Infrared Application of the Month:
Preheating Rubber Automotive Mouldings
An automobile manufacturer's plant includes many processes; one of its most challenging was the attaching of rubber mouldings to the body assemblies. The mouldings are created ahead of time (in another process) and stored in racks until they are needed. The manufacturer turned to Heraeus Noblelight to develop a custom system that would quickly heat the mouldings (either individually or in groups) to 35-45°C. The short wave infrared system from Heraeus brings the mouldings from their “cold” (room temperature) storage to the desired temperature in a mere eight seconds. Targeted, efficient IR heat technology solves the challenge.
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Infrared Application of the Month:
Curing Powder Coating on Metals
A major US-based lighting standards manufacturer sought to increase its market share by offering a higher quality product to the marketplace, and to do so without raising prices. The solution was to increase productivity. To help achieve that goal, they turned to Heraeus Noblelight. Heraeus worked with the company's engineers to develop a powdercoating system that cured the finish with medium and shortwave infrared lamps. The new system was far more efficient than the previous paint-and-air-drying process. What's more, the new system eliminated the costs associated with removal of noxious fumes and hazardous waste, and it occupied a smaller footprint in the plant.
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Tech Center Spotlight: Silicon Controlled Rectifiers (SCRs)
A silicon controlled rectifier (SCR) is a solid state switching device designed to provide fast, infinitely variable proportional control of electric power. The SCR gives maximum control of your heat process, and it can extend heater life many times over other control methods. Thanks to its solid-state construction, a properly used SCR can cycle on and off more than a billion times.
Advantages of SCR Controls over other temperature control methods
- Improved response time.
- Closer process control, infinite resolution from 0-100%
- Extended heater life.
- High reliability, reduced maintenance costs.
- Silent operation. No arcing.
- Reduced peak power consumption.
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Special Designs:
KR85 and K110 Modular IR Systems
These simple housings can be used for any standard or custom heater produced by Heraeus. Once the heater type or design is chosen for the application, a KR reflector can be used as a low cost housing option. With a housing constructed from 18 ga aluminized steel, a polished internal surface can act as as a primary or seondary reflector. The KR and K110's unique design holds up well against high temperature environments. These units can be combined on a user supplied framework to form oven walls either in straight or geometrical designs.
Learn more about the KR85 and K110 Modular IR Systems from Heraeus Noblelight.
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Technical Learning: Drying of Water-based Coatings
Efficiency Leap With IR Drying
New research on the application of IR dryers to water-based varnishes indicates high energy cost savings. With correct selection of the radiation source the infrared energy requirement for the drying process can be reduced by up to 50%.
Water based varnishes are well known in various printing processes and their usage is growing. The printing industry uses these transparent coatings mainly for in-line surface finishing of printed items to achieve a higher gloss, to reduce post-process times or for surface protection. To increase printing speeds, dryers often combine convection (hot air) with IR radiation.
This research demonstrates the practical features of IR heaters in dryers, their energy requirement (and thus efficiency), their effect compared to hot air, and the possibility of increasing the printing speed. It should also supply many more answers to help in understanding the process.
Figure 1
In order to optimize the drying process with IR heaters, the effect of the IR radiation must be precisely analysed. Figure 1 shows the spectral absorption characteristic of water films with thicknesses of up to 10µm. Obviously the spectral absorption range around 3µm is best suited for heating water. In addition, higher wavelengths of the emitted radiation are absorbed, but the spectral fraction of the IR heater is less there, as is its influence. The wavelength range below 2µm (towards the visible light end of the spectrum) has no significance whatsoever for water heating.
Which IR Source is suitable?
Figure 2
The question which IR source is best suited to the process must be answered based on the spectral absorption of water for different film thicknesses. Figure 2 shows the spectra of different IR heaters operated with the same electric power but at different heater temperatures. The main absorption range of water is marked. The different radiation intensities of the IR heaters in this range explain the results obtained in the practical tests.
The significant effect lies in the spectral range 2.5 to 3.5µm. The energy radiated by the heaters in this spectral range is different. It can be calculated from the area below the relevant spectral curve. The area below the curve of a heater at a temperature of 2600°K is hatched. In comparison with this, the area under the 1500°K curve is significantly greater.
It can be deduced from this consideration that the directly usable part of the infrared radiation of an IR heater is greater the closer its peak emission (see Figure 2, above ) gets to around 3µm. This condition is best met with medium wave heaters.
The classification of IR heaters according to temperature and peak emission is given in the table in Figure 2 above.
We calculate the effective portion of the IR radiation, taking into consideration the water absorption graph ( Fig. 1 above :10µ-film) and the spectral radiation of the different heaters.
To be continued in the next issue...
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That's it for this month's issue of Application Notes for IR Heating. Feel free to encourage your colleagues to subscribe. Just click HERE to send them an invitation to subscribe. It's quick, easy, FREE, and no-obligation.
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