With the continuous development of manufacturing technology, the technological content of automobiles has been continuously improved. Once the body is deformed by impact, the body must be repaired and reshaped in strict accordance with the requirements, otherwise it will not only affect the appearance of the vehicle, but also affect the handling and wheel alignment of the vehicle. A series of impacts are produced, which seriously threatens safe driving. Therefore, we must carry out high-precision and high-quality automobile sheet metal repair to ensure the safety of automobile driving, stability.1.The definition and maintenance of automobile sheet metal
The concept of automotive sheet metal has been continuously improved with the development of sheet metal technology. It was originally an abbreviation for auto parts, and later gradually evolved into a method of auto repair. It has become a repair technology for the body after collision deformation. The earliest automobile sheet metal technology used tools such as hammers to repair and adjust the deformed parts of the automobile body. With the use of a large number of advanced materials in the automobile manufacturing process, the automobile structure has also undergone great changes, and automobile sheet metal repair has gradually developed into secondary body assembly. We not only need to restore its appearance perfectly through repair, but also make related performance , to restore the function to the factory state. This process requires the use of a large number of tools and repair techniques. It is completely different from traditional sheet metal repair, such as: positioning tools, measurement techniques, correction stretching methods, etc. are all effectively applied, so that the current automotive sheet metal repair tasks can be achieved. Car sheet metal repair is literally just the repair work for the appearance damage caused by the car collision, but we should note that once the car collides, It will not only cause damage to the appearance, but also cause displacement and damage to the internal components due to severe impact. Therefore, for sheet metal repair work, these damages are the contents of the repair work that we need to carry out. If the sheet metal repair work cannot be carried out effectively or the repair quality is poor, it is very likely to cause the devices connected to the body to fail to operate normally, such as the failure of the engine and gearbox to work properly, vehicle deviation, tire gnawing problems and resonance problems, etc.
2. the car body repair process
(1) Body measurement
After the damaged vehicle is sent to the repair shop, we place the damaged body that needs to be repaired on the frame alignment platform, use the clamps on the platform to tighten the body, and also use the pulling clamp at the front end of the longitudinal beam. clamp. After fixing the vehicle, we need to remove the damaged part to avoid the expansion of the damaged part and it is difficult to continue to repair, and then carry out the body measurement work.
1) With the use of a large number of advanced equipment in the auto repair industry, before the sheet metal tensile repair, we also use an advanced electronic measurement system for the body measurement. Through this system, the damage of the body can be accurately diagnosed before the repair. And make accurate effect confirmation after completing the repair. In the process of body measurement, a large number of professional tools and equipment are used to measure the position of the main reference point of the car body, and the measurement result is compared with the position of the reference point of the undamaged body, and then the direction, scope and degree of damage to the body are determined. Undergo verification. In addition, the deviation of each component of the body should not be too large. If the deviation exceeds 3 ram, it is very likely to cause problems such as noise and vibration of the assembly assembled on the body and frame, which are difficult to effectively control. In the measurement process, we need to carry out key analysis in combination with each control point, which means to refer to some special positions of the measurement points during the measurement process, such as: bolts, nuts, edges, holes, etc. The repair process is to refer to these reference points. A process in which the points are all restored to their desired location.
2) In the process of measuring the size of the car body, there are two very important reference datums, namely the center plane and the datum plane.The center plane is to divide the car into two parts that are equal to the left and right. According to this idea, marks are made on the bottom plate, roof and other parts of the car to ensure that these marks are on the center plane. Through the center mark, we can quickly and accurately to measure the lateral dimension; the datum refers to an imaginary A plane that is at a certain distance and completely parallel to the ground of the vehicle is used as a reference standard for all height data during manufacturing and repair. In the process of car sheet metal repair, we must check the processing control points of the injured part against the model data, and verify the measurement results through multiple measurements.
(2) Body tensile repair
After completing the body measurement, we need to calibrate, and then finally paint, so we must do the calibration of the car’s sheet metal, only in this way can we ensure the smooth development of the follow-up work. If we compare the body of the car to the human body, then after the fracture of the body, the body must recover well before wearing beautiful clothes. If the arm is still in plaster cast, then no matter how luxurious the clothes are on the body. Does not enhance personal image.
During the stretching process, we should pay enough attention to the problem of easy cracking, especially at this stage, most ordinary cars use cold-rolled galvanized sheet, which will have higher hardness after the parts are deformed. Due to the impact, the metal grains inside the steel plate will change to generate stress, and then work hardening will occur. Therefore, we need to eliminate the stress by annealing and heating. In order to eliminate this stress, we should heat the places with severe deformation. When heating, the edges and corners or the places where the two layers are connected should be heated. As the temperature increases, its plasticity is also continuously improved. However, we also have to strictly control the temperature. Once the temperature exceeds the allowable value, it will lead to hardening, embrittlement and other problems of the parts. Generally speaking, we can use the carbonization flame to heat the metal, but the temperature should be strictly controlled, such as 400-500% at the edges and corners or places where the tension is very tight. A tool can be used to tap to accelerate the reduction of metal particles.
(3) Body scraping
After the body sheet metal correction is completed, we need to scrape the repaired parts, so that the body sheet metal can be completely repaired. Generally speaking, the scraping work is not only equivalent to restoring the body skin, but also equivalent to the mold processing program. Each body skin of the car is obtained by die stamping, and repairing the body skin is the same as repairing the die. Therefore, we must organically connect the scraping and shaping with the mold processing work to ensure the quality of the work, but it is difficult for the vast majority of maintenance personnel to complete this work at this stage. Therefore, we need to pay more attention to it and strengthen management.
(4) Sheet metal painting
There are three main steps in sheet metal spray painting, namely, the first primer, the middle primer, and the brushing of the topcoat and varnish. After each process is completed, the next process can be carried out after the paint surface is dry. The spray paint must be bright, plump, and clean. Therefore, a lot of practical work experience of the operator is required. A good spray paint effect directly determines the appearance after repair. .
To sum up, in order to ensure high-quality sheet metal repair, we must apply stretching technology reasonably. Automotive sheet metal is not only related to the appearance of the vehicle, but also to the normal use of the chassis, engine, gearbox, etc., so we must ensure that Stretch repair quality. Based on my years of experience in front-line teaching work, the author discusses the entire process of stretch repair, hoping to promote the effective development of automobile sheet metal stretch repair work.
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