Unexpected Vibrations of Relatively Simple Cutting Machine Mechanism

Abstract

Unexpected vibrations and resonance with frequency three times the rpm were detected in a relatively simple cutting machine during process of inertia force reduction (balancing). A knife of the cutting machine is actuated by two identical crank mechanisms at the ends of a crossbeam. The vibrations induced inertial forces larger than the considerable machine imbalance. The crank length to connecting rod length ratio was small enough that the corresponding excitation kinematic acceleration overtone component was practically negligible. The vibration characteristics consisting mainly of the drive shaft gyratory vibrations was determined based on measurements of forces transferred to floor, accelerations of the mechanisms and on a CAD model calculation involving the mechanism main members compliances. Improvements were proposed and tested upon the results with focus on vibrations elimination.