How to identify the quality of plywood

How to identify the quality of plywood?

The quality of a piece of plywood directly affects its use and use value. Therefore, in order to achieve a unified understanding, it is necessary to check the quality of products according to the national standards. Plywood can be inspected from the following three aspects: board size, appearance quality and physical and mechanical properties.

1、 Dimension: check whether the thickness, length and width, two diagonals and warpage of the plate meet the national requirements, especially the length and width. The dimension can only have positive tolerance and negative tolerance is not allowed.

2、 Appearance quality: according to the national standard, ordinary plywood is divided into four grades according to material defects and processing defects: special grade, first grade, second grade and third grade. The last three grades are the main grades of ordinary plywood. Each grade is determined by visual inspection according to the allowable defects on the panel, and the allowable defects and processing defects of the back plate and inner veneer are limited.

3、 Physical and mechanical properties. According to the national standard, water content and bonding strength are the two most important items. According to the national standard, the moisture content of resin adhesive should be controlled in the range of 6-14%, and the bonding strength should be controlled in the range of 0.7-0.8 MPa.

When inspecting the defects, some defects will affect the appearance, such as loose joints, cracks, decay, patches, edge defects, etc. according to the number of defects, as long as it is within the scope of the standard, it is just a product degradation. However, some defects, such as blistering, delamination, which directly affect the strength of the product, are not allowed in any grade. Some bubbling and delamination, if the area range is large, it is easy to observe by visual inspection, but if the area range is small, it is difficult to observe, you can use a small wooden stick to knock at any place on the board. If the echo of the board is clear and loud, it can be judged that there is no bubble or stratification. If the echo is heavy or hoarse, it indicates that there is bubbling or stratification.

Therefore, the quality of plywood must be judged from the above three aspects.

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