Machine vibration is a very complicated issue to study. It requires both FEM (Finite Element Modeling) as well as Modal Vibration Analysis to verify those models. That is why almost no machine builder does this. They simply do not have the resources and talent. Not so for the former Beloit Corporation, the oldest, largest, and arguably most proficient of the web machine builders. Everyone of Beloits dozen product lines had a modeler. I was their winder tech expert some 30+ years ago. However, to explain modes of vibration really required animation which in turn required learning all kinds of othertech. This was far ahead of its time back then and still may be.
Still, I would be happy if builders would just simply learn that ‘critical speed’ (of rollers) has no meaning for almost any machine. It is over-simplified and, worst of all for engineering, non-conservative. What that means is that you may upsize a roller, think you are safe from vibration and then find out the hard way you aren’t, even after all that effort. Worse yet, system resonances, the proper concept, are usually non-events IF the designer knows what they are doing. The exception, however, is certain types of winder vibration as shown below where even the best machine can have pounding vibration with grades known as ‘bouncers.’ Bouncers have two key material properties: high web-web COF and high ZD compressibility. The materials that have this in spades are adhesive tape, nonwovens, textiles and tissue. These might not be able to be run at high speeds even with foundations weighing a hundred tons and frameworks nearly as stout and with sliding clearances less than a hair’s thickness on moving parts.
Enough with the words, time for the show.
Web201.55bYouTube clip link: