structure
Single-layer hot press generally consists of frame, upper beam, lower beam, hydraulic cylinder, hot pressing plate, hydraulic system and heating device (see figure). ① The frame is an important part to bear the load of the whole press, and it must have sufficient strength and rigidity. Generally, frames can be divided into two types: frame type and column type. Frame frame is made of steel plate or section steel. It can be a single frame plate with connectors and bolts connected in series, or it can be a box frame welded with steel plates or sections. Column frame consists of circular columns, upper and lower beams fixed by nuts, and can also be welded into columns with steel plates. Upright column is the main supporting part and stress-bearing part of vertical press, which is generally forged steel. (2) The upper and lower crossbeams are parts for fixing the hot pressing plate, and bear the pressure per unit area when pressing the product. When the press is closed from bottom to top, the lower beam must be movable. If the press is closed from top to bottom, the upper beam must be movable. Generally speaking, the stress condition of movable beam is not as good as that of fixed beam. Therefore, the structural size of the movable beam is larger than that of the fixed beam. Because the hot pressing plate is fixed on the beam, the beam not only bears the load of the press, but also bears the thermal influence of the hot pressing plate. (3) Hydraulic cylinder is the executive mechanism of pressing products by single-layer hot press, and it is an energy conversion device. The potential energy of liquid pressure from the hydraulic system is converted into kinetic energy of the plunger through the hydraulic cylinder, which is transmitted to the movable beam, so that the upper and lower beams are closed, and the purpose of exerting pressure on the product is achieved. If the single-layer hot press is up-pressing, it is necessary to set up a lifting cylinder to lift the movable beam after pressing the product. (4) The hot pressing plate receives the heat from the heating system and transfers it to the product, which is the heat transfer device of the hot pressing machine. At the same time, it distributes the pressure exerted by the hydraulic cylinder evenly to the product through the movable beam. The heat transfer performance, heating uniformity, heat capacity, strength and stiffness of hot-pressed plate, as well as the flatness and roughness of hot-pressed plate surface directly affect the quality of products. ⑤ The hydraulic system is a device that generates pressure potential energy for the press. According to the technological requirements of product pressing, it controls the closing, boosting, pressurizing, maintaining pressure, relieving pressure and opening of the press. Generally, it consists of motor, oil pump, accumulator, various hydraulic valves and control instruments. The pressure medium in hydraulic system usually includes hydraulic oil, mechanical oil and emulsion. Pumps and valves with different performances should be selected for different media. The performance of hydraulic system not only determines the output and tonnage of press, but also directly affects the quality of pressed products. ⑥ The heating device is the heat source of the hot-pressing plate. The heating device used in artificial board and its surface treatment is usually determined by heat transfer medium. When steam is used as heat transfer medium, steam pipe network and boiler are heating devices; When hot water is used as a heating medium, the hot water circulation system is a heating device; When electricity is used as the heating medium, the electric heating system is the heating device; When heat transfer oil is used as heating medium, the heat transfer oil heating circulation system is a heating device. Heat transfer oil can be heated by steam and electric heating, or by a special heat transfer oil heating furnace.
type
Single-layer hot press can be divided into single-layer hot press for manufacturing wood-based panels and hot press for surface processing of wood-based panels. ① The width of single-layer hot press used for wood-based panel manufacturing is generally large, which is an integer multiple of 1220mm× 2440mm. The larger the format, the higher the output, but the higher the requirements for the frame, hot pressing plate, cross beam and hydraulic system, so the format of single-layer hot press should not be increased too much. Because of the large format of this kind of press, the uniformity of gross tonnage and heating temperature is required. ② The width of single-layer hot press for surface processing is generally small, which is generally 2-4 times that of 1220mm× 2440mm. Compared with the single-layer hot press for manufacturing wood-based panels, its gross tonnage, unit pressure and heating temperature are lower (pressure 0.3-3mpa, temperature 130-200℃), but it is more sensitive to the requirements of hydraulic system. Because of the small unit pressure, the single-layer hot press for processing the surface of small man-made board sometimes makes the hot pressing plate and the cross beam into a whole, that is, both the cross beam and the hot pressing plate. This can save steel and reduce the weight of the press itself.
Single-layer hot press can be divided into two types: upward-pressing single-layer hot press and downward-pressing single-layer hot press. (1) The movable cross beam of the single-layer hot press with upward pressure is the upper beam. The hydraulic cylinder is installed above the movable beam. Because the lower beam of this press is fixed and the working height is fixed, the auxiliary equipment matched with the press is easy to cooperate with it. However, in order to raise the movable beam again, a lifting hydraulic cylinder must be equipped. (2) The movable beam of the single-layer hot press is the lower beam. The hydraulic cylinder is installed below the movable beam. Because the reset of the lower beam depends on the self-weight of the hydraulic cylinder plunger and the self-weight of the lower beam, it is generally not necessary to equip the reset hydraulic cylinder. However, it takes a lot of energy to close quickly.
With the development of wood-based panel industry and the progress of science and technology, the upper and lower beams and hot pressing plates of single-layer hot press are gradually replaced by continuous running steel belts; Intermittent pressurization gradually developed into continuous pressurization; The heating mode has gradually developed into high-frequency heating, which makes the efficiency and quality of wood-based panels and their surface processing develop in a higher direction.