In the manufacturing process of car body in white, body coating is a crucial step. Automotive adhesive coating can improve the sealing and waterproof performance of the entire vehicle, enhance NVH performance to achieve shock absorption and noise reduction, and also play an important role in achieving automotive lightweighting, energy conservation, and consumption reduction.
There are mainly five types of adhesives used in the welding workshop: edge glue, expansion glue, spot welding sealant, vibration isolation film, and structural glue. There are three main types of adhesives used in the painting workshop: weld sealant, PVC anti stone impact coating, and cavity wax spraying.
5 types of welding adhesives
1. Folding glue
Folding glue is mainly used for edging the exterior panels of car doors, engine hood, and trunk lid, replacing welding points to connect the inner and outer cover plates, avoiding dents caused by welding on the surface of the car body, and improving the appearance quality of the car body. As shown in Figure 1
2. Expansion adhesive
Expansion adhesive is mainly used between the inner and outer panels of the engine hood, trunk lid, top cover, and doors to reduce vibration and noise during driving, thereby increasing the comfort of the entire vehicle. When applying expansion adhesive, it is generally divided into strip expansion adhesive and dot expansion adhesive. As shown in Figure 1
3. Spot welding sealant
Spot welding sealant is mainly used for sealing the front, side, and floor panels to achieve waterproof, dustproof, and rust proof effects. It can also prevent dust and other impurities from entering the joint area, as shown in Figure 2.
4. Vibration isolation adhesive
Vibration isolation glue is mainly used for door outer panels, side panel outer panels, and roof panels, with the main function of shock absorption, used to improve the NVH performance of automobiles, and the expansion rate range is 100%~300%. Apply expansion glue to the corresponding storage tank position.
5. Structural adhesive
Structural adhesive is mainly used for sealing connections between outer panel components and outer panel reinforcement components, replacing spot welding (no spot welding or poor weldability is allowed on the surface of the outer panel), improving rigidity and sealing, and preventing water, dust, etc. from entering the interior of the vehicle body. Therefore, high bonding strength is required, as shown in Figure 3.
3 types of coating adhesives
1. Welding seam sealant
Weld sealant is mainly used in the welding seams, overlaps, and holes and gaps that directly connect the inside and outside of the vehicle body between the moving parts, to ensure the sealing of the vehicle body and achieve the purpose of dust, water, and noise prevention, thereby improving the service life, enhancing reliability, and NVH performance of the entire vehicle.
The welding sealant in the invisible area after loading can be treated with a brush or scraper after coating to ensure sealing performance; For areas with appearance requirements, regular nozzles must be used to apply glue at designated locations, paying attention to covering gaps and holes. After gluing, it is not allowed to apply with a brush to ensure aesthetics. Weld seam glue must be used to fill the gap in the front floor process, as shown in Figure 4.
2. PVC anti stone impact coating
PVC anti stone impact coating is mainly used for the lower surface of the floor and the front and rear wheel covers to prevent damage to the vehicle floor and wheel covers caused by stones during driving. In addition, it also has some anti-corrosion, waterproof, and sealing functions, as shown in Figure 5.
3. Cavity wax spraying
Wax for painting is mainly used to paint the cavity of the fixing point of the slider, mainly to cover the inner surface of the cavity sheet metal with wax, as shown in Figure 6, to ensure the corrosion resistance of the sheet metal inside the cavity, prevent substances such as water, gas, and dust from directly contacting the sheet metal, and improve the corrosion resistance of the entire vehicle.
The gluing process is a very important part of the manufacturing process of car body in white. With the improvement of manufacturing technology, the types, performance, and process specifications of car body gluing are constantly optimized and improved, and the gluing equipment is gradually updated and replaced.
At present, many foreign automobile manufacturing companies have adopted the method of robot coating to ensure stable and reliable coating quality, in order to meet the requirements of shock absorption, noise reduction, NVH, and rust prevention sealing of the vehicle body.
The future development direction of automobiles is energy conservation, environmental protection, and lightweighting, and the use of car body adhesives is also moving towards green, environmentally friendly, and energy-saving directions. Considering that most car body adhesives are fluid paste like substances that can easily pollute the environment, solid adhesives are gradually replacing fluid adhesives in car body applications, such as sealing strips, vibration isolation tapes, reinforcement films, structural films, and expansion blocks, which have been applied and promoted in some car companies.
