The Liebherr Group is a family-run technology company with a very broad product range. The company is one of the largest construction equipment manufacturers in the world, but also offers high-quality, use-oriented products and services in many other areas. Liebherr was founded in Kirchdorf an der Iller in southern Germany in 1949. This is where the company develops and manufactures its hydraulic excavators, in addition to material handling machines and articulated dump trucks. For some time now, an especially developed Weber metal deburring system has been in use in Kirchdorf.
Anyone driving through Upper Swabia, in the south-east of Baden-Württemberg, will frequently come across the name Liebherr. Large machines of the manufacturer characterise the periphery of many communities in this area, which is known for its high quality of life as much as for its economic dynamism. Liebherr no doubt makes a significant contribution to this.
This is because the company stands for highest quality and reliability across the globe. Liebherr-Hydraulikbagger GmbH,based in Kirchdorf an der Iller , is no exception. The company produces around 3,500 machines a year and is the global market leader in wheeled excavators.
Components weighing tonnes
For some time now, the specialists there have been working with a Weber deburring line, which essentially consists of two systems. What's key here: The deburring machines process their workpieces in one pass from above and from below. The workpieces are components made of steel with a thickness of up to 50 millimetres, a length of up to six metres and a width of 1.60 metres. The largest ones weigh three and a half tonnes.
When they come out of the cutting line, they have to be prepared for the next processing step, either straightening or welding. This means that the cutting edges must be deburred and the surfaces must be free of slag, scale, pockets or coarse splashes. “We process more than a thousand workpieces a week here,” Torben Handeck, Head of Steel Construction at Liebherr-Hydraulikbagger GmbH, says, outlining the scale involved.
Before the new Weber system went into operation, the steel parts were deburred by hand – a hard and energy-consuming job that takes a lot of time. All the more so because the burrs that are created during plasma cutting or oxygen-gas cutting are often extremely hard and large. Once one side had been finished, the workpieces had to be turned by crane and magnet. “That was time-consuming and not optimal from the point of view of occupational safety,” Torben Handeck says. “In addition, the work was very strenuous, so the workplace was unattractive.”
Standard machines usual in the market were ruled out
So Torben Handeck set about finding a satisfactory solution. His stated aim: Machining of the steel parts was to be possible without turning, and the previous manual work with an angle grinder was to be taken over by a powerful grinding system capable of completely machining the workpieces in a single processing step.
However, most standard machines available on the market are usually only designed to machine workpieces from above. What's more: While the option of machining workpieces from below was the central requirement, it was by no means the only one, as Karl Bauer explains. As a specialist in application technology at Weber, he accompanied the project at Liebherr and played a key role in its development.
“Such large parts usually come out of the rolling mill with in part considerable distortions. The thickness tolerance of a 50-millimetre sheet, for example, is up to three millimetres according to DIN – plus and minus, therefore in total up to six millimetres. In addition, the heat generated during cutting can cause the workpieces to warp further. A good grinding machine must be able to handle such distortions effortlessly.”
High compensation for tolerances required
And that's what the Weber machines are capable of. Using slag hammers, they remove even stubborn pieces of slag cleanly – and with a tolerance of up to ten millimetres in thickness and distortion. The patented P2 planetary head unit plays a central role in this, as it can move towards or away from the workpiece depending on the load.
Added to this is the STC pin grinding beam, which is characterised not only by constant grinding pressure, but also by a high compensation for tolerances. The grinding belt is held flat, pretensioned a few millimetres downwards. Due to the long contact surfaces with the workpieces, it automatically works harder on all edges without creating secondary burrs. The result is a consistently high grinding quality and a large material throughput even with very thick and uneven workpieces. What's more: The long service life of the grinding belt keeps operating costs low.
It also helps that the deburring systems work in an input-controlled manner: As soon as a workpiece is in the machining area, the control recognises this and automatically starts to clear the surface of protruding burrs, scale particles or other unwanted segments.
But back to the user, Liebherr-Hydraulikbagger GmbH in Kirchdorf. Before the then Head of Production, Stefan Richter, and Torben Handeck decided on a solution, they wanted to be absolutely sure. After all, it was not only a question of a considerable investment, but above all that the new grinding system should ideally meet the requirements one hundred percent and reliably produce the desired results.
Weber delivers the best results
So Liebherr looked in detail at what was on offer in the market and shortlisted several potential suppliers. Then it was time for testing. Karl Bauer: “Liebherr-Hydraulikbagger GmbH delivered several tonnes of material to Kronach, which we processed before their eyes. They did the same at our competitors’. In the end it was clear: The Weber machines were the most robust and reliable in terms of process, and they delivered the best results.”
When it was clear to Torben Handeck and his team that they favoured a solution from Kronach, however, the real work began: The Weber machines had to be optimally adapted to Liebherr's individual requirements and conditions. “You must keep in mind,” Karl Bauer says, “a machine that grinds a workpiece from below must always work against gravity. That doesn't make things any easier.”
Among other things, Liebherr-Hydraulikbagger GmbH in Kirchdorf tested a P2 planetary head with slag hammers and rounded the edges in a second processing step with a different tool. Since the result had not been one hundred percent satisfactory before, those responsible for the project at Weber and Liebherr had decided to replace the grinding belt with a planetary head and slag hammers.
Two years of individual development
“This is just one example of many of how we worked together to get closer to the optimal solution,” Karl Bauer says. “All in all, the development took about two years and countless discussions until we had finally cleared all the hurdles.” Involved in this were the application technology sales department as well as design engineers and the management of Weber on the one hand and the team around Torben Handeck on the other. “Once we had agreed on the solution in principle, the actual construction at our end then went very quickly.”
Today, Liebherr-Hydraulikbagger GmbH in Kirchdorf works with two Weber grinding machines of the type MK-1600 P2uP2u and MK-1600 KP2, which are arranged in series in a grinding line. They machine the workpieces as required, one after the other, from below and above in one pass, and deliver excellent results. Not to mention, says Karl Bauer: “It's all running in a very stable and secure process.”
Torben Handeck confirms: “The solution works excellently and exactly as we wanted it to. We no longer have to turn the parts, which increases work safety and speeds up the whole process. And the workplace has become significantly more attractive. But most of all: Weber did a lot of development work with us, and together we created a customised, sustainable solution.”
In the meantime, the Kronach-based company has become a strategic partner for him. “I am quite sure we will tackle other challenging projects together in the future.”