In modern wooden furniture factories, many woodworking activities such as eye-catching and planing are replaced by machines, but the grinding process is still done by hand. Different parts and processes require different grinding tools. Workers use different tools to make furniture parts. Polished. The importance that furniture manufacturers attach to the polishing of furniture before painting can be seen.
The aesthetics of the furniture surface depends to a large extent on the quality of the sanding. Everyone knows that nowadays, whether it is a solid wood enterprise or a panel furniture enterprise, the most work and the largest number of workers, the most concentrated is the polishing workshop, and the most problematic is the polishing workshop. It is not too much to say that the human sea tactics. Due to the particularity and difference of the materials themselves, as well as the differences in the shape and shape of the processed parts, coupled with the limited processing functions and cost considerations of the sanding equipment, it has not completely replaced the manual. Sanding method.
First, polishing directly affects the coating effect
1. Sand off the burrs, floating rust, oil stains, dust, etc. on the surface of the substrate;
2. Reduce the roughness of the painted surface of the workpiece. For example, after the surface of the putty is dried, the surface is rough and uneven, and it is necessary to obtain a smooth surface by sanding;
3. Enhance the adhesion of the coating. The coating has poor adhesion on smooth surfaces and enhances the mechanical adhesion of the coating after sanding.
It can be seen that sanding is one of the important tasks to improve the coating effect. During the whole process of painting the object, not only the white blank and the bottoming putty stage need to be polished, but also the primer and the brush finish should be polished. It is the key process and important guarantee for the excellent surface effect and strength of the paint.
Second, polishing skills
1. Reasonable selection of sandpaper with different thickness: a. should not be too thick, should not use too much model; b. should not jump sand (refer to the model of sandpaper), jump from 200# to 600# or 800#.
2, polished in the sand, no vertical and horizontal grinding, otherwise the wood will crack, the furniture will leave a permanent flaw.
3. Where the corners and edges of the polished objects are not sanded, the movements should be light, and the original circular or square outline must be maintained. The decorative line must be kept straight and cannot be bent, broken or deformed.
4. When grinding, generally use four fingers and palms to hold down, and thumb to clamp the sandpaper. When sanding a large area of â€‹â€‹furniture, the wooden strips can be polished along the wood grain.
5, while grinding the edge of the brush, because the sand of the sandpaper is easy to fall off, rubbing the surface has the possibility of grinding the wood grain. In addition, the dust that has been polished is easily embedded in the eye. Therefore, it is necessary to brush the dust with a dry brush at any time while grinding, and then brush it until the surface is smooth and smooth.
6. When there are bumps and scratches on the plate, you should first use hot water to iron the iron. After heating, try to restore the original plane and then sand. If the sandpaper is pressed with the thumb, forefinger and middle thumb, it is only limited to the sand part, and it is not suitable for the large-area workpiece of the sand. Otherwise, the whole plane sand will be uneven, and the concave phenomenon can be seen after painting. It is.
7. For the outer arc type and inner bow type plate, it is necessary to use the template (and the template with the same shape and shape of the plate to polish the sandpaper on the template), such as electric or pneumatic small sanding machine. The shape of the plate should be polished to prevent the sand from forming a step.
Third, the method of polishing
1. Dry grinding:
Sanding with sandpaper. It is suitable for the grinding of hard and brittle paints. The disadvantage is that a lot of dust will be generated during the operation, which will affect the environmental sanitation.
2, wet grinding:
Grind with water sandpaper or soapy water. Water mill can reduce wear scars, improve the smoothness of the coating, and save sandpaper and labor.
It should be noted that after the water mill should pay attention to spraying the lower layer, one must wait until the water-grinding layer is completely dry before applying the layer paint, otherwise the paint layer is easy to whiten. Another substrate with a strong water absorption is not suitable for water grinding.
3. Mechanical polishing:
In large-area construction, in order to improve work efficiency, mechanical grinding methods such as electric grinding machines (disc type, vibrating type) can be used.
4, light grinding:
In addition to the above three common grinding methods, there is also a kind of sanding that requires the coating to be â€œlightly groundâ€. For example, after sealing paint, old paint film, partial repair, etc., fine sandpaper should be used at this time. And hands-on, and practically "light grinding." However, it is counterproductive.
Fourth, the importance of sanding sandpaper
1, the choice of sandpaper
(1) solid wood blank
Grinding selection of 180#â€”â€”240# sandpaper
(2) Splint or a polished
Use 220#â€”â€”240# sandpaper
(3) Polishing of the primer
Use 320#â€”â€”400# sandpaper
(4) The last primer or sanding
Use 600#â€”â€”800# sandpaper
(5) Topcoat polishing and polishing
Use 1500#â€”â€”2000# sandpaper
2, the use of sandpaper
When sanding paper is used manually, the whole sandpaper is generally cut into four pieces. After each piece is folded, the two ends are clamped with the thumb and the little finger. In addition, the three fingers are flattened on the sandpaper and sanded on the surface of the object.
According to the sanding object, it can be changed at any time, and the holes in the fingers and the expansion and contraction of the fingers are used, and the concave and convex areas and the corners are mechanically polished.
In large-area sanding, it is necessary to master the principle of â€œbeing highâ€, apply the palm to rotate the sandpaper, or attach a slightly hard rubber such as sponge or cork block, and pinch the left and right end faces with the thumb and forefinger to level the sand. mill.
The length of the sander must be moderate and should avoid hurting the fingers during operation.
3. Causes and solutions for sand marks
Counter-grain grinding; grinding with coarse sandpaper; polishing the film without drying; using too slow drying solvent, the film can not be dried for a certain period of time; the upper film is too thin; after cleaning, it is not thoroughly cleaned, the paint is impenetrable; When the sandpaper is used, the surface is retained by the paint powder, and a certain part has no sanding function, which will form a moving trace.
a. Select the most suitable sandpaper, generally the sandpaper used for the first grinding is thicker, the sandpaper used for the second grinding is finer, and the sand marks of the upper layer should be worn away;
b. Grinding should be done in the direction of wood grain according to the direction of wood grain;
c. The paint film should be sanded after drying and the dust paint powder should be removed;
d. After using the sandpaper for a period of time, check whether the powder is retained and replaced.
e. Appropriately adjust the viscosity of the paint and grasp the thickness of the paint spray to cover the sand marks.
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