The windshield, the rear window and some side windows are attached to the body using adhesive. Glued joints are relatively simple to make, provided the right products are used and the gluing instructions marked by the manufacturer are followed. Aspects like the cleaning and the preparation of the surfaces are vital to guarantee a correct paste.
The breaking of the moons, mainly of the windshield is one of the most frequent accidents that the vehicles suffer. The impact of objects in this frontal moon or the stresses generated in the event of a collision, causes the breaking of these pieces made of glass, a relatively fragile material, but necessary in the design of the vehicles.
The glass used in manufacturing has undergone considerable technological development since its inception, increasing the size of glazed surfaces in vehicles and also the number of functionalities incorporated into them.
In the case of windshields, its main function is to guarantee visibility through it, protecting the occupants from the impact of objects, dust, wind, rain or other atmospheric elements. In addition, thanks to the adhesive bonding system, it has become part of the sturdy structure of the body, improving the rigidity of the passenger compartment.
On the basis of the functionalities or services provided by the moons we can talk about different types: tinted and sun-control moons reducing the incoming solar energy in the cabin, anti- icing and anti-fog heater, hydrophobic rain repellent, Solar antireflection layer, which incorporate antennas silkscreened, reducing acoustic sound and outer panes with supports such as light and activation of the wipers.
The latest technological advances related to windshields have been the Head-Up Display (HUD) systems that project information to the driver on the surface of the windshield and the installation of video cameras and sensors of the systems of assistance to the driving through Factory pre – assembled supports on its surface.
For all these functionalities, today the windshield is considered as one more element of the active and passive safety of the vehicle, having to pay special attention to the process of its installation to avoid adhesion failures or the systems incorporated to them and in this way to restore the Levels of safety.
In the process of installing a glued moon, two of the most important aspects are the products used and their correct application. These products are supplied on the market in the form of individual kits for a single application or separately in large quantities containers directed to the specific moons workshops.
As adhesive, specific polyurethanes are used, with appropriate technical characteristics to ensure the connection between the glass and the body. These polyurethanes possess the mechanical strength sufficient to withstand impacts, and the stiffness necessary to form part of the structure of the vehicle. The joint must have some flexibility to absorb the stresses generated during the usual displacement of the vehicle. A too rigid or too elastic joint can result in a decrease in the passive safety of the vehicle.
The polyurethanes used in the gluing of moons in vehicles, have specific characteristics to guarantee the adhesion.
Other products whose use is essential are the preparation of gluing surfaces, cleaners, activators and primers, used to promote and ensure a good adhesion between the different surfaces. In any bonded joint, the correct cleaning of the surfaces (body frame and glass) is essential, so that there is no dirt, oils or particles that prevent the adhesive from contacting the surfaces to be joined. To achieve the adhesion of the adhesive used (polyurethane) to the glass and sheet surfaces, primers or activators whose function is to facilitate and promote adhesion on these substrates are applied.
Adhesive bonding of the windows to the body improves the rigidity of the passenger compartment.
The first operation to be performed in the installation of a glued moon is to separate the moon from the body by cutting the adhesive that holds it together. Cutting machines and steel cables can be used for this operation. It is important to pay attention to the cut so as not to damage the paint on the body frame. In the forms the frame with the edge of the moon accumulates easily dirt and moisture, factors that favor the oxidation of the sheet. For this reason, any scratches on the paint must be protected. The manufacturers usually indicate the application of some of their products of the kit for this situation, usually it is usually the black primer. If it is the case that we find a surface of bare plate too large, it will have to perform the usual process of painting.
The bonding surfaces will then be prepared to achieve a good adhesion of the glass to the body by applying the intermediates (cleaners, activators, primers). Depending on the nature of the surface that we find, we will apply the preparation product indicated by the manufacturer. The surfaces to be treated will be: bare or painted veneer, remnants of the old adhesive and glass.
Glass and sheet metal surfaces should be cleaned properly with the cleaning agent. The next step is to activate or prime these surfaces to promote adhesion to them. Some manufacturers have products that combine several functions (cleaning, activation, and priming) at the same time, so always follow the instructions given by the manufacturer of the products, since the application process can vary from manufacturer to manufacturer.
In the case of polyurethane debris remaining in the body, the usual instruction of the manufacturers is to trim the old adhesive remains leaving a base of 1-2 mm where the new polyurethane will be applied. In this case there is a freshly cut clean base where the new polyurethane with old polyurethane will adhere without problem. If there is a long time between the cut and the time of application of the adhesive, a cleaning or activation of the polyurethane debris must be carried out with the suitable product. This instruction is valid provided that the old adhesive is a polyurethane of moons and that the base is well adhered, if not all the remnants of adhesive must be removed and a new complete cord is added.
To avoid glue failure of the bodywork, it is vital to follow the bonding instructions of the manufacturer of the products used.
Once the surfaces are prepared and the indicated drying times are expected, the adhesive is applied to the frame of the bodywork or to the windshield, then the moon is placed in the frame without pressing too much in order not to diminish the resistant section of the cord, and Keeps the drying time necessary for the adhesive to cure and to acquire adequate resistance, allowing a safe driving under safe conditions, without risk to the windshield falling or falling. Regarding the application of the cord, it should have a triangular shape, be applied regularly and continuously, avoiding cuts in its application since they present a risk for water ingress.
The installation procedure of a glued moon is a simple job, however the professional must know exactly the work process to follow, use a suitable products, and be very rigorous in the preparation phase of the gluing surfaces. The correct adhesion of the moon depends fundamentally on this operation, so it must be done with great care. It should not be forgotten that the windshield is now considered an element of vehicle safety.