Infra-red emitters optimise powder coating process

Edited by the Engineeringtalk editorial team Aug 11, 2006

At the PaintExpo exhibition in Karlsruhe, Heraeus Noblelight is showing infra-red emitters which help to make the powder coating process more efficient.

Metals, plastics and wood - many materials today are powder-coated.

Powder-based paints and lacquers are applied as powders, melted by the introduction of heat and finally cured.

Hot air heating and infra-red radiation are both suitable in their own way, according to the properties of the product and the coating system.

Increasingly, combinations of the two technologies are being used.

Infra-red emitters transfer large amounts of energy in a short time without the need for a contact medium.

As a result, the oven length can be reduced or the production rate speeded up compared with conventional methods.

Moreover, rapid melting of the powder helps to improve the surface quality of the coating.

At the PaintExpo exhibition in Karlsruhe, Heraeus Noblelight is showing infra-red emitters which help to make the powder coating process more efficient.

Infra-red systems transfer heat without the need for a contact medium, where electromagnetic waves generate heat in the material to be heated.

Infra-red radiation is absorbed very well by powder, so that the powder mass heats up very quickly.

Powder is gelled significantly faster than in a convection oven.

Fast melting improves the surface quality and increases the throughput speed.

In most cases, ovens are significantly shorter or the product speed is higher.

It has also been demonstrated that the holding and curing times for powder coatings are greatly reduced or, in some cases, completely saved by using infra-red radiation.

Flat plates, such as perforated plates for control cabinets or top plates, needed a holding time of around 15 minutes at approximately 180C.

Tests in the in-house Applications centre at Heraeus Noblelight showed that these plates could be heated up in around two minutes, depending on the plate thickness and the coating system.

There was no longer any need for a holding time and the coating successfully underwent bending tests, cross-hatch, tape pull-off tests and MEK (Methyl Ethyl Keton) tests without any holding time.

Infra-red emitters have very short response times.

Short wave and carbon emitters from Heraeus Noblelight have response times of between one and three seconds.

This means that heat is controllable and it is possible to carry out fast change-overs of different types of coatings with different curing temperatures in the same oven.

In addition, energy is saved when the heat source is switched on only when it is needed.

Infra-red radiation heats flat materials uniformly and quickly.

Consequently, they need be heated only from one side.

Rotationally symmetrical components are mainly suspended as they pass through infra-red ovens, as for example metal gas bottles, which are turned about their central axis while being irradiated from two sides.

For a uniform heat distribution, infra-red emitters can be so installed in an infra-red oven that their power density is matched to the product shape and the wall thickness.

More heat is generated in thicker zones than in thinner walls.

Another advantage of infra-red compared with convection ovens is that the powder is not disturbed or blown about.

With no air movement, dust inclusions are also eliminated, so that quality is improved.

Infra-red systems are compact and can be easily integrated in existing drying lines.

This helps in the modification of warm air ovens and speeds up production.