Influence of Guides on Critical Speeds of Circular Saws

Abstract

This paper investigates the influence of guides on the critical speeds of circular saws. Guides constrain the out-of-plane lateral motion of these rotating saws and have a stabilizing effect by increasing the critical speeds, below which the rotating saw is stable. We present expanded analytical formulations in which guides are modelled as multiple discrete spring-damper elements approximating the distributed nature of the guide pad and saw interactions. We observe that for a given guide pad area, convergence analysis is necessary to understand how many discrete spring-damper elements are actually necessary to approximate the distributed nature of the guide pad and saw interactions. Curiously, we observe that damping in the guides has no significant influence on the critical speed and that it only changes the nature of frequency-speed characteristics of the rotating saw. We also find that critical speeds are sensitive to guides modelled with a distribution of discrete spring elements along the radial and/or circumferential directions. These observations suggest that more generalized formulations that model the guide pads as distributed spring-damper systems, rather than multiple discrete spring-damper elements, are necessary. We expect our findings to instruct and advise the placement of guides on rotating circular saws, such that a preferential increase in critical speeds can be obtained to make possible high speed and productivity circular sawing operations in the wood-working and metal-cutting industries concerned with circular sawing processes.