In sectors dedicated to the restoration / repair of cars and commercial vehicles, the sanding process occupy approximately 65% of the time spent during the entire process of preparation and paint application, for this reason it is necessary to know the type of sandpaper, sander and suitable process in order to optimize and achieve high quality on the workpiece.
The sanding operation is used in the field of paint in order to perform any of the following functions:
Removal of material.
Preparation of surfaces (adhesion promoter).
Smoothing and surface embellishment.
Reparation of defects.
The base material used in the sanding process is the sandpaper; the operation can be performed manually or in an automated way by using sanding machines called as sanders.
Manual or hand sanding is the oldest known method of sanding used, due the advantages offered by the sanders, manual sanding only uses when the machine cannot be used, such as sanding small and hard surfaces access, etc...
Prior to the sanding operation always is necessary clean and / or degrease the surface on which will proceed to work in order to prevent possible external contaminants embedded into the surface and produce adhesion defects and failures in future layers coatings.
Hand sanding operation consists in rubbing the surface until achieve plans magnitude, roughness or particle elimination desired. During the manual process it requires that the sanding occurs always in one direction and without pressure on the surface, in order to avoid marking and extend the life of the sandpaper.
The hand sanding can be done using 2 techniques:
Water sanding or wet sanding
Water or wet sanding is done by immersing the sandpaper in a bucket of water; once the sandpaper is wet we can proceed to sand. The main advantage of wet sanding is the fact that it produces less dust, longer life of the sandpaper and allows obtain a smooth surface compared with dry sanding.
The main disadvantage of the wet sanding lies in the need to remove residual water of the surface on which contains humidity, in order not to affect the next layers of paints.
Dry sanding is applied directly on the surface, this type of sanding causes excessive dust resulting abrasive action of the grain on the surface, this dust is transported through the air and deposited in adjacent areas where it is working, so it is necessary isolate the work area to avoid some of the dust that is deposited on freshly painted workpieces, avoiding costly rework.
On the other side is necessary the use of protective equipment such as goggles and breathing masks, to prevent entry of dust into our bodies.
Automatic sanding is done by sanding machines called as sanders, this type of tool allows reproduce the same movements and the same effect if realizes manual or hand sanding in an efficient and effective way, greatly reducing the effort and time of work compared to hand sanding.
The main disadvantage is that sanders not arrive well in difficult areas or edges, where it is necessary sand by hand.
Sanders have specifically holes designed to absorb all the dust that is generated during its use, collecting and depositing in specific zones for subsequent removal, which will improve the environment, extend the life of the sandpaper and improve the quality of work.
Finally, and regardless of sanding system chosen, it is important to remind than ever before starting sanding work should:
Clean and / or degrease the surface.
Select the properly sandpaper (more or less abrasive) that fits to the work.
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