How many sheets of veneer in plywood
Finished plywood is significantly influenced by the veneer itself, selected by the features of the future product. The quality of this product will depend on the quality of plywood, determined by grade. But above all, veneer, or rather its quantity, is the determining factor for the thickness of a given building and production material. In accordance with GOST for the manufacture of plywood slabs, the minimum pure veneer sheets should be 3, since it is customary to perform in an odd number of them.
According to GOST 3916.1-96, the nominal thicknesses and layers for general-purpose plywood slabs with hardwood external veneer are listed in the appropriate table. For example, the most common options have the following relationship: 3-3, 4-3, 12-9, 18-13, 21-15, 30-21. Intermediate options can be set by analogy. Moreover, the presence or absence of grinding treatment does not affect the result. Laying sheets also has a certain order.Thus, the laying of the central element is performed by directing the fibers along the length of the sheet, and applied to it - across. The follow-ups are put along again, and the process is repeated until the desired value is reached. In this case, the outer layers will always have the same direction. Such structural features set plywood plates with flexural and tensile strength in a single value over the entire plane.
What affects the amount of veneer in plywood
Each brand of plywood has its own distinctive features, characterized by many values, which include the number of veneer. The most influential factors on this parameter are:
finished product thickness;
thickness of the veneered sheets;
a layer of glue;
The percentage of pressing during the gluing of plywood.
By type of wood and method of producing veneer, its sheets are made of different thickness. Thus, for peeled, the characteristic is 0.1-10 mm, for sawn - 1-10 mm, for planed - 0.2-5 mm. At the same time, smaller values are typical for hardwood, and coniferous veneer variants are made thicker.For example, birch veneer rarely perform more than 1 mm, and pine for building thick plywood - up to 4 mm. The effect of glue on the number of sheets directly depends on the pressure used in the assembly of the press. The stronger the pressure, the more evenly and thinner the layer will be, which is partially absorbed into the wood in a hot press. The loss of thickness during pressing during gluing for plywood marks has the following figures in%:
Plywood FC, which has a common or export value - 7%;
FBA, private or export value - 9%;
FSF of general purpose, as well as BS-1, BPS-1B, BP-A and BP-B - 12%;
Decorative plywood boards DF-1 and DV-2 - 15%;
Bakelised - 25%.
The effect of the number of veneer sheets on the characteristics of plywood
The total number of veneer sets the plywood slab a set of characteristics and, therefore, determines future use. So, thinner plates containing 3-7 interlayers of birch veneer. With good strength, they have the highest rates of flexibility. Therefore, they are used in plating and decorative products. This thickness and easier to handle hand tools, such as a jigsaw on the lessons of labor.With a set of thickness, flexibility is lost, but the overall resistance to mechanical loads increases, as well as the quality of sound and heat insulation.
The influence on the characteristics is significantly exerted by the amount of glue mass, the density of application is directly related to the number of layers of plywood material. Therefore, these features are also taken into account when choosing a plywood slab with the required thickness.
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