Automotive sheet metal maintenance technology paper-automotive sheet metal maintenance technology.
Based on many years' working practice, the author expounds the importance of maintenance in automotive sheet metal and discusses the maintenance technology in automotive sheet metal.
Keywords: automotive sheet metal maintenance importance maintenance technology
Classification number: TD353.5
With the continuous improvement of China's economic strength, people's living standards and economic income are getting better and better, and the number of various cars is getting higher and higher. Although the road construction in China has made great progress, it still cannot meet the needs of automobile transportation. In addition, the number of new drivers has increased rapidly in recent years, and the development of new automobile technology has also changed with the progress of society. From the overall technical point of view, cars have many automation functions, which greatly improve the power of cars and other objective reasons.
First, the importance of maintenance in automotive sheet metal
As a pillar industry in China, the automobile industry is developing with each passing day and has penetrated into all fields of social life. With the development of automobile technology and the wide use of new materials, there is a huge gap between modern cars and traditional cars, which also brings new problems to the collision maintenance of modern cars. Since 1940, the car without beam structure appeared, in order to meet the needs of economic and environmental protection in the automobile industry, the weight of the car body steel plate is getting lighter and thinner, and the alloy composition of the material is getting more and more complicated.
Automotive sheet metal maintenance is the work of repairing the large and small damages caused by automobile collision, that is, automobile body repair. It is different from the traditional blacksmith and cold-working sheet metal worker and plays an important role in the whole automobile maintenance process. The repair degree of car body collision damage will directly affect the service performance and safety structure of the car after repair. Generally, after a car accident, the damaged parts are damaged to varying degrees, and the structure and theoretical parameters of the car body will always change to varying degrees. The changes of these injuries have caused different degrees of damage to the hit vehicles, and the repair of these injuries is the specific work for our maintenance workers in automotive sheet metal.
If the car body collision damage is not repaired in place, then all the equipment connected to the car body, including the engine and gearbox, will not work normally. For example, if the position of the front and rear axles connected with the cross beam of the car body is not repaired by stretching, the front and rear axles will not be connected normally, so that the engine, gearbox, steering system, braking system, etc. will not work due to the change of position, resulting in new, more and greater failures. For example, * * * vibration phenomenon, deviation phenomenon and tire gnawing phenomenon. For example, after the roof of the car body collapses in a large area, if the roof maintenance is not in place, the roof skylight will be badly damaged, which will shorten the service life and even cause water leakage and dust leakage. This is especially true for the car body. If the recovery is not in place, the body glass can't rise and fall normally, and the door is not closed properly.
Nowadays, new cars are made of high-strength rigid materials, and the body structure is mostly used? 3H？ Structure. What if? 3H？ If the structure cannot be effectively repaired, it will bring greater safety hazards to the repaired vehicle. Car body safety is active safety, and drivers and passengers wearing seat belts are passive safety during driving. First of all, under the condition of ensuring the safety of the car body, the seat belt worn by the driver and the airbag installed on the car can work effectively, and effective safety protection can be ensured in the event of an unfortunate collision.
Second, automotive sheet metal maintenance technical points.
1, automotive sheet metal correction
(1) Body correction and fixing.
① For the correction of the car body, it is necessary to ensure that the car body is fixed, otherwise the overall displacement will occur under the action of tension, and the purpose of index correction will not be achieved. Understand the equipment performance and safe use measures, analyze and judge the damage of the car body, determine the fixed-point correction positioning point on which the preliminary correction of the traction scheme is based, check the correction effect, and carry out traction correction as planned. Before traction correction, the inside and outside of the car body should be protected as follows. Try to take out the internal components, such as seats, instrument panels and car cushions. When welding, cover the glass, seat, dashboard and other parts with heat insulation material to prevent burns. Remove the external parts of the car body and protect the car body with cotton cloth or protective tape to prevent scratches. If there are scratches on the paint surface, they must be repaired to prevent corrosion.
(2) The repair of the damage of the front end of the car body is mainly caused by the collision of the front end (such as rear-end collision). The damaged parts include the fender on one side of the front cross member, the side member and the front fender on the other side. The front end should be repaired from the side member of the front fender. First of all, the supporting structure needs to be repaired, and the side beam should be pulled first.
③ When repairing and correcting the damage at the rear of the vehicle body, connect the clamp or hook to the rear of the rear side member, the rear floor or roof and the rear end of the side panel. While pulling, measure the dimensions of all parts under the car body, observe the fit clearance of the car body plate, and determine the necessary repair degree. When the rear side member seriously collides and the deformation switch of the rear door frame is not good, the stress of the rear roof side plate can be relieved by pulling the side member.
(2) Renovation of concave and convex surfaces.
