At the heart of technological innovations in the tissue paper production sector, the creping blade stands out as a fundamental and essential component to ensure the excellence of the finished product. This element not only determines the physical properties of the paper, such as softness, elasticity and tear resistance but also significantly affects the perceived quality of the product by the end consumer.

Giovanni Policastro, CEO of Polimek.

The creping of the paper sheet is achieved through the interaction of a very hard steel blade, inserted in the creping knife, with the hot surface of a cylinder that, during its rotation, brings the sheet into contact with the blade. The blade is made of hardened steel and, in the area of contact with the cylinder (also known as the Yankee cylinder) is coated with a very hard ceramic material whose hardness reaches 1,000 HV. Since the coating of the cylinder also has a similar hardness (900 to 1,100 HV) and the blade load during contact with the cylinder is about 300 daN/m, a protective film called coating is interposed between the two elements. Incorrect operation of the creping blade can lead to damage to the surface of the Yankee cylinder and, if the problem persists, it becomes necessary to grind the cylinder with a consequent machine stop and production loss. This possibility greatly frightens mill managers, whether they are in production or maintenance, because it requires the machine to be stopped for several days, the use of highly specialized companies in grinding and the reduction of the hard coating thickness of the Yankee cylinder.

The phenomenon of Yankee cylinder damage is quite complex, and mill technicians often feel alone in facing a problem that generally gives signals several weeks before the problem manifests. With the Never Alone policy, Polimek provides tissue paper manufacturers with a team of expert installers and maintainers capable of optimizing the operational parameters of the creping systems and supporting the customer throughout the year. Thanks this initiative, Polimek intervenes with tailor-made solutions ranging from the optimization of operational parameters to scheduled maintenance and precise profiling of the creping blade. This proactive approach not only prevents damage to the Yankee cylinder but also ensures operational continuity and consistency in the quality of the finished product. Thus, scheduled maintenance and inspection visits are organized with machine downtime during which Polimek experts check the wear of mechanical elements, such as bearings, oscillators, pneumatic systems, the profile of the creping blade and the worn blade. Once the inspection and maintenance work are completed, Polimek technicians remain in the mill during the machine start-up phase to monitor the dynamic behaviour of the Yankee doctoring systems.

Dynamic and structural checks of the doctors in the Yankee area involve checking the natural frequencies of the mechanical components of both the doctors and the machine structure to verify their interaction. With the Poli-Check vibration analysis tool, it is possible to see in real-time how the entire system behaves and ward off the annoying phenomenon of chatter marks, which results in the grinding of the Yankee cylinder.

POLIMEK is capable of performing alignment, profiling and maintenance interventions on every type of creping blade, whether rigid or flexible; it also performs regular technical services on all the scraper systems of the paper machine. Polimek, an Italian company based in Paruzzaro – a few kilometres from Milan – designs and produces every doctoring system; its technicians boast over 30 years of specific experience in the field of doctoring systems and in the profiling and maintenance of creping, cutting and cleaning doctors.

Poli-Check for the vibration monitoring.