: planning, external system design, internal system design, and manufacturing and sales. Compared with the traditional design, the traditional design focuses on the internal system design. The emphasis is on improving the characteristics of the parts or subsystems, and less consideration is given to the interaction and impact between the parts and the internal and external systems. When the mechanical system design follows the viewpoint of the system, the relationship between the internal and external systems and the subsystems is comprehensively studied, and the physical model of the design problem is converted into a mathematical model. Optimizing mathematical theory, selecting appropriate optimization method, solving the mathematical model by computer, and achieving the best overall function of the entire system through the coordination of each subsystem. (4) Modular design Modular design is to divide and design a series of functional modules on the basis of functional analysis of different functions within a certain range or products with different functions and different specifications. Through the selection and combination of modules, different products can be formed to meet the different needs of the market. One of the main goals of product modularization is to make up as many modules as possible with as few types and numbers of modules as possible