Automatic analysis of tool status in band saws

Sammanfattning: The products with the highest return and longest life cycle in the sawmill industry are boards and planks. Unfortunately, a large part of the log becomes bi-products during the cutting process. One way to reduce the amount of bi-products in a sawline is to saw with as thin kerfs as possible. That is the cut of the blade. It is made possible by using as thin tools as possible. A thinner tool means using a tool with a thinner construction, which can be more sensitive to forces and vibrations. Thus it is important to know the performance of a bandsaw blade and the wear during a working cycle. This is to optimise how often the blade needs changing, but also to ensure that a blade does not break during the cutting process. This project is about analysing the forces on a tool during a working cycle. Can the already installed measuring systems help predict when a bandsaw blade will lose performance ? Data was extracted from the variable frequency drive connected to the motor driving the bandsaw, when cutting spruce and pine. The experiment was designed to test high and low values for several sawing parameters e.g., tool speed, feed rate, gullet fill ratio and bite per tooth, using bandsaw blades used for eight hours and newly serviced blades. A partial least squares regression model was fitted to the data to explain force per tooth. The linear model shows a similar behaviour in comparison with laboratory experiments. Although the values indicate larger forces, which may be due to various energy losses in the process and the instruments. It is shown that it is possible to explain force per tooth, with a value of determination R2 = 0.84, using bite per tooth, feed rate and gullet fill ratio as explanatory variables. The result of the analysis points at the working cycle of 8 hours being to short to be a significant factor in explaining the forces on a blade. Hence further work would be to design an experiment with a longer working cycle, but also with more extreme values of the sawing parameters.