Infrared Application of the Month #1:
Drying Paint on Injection Molded Plastics
A major injection molding facility sought a method for drying a protective clear lacquer applied to parts. Previously, the components had to be dried for around 20 minutes in a hot air oven. During this extended period, dust could settle on the product to adversely affect the quality.
An infrared oven from Heraeus Noblelight is now drying and curing the coatings on the parts in less than 20% of the time required by the convection ovens. The small-footprint IR oven fits easily into the available space. Pre-installation trials proved the mediumwave infrared system as a successful and faster alternative to hot air.
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Infrared Application of the Month #2:
Powder Coating of Metal Signs
As part of an ongoing upgrade to its facilities, a manufacturer of aluminum and steel signage set a goal of increasing produciton line speed and quality for the powder coating component. Previously, the sprayed-on powder had been pre-heated by a gas-fired heat system before entering a warm air convection oven for final curing. That system was plagued by maintenance problerms.
The solution was a purpose-built medium wave infrared oven from Heraeus Noblelight, conveniently retrofitted into the existing powder coating and curing line. The oven has helped to speed up the powder coating process as it heats the powder faster than the old system and it has also reduced the cure dwell time in the convection oven. In addition, quality has improved, as the medium wave heaters provide a uniform flow and fusion of the powders.
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Tech Center Spotlight:
Shortwave Heaters
Fast and Intensive
Shortwave IR heaters from Heraeus are suitable for all applications in which the attainment of high temperatures in the shortest possible time is what counts. Their emission maximum is between 0.9 and 1.6 micron.
Performance advantages include high radiation density in the most compact space; near-instant heating-up and cooling down times; optimized reflection; much more.
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Special Designs:
Watercooled Heater
Heraeus designed a special twin tube lamp heater with one water cooled channel. This heater type transfers a large amount of energy (more than a million watts per square meter) in a very short time. Temperatures of more than 1000°C on the surface of the product can be achieved within seconds. Popular applications include coil coating, edge coating on wood, and surface sealing.
For more on watercooled heaters, click HERE.
A wide assortment of other special design heaters is available from Heraeus. Click HERE for details.
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Technical Learning: Introduction to IR Technology, Part 1
There are two basic means of heating a product electrically, by direct and indirect methods. With direct heating, heat is generated within the mass of the material (e.g. by microwave and radio frequency energy in the case of dielectric materials or by induction or resistance heating in the case of electrically conducting materials). With indirect heating, heat is transferred to an article by any of the three familiar methods of conduction, convection, and radiation.
Conductive heating is achieved by placing an article into touch contact with a heat source. The rate of heat transfer is determined by several factors, not just the thermal properties and temperatures of the two bodies.
The surface conditions over the contact area, the pressure of contact and the nature of any gas, liquid or solid films at the interface all play a part in the conductive process. Radiation can also contribute to heat transfer across the interface.
Convective heating relies on the movement of a hot fluid or gas, such as air, which acts as a carrier of heat from one body to another. Natural convection occurs when different zones of the gas or liquid have different temperatures and densities. Industrial process heating commonly makes use of forced (air) convection, whereby the air is directed towards the substrate by a fan.
The rate of heat transfer depends on many factors including the temperature differential between the heating air and the substrate, and the density and rate of movement of the air.
In the context of heat transfer, radiation refers to the thermal variety (non-ionizing radiation), and should not be confused with radiation produced at wavelengths shorter than the visible spectrum (e.g. X-rays).
Thermal radiation takes place without the need for an intermediary agent such as air because energy is transmitted as electromagnetic rays emitted from a heated body. The rate of heat transfer depends on such factors as the temperatures of the heater and the receiver, the ability of each to emit and absorb radiant heat, their geometrical shape, their active areas, and relative positions or proximity.
The human eye differentiates between light-producing or glowing sources and invisible emissions. Infrared radiation occupies a waveband immediately adjacent to the red end of the visible spectrum. "Black heat" is a term sometimes used to describe the infrared band.
Heaters of visible radiation produce thermal radiation within the IR band as well as the visible band. Even at the very intense light producing temperatures in the order of 5000°C, a heater produces more energy in the infrared than in the visible band. Heaters that produce some light energy are also classified as infrared, although in scientific terms the description is not absolutely accurate.
Coming in the next issue: Intro to IR Technology, Part 2.
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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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