Zusammen mit Hamm hat Wörwag einen innovativen Einschichtlack für die Bandagen entwickelt

Hamm: Innovative Coating System for Rollers

Am 10. May 2021

In one layer

Looks like topcoat, but works like primer: Hamm AG, together with Karl Wörwag Lack- und Farbenfabrik, has developed an innovative single-coat paint for the drums of rollers that helps the Tirschenreuth-based manufacturer of road construction machinery to significantly increase capacities, optimize processes and improve quality.

The world is flat. At least in Tirschenreuth. In the tranquil little town of 9,000 inhabitants in the Upper Palatinate, almost 15 kilometers from the German-Czech border, Hamm produces machines that flatten and extrude many materials to an optimum and have become indispensable helpers even under hardest construction site conditions. The oldest manufacturer of road construction machinery has literally been on the go for more than 140 years.

Günter Kolberg, Leiter Montage bei Hamm AG.

This coating and its joint development are a success story.

Günter Kolberg, Manager assembly, Hamm AG

Every fifth road roller worldwide now comes from Hamm. And the demand is increasing. Every visitor who turns into the Hammstraße when approaching the Wagnerholz industrial estate will see this. Rollers, bandages – construction helpers in rich company color orange almost as far as the eye can see. In the past 15 years, the number of units has increased fivefold. This further increase is an important competitive factor for the company but is linked to the expansion of production capacities. To be able to build more machines, inventiveness in assembly is required. And courage. This is why Hamm has taken a path that no one has dared to take before with the construction of a new painting plant and a related efficient painting process.

Together with Wörwag, Hamm has developed an innovative mono-layer coating for the bandages that has never been seen before. „We can all be proud of this project,“ says Günter Kolberg, head of the assembly. „This coating and the joint development behind it are a success story.“ Developing the coating is one thing, but fine-tuning the process and bringing it to series production is another one. Kolberg: „You can only do that with a strong partner like Wörwag.“

„We need a whole new concept“

The starting position in summer 2016 is tricky. Kolberg still remembers the planning phase in detail. Again and again, the desired quantities are put into relation to the space required in the bandage plant. The wrinkles of concern are getting bigger. The quantities are to increase to 22,000 bandages per year. Including add-on parts, the people in charge are planning 700 to 800 coating processes per week. The coating process quickly becomes a limiting factor and therefore plays a decisive role from the very beginning. At this time, two layers of coating (primer and topcoat) are still applied. The two curing steps cost time, energy, and influence the processes.

Painting is not yet done in a mix of large and small drums. In the end, the solution is simple: the more rollers, the larger the coating system must be. Actually. Because the calculation does not add up. In the new drum unit, which has been extended by 3,600 square meters, there is space for a 45-meter long, almost 20-meter wide coating booth including curing chambers. Nothing more. But it should be twice as large. „It quickly became clear to us: we need a completely new concept – and the help of Wörwag,“ remembers Kolberg, who has been working successfully with the paint experts from Stuttgart for twelve years.

„I knew that we could solve the problem together. Because Wörwag does not only want to sell coatings but can help us.“

One coating application, more than 80 % solids content

The solution is innovative. A mono-layer structure from Wörwag is already in use for the rolled coating of small bandages.Why shouldn‘t this also work in the automated process for all products? The ambition is awakened – in the laboratory at Wörwag and in production planning at Hamm. Uwe Block, who has been Wörwag‘s application engineer at Hamm for many years, is in Tirschenreuth every four to six weeks.

„The key to our joint success was that with Hamm we had a target customer with specific requirements. Since we were involved in the development at an early stage, the plant could be optimally adapted to the needs of the customer and the paint material,“ says Block. His counterpart at Hamm is Jürgen Dötsch. „The requirements were not without their problems. To achieve a solid content of more than 80 percent with a single coat of paint, for example, is ambitious. To achieve this, we have to work closely together. You don‘t find a partnership like this everywhere,“ emphasizes the work preparation expert at Hamm.

Direct-to-Metal success formula

Both sides invest a lot of heart and soul in innovation. If there are problems, the heads are put together. Especially the transfer from development to series production regularly holds surprises. A new bandage type, different programming, changed overlaps in the painting process, new welding seams, or the stability – many topics need to be discussed in practice. „High praise to Wörwag. They reacted very quickly and pulled out all the stops so that we could always paint,“ says Dötsch. The trust in Wörwag is enormous. Because soon, there will be no way back.

As part of the expansion measures, Hamm decides to dismantle the old paint shop before the new one is ready.The result convinces everyone. In September 2018, the paint shop will be put into operation. In the meantime, 50 to 60 road rollers leave the production line every day. The concept with a Direct-to-Metal (DTM) mono-layer coating has proven itself practically from day one. Facts and figures underline this.

Throughput times today are about one-third shorter due to the elimination of one process step and the related curing process. The new paint shop is integrated optimally into Hamm‘s lean and efficient production process. Regardless of their size, the bandages are driven into the cabin on one side, washed fully automatically, then painted and finally cured at 85 degrees Celsius for around 40 minutes. The drums then leave the plant on the other side and are ready for the final assembly. At the same time, actuators and add-on parts can be processed in a manual painting booth. All in brilliant slate grey, RAL color 7015. One coating in one go.

1000 hours splash water test

„I always had reservations about a mono-layer system providing the same corrosion protection properties as a dual-layer material with primer, but when I saw the first sheets, I was very concerned: Wow, I had not expected this quality.“, recalls Sven Pechwitz, Head of the Industry Division at Wörwag. For example, the painted bandages pass the salt spray test after 1,000 hours and the condensation water test after 560 hours with excellent results.

Another positive effect of the DTM paintwork: Despite an increase in production and the associated higher number of coating processes, the VOC content does not exceed the critical value of 15,000 kilograms of solvent per year for the Tirschenreuth plant. If this had happened, Hamm would have needed an expensive thermal afterburning system. And all this because in the future, one coat of paint will be enough. Hamm is endowed ideally to compete with strong competitors.

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