Mid Sweden University

In modern sawmills, chipper canters are used to transform the approximately circular cross section of logs into a rectangular shape before the log is sawn into planks and boards. The chipper canter is in essence a conical disc equipped with knives on its periphery and a circular saw blade at its base. Thorough the action of the chipper canter, the outer parts of a log is removed and transformed into sawdust and chips. In some situations it might be important to be able to predict the energy consumption during canting, for example when one wants to know whether a particular canting strategy can be used considering that there is a limit to the electrical power supply. The aim of this paper was therefore to develop a theoretical model that can perform such a prediction. The canting process can be divided into two parts; the chipping performed by knifes and the sawing performed by the saw blade on the chipper head. The sawing part is performed in order to get a smooth enough surface of the reduced portion of the log. In this paper, emphasis is put on the chipping part of the process and the contribution from sawing is treated only in principal. The results from the theoretical model were compared to results from a field trial and it was concluded that the model gave a fair prediction of the power needed.

Canter chippers are used in sawmills to reduce the circular cross section of logs to a rectangular shape before sawing. The canter chipper is a conical disc equipped with knives on its periphery. When rotated at high velocity it transforms the outer parts of a log into sawdust and chips. It is important to be able to predict the energy consumption during canting since it is useful to know whether a particular canting strategy can be employed in situations where there is a limit on the power supply. A theoretical model in which energy consumption can be calculated is necessary for such a prediction. Data concerning the specific cutting energy is needed to develop the model for the canting operation. In this paper the energy consumption during chipping of spruce is determined by using a pilot wood chipper at two different cutting rates and for several cutting angles. The results indicate that the specific energy to cut wood chips increases as the angle between the fibre direction and the cutting plane increases.