The deformed places of the panels are straightened, as a rule, manually using a special tool (hammers, levers, various mandrels) and fixtures.
Heated straightening is used for upsetting (contractions) highly stretched panel surfaces. To prevent deterioration of the mechanical properties of the metal, the panels are heated to 600-650°C (cherry red). The diameter of the heated spot should be no more than 10-15 mm.
Straighten panels with metal shrinkage as follows:
- with a carbon electrode of a semi-automatic welding machine or a gas torch, heat the metal points from the periphery to the center of the defective area and, with blows of a wooden mallet or hammer, upset the heated places on the reverse side of the upset area using a support or anvil;
- repeat the operations of heating and depositing the metal until the required surface of the panel is obtained.
Irregularities in the panels can be smoothed out with polyester fillers, thermoplastics, cold curing epoxy putties and soldering.
Pic. 8-5. The main reference dimensions of the attachment points of vehicle components and assemblies:
1 - holes for installing a radiator;
2 - base holes with a diameter of 20 mm;
3 - fastening of the steering mechanism;
4 - mating plane of the pendulum arm bracket;
5 - stabilizer mounts;
6 - fastenings of the rear support of the power unit;
7 - fastening of the transfer case;
8 - fastening of the rear suspension arms;
9 - rear shock absorber mounts;
10 - base hole;
11 - fastenings of the transverse rod;
12 - mating plane of the steering mechanism.
Polyester putty type «Chempropol-P» or PE-0085 form reliable connections with panels cleaned to metal. The temperature in the working room should not be below 18°C. The prepared polyester putty must be used in no more than 10 minutes. It finally hardens 60 minutes after application. The thickness of the putty layer on the treated surface of the panel should not exceed 2 mm.
The thermoplastic is available in powder form. Elastic properties necessary for applying it to the metal surface of the panel, it acquires at a temperature of 150-160°C. The surface to be filled must be thoroughly cleaned of rust, scale, old paint and other contaminants. Thermoplastic adhesion is better to rough metal surfaces. To apply thermoplastic, the area to be leveled is heated to 170-180°C and the first layer of powder is applied, which is rolled with a metal roller. Then a second layer is applied and so on until the roughness is filled. Each layer is rolled to obtain a monolithic layer of plastic mass. After curing, the thermoplastic is processed with a straightening saw.
Solders such as POSSu 18-2 or POSSu 25-2 are used to level areas previously filled with solder, build up the edges of parts and eliminate gaps.
In case of significant damage to body parts, they are replaced with new ones using electric arc welding in a shielding gas environment.