Method of sheet processing using a tension exciter

A method of processing sheet metal having a certain modulus in a process using apparatus having a natural frequency and rotating components that have certain inertias, with tension changes in the sheet material propagating upstream and/or downstream from the location of the occurrence of the tension changes, the sheet metal having a mass flow balance as it travels through the process, the method comprising:

• momentarily upsetting the mass flow balance of the sheet metal by means that introduces tension changes in the sheet metal at a location at which the metal is otherwise unsupported in its travel through the apparatus and process to determine the existence of any amplification of tension change occurring through the relationship of the mass flow of the sheet metal to sheet tension,
• the means for introducing tension changes having a known spring rate,
• describing said tension changes as a function of time and frequency,
• relating tension changes occurring in an upstream or downstream location of the process to another upstream or downstream location, and
• including as operating parameters of the relationship between mass flow and tension (1) the sheet metal modulus, (2) the inertia of the rotating components, (3) the spring rate of the means employed to introduce tension changes in the sheet metal, and (4) the natural frequency of the apparatus,
• measuring the forces at which the tension changes in the sheet metal are momentarily introduced with a sensor that provides signals representing said forces,
• measuring tension changes in the sheet metal with a second sensor that provides signals containing a plurality of frequencies representing a plurality of sheet tension changes propagating upstream and/or downstream from the location at which the tension changes are introduced,
• analyzing the signals from said sensors to determine the influence of the above-named parameters on the relationship between mass flow and tension, and
• using such determination to identify one or more of the rotating components of the apparatus contributing to tension changes.