Design and Manufacturing of Automobile Inspection Fixtures-Functions and Functions of Inspection Fixtures
The car body is an important part of the entire car. Its manufacturing cost and weight account for about 40%-60% of the whole car. The manufacturing quality of the car body determines the overall performance of the car to a large extent. Therefore, the quality of the car body manufacturing is An important part of automobile manufacturing quality. The automobile body manufacturing process is a complex process that integrates sheet metal stamping and forming, automated assembly lines, welding and inspection technology, quality control and management and other multidisciplinary fields. Therefore, it can be considered that the quality of automobile body manufacturing can be improved To a certain extent reflects the technical level and manufacturing capacity of the country’s industry
Usually the car body is made of 300-500 sheet stamping parts, which are assembled at 70-120 assembly stations through parts, components, sub-assemblies, and from the assembly to the body-in-white level by spot welding. The car body is manufactured The size deviation will affect the performance of the whole vehicle such as wind noise, airtightness, driving stability and so on. In the production of car bodies, inspection technology is an important part of monitoring the production process and ensuring product quality. Generally, the car body is composed of thousands of parts, and each part needs to control the quality in the process of processing and assembly. All processes from casting and forging blanks, machining, heat treatment to assembly require necessary quality control. In the mass production process, fast and accurate measurement methods are very important.
The checking fixture is simple in structure, convenient to use, and its own manufacturing cost is relatively low compared with other measurement technology tools, and it is consistently widely used. Especially for the relatively large tolerances of parts and components in automobile products, and there are more random components in the production process, the
inspection tool has its unique advantages. In the production site of automobile parts, inspection tools are used in large quantities. Judging whether the product is qualified is not the only purpose of using the inspection tool. It is more to find the cause of the quality problem through the analysis of the measurement data, to provide a reliable scientific basis for the further improvement of the production process or the process, and ultimately to ensure and improve the product. The purpose of quality.
In modern automobile factories, especially car factories, quality inspection and quality control in the production of cover parts and car bodies mainly rely on special inspection tools, three-coordinate measuring machines, portable multi-joint measuring machines and laser online inspection systems. means.
The dimensional quality of car body manufacturing mainly includes two aspects, one is dimensional accuracy (that is, the mean value), and the other is dimensional precision (that is, stability). The dimensional quality control standards for car body manufacturing are given in the form of “theoretical value + tolerance”. For a car body production line involving hundreds of stamping parts, dozens of assembly stations, and thousands of solder joints, due to material changes, mold wear, tooling equipment wear, and process changes in the mass production process , The change of operators and other factors make the body manufacturing dimensions inevitably produce deviations from the original design dimensions in all aspects. If these deviations cannot be controlled in a timely manner, with the accumulation of time and space, the body manufacturing size will have a mean shift and an increase in variance. Mean shift refers to the deviation of the body manufacturing size from the design value, and the expansion of the variance means that the body manufacturing size fluctuates sharply. Generally speaking, these two situations are interacting and getting along with each other, which makes the size and quality of car body manufacturing complicated.
The following two methods are mainly used to control the size and quality of car body manufacturing: First, from the perspective of product and process design, study the mechanism and transmission law of complex deviations in the car body assembly process, summarize the actual production experience and knowledge, and determine the reasonable Car body size theoretical value, tolerance and manufacturing process to prevent dimensional quality problems. Second, from the perspective of detection and control, research advanced body size detection technology and diagnostic control technology, summarize actual production experience, and determine a reasonable detection and control system And methods to quickly find and solve dimensional quality problems.
Common automotive inspection tools are mainly used for vehicle body-in-white, interior and exterior parts, and are used in the development process of new projects and mass production management. They play an important role in mold debugging in the production preparation stage, optimization of production process design, and quality monitoring of mass products. Role, automobile inspection tools are of great significance in shortening the project cycle, improving productivity and product quality. It is the basic process testing equipment of the automobile industry and one of the important signs of the rapid development of my country’s automobile industry manufacturing technology in line with international standards.
