Frank Wilson: Understanding infrared heat can boost efficiency and cut costs

It is easily forgotten that the thermal systems installed as part of the thermoforming process are the engine of production. Without maintenance and sufficient analysis, production output and quality will suffer. Infrared heaters, ceramic heaters, quartz heaters, and ceramic elements are all based on a specific and particular technology, and the better a business understands infrared science, the more efficient its production will be.

Heating systems are often cited as a possible cause of packaging deformation and quality issues but as a general rule they are rarely the cause of production problems. Instead, the complexity of the packaging design – dimensions, the depth of the thermoforming ‘draw’ and the characteristics of the material composition – is the prime factor, which must be calculated and overcome in order to make a top-notch product.

There are three principles central to infrared heating: absorbtion, transmission and radiation. The misunderstanding of these factors generally leads to the misuse of thermoforming equipment and the consequent expense in energy, cost and capital plant.

A good infrared heating system converts electricity into infrared output quickly and efficiently. In thermoforming production, a number of infrared ceramic heaters are generally mounted on reflectors arranged on a platen. The performance of the background reflectors, and the platen in general are vital factors in directing the infrared heat to the plastic. But, too often, operators of thermoforming machines end up fighting the demands and design of their machine in order to get some efficient heat work done.

Avoiding burn-out
For example, stainless steel is not an adequate material for use in infrared reflection work, as it absorbs much of the emitted energy and, over time, will cause the electrical wiring behind the reflector to burn out. It will also start to discolour above 120C. Polished aluminum, on the other hand, is, in most cases, the best reflector for ceramic infrared heating, but above 500C it also will start to fail. Thermoforming thin and clear plastic sheet requires some passive ceramic tiles to be installed in the base of the platen in order to reflect back the heat. Every system, in some way, has its custom features.

Furthermore, in many cases, as a platen system starts to discolour and degrade in operation due to dirt, process plastic and other materials, the reflectivity will be compromised, often forcing the machine operator into a vicious circle of increasing the temperature in order to achieve the same performance. Regular review and maintenance could pre-empt this bother, and the subsequent loss of control and extra cost.

Around a 30-40% improvement in the operational efficiency of most packaging thermoforming systems could be achieved by carrying out this single and simple step of reviewing and renewing the infrared heating platen. The ideal control for this situation is to mount a thermocouple on the existing reflector system – keeping a temperature watch. When this starts to rise – taking more and more energy – the user should be alerted to take action.

This issue will continue to bear on the packaging industry as both cost pressures and the demand for higher quality continue. In these cost and energy conscious times, the sector should take the opportunity to investigate where its ‘heat work’ is letting production down – and also take the trouble to understand the principles of infrared a little better. The savings could be considerable.

Frank Wilson is founder and managing director of infrared heating supplier Ceramicx

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