The most critical part of the tissue papermaking is performed in the yankee cylinder. The creping doctor is composed of a metallic body containing a blade holder. The doctor oscillates laterally from one side of the yankee to the other by an electric motor, and the blade holder regulates the pressure of the blade against the yankee. The pressure level, the creping angle, the peripheral or paper speed, the humidity, the blade material and the adhesive materials are the most important variables in the tissue paper-making process.

In general the price of the tissue paper mill is high (around 20M€) and only few high tech companies can afford the design of the complete solution. European large companies like METZO, VOITH and ANDRITZ are the main references in the world in this type of paper mills. The paper mill is a really complex machine and therefore the main constructor uses to subcontract parts of the machine to different companies, like Lantier.


The most critical part in tissue paper machines is the creping doctor which has an average price of 40k€  epending on the installation. In the creeping doctor is placed the bladeholder witch permits to locate the blade with the right angle. The bladeholder costs around 6000€. The objectives of the project are focused on the development of highperformance blades for creping. The blade is located on the blade holder and performs the creping operation attacking the humid paper with a certain angle. There are blades with different metals and ceramics, but steel blades are now dominant in the market. The lack of damping of steel blades is one of the main drawbacks of these blades especially in tissue paper mills considering the vibrational problems that it can appear.
However, the price has to be competitive considering that the blade is changed every 10-15 hours. The approximated price of a steel blade is 200€. The Vibration Problem The creping doctor blade chatter is a fairly complicated process where converge dynamic parameters of different parts of the doctor (such as, the
natural frequency, the stiffness, the damping), and tissue making process parameters (such as the creping blade pressure, the creping blade angle, the peripheral speed of the yankee, the adhesive material and the blade material and dimensions).

As any self-excited vibration, the chatter makes the process become unstable and the vibration starts increasing up to unacceptable levels. The presence of chatter entails the tissue paper breakage, the accelerated removal of the adhesive from the yankee's surface and can lead to the marking of its metal surface, generating a chronic damage on it. Therefo re, the economic losses caused by the chatter can be enormous due to both the stop of production and the costs of the yankee cylinder regrinding.

Most of the efforts for chatter avoidance in the paper industry have been focused from a strictly process point of view, trying to get the most appropriate process parameters to eliminate chatter and maximize the creping process. The total market size for creping blades and doctors is 100 M Euros, and Lantier has a market share of 12%. Lantier is expecting an increase of revenues of 10-20%, based on a market share increase to 16-20%.