Heating System of Hot Press
(1) The comparison of heating modes affects the selection of temperature, process control and the quality of processed products. The traditional heating methods are steam heating and electric heating. Steam heating is fast, but it needs to be equipped with pressure boilers, high pipeline pressure,.
_ The advantages of heat conducting oil heating are: high heat capacity, uniform temperature, high temperature can be heated under atmospheric pressure, low heat loss, and can reduce production costs. The disadvantage is that the heating speed is slow and temperature control is not easy. In furniture industry, when the temperature requirement of hot pressing is not high, using hot water circulating furnace can also achieve satisfactory results, and the fixed investment and operation cost are very low.
(2) Performance of hot-pressed sheet_
_The performance of hot-pressed plate can be evaluated from several aspects. First, the use of pressing material, then the accuracy of processing, and finally, the arrangement of medium channels in hot-pressed plate. Hot pressing plate is generally made of whole pressed steel plate by deep hole drilling, mainly used for oil heating and steam heating; the other is the form of aluminium plate on the back surface of welded pipeline, mainly used for electric heating. Oil leakage due to poor sealing can be avoided by using whole steel plate.
At the same time, the stiffness and strength are high, but the hot-pressing plate is thicker; the latter is usually in the form of thin plate, because of the stress in welding and processing, it requires high processing accuracy. Hot-pressed sheet is easy to preheat and temperature control, but the requirement for workpiece is high. The uneven thickness of workpiece will cause the deformation of hot-pressed sheet and affect the subsequent processing quality. Thicker hot-pressed sheet is beneficial to increase the thermal capacity and strength and stiffness, but it will increase the exterior dimension of the press and consume more steel. The plane of hot pressing plate should be guaranteed in manufacturing and processing
The flatness tolerance of hot-pressed plate should be within 0.1-0.18
mm, the parallelism tolerance should be within 0.15-027 mm, and the
surface roughness of hot-pressed plate should be 3.2 um. Temperature
difference should not exceed 2-3 C in the whole width of hot-pressing
plate. If the temperature difference is too large, the moisture content
will be uneven, the product is easy to warp, and the strength and
appearance quality of the product will be affected. Heating channels for
the flow of hot media in hot-pressed panels are generally not taken
seriously by the furniture industry. Correct circuit design should be
based on the principles of facilitating the flow of heat medium, uniform
heating of plate surface and reducing the leakage of heat medium. For
the small press hot-pressing board used in furniture industry, the
design of single channel and double circuit is generally adopted, which
can meet the requirements of use. Chinese style
(3) Connection and Sealing_
_It is very important to ADO At present, the connection pipeline of hot-pressing plate is mainly hose, which makes the connection very convenient. In China, metal hose is mainly used, and imported Teflon hose is also used by some manufacturers. Flange connection can be used in both ways. Teflon hose has better fatigue resistance than metal hose. Asbestos rubber sheet is traditionally used as gasket material. New materials such as polytetrafluoroethylene and wrapped graphite have better sealing effect.