One of the most dreaded words uttered in a tissue manufacturing facility is “chatter”. The thought of Yankee chatter makes many vendors, suppliers, and operators queasy. As tissue mill technology has evolved with improved controls, hardware, drives, clothing, and chemistry, Yankee speeds have increased leading to production limitations of the asset.
When a tissue machine is pushed to the limit of its design speed, blade chatter often develops. Blade chatter occurs when the tip of the blade moves out-of-plane due to vibration and a stick–slip motion develops between the blade surface and the Yankee surface. Chatter is a destructive process where the doctor blade damages the metal surface and the only fix is to regrind the Yankee surface.
Chatter has been an issue on MG, wet crepe, dry crepe, and TAD processes; no type of manufacturing is exempt.
|A Yankee dryer surface with chatter marks.||Bath tissue produced on a Yankee with chatter.|
Significant advancements have been made in recent years with tools and techniques to track, predict, and limit blade chatter in Yankee dryers. Equipment vibration monitoring around the creping process is the most noteworthy tool to control chatter (it is impossible to eliminate in some cases). Various suppliers and manufacturers are adding accelerometers to creping and cleaning blades, and many times the suction pressure roll, to measure and record vibration patterns developed during the creping process. This stream of information is used to establish strategies and procedures to control the blade changing process, drying, grade specifications, and how to effectively minimize chatter-related issues. Suppliers utilize this information to improve structural design of the blade holder, blade tip geometry and coatings, and other components to reduce the risk of chatter marks.
As technology develops and more operators began to dabble with vibration monitoring, the information gathered becomes increasingly valuable and useful. Present day systems can be used for instant feedback regarding blade type and loading, chemistry, sheet dryness, speed, pulp quality, trial set ups, and much more. To learn more about Kadant’s Yankee solutions, including vibration monitoring, contact me at firstname.lastname@example.org.