Microwaves

Story

Born before the end of the 2nd world war along with the development of the radar, the microwaves technology has nowadays a fundamental importance in the domain of telecommunication. The idea of using the microwaves for heating up materials was commercialized for the first time in 1952, when Raytheon introduced for the first time microwave ovens on the market. In the last ten years, the use of microwaves have been extended to various application fields in the industrial processes using systems heating, in which the conventional conduction mechanisms, convection and radiation, do not allow a homogeneous temperature rising. Wikipedia contains a very good webpage offering broadening information about microwaves.

Developments

The success of the microwave technology derives either from the possibility to obtain particular operative conditions, otherwise impossible with conventional technologies in sustainable time, or from considerations on energy saving and final product quality. Development of the microwave technology has become a trend in the last years, which includes improving of numerous innovative technical applications in various industrial domains, such as high-temperature treatment of noxious waste or fast reticulation of polymeric resins, etc. However, the microwave heating in the industrial processing of materials remains a non-ordinary technology because of the technical problems connected to various applications. A multidisciplinary approach is required in order to solve successfully such problems.

The microwaves for Microglass

Estimating the type of material to be processed, analyzing the drying curves, evaluating the best proportion between radiation cost/employed power and the frequencies conceded by the international conventions regarding free use of power, Microglass has individualized the most appropriated frequencies and created an own microwave heating system, fundamentally composed of three blocks: generator, waveguide, applicator. The generator is usually (but not necessarily) a magnetron, electronic tube apt to generate higher microwave power. In the proportion cost/delivered power, it is a magnetron of 1.2 ÷ 6 kW supported by a power supply kit that electronically ensures power supply for functioning and output only in safe conditions of the whole system. The waveguide enables the energy transport via successive reflections from the point of generation to the point of application without significant losses, since it is produced from highly conductive material with geometric dimensions depending on the wave frequency that is propagated internally. The applicator, which is the distributor of energy over the material to be processed, is a structure specially designed to expose to the radiation the material to be heated in effective, secure, reliable, repeatable and economically convenient manner. The mono-modal applicators have at least one of the dimensions of the wavelength that is propagated internally. For this reason, the configuration of the field is properly determined and not much influenced by the presence of material to be heated. On the contrary, multi-modal applicators are composed of one structure with metallic walls having much greater dimensions than the radiation wavelength. Such a structure comprises an echo box in which, unlike in the unimodal cavities, a multiple reflection occurs producing an overlap of a big quantity of waves that are being propagated in various directions. The use of mobile metallic surfaces, together with the movement of the material to be processed, helps to improve the heating uniformity. However, the homogeneity of process connected to induced thermal effects is strongly dependant on the frequency chosen for the radiation and on the intensity of the electrical field. At this point, the problems are due to the radiation density of such an electrical field, since the absorbed power is connected by means of a quadratic factor to the intensity of the radiation field. In order to improve the process performance and the flexibility of use of the heating, drying or polymerization machines, Microglass have employed in some applications a system in which the waveguide, united to the mono-modal applicator, is inserted in a multi-modal cavity, thus eliminating the utilization of mobile metallic surfaces.

Infrared

Microglass with the radiant panels MICRORED has brought an innovative contribution to this technology, for a long time now consolidated in the industrial sector. The Microred plates, unlike the traditional IR lamps, present a double peak in the emission spectrum, with adjustable frequencies. This particularity helps to optimize industrial processes, such as the polymerization and the drying of resins and varnishes. In fact, resins and varnishes are very often composed of more chemical agents (solvents, polymers, catalysts, etc.), each of which reacts in a different way to the IR radiation, according to the used frequency. Regulating both frequencies of the Microred plates, it is possible to use the wavelengths that are more effective on individual chemical agents, optimizing the process of drying or polymerization in terms of time and uniformity.

The radiant panels Microred are characterized by a modular ‘matrix’ structure that helps to create radiant profiles of any kind of geometry, easily adaptable to any kind of plant and process.

Thanks to the know-how achieved from research and development, Microglass produces also traditional infrared high-power curing tunnels (40-50kW/m2), secure and reliable, moreover offering the possibility to combine them with the innovative microwave technology.

Ultraviolet

The UV lights have for decades found multiple applications in both domestic and industrial environment. In the latter one, Microglass has directed its own studies with the aim to improve the security of the working cycle of the UV lights, setting as primary objectives the reliability and the energy saving.

The existent applications are based on power-on systems of the lights that are using magnetic flux saturation transformers, which are not using wave trains systems and neither effective switching solutions. Moreover, the traditional systems work with emission frequencies equal to 50Hz without the possibility of variable power control. This makes the traditional technology less effective and perfectible.

Microglass has recently developed MUV, an innovative electronic power supply system for 30MHz UV lights, allowing saving from 15% to 40% of electric energy, increasing the lifespan of the light itself (avoiding violent flashovers used for light turning on with the traditional method) and also guaranteeing the constancy of the irradiation, continuously electronically controlling and diagnosing the UV emissions.

Combined technology

Every technology offers peculiar characteristics that can be combined in a way to render the processes of treatment of different materials maximally effective and efficient. For instance, the microwaves penetrate in depth to evacuate the water particles; the infrared is specific for a small depth action and for a temperature raising; the ultraviolet for varnish drying and photosensitive resin polymerization.

The principal advantages of the Microglass technology

• Immediate capacity of the energy penetrating with a very high speed of heating
• Instantaneous activation and deactivation
• Exceptional heating selectivity of various materials even when there is a contact between them, provided that they are characterized by different electromagnetic properties
• Considerable energy saving, resulting from the possibility to heat up only the object or the product of interest, absorbing directly the energy of the electromagnetic field, radiated from the generator, and avoiding the heating of another material (transporter fluids, curing tunnel walls, etc.)
• Optimization of the radiation process resulting from the fact, specially for materials with high thickness, the heating is starting from the depth to the surface of the object rather than vice versa as it is generally the case of the heating methods for conduction (via fluids or contact with solid hot bodies) or infrared irradiation.

All the commercialized products are warranty-covered by the producer. Moreover, the machines of the combined line possess the CE mark.