The mold and the inspection tool are related to a certain degree. They serve the parts together, and the parts originate from the mold. The inspection tool inspects the parts. “No rules, no squares” molds are “rules”. The structure and accuracy of the mold itself are in production. The process parameters determine the dimensional accuracy and surface quality of the product (part). However, “whether it is round or not” cannot be judged by the “rules” that produce “square round”. That is, do the shapes and dimensions of the produced parts meet the design requirements? -It cannot be judged by the mold used as a manufacturing tool, and you cannot simply say “The size of our parts is guaranteed by the mold”, and everything will be fine. The part size is qualified-it needs to be measured with the help of measuring tools or inspection tools, especially in mass production. We say that the inspection tool is a special inspection tool used to measure and evaluate the size and quality of parts. The quality control process plays an important role that cannot be ignored and cannot be replaced. There are many types of auto parts, and the size matching requirements of related parts are high. Auto parts product development and quality workers should upgrade the design, manufacture and use of inspection tools to the same important position as molds.
The function of the measuring stand
The measuring bracket is an auxiliary bracket when measuring parts with a three-coordinate measuring instrument. Its main function is to locate the parts and facilitate the three-coordinate measurement. All supporting surfaces (points) and positioning reference planes (points) must be based on the CAD data of the parts In milling processing, the structure design of modern inspection tools is often considered as a measuring support. When the online inspection function of the inspection tool and the function of the measurement support cannot be satisfied at the same time, the online inspection function of the inspection tool should be satisfied first.
Qualitative and quantitative inspection of parts
In order to realize the on-line inspection of parts, it is necessary to accurately install and position the parts on the inspection tool, and then use visual inspection, measuring table or caliper to test the key product characteristics (KPC) of the part profile, peripheral tangents, and functional hole positions. , The key control characteristic (KCC) is checked, so as to realize the rapid judgment of the dimensional characteristics of the part, and the deviation between the part and the CAD theoretical value can also be obtained through the counting type measuring tool.
Key Product Characteristics=Key Product Characteristics “KPC” is the special characteristics of the product, such as the key, important size, all the characteristics of the bad review itself
Key Control Characteristics=Key Control Characteristics “KCC” is a process control characteristic, such as equipment process parameters or key, important process process parameters
Debugging molds, welding fixtures
Auto parts molds need to be tested to verify the stable performance of the mold and machine process parameters, optimize the structure of the mold, and ensure that qualified products can be produced in batches without interruption. Generally, mold adjustment is based on the full-size report of the product as a guide. Although this method can accurately find the problem of the mold, it usually takes several rounds of adjustment to achieve the desired effect. Now, as a guide tool for mold pre-testing, the inspection tool can directly reflect the size defects of the product, which is convenient for mold workers to quickly and accurately find mold problems. There is no need to perform multiple rounds of three-coordinate measurement, which saves a lot of labor and equipment loss. the cost of.
When the welding fixture welds the assembly or sub-assembly parts, the parts will produce welding errors. In order to reasonably analyze the causes, it is necessary to compare the results of the inspection tools. In order to determine whether it is the wear of the fixture positioning element, the failure of the positioning element, the unreasonable fixture design or insufficient clamping force and other factors that have caused the instability of the part size.
Matching verification during welding of prototype body-in-white parts
The body-in-white assembly is composed of hundreds of sheet metal parts. Due to the complicated process, these parts will undergo geometrical changes such as distortion and deformation during the welding process. In order to better analyze and study the consequences of these changes. It is necessary to simulate the overlap between parts when they are not welded, so as to discover the influence of a single part on the assembly. The screw car inspection tool uses the fixing method of riveting and screw connection to replace the welding process to eliminate the influence of welding deformation. The body-in-white parts are assembled in the screw car inspection tool according to the welding flowchart to assemble the body-in-white assembly. . In the process of part assembly and screw connection, the impact of a single piece on the assembly was found, and the application and product and mold rectification analysis.
Matching verification of vehicle samples
The integrated matching check tool function is to simulate installation through real parts. After measurement, it is comprehensively evaluated whether the parts meet the matching requirements. This process can be installed through a combination of different parts,-parts and simulation blocks, parts and parts, the results of measurement and analysis may be possible It is a part problem, it may be a design problem, or a process problem
In the early stage of automobile development, the integrated matching inspection tool can be used to evaluate the rationality of the design structure and matching relationship of the parts by installing the parts manufactured by the soft mold. It can be used to find early design problems and modify them in time, or through the assembly of parts. Evaluate the impact of the process on matching, and formulate a reasonable installation process
In the matching evaluation of trial production, since the part inspection tool is far away from the vehicle manufacturer, the comprehensive matching inspection tool is used to quickly analyze the matching problem. By comparing the matching of the parts on the body-in-white with the result of the comprehensive matching inspection tool, it is found that the part inspection Fix the problems in the design and manufacture, improve the parts inspection tools