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Body Repairs - Cementing
"Cementing" means the bonding of similar or different materials with an anorganic or organic substance at room temperature or with moderate heating. The cementing process can be used on both metallic and non-metallic materials.
The costs of repair and maintenance for a vehicle contribute greatly to its attractiveness for the customer and therefore to its competitiveness.
Therefore, it is obvious that cost development must be constantly supervised, and that work methods that reduce costs be developed.
The cementing techniques developed by Opel to suit the requirements of body repairs are a logical consequence of the principle of taking modern technologies that have proved themselves to be useful and economical in other commercial fields (e.g. in the aerospace industry) and then making them practicable for the automobile industry.
The starting point for the development of the cementing technique was the frequency of comparatively expensive damage to the vehicle tail, which, for example, in the Federal Republic of Germany, occurs in a large percentage of all traffic accidents.
Using the previously employed repair method, welding in new sheet metal parts, an assortment of interior parts sensitive to fire and heat, e.g., inner trim panelling, seats, screens, fuel tank, etc., had to be removed. With the cementing method, removal and installation of these parts is, to a large extent, no longer required, which means a reduction in the amount of time required for the repair operations and therefore savings in cost.
The cementing technique has a series of advantages compared to the welding process:
The bond produced by cementing between the body and the new component is free of tension. No changes are made in the material jointing due to the effect of heat, as is the case with welding.
The bond is water-tight and does not corrode. Electrochemical corrosion between different materials is not possible.
The standard corrosion protection is completely unaffected.
The removal and installation of components sensitive to fire and heat required previously is no longer necessary, which leads to considerable savings in costs.
The cementing technique can be used universally. It can be used after a short period of instruction.
The cement bond is nowadays extremely reliable. A precondition for a stable bond which can tolerate the forces present in the bonded area is, besides exact observation of the processing instructions of the cement manufacturer, proper preparation and positioning of the joint surfaces and joining parts. The joint surfaces and joining parts must be laid out according to the anticipated demands and requirements.
The joint surfaces shape which has been proven itself to be the most efficient in bodyworking and in repairs is the offset overlap with tapered upper plate, which is the preferred method to be used.
The adhesion of the cement bond depends on the inner bonding force of the cement and of the bonding force between the cement layer and the surface of the parts being bonded. Therefore, as well as the specific properties of the cement, the condition of the surface of the parts being joined is also an important consideration.
Thorough cleaning of the joining parts in the area to be cemented is a precondition for a stable cemented bond.
Any grease and wax remains, oxide layers, rust, scales, paint and primer must be completely removed from the surfaces being cemented. For degreasing, only the solvent included in the "Cement" Repair Set - 90 114 718/15 04 800 - may be used.
IMPORTANT
Never use alcohol, benzine or paint thinner.
In areas where the new component cannot be fixed with clamps until the cement has hardened, Steel Flat-headed Blind Rivets type 4 x 8 mm/0.16 x 0.31 in., - 90 140 401/17 57 170 - must be used. The rivets transfer practically no force but serve only to hold the new component firmly in place while the cement is hardening.
The Two Component Cement - 90 114 718/15 04 800 - intended for cementing body components, is designed for the special requirements of body repairs and must only be used in the prescribed combination. It must never be replaced by or mixed with other unauthorized materials.
When using two component cement based on epoxy resin, observe the processing instructions and safety precautions of the manufacturer and the relevant regulations of the trade associations. When processing cementing materials, special safety precautions must be observed in order to avoid damage to health.
The same restrictions apply here as for paint materials.
Avoid direct skin contact to cements. Unhardened epoxy resin cement can induce iritations in sensitive skin.
If cement comes into contact with skin, wash immediately with warm water and soap. Then rub in skin protection creme. If cement spray gets into the eyes, wash out immediately with plenty of luke-warm water for 10 to 15 minutes. Contact an eye specialist.
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