A summary of research methods on the assembly devi

  • Detail

Summary of research methods of car body assembly deviation

car body manufacturing is a process integrating stamping forming, automatic assembly line, robot welding and detection technology and other multidisciplinary fields. In recent years, the excellent service of the world-famous automobile is the cornerstone of the brand. The international merger of automobile manufacturing enterprises is constantly intensifying the competition in the automobile market. The research on the dimensional deviation control of car body manufacturing is becoming one of the hot issues in industry and academia

vehicle body manufacturing deviation is a common quality problem in global automobile manufacturing enterprises, which directly affects the performance of vehicle body, such as wind noise, sealing and smoothness. In the early 1990s, the comprehensive deviation of car body manufacturing in the United States was more than 2mm, significantly higher than that of Japanese taxis, which lost about 30% of the domestic market. With the success of the three-year "2mm project", the American car body manufacturing caught up with the world's advanced level in 1996, gradually regaining its original market share. The best level of European car body manufacturing deviation is ± 1 At present, attempts and efforts are also being made to improve the manufacturing quality of car bodies, such as the RPS reference point system being implemented by Volkswagen AG. However, the manufacturing deviation of car body in China is not stable enough, with an average of more than ± 3mm, which is far behind the world advanced level. In order to revitalize the national car industry, it is urgent to carry out research on controlling the manufacturing deviation of car body

car body (i.e. body in white) is usually welded by sheet metal stampings at assembly stations. Based on the deformation characteristics of sheet metal stampings, the dimensional deviation of parts caused by the stamping quality of parts in the process of body manufacturing and assembly, the instability of clamping and positioning of assembly and welding fixtures, welding deformation and the interference of parts assembly occur coupling, accumulation and propagation in the process of body assembly, forming a comprehensive deviation of body manufacturing

assembly deviation facing the body manufacturing process

car body assembly is a multi-level complex assembly process of multi sheet stamping parts. Based on the deviation flow theory of car body assembly process, the propagation law of assembly deviation in the car body assembly process is revealed. In order to predict the car body manufacturing deviation according to the part deviation, positioning stability, fixture deviation and part interference, and determine the contribution rate of each assembly deviation source to the car body comprehensive manufacturing deviation, It lays a theoretical foundation for the deviation control of car body assembly

welding is the main form of car body assembly, especially spot welding. The car body has an average of welding spots. Therefore, the welding and assembly process deviation of the car body is one of the main sources of the comprehensive deviation of the car body. According to the different assembly forms of car body parts, the car body assembly forms can be divided into two basic forms: parallel and series. The research shows that the series assembly deviation is only related to the part geometry and the deviation is cumulative; The parallel assembly deviation is related to the part geometry and the force on the part. The algebraic sum of the influence coefficients of each deviation difference source on the comprehensive deviation is 1. The comprehensive deviation after the parallel assembly of parts is less than that of a single part. In particular, when the stiffness of one of the two parts assembled in parallel is much greater than that of the other, the comprehensive assembly deviation mainly depends on the part deviation of the part with large stiffness, which is far less than the part deviation itself

fixture is the carrier for the assembly of all parts of the car body, which plays an important role in the assembly quality of the car body. The correctly designed fixture should have good shape and surface positioning ability, correct positioning points and fixture types to ensure the shape closure, force closure and self-locking characteristics of the fixture

in addition, with the wide application of welding robots in automobile body manufacturing lines, the research on flexible assembly of multiple robots in car body assembly lines is also gradually deepening

detection and statistical technology of vehicle body assembly deviation

tracking of vehicle body size data is the basis for realizing vehicle body assembly process monitoring, and the detection method determines the accuracy and effectiveness of vehicle body assembly process monitoring

detection sample is a traditional detection tool widely used before the 1970s. The detection speed is extremely slow, and it is unable to quickly provide enough characteristic sample data. With its high accuracy and flexibility, coordinate measuring machine (CMM) has become a popular testing equipment in automobile manufacturers at home and abroad in the early 1980s and even now, but the measurement speed is restricted. When quality problems are found in the manufacturing process, several products with such defects have been transferred to the subsequent processes, so the defect detection and diagnosis in the assembly process is not very effective. At the end of the 1980s, the appearance of optical coordinate measuring machine (OCMM) made it possible to measure the car body assembly process. 100% sampling measurement was achieved on the sample points (20), which provided rich multivariable dimension information for the quality definition and error source location of the assembly process

at first, the traditional statistical process control chart analysis method was used to monitor and control the car body assembly process. However, the measurement data of vehicle body assembly dimensional deviation often has a strong correlation, and principal component analysis (PCA) method has gradually become the main method of statistical analysis of vehicle body assembly deviation

research on vehicle body assembly deviation

extreme value method, statistical analysis method and Monte Carlo simulation method are three common methods to analyze assembly deviation. These three methods all assume that the part is a rigid body, and the set characteristics of its assembly deviation are determined only by geometry or (and) motion relationship

In 1980, takezawa pointed out that "the error accumulation theory based on rigid body assumption is difficult to apply to the assembly of flexible sheet metal stamping parts of car body, and its assembly error can be less than the part deviation and close to the part with larger rigidity", which opened the prelude to the research on the assembly error of flexible parts. Especially in the early 1990s, the University of Michigan took the lead in systematic theoretical research on the assembly error of flexible parts of car body, and successfully carried out the "2mm project" to reduce the manufacturing error of car body in American automobile manufacturing enterprises, finding a group of effective methods to solve the quality problems in the process of car body manufacturing

some suggestions on the development of body assembly deviation control technology in China

for a long time, the sequential serial engineering method has been used in the development of automobile body. The design tolerance is required to be as small as possible in the body design stage at the early stage of the whole life cycle of the body. However, the manufacturing cost is inversely proportional to the design tolerance. The smaller the allowable tolerance, the higher the manufacturing cost. The car body assembly of multi sheet stamping parts is affected by the factors of manufacturing and assembly process. Because the car body manufacturing process is at and near the end of the whole life cycle, the manufacturing deviation of the car body cannot be considered early in the design process, resulting in the manufacturing quality not fully meeting the design requirements

in order to meet the needs of the development of China's car industry, on the basis of looking forward to the development of car body assembly deviation control technology and increasing investment attraction, we must carry out the research on car body assembly quality control in China as soon as possible, especially the research on the following car body assembly deviation system:

1 Design oriented assembly deviation control technology

the body manufacturing and assembly process is designed in parallel with the body

design, so as to shorten the development cycle of the body and improve the quality of the body to promote the optimization of the industrial structure with the concurrent engineering mode. Feedback the body manufacturing deviation information to the initial stage of body design. Through the design, we often use the third experimental method stage to preset the assembly clearance to realize the self compensation of the assembly process deviation; The assembly design of vehicle body structure is quantitatively evaluated by assembly deviation. Design deviation control that is conducive to manufacturing and manufacturing process control that is suitable for design are the goals of controlling the comprehensive deviation of the car body

2. Establish the body assembly deviation control system

the existing body assembly deviation research is still in a piecemeal and block research method. Based on the case-based body parts deviation research, establish the body assembly deviation control system. It includes more reasonable flexible sheet metal assembly system, such as optimal design and robust design of fixtures, adaptive compensation of assembly deviation of parts, optimization of welding spot distribution and welding sequence of car body assembly, etc

3. The virtual system of car body assembly simulates the flexible assembly process of car body parts, checks the possible interference of flexible assembly, feeds back the design information of car body parts, and optimizes the car body assembly line. (end)

Copyright © 2011 JIN SHI