Headbox rebuild for Ahlström Munksjö’s Dettingen

"We are the inventor and today’s market leader in pre-impregnated papers, which are preferred by some of the biggest printers in the decor paper market. Our customers have clear quality expectations in terms of paper printability, internal bond level and flatness,” says mill manager Thomas Gehring. To further enhance the quality they produce, the mill decided to invest in a wet end rebuild at its PM 34.  “When I started here as mill manager, I noticed the good performance of the PM 31 headbox in the decor paper it produced. Deciding to stay with the same supplier was easy,” he says. The wet end rebuild Valmet supplied for the PM 34 included a new OptiFlo headbox as well as an upgrade of the approach flow system and a new breast roll shaker to ensure that the ambitious quality targets would be met by a streamlined process.  

“The start-up was quite relaxed. It was almost like a plug and play. Since the start-up, we’ve had very good quality, which clearly demonstrates the advantage of the new dilution control headbox,” says Gehring.

Flatter sheet and improved strength

Gehring says the project has been a success: “I think the results of the project speak for themselves. We have the same PM 31 performance – or even better now on the PM 34. Since the rebuild, we have more constant and flatter grammage variation in both machine and cross direction. After the start-up, the CD deviation improvement was immediately evident from the scanner data. We’re talking about a reduction in deviation of more than 15 percent,” he continues.

The increasing speed of printing and converting means their customers can run their processes in a more stable way.

Valmet’s dilution headbox can meet the quality requirements of decor paper production at PM 34.

The paper strength has also improved. The mill has been able to reduce the tensile strength index by more than 50 percent. The new breast roll shaker will also allow them to influence formation better and further optimize a wider range of paper properties in future.

Consistency is the key to efficiency

The rebuild has increased machine efficiency, because less time is lost on grade and grammage changes, and the PM 34 now operates at a more constant level because of the higher automation level. This is seen in the drying section’s runnability and sheet behavior, for example. Thanks to the renewed approach flow system, dirt levels have also decreased. “We have a clear expectation that all this will help us to run with significantly fewer breaks in the future,” Gehring says.

We’re talking about a reduction of more than 15 percent in grammage deviation.

The PM 34 produces colored decor paper, and the less color deviation the paper has, the better. Since the rebuild, the mill crew has been able to assess the right color level needed for each customer more quickly. The flatter sheet also helps with changes in color constancy: A more constant sheet means a more constant color level.

The new Valmet machine screens ensure the PM 34’s risk-free operation. The outflow-type machine screen, with its innovative rotor and foil designs, ensures efficient impurity removal.

“We have a very good market position in pre-impregnated papers because of our very high and constant quality. We’re therefore looking for partners who have the same quality mindset. We found Valmet the perfect partner,” Gehring concludes.