The roots of the Vereinigte Wollwarenfabriken Marienthal (VWM) wool factory go back as far as 1831. But let's be honest – who has heard of this company from Hamlin? And that's not all. We treat their products in the most shameful of ways – we even tread all over them each day! VWM, a member of the Allibert group since the summer of 1988, has a staff of approx. 150 and manufactures needlefelt covering for almost all well-known automobile manufacturers.

Up to 6,000,000 m² of this raw material are produced for floor coverings, door linings, hat racks and hub coverings.

To make these materials resistant to wear and tear in the harsh everyday environment, the back of the needlefelt is coated with a plastic laminate. The felt is sprinkled with granulated plastic powder and melted in a sintering furnace and then impressed in a cooled calender plant.

The sintering furnace is precisely where this all takes place. 126 glass tube radient heaters ensure the necesary melting temperature that has to be kept within a bracket of 3°C due to the nature of the material. If the temperature is too low, the plastic granulate does not melt, if the temperature is too high, "it runs into the carpet" and is thus a reject.

Flexible individual control for top quality

Groups of radient heaters used to be controlled with mechanical or complicated manual methods. 150 m² reject needlefelt was nothing unusual.

The call for individual controlling for each radient heater became louder. There was also the wish to provide different heat curves to better suit the different materials.

And that was the challenge facing the technicians! – A look around the market brought to light only sintering furnaces with control systems inadequate for the requirements, or models that far exceeded the budget. The idea that came to the rescue: 126 single phase electronic load relays for switching the glass tube radient heaters and 126 circuit monitoring modules were quickly ordered. A fast PLC or PID regulator was also needed.

Within a complete cycle period of 6 s , the sturdy wear-resistant ELR 1/35-600s switch the radient heaters at an ideal ratio of impulse to pause. The circuit monitoring modules integrated in the control circuit reliably recognize the failure of individual heating elements. A drop in temperature is compensated for by increasing the temperature if the adjacent elements.

For over six months, the electronic load relays have been carrying out their duty in three shifts with the following result: Top quality with no waste.