Things that melt in Switzerland

There is something of a tradition of melting things in Switzerland: snow on the Alps turns to water, chocolate becomes chocolate fondue, cheese melts for raclette. The Swiss engineering firm Maschinenbau-AG Leister Technologies has continued the tradition – and is now getting industrial fabrics to melt with their Seamtek welding machines.

As one year gives way to the next, it is not only on the Matterhorn that melting enjoys a high profile: as the stress of Christmas present buying begins to slowly melt away, many people amuse themselves by getting molten lead or (more environmentally friendly) wax to congeal into bizarre shapes, portents for the new year. The Leister Group, with its headquarters in Kägiswil in the Swiss canton of Obwalden, on the other hand, is involved in the melting process all year round. As manufacturers of welding machines for plastics, components for process heating and laser systems, with 900 employees worldwide, the company knows a thing or two about correct melting points.

This experience has also gone into their latest foray into the fusion business, with the product name ‘Seamtek W-900 AT’ that doesn’t exactly melt gently in the mouth. This new type of welding machine makes short work of cool-headed plastics such as polyvinyl chloride, polypropylene, polyurethane or polyethylene with temperatures of up to 680 degrees centigrade. (By way of comparison: aluminium has already got pearls of sweat on its brow and is well on the way to melting by the time the temperature reaches 660 degrees centigrade). Those working with industrial fabrics in particular may well be feeling a warm glow of pleasure; many of them have already installed the machines for, say, joining plastic and plastic-covered sheeting in the manufacture of tarpaulins, bouncy castles, ventilation pipes for mine shafts and stadium roofs.

Welding, cutting, gluing
Leister are justly proud of their innovative fusion welding process, as it was the result, says the company, of “laborious and intensive” development. “It involves technology that represents a revolution for the technical textiles market,” says Patrick Schnider, Junior Product Manager at Leister, with some assurance. This is how it works: first a wedge-shaped plate, about two centimetres long, is heated electrically in a matter of a second or so and then brought into contact with the material to be welded. The plastic coating of the woven fabric cannot withstand this contact – it immediately melts away. And during the welding process, two rolls of silicone ensure that the pieces of material are permanently joined.

But does the welding process à la Seamtek have any advantages over other seaming procedures, such as the use of adhesives? “With welding the two pieces of material are fused together,” explains Schnider. With gluing, on the other hand, there is an additional layer of foreign material – the adhesive itself – that comes into play, in order to create the permanent bond. For the experts at Leister, therefore, it is a no brainer: welding beats gluing every time. One advantage compared to other welding techniques, according to Schnider, is that the wedge-shaped plate is heated only during the actual welding process. This, he points out, not only protects both user and material, it also saves electricity.