First, local shaping
When the body is partially reshaped, the damaged part can be put into the template, and the body surface can be repaired with the sheet metal template. There are two plastic methods for using sheet metal formwork support: positive support method and local support method. The front support method is to directly put the sheet metal support die on the convex part of the back of the sheet metal, and directly hammer the deformed part on the other side with a sheet metal hammer. This is very effective for repairing bumps and flattening smaller bumps. However, the positive support method is easy to cause the extension and deformation of the metal plate, and the metal in the hammering part will become thinner and the area will increase.
1. Partially supported methods
In the practical work of plastic repair with formwork support, we often use the method of partial support, as shown in figure 1. Offset method is usually used for continuous deformation and forming of multiple parts. During operation, the metal plate die holder is placed at the lowest position on the back of the metal plate, and the metal plate hammer hits the highest position of deformation on the other side. When hammering, the die holder is also used as a percussion tool to repair deformed parts. For the deformed parts of the car body shown in Figure 2, two metal hammers can also be used to strike the deformed parts at the same time, and the offset method can be used to avoid the process defects such as uneven stress in the repair process.
2. Trimming knife forming
Many parts of the automobile body structure can't be put into the template, and some parts can be repaired by leveling knife. 4. When operating, stick the leveling knife on the back of the deformed part and strike the deformed part with a sheet metal hammer. This method is particularly effective for repairing tiny bumps and scratches on the car body surface.
The trowel can also play an auxiliary role in the shaping process, for example, it is very effective in repairing the local deformation of the car door without damaging the internal structure of the car body parts. Use a leveling knife to pry for shaping first, and then bounce the protruding pry back to the normal position. Then, according to the method shown in Figure 4(b), the door panel is repaired and leveled with the help of leveling knife and sheet metal hammer. During operation, the hammering force should be well controlled, and the position of the supporting point of the leveling knife should cooperate with the hammering force and position. If the hammer force is greater than the top contact force of the leveling knife, the leveling purpose will not be achieved, and even the deformation of the parts will be aggravated. Generally, the top adhesion force of leveling knife can be slightly greater than the hammering force, so the effect will be better. The operation should follow the principle of "high knocking and low knocking", and pay attention to adjusting the position of vertex and hammer point at any time. Continuous tapping on a point or excessive force and times will inevitably extend the surface of the metal plate and cause the plate-like member to warp.
Second, local concave-convex shaping
Shape shaping often needs local concave-convex shaping, and the operation method is summarized as "convex in the middle, knocking at the periphery, knocking at the middle with seven twists and eight inclinations". Pay attention to the selection of tapping point, hammering strength and tapping sequence when tapping. Generally, after preliminary leveling, the tiny concave and convex remaining on the surface should be leveled more finely.
When operating, start from the damaged part. If the area is large, start from a place far away from the operator or inconvenient to operate. Pay attention to the accurate coordination of hands and eyes during plastic surgery, and ensure that the center of the top surface of the hammer, rather than the edge of the top of the hammer, falls on the hitting point.
Be careful when hammering.
1. The hammering sequence shall be carried out according to the sequence number shown in Figure 7, with the impact point at the highest point and gradually moving from the hammering point to the center.
2. The speed of hammering operation should be fast rather than slow (if flame heating is used as an auxiliary method), and the heat dissipation speed of thin parts is very fast, so we should pay more attention to the flat speed, otherwise the effect will be greatly weakened.
Don't hammer too hard. If hammering is excessive, the plastic area will be stretched again.