Induction brazing of steel support bars
A Stressless E200 sofa, just one of the wide range of armchairs and sofas manufactured by Ekornes. Photo:

Ekornes uses induction heating to braze steel support bars

Ekornes, the largest furniture maker in the Nordic countries, uses an EFD Induction mobile ‘Minac’ converter to braze steel support bars in their sofas.

It isn’t easy being a sofa. You have to look good. You have to be comfortable to sit on. And you have to be strong enough to support years of relaxing adults, jumping kids and visiting relatives.

The Minac, which has been in use by Ekornes since the middle of 2012, is a Minac 18/25,  meaning the system has a continuous power  output of 18 kW and a maximum power output of 25 kW. But why choose a Minac for such an application, particularly when there are alternative methods such as flame brazing on the market? For Terje Solgaard, Application Engineer at EFD Induction Norway, one of the main reasons why companies such as Ekornes opt for a Minac is the productivity of automated  induction brazing. ‘Induction heating is  unrivalled when it comes to output. Put simply, induction can braze more parts per hour than any alternative process.’ 

But the real attraction of induction brazing is that it boosts output while simultaneously ensuring consistent, high-quality joints. ‘Indeed,’ says Solgaard, ‘since induction quickly brazes individual work pieces, we can integrate the brazing process into a continuous production flow. And as each work piece is brazed separately and with electronic controls, we can repeat the desired heating cycle with amazing accuracy and at high speed, too.’

Brazing is a relatively straightforward process that involves using heat to melt a filler metal that is absorbed by capillary action into two close-fitting pieces of metal. The resulting joint is exceptionally strong, typically being as strong, if not stronger, than the base metals it joins. But unlike welding, brazing preserves the integrity of the base metals by not melting them.  ‘There are other benefits, too,’ adds Solgaard. ‘The joint is a neat bead that is leak proof and shock resistant. Moreover, induction brazing is a non-contact process. No flames or other heat sources ever directly touch the base metals, which can warp the metal. And unlike gas brazing, where flames obscure the brazing process, induction brazing gives the operator a clear view of the complete brazing operation.’  There are health benefits too, as induction means less noise, heat and dust.’