Cold and hot pressing in plywood production

The production process of plywood refers to the process from the log entering the factory to the finished product leaving the factory. Due to the different production methods of plywood, the processes experienced are also different, and the production process is slightly different.

The manufacturing method of plywood can be divided into the cold pressing method and the hot pressing method.

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Among them, cold pressing refers to pre-pressing. After the veneer is paved, it will be pre-pressed first, so that the veneers in each layer of the slab are bonded to each other to achieve the effect of a firm slab and flat surface, which is convenient for hot pressing. Plate loading is suitable for mechanical loading and unloading without a backing plate or manual loading and unloading of slabs because it can be carried out at room temperature, so it is called cold pressing.

The cold-pressed slabs are further repaired and hot-pressed after the repairs are complete. Hot pressing is to cure the adhesive so that the bonding strength between the veneers meets the standard requirements. It can be said to be the most critical link in the production of plywood. The temperature, time, and pressure need to be strictly controlled.

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Generally speaking, the hot-pressing temperature of melamine-modified phenolic resin adhesive is about 110 degrees, and the hot-pressing temperature of phenolic resin adhesive is about 130 degrees. If the temperature is too high, it will cause bubbles, and if the temperature is too low, it will cause adhesive Adhesive is not cured enough.

According to different substrates, the hot pressing pressure is generally between 0.8-1.5 MPa, and the hot pressing time is about one minute. Of course, due to different uses, the process flow and equipment parameters of different board types will have certain differences.

In addition, some people think that the so-called two-time forming of the plate means that it goes through a cold press first, and then a hot press. This is wrong.

The two moldings of plywood refer to hot pressing, one hot pressing is one molding, and two hot pressings are two moldings. Whether it is one-time molding or two-time molding, there is a pre-process of cold pressing.

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