The glue coating process is a very important part of the manufacturing process of automotive body in white. Body coating not only improves the sealing and waterproof performance of the entire vehicle, enhances NVH performance to achieve vibration reduction and noise reduction, but also plays an important role in achieving automotive lightweighting, energy conservation, and consumption reduction.

With the development of manufacturing technology, sealant, as an essential auxiliary material in automobile production, is becoming increasingly widely used. Body coating not only improves the sealing and waterproof performance of the entire vehicle, enhances NVH performance to achieve vibration reduction and noise reduction, but also plays an important role in achieving automotive lightweighting, energy conservation, and consumption reduction. In the production process of automobiles, adhesive coating technology is applied in welding workshops, painting workshops, and final assembly workshops. Here, this article focuses on the classification, performance, and process characteristics of adhesives used in welding and coating workshops.

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.

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. The cross-sectional size of the folded edge adhesive is a semi-circular arc with a diameter of about 3mm, and the center of the semi-circular arc is about 2.5mm away from the inner surface boundary of the outer panel.
HY568 epoxy folding adhesive, solid content, is a single component modified epoxy resin adhesiveIt does not contain solvents, isocyanates, and does not flow when heated and cured. It has excellent oil resistance, water resistance, acid and alkali resistance, chemical resistance, good anti-corrosion performance, and good heat and moisture resistance. It can be used for folding the inner and outer panels of car doors, the junction of the cab floor, the cab top cover, trunk lid, side panels, wheel covers, engine hood and other folding parts, playing a role in bonding, sealing, shock absorption, and rust prevention.

Expansion adhesive

Expansion glue 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 and increase the comfort of the entire vehicle. When applying expansion adhesive, it is generally divided into strip-shaped expansion adhesive and point shaped expansion adhesive. The cross-sectional size of strip-shaped expansion adhesive is a semi-circular arc with a diameter of about 8mm, each segment is about 60-80mm long, and the interval between segments is about 40mm; The diameter of the dot shaped expansion adhesive is about 20mm (adjusted according to the distance between the plates), and the spacing between adjacent adhesive points is generally greater than 50mm.

Spot welding sealant

Spot welding sealant is mainly used for sealing the front, side, and floor panels to achieve waterproofing, dust prevention, and rust prevention, and to prevent dust from entering the joint area, as shown in Figure 2. The cross-sectional size of spot welding sealant is a semi-circular arc with a diameter of about 3mm, and the center of the circle is 7mm away from the boundary.

HY565PVC sealant has advantages such as solvent-free, isocyanate free, anti pollution after curing, green and environmentally friendly, excellent heat resistance and anti-aging ability. Suitable for sealing seams on car bodies, train carriages, ships, and other similar structures.


Vibration isolation glue

Vibration isolation glue is mainly used for door outer panels, side panel outer panels, and roof panels, with the main function of vibration reduction and improving the vehicle's NVH performance. The expansion rate range is 100% to 300%. The cross-sectional size of the vibration isolation adhesive is a circle with a diameter of about 6mm, and the adhesive is applied to the corresponding storage tank position.

HY561 vibration isolation sealant is a single component rubber modified polyvinyl chloride sealant, which is solvent-free, isocyanate free, anti pollution after curing, environmentally friendly, and has excellent heat resistance and anti-aging ability. Suitable for vibration isolation sealing of car bodies, train carriages, ships, etc.

Structural adhesive

Structural adhesive is mainly used for sealing connections between outer panel components and outer panel reinforcement components, replacing spot welding (no welding points or poor weldability are 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. The cross-sectional size of the structural adhesive is a circle with a diameter of about 3mm, and the adhesive is applied at a distance of about 7mm from the edge of the part, as shown in Figure 3.
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HY569 Toughened Structural Adhesive is a single component modified epoxy resin adhesive with solid content, no solvents, no isocyanates, and does not flow when heated and cured. It has excellent oil resistance, water resistance, acid and alkali resistance, chemical resistance, good anti-corrosion performance, and good heat and moisture resistance. It can be used for folding the inner and outer panels of car doors, the junction of the cab floor, the cab top cover, trunk lid, side panels, wheel covers, engine hood and other folding parts, playing a role in bonding, sealing, shock absorption, and rust prevention.

Constraint conditions for welding and adhesive coating

In order to ensure the quality of the adhesive coating, process constraints need to be proposed for the vehicle body at the beginning of the design.
 & nbsp; & nbsp; & nbsp; & nbsp;& nbsp; (1) When applying edge glue to the car body, in order to ensure the quality and space of the glue application, and to have good edge wrapping, there are the following requirements for the design of the edge wrapping (see Figure 4): d2≥ d1/2; d1≥ Glue width≥ d2。

(2) The location of the expansion adhesive coating should be clearly marked, and a sinking platform should be left at the adhesive point. At the same time, the coating form should be as similar as the spot welding form as possible, and grooves should be left at the adhesive strip.
(3) The direction of adhesive application requires that when applying adhesive to the vehicle body, it is not allowed to apply double-sided adhesive at the same position, only single-sided adhesive is allowed.

The purpose and performance of coating adhesive

There are three main types of adhesives used in the painting workshop: weld sealant, PVC anti stone impact coating, and cavity wax spraying& nbsp;.

Weld seam sealant

Weld seam sealant is mainly used for welding seams, overlaps, and holes and gaps that directly connect the inside and outside of the vehicle body between various sheet metal parts, to ensure the sealing of the vehicle body, prevent harmful substances such as water, gas, ash layer, and noise from entering the vehicle, improve the service life of the entire vehicle, enhance reliability, and NVH performance. The weld sealant in the invisible area after loading can be treated with a brush or scraper after the coating is completed to ensure sealing performance; For areas with appearance requirements, regular nozzles must be used to apply glue at designated positions, paying attention to covering gaps and holes. After gluing, it is not allowed to brush with a brush to ensure aesthetics. Weld seam glue must be used to fill the gap in the front floor process (see Figure 5).