In the past ten years, the automobile industry has developed with each passing day, and the surrounding industries combined with it have penetrated into all fields of social life. With the development of automobile technology and the extensive use of new materials, modern automobiles bring us new changes every day. With the rapid development of the automobile industry, automobiles are deeply integrated into our lives, which is followed by new problems of modern automobile collision maintenance. In order to meet the demand of economy and environmental protection of automobile industry, various new technologies are constantly applied to automobile body. The weight of automobile body steel plate is getting lighter and thinner, and the alloy composition of the material is getting more and more complicated. Therefore, higher requirements are put forward for the door maintenance technology, which is mainly reflected in the change of body materials, the update of maintenance technology and the change of equipment.

First, the importance of car door repair

The door is one of the important parts of the car body, and it is also the passage for passengers to get on and off. It is not only convenient for passengers to get on and off, but also to ensure the safety of passengers and good vision and lighting when closing the door. In recent years, sliding doors and sliding doors, which used to be used only in passenger cars, have been applied to cars, and gull-wing doors have appeared, which are very convenient to get on and off. The design of various doors is a combination of innovative ideas and practical application of ergonomics, and the ultimate goal is to show their differences on the premise of making it easier for passengers to get on and off. A car door generally consists of a door body, door accessories and an inner cover. The door body comprises an inner door plate, an outer door plate, a door window frame, a door reinforcing beam and a door reinforcing plate. Door accessories include door hinge, door opening limiter, door locking mechanism, inner and outer handles, door glass, glass lifter and sealing strip. The inner cover plate includes a fixed plate, a core plate, an inner skin, an inner handrail and the like.

Plastic repair of automobile door outer panel is aimed at repairing the large and small damage caused by automobile door collision, that is, automobile door repair, which is different from traditional platinum work and cold working and plays an important role in the whole automobile maintenance process. The recovery degree of collision damage will directly affect the performance and safety structure of the collision vehicle after repair.

Second, the door maintenance process

According to the damage form of the door panel, the repair of the door panel is generally divided into the following parts:

(1) Replace the metal plate at the door hinge. The method is as follows:

1. Select the same material according to the damage range.

Material, according to its size to make repair welding panel.

2. Correct the door and restore it to its original positioning size. Before calibration, check the parallelism and parallel surface of the door hinge. If there is any deformation, cut it at an appropriate position and heat the inner layer to correct and reset.

3. Mark and locate the bolt holes according to the prepared metal plate.

4. Cut the replacement metal plate by marking. If the internal parts are found to be damaged, they should be replaced in time, and then the repaired welded parts should be butt welded and welded.

5. For the welded parts, all the parts that can be pushed out from the inside with various shapes of lining iron should be flattened and stretched to eliminate the internal stress generated during welding. If it is necessary to replace the door frame together, it is also necessary to deal with the edge wrapping, add solder joints at the edge wrapping, and finally re-check the geometric dimensions of the door and correct the unqualified places.

(2) Maintenance of door shell

1. Repair of the lower part of the door: the lower part of the door is corroded and can be repaired by local replacement.

1) Rust-proof Maintenance Technology of Door Outer Panel

(1) Select the position of the cutting line on the plane to avoid the edge lines and corners of the reinforcing plate.

(2) blanking according to the replacement size. Reserve flanging allowance when blanking. First, make the plate into the required curved surface shape, then put the plate on a flat plate with a rubber plate under it. Make reinforcing lines and folding lines at the marked rib lines and folding lines.

(3) Remove the relevant accessories in the door, and cut with a welding gun at a distance of 3 ~ 5 mm below the cutting line. Use a hand electric drill to drill holes to separate the connection solder joints of the inner and outer panels of the relevant doors, and the diameter of the holes is about 6mm. Pry open the folding line of the door with a crowbar until the folding line is higher than the cutting line10 ~15mm. After the corroded panel is separated, cut along the cutting line with sheet metal scissors to remove burrs, residual solder joints and paint layer around the cutting line.

(4) After replacing the positioning, weld the butt joint flat. First, carry out positioning welding at a distance of about 30 ~ 40 mm, and then carry out sectional welding correction. After all welding, conduct comprehensive fine correction, and protect the welding with carbon dioxide.

⑤ Fasten the folding line. Don't buckle the broken line until the door is adjusted to the door frame and the gap between the door and the door frame is even.

