Hem flange bonding

For some fast applications such as on automotive production lines, for windshield application or hem flange bonding, the flow rate may be quite high several litres per minute we have discussed in Table 2 how to compute the flow rate according to the pump ratio. 

Typical Use Automotive (hem-flange). Bonding of body panels (together with spot-welding). Good adhesion to oily steel (2 - 3 g.m-. ... 

One-component epoxy adhesives can be formulated using DiCy as the hardener. DiCy is called a latent hardener because it is insoluble in epoxies at ambient temperatures and becomes soluble and active only if the systems are heated. These types of epoxies have become widely used in the automotive industry, for example, in hem-flange bonding. 

Authors from 3M [14] described the testing of two epoxy adhesives for aluminium designed for hem flange bonding and panel bonding. These adhesives showed outstanding sustained load durability in cyclic corrosion tests even if stressed to 40% of their initial shear strengths. 

This application covers adhesive bonding of the hem flange for automotive doors. For hem flange bonding the door is made up of an inner skin and an outer skin. The inner skin mounts the lock and window mechanisms as well as the various trim pieces, hinges and crash bar while the outer skin provides design contour and accepts the color coat of paint. 

The process of building door assemblies requires the application of a structural adhesive to the outer door panel. The next step in the assembly of doors is the joining of the inner and outer panels. Finally, a hemming die is used to turn a small section of the outer panel over the inner panel to form a hem. Accurate bead placement and uniform material deposition are critical to achieve a structural bond. These requirements, combined with high production speeds, make hem flange bonding well suited for robotic automation. Fig. 11 depicts the entire door assembly line process complete with hemming die and induction cure fixture. The induction cure fixture applies localized... 

Typical uses of adhesives in the body shop are hem flange bonding, anti-flutter bonding, and hybrid joining. 

On top of these general requirements, adhesives need additional very specific profiles depending on if they are used for bonding of the structure, for anti-flutter bonding, or for hem flange bonding. 

Bonding of hem flanges is now practiced for more than 30 years. At the beginning the reason was more corrosion protection than increase in stiffness. Meanwhile, the hem flange bonding contributes to the structural stiffness of hoods. And it is an important element for the resistance of the doors against side impact. The adhesive prevents the inner door panel with the reinforcement bar to slip out of the hem flange upon impact. 

Acrylic adhesives can also be used in automotive assembly. For example, the hem flanges between the inner and outer panel of automotive doors can be bonded with acrylic adhesives [153]. There are many smaller industrial assembly applications where acrylic adhesives are applicable. An interesting recent example is the bonding of cable splice enclosures, using a borane initiated adhesive [154]. 

In addition to the preforms and pellets mentioned in Section II.A.l.c., there are other forms of solid adhesives that have much versatility of use. Films and tapes have long been used in the manufacture of bonded flat structures. In particular, the aerospace industry has used a wide variety of film adhesives. In general, these products are handled manually. Occasionally such equipment as tape dispensers are used as assists to manual applications. Work is presently in progress to develop an automatic device to apply strips of film adhesive to automobile hoods. This device will be a curve-following robot that will place the adhesive in the hemming flange around the outer edge of the hood. 

Hem flange adhesives based on epoxies and other adhesives to bond sound deadeners or other panels (see Fig. 32). 

Sealers play an important role in automobile corrosion protection by preventing water and contaminants from entering crevices and joints. They are usually rubber, vinyl, asphaltic, or hot melt or wax compounds [24,25]. The choice depends on the specific application such as at door hem flanges, brackets, fasteners, and body joints. Structural adhesives are also used to bond assemblies such as doors, deckUds, and hoods, thereby sealing crevices and eliminating welds. 

Typical Use Automotive (hem-flange structural bonds). Bonding of Typical Use Automotive. ... 

Typical Use Automotive, bonding of body panels (hem flange seams). Typical Use Magnetic rubber bonding. ... 

Hershey drops of plastisol adhesive are used in the assembly of hood inner and outer panels. The outer panel is often hem flanged around the periphery of the inner panel to immobilize the parts until they cure in the paint oven. Modem plastisols are able to absorb thin films of oil from the metal as they cure. This ability to bond through oil is of immense value in an industry where thorough cleaning before assembly is traditionally a problem. 

What is the real strength required for structural bonding This central question cannot be answered in a simple way. The most important property is not the lap shear strength but the G-modulus or E-modulus, which can be used in calculations for the stiffness of a bonded structure. The bonding of a sun roof lid gives an idea about this effect. In this example, the lid is bent as shown in O Pig. 46.7 with a force of up to 500 N, and depending on the modulus of the anti-flutter and hem flange adhesive, the deformation is measured and calculated. 

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