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Dynamics of bandsaws

University of British Columbia

This study investigates some of the basic dynamic problems in the use of handsaws in industry. As the main purpose in bandsaw study is to understand and improve the cutting performance of the sawblade, this study emphasizes those dynamic problems that most affect the sawblade performance. These include the bandsaw structural dynamics, the top wheel dynamics, the global behavior of sawblades, and the washboarding problem in cutting. The study of bandsaw structural dynamics investigates the possible structural modes affecting the performance of the sawblade. Three structural modes within a frequency range of interest from 0 to 60 Hz were found and analyzed. The corresponding critical structural elements are indentified. The role of top wheel straining mechanism in bandsawing is discussed in the study of top wheel dynamics. Top wheel displacement during cutting and its effect on the performance of the sawblade are also investigated. The causes of top wheel displacement are the speed change of handsaws and temperature rise of the sawblades. In the global behavior of sawblades, the sawblade between the guides is modelled as a narrow, axially moving, thin beam with end loading. The Euler's equation of motion is developed by applying Hamilton's Principle to the model. A simplified finite element method by using a modified cubic beam element is used to solve the eigenproblem. These results are verified by tests with an idling sawblade. A finite element approach capable of calculating the natural frequencies and mode shapes is obtained. The washboarding phenomenon is investigated. Extensive experimental results are obtained and an analysis of the resulting washboarding is presented. Two types of wash-boarding have been observed and identified with the tooth impacting problem and the chatter vibration problem. The results of this study will be of interest to those who wish to improve their understanding of the dynamic behaviors of bandsaws and also to improve the performances of handsaws.

Text

2010-09-27

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http://hdl.handle.net/2429/28734

Mechanical Engineering

University of British Columbia

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