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Modeling of static and dynamic components of cutting force in sawing Echeverri, Rodrigo

Abstract

The research presented in this thesis is directed towards the development of models for the calculation of cutting forces in bandsaws. The motivation for this work is the search for a solution to the washboarding problem in sawing. Washboarding is a cutting accuracy problem that is often found in sawmills which causes losses in material and labor. The first chapter of this thesis presents a literature review of previous research conducted both in cutting mechanics and the washboarding problem. The references consulted indicate that the presence of lateral cutting forces is caused by unbalanced chip loads on the saw teeth during vibration. A survey in the literature in wood cutting reveals that no previous research is available which can be directly applied for the estimation of these lateral cutting forces in bandsawing. Therefore a series of models from metal cutting are studied and their application to wood cutting considered. The body of the work divides the cutting process in two major, independent components. The first part is the static process that would occur under unbalanced chip loads but no tool vibration. The second part is the portion of the process that creates components of force which depend upon the kinematics of the cutting process. A series of cutting models to estimate the forces under static conditions in bandsawing are proposed in the second chapter of the thesis. The third part of the work shows the development of a series of fundamental models that cover the analysis of the dynamics of the simple orthogonal cutting process. The theories proposed in that section are compared to the findings of other researchers and it is concluded that the model improves the understanding of the cutting process during tool vibrations. The fourth section of the work provides a series of experimental results that support the developments achieved for the static portion of the cutting force model for bandsawing. Finally, the last chapter of the thesis presents a series of conclusions and suggestions for reducing the washboarding problem by decreasing the magnitude of the lateral forces exerted in a vibrating bandsaw tooth.

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