The basics of assembly

In automotive assembly, vehicles are equipped with a wide variety of profile seals. The profile seal is not only used for cosmetic purposes and must meet a range of requirements.

Requirements for the profile seal:

• Cover the sheet metal flanges of the vehicle body

• Conceal transitions between cladding and sheet metal flange

• Protect the vehicle from water ingress

• Keep dust out of the vehicle interior

• Keep driving noise away from the occupant

In order to give the seals a firm hold on the sheet metal flange later on, they contain a strength support (also known as a scaffolding strap) as the base body. This usually consists of a bent expanded metal sheet strip or a meander-shaped bent spring wire with fabric reinforcement. The strength support influences the flexible and elastic behavior of the profile seal on the vehicle. It is usually made of aluminum or steel.

During the production of these profile seals, the strength support is pre-bent into a V-shape. This allows the raw rubber to be injected very close to the contour of this strength support during extrusion. Special extrusion tools then bring several rubber materials together under high pressure and shape them into the desired form.

A thread, e.g. made of cord, is integrated during production to prevent significant elongation of the seal. Depending on the desired properties, final coatings are applied, e.g. with fabric or anti-friction coating. In addition, a sealing compound is often injected into the base of the mounting area, also known as the clamping area. This is also intended to ensure that no water can get into the vehicle interior.

The individual elements of a profile seal are newly developed for each vehicle type and the design and function are adapted to the desired use.

Due to the diversity of vehicles on today's automotive market, a wide variety of designs are available, such as:

• Seals with sponge rubber lips

• Anti-friction coated seals

• Flock-coated areas

• etc.

Car bodies are assembled from many individual sheet metal parts. At the joints, several sheet metal parts are often joined using different joining methods such as gluing or spot and laser welding. This results in different sheet thicknesses and transitions between the sheets. The resulting sheet metal flange can vary greatly in thickness. This must be compensated for by the seal and places the highest demands on the profile seal.

In contrast to roll forming, the strength support for hammer assembly is delivered without a bending angle. The seal is already in the closed U-shape. A great deal of force is also required to place the seal on the sheet metal flange using a hammer. The hammer blows irreparably damage the profile seal! The impact marks from the discontinuous hammer assembly process remain visible from the outside.

The strength support is deformed at the impact marks, causing the seal to form a V-shape with thick sheet metal flanges and with thin sheet metal flanges the clamping lips do not lie close enough to the sheet metal. This results in a reduced holding force of the profile seal. The clamping foot of the profile seal will not sit on the flange as far as it can go at the inner radii of the vehicle body, which will result in leaks. Subsequent reworking, e.g. using roll forming, will be necessary.