(1) comparison of heating methods
The traditional heating methods are steam heating and electric heating. The steam heating heats up quickly, but needs to equip the pressure boiler, the pipeline pressure is high, the steam condenses into water easily causes the plate surface temperature uneven; Electric heating has the characteristics of fast heating up, high heating temperature, simple control, but large power consumption, high work cost, specific use of resistance wire defects not easy to replace and other shortcomings.
The advantages of heat conduction oil heating are: high heat capacity, uniform temperature, can be heated to a high temperature under normal pressure, low heat loss, can reduce production costs, its disadvantages are slow heating speed, not easy to carry out temperature control. In furniture industry, general hot press temperature requirement is not high, with hot water circulatory furnace, also can achieve satisfactory result, and fixed capital contribution and working expenses are very low.
(2) hot plate function
Hot pressing plate function can be evaluated from several aspects, first is the use of pressing plate material, then the accuracy of processing, the end is hot pressing plate medium channel placement.
The hot pressing plate is generally made of the whole restrained steel plate through deep hole drilling. It is mainly used for oil heating and steam heating. The other is to use welding pipe surface paste aluminum plate method, first used for electric heating. With the whole plate can prevent sealing bad leakage, together with high stiffness and strength, but the hot plate is thick; The latter as a result of the general choice of thin plate method, due to welding and processing will occur in the stress, high processing accuracy.
Hot pressing plate thin easy to preheat and temperature control, but the requirements of the workpiece, workpiece thickness will cause deformation, affect the subsequent processing quality; The thick hot pressing plate is beneficial to increase the heat capacity and forward strength and stiffness, but it will increase the size of the press and consume more steel.
The flatness of the hot pressing plate and the upper and lower surfaces should be ensured enough parallelism when making and processing. The flatness tolerance of the hot pressing plate should be within the range of 0.1-0.18mm, the parallelism tolerance should be within the range of 0.15-027mm, and the surface roughness of the hot pressing plate should be 3.2m. The temperature difference in the whole space of hot plate should not exceed 2-3℃, if the temperature difference is too large, will make the moisture content uneven, the product is easy to warp, the strength of the product and appearance quality will be affected.
The heating channel of heat medium activity inside hot pressing plate is not taken seriously by personage inside furniture course of study commonly. The correct circuit planning should be in favor of the activity of the thermal medium, the plate surface temperature uniform, reduce the leakage of the thermal medium as the principle. The hot pressing plate of small press used in furniture industry generally chooses the plan of single hole road and double circuit road, which can satisfy the application requirements.
(3) connection and sealing
It is very important to select suitable connection method and sealing element for heat transfer under high temperature and high pressure.
At that time, the connection pipe of hot pressing plate basically is given priority to with hose, such make connection is very convenient, domestic first is given priority to with metallic hose, also have manufacturer to choose to import teflon hose, two kinds of method all can use flange connection, teflon hose resist fatigue function is better than metal hose. Gasket material traditional use of asbestos rubber plate, new materials such as ptfe, coiled graphite, the sealing effect is more ideal.