Infra-red emitters speed drying operations

Edited by the Engineeringtalk editorial team Jul 15, 2003

Heraeus Noblelight will showcase its infra-red emitters at the PaintTech exhibition in October and will also be providing the opportunity for visitors to ask questions of specialists in the field.

Heraeus Noblelight will showcase its infra-red emitters at the PaintTech exhibition in October at Sinsheim and will also be providing the opportunity for visitors to ask questions of specialists in the field.

In addition, there will be a lecture on the theme of wood coating and infra-red at the PaintTech Forum.

Wood is treated with a wide range of different coatings before it reaches the end user.

Base coatings, varnishes or powder coatings need to be dried as quickly as possible, whilst ensuring that there is no damage to the wood.

This requirement is best achieved with infra-red technology.

Infra-red heat dries much faster than conventional hot air methods, because infra-red acts specifically on the coating.

Radiation which is precisely matched to the absorption characteristics of the of the coating is rapidly converted into heat, so that water or other solvents are evaporated, while the coated material and the immediate surroundings remain cool.

This careful heating of the material avoids stress on the surface of the wood.

In the shorter heating time, the wood is not heated enough for the wood fibres to change their alignment because of the heating effect.

Moreover, because of the rapid heating, very little water can penetrate from the coating into the wood surface to soak the fibres.

The infra-red heating also reduces the need for intermediate grinding and allows an improved quality of coating no matter what the season as it is independent of the storage temperature of the wood.

Heraeus Noblelight matches infra-red emitters precisely to the requirements of the particular process, in terms of optimum wavelength of radiation and the length and power rating of emitter.

Carbon infra-red (CIR) emitters are particularly effective for drying water-based varnishes on wood, as these emitters give out medium-wave radiation.

The wavelength of the infra-red radiation has a significant effect on the drying.

Water and many solvents evaporate especially quickly when subjected to medium wave infra-red radiation.

This is because the medium wave radiation is converted directly into heat in water and solvents.

This is not the case with, for example, near infra-red (NIR) radiation.

Powder coatings are reliably gelled and cured in a short time with infra-red radiation.

Powder absorbs infra-red radiation very well and the powder heats up very quickly.

Compared with conventional heating methods, such as convection ovens, the gelling of the powder is significantly accelerated.

Rapid melting improves the coating quality and speeds up throughput.

Powder coatings can be baked into MDF and HDF plates with short wave or CIR infra-red emitters, according to the absorption characteristics of the coating.

A combination of efficient infra-red radiation and a sharply defined air stream, the so-called air knife, is particularly effective for drying water-based foundation coatings on parquet flooring tiles.

The UV primer on these tiles must be completely dried before any following coating stages.

An airknife heats the water with infra-red and the additional air stream removes the ensuing water vapour from the coating.

This eliminates the need for vapour barriers and makes the coating drying even more effective.

In the manufacture of laminated boards, there is a requirement to dry the edges of the boards.

The front edges are coated with a water-based coating, which must then be dried as quickly as possible.

This is best done using a short wave high power emitter, which allows production speeds to be increased up to 180m/min.

Heraeus Noblelight can carry out tests in its in-house applications centre or on-site, to determine which infra-red emitters will provide the fastest drying and curing while providing optimum care of the material to be coated.