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Innovative solutions for IR vulcanization ovens

06.03.2013

The innovative line developed by Zamak Mercator enables a process for rubber vulcanization and silicone in an infrared radiation field. The new technology is based on the application of special ovens equipped with IR radiators, which, in comparison to a conventional hot air oven provide more efficient vulcanization with respect to crosslinking time, product quality and cost of the process.

There are many vulcanization methods, among which the most popular technology is based on convection ovens, using hot air as a carrier for transporting heat. Rubber and silicone are not good conductors, resulting in uneven distribution of heat thus obtaining a uniform vulcanized product is very difficult, especially inside a profile. Convection heating usually needs much more energy to compensate for low efficiency. With regard to product quality, traces of the conveyor belt and other deformities very often appear on the surface, caused by too slow heating of extruded profile layers. To eliminate these problems Zamak Mercator developed a rubber and silicone vulcanization line, where next to the extruder and receiving system are an IR shock oven and IR tunnel ovens. These ovens allow to conduct the vulcanization process by means of radiators emitting infrared radiation. The ovens can be used primarily for the production of profiles of much differentiated shapes.


Infrared radiation provides high efficiency of heat transfer to the vulcanized material without using an intermediate medium. The absorbed IR radiation causes polar molecules to vibrate and generates heat production. Such a solution minimizes the loss of heat required to warm the media used in other methods of vulcanization, such as water, steam, air or inert gases.

 


 The slotted oven manufactured by Zamak Mercator is equipped with high power IR radiators, designed to pre-consolidate the shape of extruded profiles. Slotted ovens are able to achieve a temperature of 700°C and are therefore very effective, in particular in the pre-vulcanization process. The profile formed in the head is fed into the slotted oven chamber and under the influence of infrared radiation pre-crosslinking of its surface takes place. The pass-through design of the oven and the possibility of adjusting the angle of the chamber facilitates the correct position of the ovens in relation to the profile passing through. The chamber is equipped with a mechanism of "easy start-up", which provides a quick and easy line changeover. The innovative design of the oven allows for smooth adjustment of the position of the chamber in the range of -150 ÷ +900 and height up to 2000 mm. By setting the position of the chamber to +900, it is possible to consolidate the shape of extruded profiles of low viscosity in a vertical position, which in the traditional horizontal position would be deformed.

A mobile design of the oven is provided by a guiding system and trolley equipped with wheel sets.

IR tunnel ovens developed by Zamak Mercator provide short heating time and the vulcanization of the entire volume of the extruded profile. The use of infrared radiators allows for a faster vulcanization and improved temperature distribution across the section, providing high dimensional stability of the product and thus a higher quality. Energy consumption can be reduce thanks to the optimized design of the reflector. There are separate zones in the oven enabling selection of the individual parameters of the vulcanization process, depending on the shape of the vulcanized gasket, and the extrusion rate. Adjustment of the vulcanization process is performed by controlling the radiators power or by means of stabilizing the temperature in the tunnel. A divided structure of the oven allows for the opening of individual segments, enabling easy changeover of the conveyor belt in the tunnel chamber and control of the process during line operation. The tunnel segment is equipped with a transport system consisting of drums and rollers, a positioning and tape tension correction system, gear motor and conveyor belt. The built-in forced air circulation system ensures temperature stability inside the chamber and removal of vapors and chemicals from the zone, which form during the vulcanizing process. The IR tunnel is available as a segment version with a module length of 3000 mm clamping grips for installation and aligning a larger number of tunnels in sequence. More efficient delivery of energy to the extruded profile of the crosslinking process in the IR environment requires a shorter length of the oven compared with convection ovens. Depending on shape of the profile the vulcanization rate in infrared ovens may even be three times larger than in conventional hot air vulcanization ovens. IR ovens offered by Zamak Mercator enable crosslinking of profiles with complex shapes while maintaining high dimensional accuracy. The products obtained by this technology have a smooth surface and dimensional stability even in the case of low viscosity mixtures. The great advantage of infrared ovens is their very short (less than 3 minutes) time required to obtain fully operational status. This considerably reduces waste of energy needed to heat the chamber. The effective isolation of the oven minimizes the emission of heat to the environment, reducing additional loss of electric energy. The use of IR ovens significantly increases the capacity of the line through the rapid generation of energy and provides greater stability of the whole cross-linking process. The advanced, highly intuitive control system developed by the Department of Automatic Control Zamak Mercator enables the control of individual radiators and panels and their partial extinguishing and activation depending on profile shapes. The user also has the ability to create vulcanization processes recipes so that retooling the ovens for an individual production profile is performed in a quick and simple way.

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