⑥ Spot welding or plug welding shall be carried out according to the original drilling position. Check the outer surface of the door, especially around the butt weld, and press it with your fingers to see if there is any movement. If there is any activity, acetylene flame can be used for point heating or shrinkage correction, but it is not advisable to add too many hot spots, generally 3 ~ 5 o'clock is more suitable.

2) Maintenance technology for the corrosion of the lower part of the door inner and outer panels.

There is little corrosion on the lower part of the outer panel of a single door, and most of them are corroded at the same time. The steps of its maintenance process are as follows:

① Determine the replacement scope. On the premise of ensuring the removal of corroded parts, the disassembly line of the inner door panel should avoid the rib line and positioning installation hole of the door; If the cutting line is in a higher position, it should be located in the inner door cover, and the cutting of the outer door panel has been mentioned above. But the position of the cutting line of the outer door panel is lower than that of the inner door panel.

(2) template making, blanking, processing and molding. According to the determined replacement range, the template is manufactured, the hem size of the edge is released according to the template shape, and then the blanking is carried out, and the blanking is processed and shaped according to the shape of the replacement part, and a drainage hole is drilled at the bottom of the inner door panel replacement.

③ Remove the corroded parts of the door inner and outer panels. The method is as above. First pry open the folding line of the door outer panel, separate the spot-welded parts of the inner and outer panels, and then cut and separate the corroded parts of the inner and outer panels. Finally, directly cut off the corroded part of the door outer panel along the cutting line with silver and gold scissors, and remove the paint layer around the cutting line of the inner and outer panels.

④ Welding and correcting the replacement parts of the outer door panel. After welding and correcting the replacement parts outside the door, install the door on the door frame and check whether the gap between the door and the door frame is consistent, otherwise, it is necessary to change the position of some folding lines of the replacement plate until it meets the requirements.

⑤ Weld and correct the replacement parts of the inner door panel. Fix the replacement part of the inner panel on the outer door panel according to the original position with pliers, and butt weld the inner door panel. After spot welding or plug welding the edges of the inner and outer door panels according to the original position, remove the pliers and fasten the hemmed parts.

⑥ Install the door to the door frame for inspection. After passing the inspection, install the door fittings and carry out anti-rust treatment inside the door.

2. Replacement of door outer panel

When the outer door panel is severely deformed due to impact and the lower part is corroded in a large area, the method of replacing the outer door panel should be adopted. The replacement steps are as follows:

1) Before removing the door, check the deformation of the door. After removing the door, remove the door from the door frame, drill holes with an electric drill, and separate the solder joints connecting the inner and outer panels of the door.

2) Stick a marker strip on the door frame, and measure the distance from the edge of the outer plate to the lower edge of the marker strip and the distance from the edge of the outer plate to the door frame respectively.

3) Use a grinding wheel cutter to remove the brazing between the outer door panel and the inner door panel, and polish the edges of the outer door panel, but not the inner door panel, just wipe off the outer edge and break it.

4) Separate the outer door panel from the inner door panel with a hammer and an oath device, and smooth the remaining solder joints, solder and rust spots with a grinding wheel cutter. Check the damage of the inner door panel. Leveling the concave and convex parts of the inner door panel hem with a hammer pad iron.

5) Prepare to install a new outer door panel, drill the welding hole, and remove the paint on the welding or brazing parts; Some exterior door panels are equipped with sound insulation panels. When installing, clean the outer door panel with alcohol, heat the sound insulation panel and the outer door panel with a blowtorch, and bond them with adhesive. Apply body sealant on the back of the door outer panel, fix the door outer panel on the door inner panel with pliers according to the required position, and braze the parts that need to be brazed.

6) Fold the edge of the outer door panel. When wrapping the edge with a hammer and pad iron, the pad iron should be covered with a layer of cloth pad to avoid scratching the outer panel.

Three. Concluding remarks

Automobile maintenance has high technical content and high technical requirements. At present, many automobile maintenance enterprises at home and abroad are training the majority of sheet metal maintenance personnel in theory and practice to enrich their technical connotation, so that they can master the repair technology of collision damage of modern new car bodies and skillfully use various maintenance equipment and tools at home and abroad. The introduction of accurate human body correction platform, three-dimensional electronic measurement system and rapid shaping machine, the maturity of pneumatic and plasma cutting technology, and the update of welding and grinding equipment are all promoting the innovation and progress of human diet maintenance technology.