The rapid growth of China's economy, the influx of fast-growing and high-yielding forest wood, and the continuous replenishment of high-quality broad-leaved wood abroad have prompted the rapid development of China's plywood industry. There are also many China Wood Cutting Machine Suppliers. Plywood is one of the commonly used materials for furniture, which can be used for aircraft, ships, trains, automobiles and packing boxes. Generally, in order to ensure the quality of plywood, people use electric steam generators to hot-press the plywood. At present, China is not only a major exporter of plywood, but also the largest plywood producer in the world. Faced with the uneven quality of plywood in the Chinese market, many small and medium-sized enterprises cannot effectively control the problems arising in the production of plywood due to lack of production experience.
First, let's briefly review the production process of plywood. The process flow of plywood production mainly includes glue coating, blank assembly, hot and cold pressing, plywood, edge trimming, sanding and other procedures. Plywood production follows two basic principles, one is the principle of symmetry and the other is the principle of verticality. Because manufacturers can not effectively prevent and solve the plywood quality defects that occur in the production process, resulting in uneven plywood quality.
1. Hot pressing defect of plywood
Hot Press Machine too fast depressurization speed or high hot pressing temperature will cause plywood bubbling and local degumming; if the pressure is insufficient, the temperature is too low, and the hot pressing time is too short, it will lead to low glue strength or degumming; too high temperature and pressure Will warp plywood, glue through and so on. Therefore, in the plywood production process, the quality of the plywood is determined by the quality of the hot pressing process. The use of electric steam generators can accurately control temperature and pressure.
Hot Press Machine
2. Structural defects
Structural defects refer to the failure of the content integrity and reasonable arrangement of the internal and external structures of the plywood, which mainly include warpage of the plywood, core stacking, seams and corner defects.
(1) The moisture content of the veneer after drying is strictly controlled within the range of 8% to 14%.
(2) Pay attention to apply evenly when glue is applied, neither leave blank spots or glue accumulation, and clean up the debris on the surface of the board.
3. Appearance defect
Appearance defects refer to defects that can be perceived by the hand of the eye on the surface of the plywood, including defects such as translucent, uneven, indentation and discoloration.
4. Glue defects
Permeability refers to the defect that the adhesive penetrates into the surface of the plywood through the surface plate and causes the surface pollution. Aiming at the glue defect, a high-quality veneer should be selected, and a "one-sheet-one-press" hot-pressing process should be adopted to correct the press installation to a horizontal level to correctly calculate and adjust the hot-pressing pressure. This defect should be carefully checked for any debris on the hot-pressing pad and the surface plate when closing the board and hot-pressing the board. If any foreign matter is found, clear it in time.
5. Exceeding formaldehyde release
The free aldehyde released in plywood exceeds the national standard limit, that is, the formaldehyde release exceeds the standard. This is a very headache in the production of plywood. Once the formaldehyde release exceeds the standard, it is difficult to have a remedy. Generally, the formaldehyde content of the adhesive used exceeds the standard and the sizing amount is too large. The uneven coating will cause the formaldehyde release to exceed the standard.
The above is the Hot Press Machine Supplier introduced the common defects and countermeasures in plywood production from several aspects. During the production process, the possible problems should be prevented in advance, and I hope to help everyone.