Effects of Non-Proportional Damping on the Residual Vibrations of Mode-Coupled Ultra-Precision Manufacturing Machines

Ultra-precision manufacturing (UPM) machines are used to fabricate and measure complex parts having micrometer-level features and nanometer-level tolerances/surface finishes. Therefore, low-frequency residual vibrations that occur during the motion of the machines’ axes must be minimized. Recent work by the authors has revealed that coupling vibration modes of passively-isolated UPM machines can provide conditions for drastic reduction of residual vibrations vis-a-vis the recommended practice of modal decoupling. This paper presents an investigation into the effects of non-proportional (NP) damping on the conclusions reached in the authors’ prior work. With NP damping added, the conditions under which mode coupling is beneficial relative to decoupling are seen to remain largely the same. However, NP damping is shown to significantly influence the conditions under which the system’s response is most sensitive to mode coupling. Design guidelines for maximally exploiting the benefits of mode coupling are presented and demonstrated experimentally on a UPM machine.