Second, pry open the roof repair method: use leveling knife (or spoon-shaped plate) and pointed tools (such as various picks) to pry open the top concave part, so that the concave part will gradually restore to its original state.
3. Stretching repair method: Pull out the dent with a retractor, which is also one of the commonly used dent shaping methods. The traction device comprises a sucker, a traction cylinder and a special traction device.
There is a suction cup at the end of the pneumatic concave puller to generate vacuum, and the force exerted by the inertia hammer pulls the metal concave back to its original shape. Screw the screw at one end of the pull rod puller into the pre-drilled hole in the concave part, and repeatedly pull it in the direction of the handle with one hand to eliminate the concave part, and then block the through hole with filler. In order to avoid the inconvenience caused by drilling, it is also possible to use a pin instead of screwing in the screw when spot welding the concave part, and then cut off the spot welding with a tool after pulling out, so as to maintain the integrity of the metal surface.
4. Thermal shrinkage method: quickly heat the midpoint of the concave part of the sheet metal. During the heating process, the steel plate centered on the heating point spreads around, and compressive stress is generated around. When the temperature continues to rise, the local steel plates turn red and soft, which reduces the pressure in the central area and restores the deformation of the surrounding steel plates. The red-hot area is compressed and thickened, and the surrounding steel plates can freely deform, stretch and recover their shapes. For local hot spots, you can spray water or wet cloth suddenly, so that the heated parts suddenly cool down, and the steel plate immediately shrinks, and the central part produces tensile load at the periphery, which makes the periphery strongly stretch toward the center, offsetting the compressive load generated during deformation and restoring to the original state.
5. pleating method: pleating method is a method to deal with tensile deformation. It will not cause metal to shrink, but use a hammer and anvil to make some folds in the tensile deformation part. In the process of operation, the anvil is dislocated, and knocking with the crane's beak hammer will wrinkle the parts. The folds will be slightly lower than other parts. After filling, use a file or sandpaper to polish this part so that it is flush with other parts.
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