UBC Theses and Dissertations

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UBC Theses and Dissertations

The cutting behavior of bandsaws Lehmann, Bruce


A model of a bandsaw, subjected to lateral cutting forces on the teeth and restrained by the sawn surfaces of the wood, has been developed. The blade model includes the effects of blade dimensions, bandmill strain, in-plane stresses, tooth (gullet) depth, tooth bending stiffness, blade speed, strain system parameters, and the span between the guides. The lateral cutting forces along the length of the cut were found to have dominant low frequency components and are modelled by functions having spectra that are inversely proportional to the frequency. The results of the model simulation show that when there is little or no contact between the body of the blade and the sawn surfaces, the sawing accuracy is governed by the tooth-tip stiffness and the magnitude of the lateral cutting forces. When the clearance gap is small compared to the blade deflection, the contact forces dominate and poor cutting accuracy results because the blade cannot recover quickly from disturbances. The clearance gap between the blade and a sawn surface is shown to be less than the side clearance of the teeth because of sawdust spillage and surface roughness. A formula is developed that defines how blade stiffness, the clearance gap, and the cutting forces affect sawing deviation. It is found that the tooth-tip stiffness is the blade parameter that most significantly affects cutting accuracy. An example of determining the optimal side clearance and some practical implications of the results are presented.

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