When people visit Wolfgang Reith in the Swiss town of Yvonand they are generally looking to do one thing – buy time. Reith promises them coils that never end, a fantasy of their punching machines and tube formers running on and on, without constantly having to be reloaded.
In short, he promises the real deal of continuous production. Of course Reith would never say he gives people the chance to buy time. He prefers to be more specific. “My customers acquire the ability to exploit the productivity of their manufacturing facilities to the full.”
Reith stands out somewhat from his colleagues around him who are casually chatting away in Swiss French. He speaks crystal-clear standard German, enunciating every single word. Originally from Dortmund, he moved to the west of Switzerland to join a company named THE Machines Yvonand SA seven years ago, and he’s been running things there for the last five years.
But Reith’s passion for precision is obvious from more than just his choice of words. He demonstrates his machines with genuine enthusiasm, explaining the amazing levels of precision they achieve.
Right now he’s standing in front of the SLT cross welding system that is the key to his promise of continuous production. “That’s where the coil runs through the cross welding machine,” he says, pointing to the strip guide. “When the sensors in the decoiler find that the coil is reaching its end and that there are only 200 meters left in the strip accumulator, that’s when things get serious.”
Everything ready for the coil countdown
Time for action! The laser cuts the strip from the old coil to an oblique angle... Photo | Remo Zehnder
... and quickly does the same with the strip from the new coil... Photo | Remo Zehnder
... then the clamps move together and line the ends of the strips up perfectly. Photo | Remo Zehnder
The same laser optics are then used to weld the ends of the coils so that production can continue. Photo | Remo Zehnder
The machines further down the line stubbornly continue calling for up to 100 meters a minute. The operator activates the accumulator and the coil stops, so now only the strip accumulator is delivering the metal strip to the machines. There are now 150 meters left in the accumulator.
The SLT clamps the end of the old coil and a laser beam cuts it. Only 120 meters remain in the accumulator! By now the operator has threaded in the new coil. It is also clamped in place and cut to the same angle. 80 meters to go.
The clamping jaws move simultaneously, guiding the laser-cut ends of the two coils together and creating a “perfect zero-gap joint” as Reith puts it. In the meantime, the control system has switched the parameters for the laser and the same laser optics now weld the ends of the metal strips. There are still 40 meters remaining in the accumulator.
The clamping jaws open and the “lengthened” coil now races into the accumulator and continues down the production line. The people and machines downstream from the accumulator are blissfully unaware of what’s been going on. To them, it simply seems as though the coil will never end.
Zero-gap joints thanks to laser
Cross welding machines are essentially nothing new. They have been around a long time in the form of shears and TIG welders. But when strip thicknesses fall below 0.3 millimeters, the metal warps too much during shear cutting, and that has a negative impact on the quality of the seam. “That kind of seam could easily tear somewhere down the line, given all the tensile forces it’s subjected to,” says Reith.
But the machine built by THE avoids this problem thanks to the precise interplay of the clamping jaws and the contact-free cutting with a laser. “Once the clamping jaws are closed, we have a tolerance of just 0.01 millimeters over a length of up to 750 millimeters. The laser beam cuts the strip smoothly without any warping. There would be no way of creating a perfect zero-gap joint if we used mechanical shears for cutting.”
The second problem of conventional cross welding machines is that TIG welding causes scorching at the seam, which often results in problems further down the line. “What’s more, TIG seams are often harder than the base material. These hardened sections can damage tools, especially in punching applications.”
Two ticks for more tensile strength
Reith has two other apparently simple tricks up his sleeve to increase the tensile strength of the seams. One is that the SLT always cuts and welds at an angle of between 15 and 45 degrees, depending on the model. That makes the seam longer and distributes the tensile forces over the length of the seam.
THE Machines Yvonand SA is headquartered in Yvonand, in the French-speaking region of Switzerland, and is part of India’s Jain Group. The company specializes in two key areas: welding systems for very thin and small precision tubes and machines for producing plastic pipes for drip irrigation.
“Plus, we always try to produce a weld factor greater than one, which means the seam is thicker than the strip. The only way to do that without filler material is by cutting at tremendous precision and positioning the ends of the strips in a zero-gap configuration. The strips undergo thermal expansion during welding, pressing the melt together, and that creates a stable convexity.”
However, this shape is sometimes problematic for subsequent processes, so the SLT can be combined with a press that compresses the seam to the original thickness of the strip immediately after welding.
“The combination of light from the fiber laser TruFiber and careful positioning of the clamping jaws lets us create a homogeneous joint that can handle the tensile forces involved. The seam is still visible, but the strip has the same characteristics as an unsullied coil that has never been welded, just as if the cross welding process had never taken place.”
Our customers acquire the ability to exploit the productivity of their manufacturing facilities to the full.Wolfgang Reith, Managing Director THE Machines Yvonand
By default, the machines by THE can handle strip thicknesses from 1.2 millimeters down to 0.05 mm, which is only slightly thicker than the aluminum foil used to package foods. In certain cases, it can also be customized to handle other thicknesses.
Say goodbye to wasted time
Reith’s customers are all after the same thing: they don’t want their production line to stop. “When you’re producing tubing, you obviously need a feedstock you can draw on constantly. And in many cases continuous production also makes sense for downstream punching processes. Some of my customers punch thousands of electrical contacts a minute. Whenever the time comes to thread a new coil into their sophisticated punching tool, they have to work laboriously through as many as 90 steps. That takes a half hour and may have to be done six times a day, depending on the length of the coil! In this case, the SLT could give them three hours of additional production time, equivalent to 180,000 additional parts a day!”
Originally, the SLT was conceived as a permanent component in tube welding machines. Three to four hours generally pass between cross welds, and that gave Reith the idea of designing the SLT as a mobile system. “That means customers with multiple lines can organize their production process to ensure that the SLT is always in the right place at the right time, so they only have to purchase one machine. This became practical only after TRUMPF launched the new, compact generation of its fiber lasers.”
The seam is clearly visible but has the same characteristics as the strip. The cross welding machine can weld virtually any metals and alloys, with maximum repeatability. Photo | Remo Zehnder
This is what Reith's customer produce in continous production: electrical contact, for example for the automobile industry, ... Photo | Remo Zehnder
... tubes and cables. Photo | Remo Zehnder
The SLT family cuts and welds a huge range of metals and alloys, including copper, bronze, aluminum, stainless steels, bimetals, gold-plated strips and “all your everyday metals – and all with the same optics”. Reith adds with conviction, “It’s essential to use non-touch methods for both cutting and welding. My customers often tell me that this is the approach that works best.”
And when Reith’s customers leave Yvonand and head back home, they know they will soon be making money from time that used to be wasted.
phone: +41 (0)244 23 50 50