① Small-scale local concave-convex shaping: stick a pad iron on the back of the concave-convex, and compress the concave-convex to its original shape with a hammer. During operation, it is required that the hammering force should be light, and it should be continuously impacted at a frequency of 2 times per second, and the hammering points should be evenly distributed, so as to reshape the local depression: unlike the trimming of bumps, the hammering points are not above the top surface of the pad, but at the raised parts of the iron sheet. Stick the pad iron on the lowest place, tap the raised part nearby with a hammer to pry up the depression, trim the depression with a leveling knife, use the leveling knife as the pad iron, and repair the depression by tapping the raised part on the surface.
(3) Surface shrinkage molding: the shrinkage of the deformed part on the metal plate will be heated by torch flame, and the most convex or concave point (stretching center) has no cherry red. The amount of heating is related to the degree of stretching. After heating, quickly pat the area around the blush and gradually be surrounded by the center of the heating point. Metal structure shrinks. When knocking, use a pad iron on the back of the part, knock with a wooden hammer, and then gently knock with a hammer after cooling. If a little reduction can't achieve the purpose of leveling, you can use the same method to reduce it at an appropriate position around the point, but at this time the heating range is smaller. After all the contraction points are cooled down, make a comprehensive leveling, and knock lightly.
2, car body scraping ash (plastic)
After sheet metal correction, there are still some defects that sheet metal work can't make up for, and even if new parts are replaced, there will be imperfections. In order to be more perfect and accurate, we must use sculpture skills to make up for the defects. After the car is damaged due to deformation and other reasons, its flatness, wheel angle and lines need to be scraped and polished. This formula is used to explain: scraping = restoring the body skin = mold product = mold processing program. The body skin of any car is stamped with a mold, and we repair the body skin just like repairing the mold, so our scraping molding process should be connected with the mold processing, which is impossible for ordinary painters. Many painters who have worked for many years will sigh? It is easy to spray a car well, but it is difficult to do a good job. It is difficult to grind a ball of ash in ten years. The person who said this may really know what car paint is.
3. automotive sheet metal painting
Automotive sheet metal painting is usually divided into three steps:
(1) Head primer. Filling the sand marks and micropores at the bottom of the workpiece increases the adhesion of the lower coating and also has the function of defect indication.
(2) kindling. In the very important painting part, a complete and smooth working surface is prepared for the topcoat, and the last procedure of all primer work is completed, which increases the adhesion of the intermediate layer and has a certain isolation effect, ensuring the quality stability of the topcoat.
(3) topcoat. Top coat is divided into single-layer paint and multi-layer paint, which is a color fixing layer and a decorative protective layer. Single-layer paint is commonly known as plain paint, also known as ordinary paint, and can be completed in one layer. Multi-layer paints are divided into silver powder series paints and pearlescent series paints, which are completed in two-layer and multi-layer construction procedures. Silver powder paint adopts special aluminum material, which has high protection, strong outdoor stability and strong observability. Pearl series paint is made of mica and shells through high technology, which is a kind of high-grade paint with rich colors and strong decoration.
The spraying quality of topcoat is very high. It is not easy to be clean, plump, bright, not sagging, not hanging flowers, uniform luster, not leaking flowers, not flashing flowers, good leveling, not biting, not impetuous, not color cast. It's really not easy to accomplish these things in one go, which requires extremely rich experience and troubleshooting ability.
4. Surface treatment of body panel and painting
As the name implies, it is the last process of topcoat. After the paint surface is dried and solidified, the defects on it are treated. If we do our best, we will leave some imperfections, which can only be made up later. In fact, the satisfactory paint surface is not perfect. For example, the painting of (Mercedes-Benz) (BMW) will have a slight fine fish scale phenomenon. We generally call it orange peel phenomenon, which is a natural phenomenon caused by the drying time difference of paint film during leveling. Mirror therapy? . First, use 1500-2000 mesh beauty sandpaper to level and polish (2500 mesh if necessary), then use coarse wax made of pumice or clay to polish to remove the traces of sandpaper, then use fine wax to polish (without silicon) to remove the traces of coarse wax, then use reducing agent to achieve perfect luster, then use mirror treatment agent to completely remove halos and scratches, and then spray paint.
Three. Concluding remarks
In a word, the maintenance work in automotive sheet metal has high technical content and strong technological requirements, which needs the attention of the management departments of the auto repair industry, auto repair enterprises and the majority of car owners. Paying attention to physical repair is actually a concrete manifestation of cherishing life and traveling safely.
refer to
1, Tu Weixing. Practical technical manual for automobile maintenance sheet metal workers [M]. Nanjing: Jiangsu Science and Technology Press, 2007.
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