Thesis (doctoral)--Finland's Institute of Technology, 1950. / Includes bibliographical references (p. [102]).

Thesis (doctoral)--Finland's Institute of Technology, 1950. / Includes bibliographical references (p. [102]).

Thesis (Ph. D.)--Oregon Graduate Institute of Science & Technology, 1994.

To make low grade lumber into high-valued products, finger-jointing is a widely used method in the timber industry. In certain situations, chip-out occurs degrading the quality of the joint. To better understand the machining process, a beam-type dynamometer based on strain gages was designed to analyze the dynamic cutting forces parallel and vertical to the feeding direction. The test results indicate that the dynamometer design was sensitive enough to measure small force changes at relatively high frequencies during the cutting operation. The test conditions were set as close as possible to that in industry. Cutting force behavior of the rotating cutterhead was examined, and test samples with different fiber angles were used for inspecting the influences on the chip-out occurrence and cutting forces. The results show that cutting forces are determined by the density of the wood and the maximum chip thickness. Slight differences in tool shape and the balance of the cutterhead can vary the cutting force behavior. The occurrence of chip-out is dependent on the fiber angle and the chip thickness. No relationship between chip-out and cutting force was found, within the sensitivity of the dynamometer. Fiber angle has some effect on the cutting force, and also influences the cutting surface quality. A high speed video camera was also employed to visually observe the formation of chip-out. Frame by frame analysis showed that the chip-out occured when a knife passed through the trailing edge of the cut-block, and the failure developed in the sequel cuts. Cutting force and chip-out models were developed from the experiment results, and can be used to reduce chip-out and increase recovery during finger-jointing in ponderosa pine cut-stock operation. / Graduation date: 1993

In the manufacturing industry, the mechanics of metal-cutting is well-understood and used to improve cutting processes. The mechanics of wood-cutting are still in its early stages and further research is required. Although there is a lack of knowledge regarding cutting mechanics for wood, today's cutting speeds in modern sawmills are as high as 100 m/s and the production rate and quality are high, to the cost of unnecessary wood-based waste. To be able to reduce waste it is necessary to understand the process of wood machining in detail. A Kistler 9129AA dynamometer was commissioned in a custom rotation machine and compared to an already existing sensor. It was shown that there were significant deviations between the measurement results of the evaluated sensor system and the Kistler 9129AA dynamometer. In this specific setup, the Kistler dynamometer was not able to deliver the same results as the existing sensor system. Therefore, the eligibility of the Kistler 9129AA dynamometer to measure cutting forces in wood could not be concluded.

<p>In the last decades, high speed cutting has become an attractive technology in the wood industry. The possibility of reducing global costs in addiction with an increase in productivity, were the main reasons for the enlargement of the use of this technology. </p><p>As usual, these advantages are accompanied by disadvantages that should be carefully analyzed. If on the one hand cutting forces are reduced with increasing cutting speeds, on the other hand, the centrifugal forces affecting the tool are higher. Exposed to such high loads, there is a considerable risk of tool failure that embeds hazards for both machine and workers. </p><p>To prevent the risk of accidents and to guarantee safety in use, security standards have been implemented in industrial fields, imposing specific experimental tests, with defined procedure modes. Accordingly with these standards, the results obtained through the tests should fall inside limited ranges. The experimental tests suggested on the European Standards are intended to simulate the real working conditions of a rotating cutting tool, where extreme centrifugal forces are imposed by the high values of speed. Although their main importance, these destructive tests aren’t always practicable. It happens, for instance, with tools produced in small batch sizes, or as an ascertainment for the fail-critical speed during the development stage, or even due to physical incompatibilities between the tool and the laboratory testmachines. </p><p>The high value of weight associated with the cutting tool prototype developed and patented by Verktygs Larsson AB was an impediment to run the laboratorial tests specified by the standards, forcing the company to find a new way to assure the safety requirements of their product. </p><p>The main goal of this project was the development of an alternative method based on finite element theory to perform a safety analysis to the prototype of a wood cutter. This tool is used as a component in high speed planers. </p><p>In addiction to this primary objective, some considerations were made about other available models, with increased dimensions or even with different parameters. If there was the need, design changes could be assumed in order to guarantee that the tool reached the requisites of the safety standards. Considering an optimization effort, material changes would also be considered, to aim in the direction of reducing the tool weight and the consequent centrifugal forces.</p>

In the last decades, high speed cutting has become an attractive technology in the wood industry. The possibility of reducing global costs in addiction with an increase in productivity, were the main reasons for the enlargement of the use of this technology. As usual, these advantages are accompanied by disadvantages that should be carefully analyzed. If on the one hand cutting forces are reduced with increasing cutting speeds, on the other hand, the centrifugal forces affecting the tool are higher. Exposed to such high loads, there is a considerable risk of tool failure that embeds hazards for both machine and workers. To prevent the risk of accidents and to guarantee safety in use, security standards have been implemented in industrial fields, imposing specific experimental tests, with defined procedure modes. Accordingly with these standards, the results obtained through the tests should fall inside limited ranges. The experimental tests suggested on the European Standards are intended to simulate the real working conditions of a rotating cutting tool, where extreme centrifugal forces are imposed by the high values of speed. Although their main importance, these destructive tests aren’t always practicable. It happens, for instance, with tools produced in small batch sizes, or as an ascertainment for the fail-critical speed during the development stage, or even due to physical incompatibilities between the tool and the laboratory testmachines. The high value of weight associated with the cutting tool prototype developed and patented by Verktygs Larsson AB was an impediment to run the laboratorial tests specified by the standards, forcing the company to find a new way to assure the safety requirements of their product. The main goal of this project was the development of an alternative method based on finite element theory to perform a safety analysis to the prototype of a wood cutter. This tool is used as a component in high speed planers. In addiction to this primary objective, some considerations were made about other available models, with increased dimensions or even with different parameters. If there was the need, design changes could be assumed in order to guarantee that the tool reached the requisites of the safety standards. Considering an optimization effort, material changes would also be considered, to aim in the direction of reducing the tool weight and the consequent centrifugal forces.