THE CURING PRESS IS PERFORMING A POINTLESS OPERATION
During vulcanization due to the high pressure and temperature, the structure of the tread of the green tire is changed where it is shifted from plastic to elastic state. Pressing then changes the shape because the tread mixture is pushed to all parts of the mold. These 2 operations, taking place at the same time, are the function of the curing press and thus make it irreplaceable. However, in case of large-sized tires a third operation is unnecessarily performed and that is the reaching of curing temperature. It is the time when the tire occupies the curing press until a temperature of 100°C in the core of the tread is reached. This time could have been utilized for the real purpose of the curing press; that is pressing and curing! It is the microwaves that should be taking this part, not the curing press! The rubber compounds used for tire production have great ability of absorbing electromagnetic energy which makes them predestined to be heated dielectrically. From the very physical essence microwaves have no competition in steam, hot water or a heated plate. Through the metallic mold or a bladder the heat penetration inside the thick tread layers of the large-sized tires is significantly slower. That is due to the fact that elastomers are very bad heat conductors. The heat penetrates through the tread from the place of contact with the hot wall of the mold or the bladder slowly molecule by molecule from the surface to the cold core. From its physical nature dielectric heating acts instantly in the depth of the material and at the molecular level heats the product at the same pace in its whole volume.
- using the full potential of the curing press
- production time reduced by 50%
- modest installation space
THE NON-PRODUCTIVE TIMES OF THE CURING PRESS
We can consider the smallest large-sized tire for agricultural and construction machinery to be around 40 kg of weight. For demonstrational purposes a medium to heavy weight tire of 150 kg was used and in this case it is labelled as a “medium tire”. It is apparent that 40 minutes of the pressing time can be saved if the preheating to 90°C ± 5°C is done by microwaves outside of the curing press. For the large 500 kg tires more than 90 minutes can be saved. These times necessary for the processing of each piece multiplied by the daily/annual production with the time of the return of the investment together provide the basis for decision making. Since one cycle of the microwave is faster than once cycle of the press, one microwave can serve several presses and thus significantly increase production. The technology works best with thick treaded tires.