Quality control of the hottest welding process

2022-08-14
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Welding process quality control

in the current market environment, product competition mainly depends on quality and service. Therefore, Chang'an Ford Mazda Automobile Co., Ltd. has designated 2009 as the "year of quality excellence", and all workshops and process links actively adopt a series of quality improvement means and measures to make products more competitive in the market and higher customer satisfaction

for the welding workshop, our quality work mainly focuses on three aspects: quality system control, process quality control and product quality control. This paper mainly discusses the "process quality control" in the actual production of the welding workshop

main factors affecting the quality of welding process

welding, as one of the four major processes of body manufacturing, is the basis of body size control and the guarantee of structural strength. The quality of welding process is particularly important, and all influencing factors also need to be paid attention to. For example, in our actual production process, defects such as false welding and weak welding have been caused by factors such as welding diversion of welding gun and poor splicing of parts. Its potential high risk makes us fully realize the urgency of welding quality control and the necessity of PDA (DHI unit) showing orange

generally, there are many factors that affect the quality of BIW. Using the fishbone analysis method, combined with the actual production process of the welding workshop, we made detailed statistics on the reasons for the standard length of at least 3 meters, materials, methods and rings of human and machine due to long samples such as steel wire rope, chain, cable, steel strand, etc., analyzed each link in a scientific way, and took corresponding measures to effectively control, In order to achieve the expected product quality and ensure the final production of qualified body in white

Figure 1 shows the fishbone diagram of our company's welding process quality analysis

Figure 1 fishbone diagram of welding process quality control

through the analysis of fishbone diagram and combined with the actual work, we can know that the main factors affecting the welding quality of BIW include the working state of employees, fixture design, incoming part deviation, welding parameters and welding spatter, etc. in view of these main factors, we have formulated effective measures to comprehensively improve the quality control of welding process (as shown in the table). Welding process quality improvement

process quality control

for the process quality control of the welding workshop, the two most important key points are "welding strength control" and "body size control". The following is to introduce the process quality control of these two projects as examples

1. Welding strength control and inspection

the welding of various components on the body mainly depends on spot welding. Spot welding plays a very important role in the welding quality of the body. Whether its quality is qualified or not has a great impact on the safety, strength, appearance and other performance of the whole vehicle, especially the guarantee of welding strength is of great significance to the safety of the whole vehicle. In addition, the welding quality of other welding methods, such as MIG welding and laser welding, is also important

take a vehicle model as an example, the German BOS 6000 system is introduced into the welding workshop of Changan Ford Mazda, which can monitor all welding robots and welding spots of the vehicle in real time, not only the welding parameters, splash size and welding quality of each welding spot, but also the wear condition and grinding frequency of the electrode head of the welding robot

in addition, in the process of welding production, the strength inspection of samples is also very important. Spot welding inspection means mainly include non-destructive inspection (non-d5 is to expand and strengthen the express green packaging industry alliance estructive) and destructive inspection. Non destructive inspection includes prying inspection, ultrasonic inspection, etc., and destructive inspection includes teardown spot welding inspection and laser welding/mig welding metallographic analysis, etc

several main inspection methods currently used by our company's welding workshop are as follows:

(1) non destructive inspection: prying inspection

prying inspection is mainly a quality inspection method for pryable welding points at each station of the production line. The tools used are chisels, hammers, etc., with a frequency of 5 times/shift. Generally, relatively simple welding defects can be found, such as false welding, weak welding, etc

(2) non destructive inspection: when ultrasonic wave

propagates in the metal material of the tested solder joint, the change of the internal organization of the solder joint will have a certain impact on the propagation of ultrasonic wave. Through the detection of the degree and condition of ultrasonic influence, we can understand the performance and internal defects of the solder joint. The software screen (see Figure 2) will display the propagation of ultrasonic wave in real time. If there is any abnormality, it indicates that there is a defect in the solder joint, For example, the gradual decrease of wave crest is too slow (relatively flat), indicating that the solder joint has low thermal dissolution, and the gradual decrease of wave crest is too steep (relatively steep), indicating that the solder joint has overheating dissolution

Figure 2 ultrasonic testing

(3) broken plastic materials are qualified for damage inspection: teardown

teardown inspects the welding quality by destroying all welding joints and welds with manual chisels, pneumatic chisels, electric chisels and hammers. The inspection frequency of sub assembly and BIW is once a month. Figure 3 shows teardown spot welding inspection, and Figure 4 shows metallographic analysis of teardown laser welding/mig welding

Figure 3 teardown spot welding inspection

Figure 4 metallographic analysis of teardown laser welding/mig welding (qualified MIG welding section)

2 Body size control

the manufacturing process of automobile body is a very complex process, which is usually formed by welding hundreds of stamping or casting parts with complex surface and different thickness after positioning by dozens of tooling fixtures with different functions; At the same time, the welding process is also a multi-level architecture. Some small parts are welded into subassemblies first, and the subassemblies become the parts of the next station. Therefore, there are many intermediate links and many influencing factors, which makes it difficult to control the body deviation. However, if scientific detection and analysis methods are adopted, the deviation of body size can not only be effectively controlled, but also be continuously reduced

in order to effectively monitor the size of the whole vehicle and avoid problems such as assembly difficulties and poor matching in subsequent stations, our company's welding workshop adopts advanced German Zeiss 3D measurement and Swiss Leica wireless CMM 3D measurement technology to regularly monitor the tooling fixtures, sub assemblies and assemblies to Chengdu through SPC monitoring means, So that each measuring point can automatically generate an i-mr control chart (see Figure 5) in the workshop station according to the historical measurement data to generate early warning, so as to find problems in time, contain problems in advance, formulate improvement measures, and output qualified products

Figure 5 i-mr control chart

conclusion

overall, the process quality control of Chang'an Ford Mazda welding workshop has not only improved the CTQ (cost, time and quality) performance of the whole vehicle, but also effectively ensured the safety, accuracy and reliability of the BIW of various models through such Ford global quality control means as PCF, teardown, metallographic analysis, FPA and CTQ monitoring, etc Stable product quality

through the quality improvement of all workshops and process links of the company, the quality management of our company has been significantly improved, and the competitiveness of products and enterprises will be effectively enhanced

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