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Wood Chipping with Helical Chippers: A Theory about the Process of Chip Formation Dependent on the Tool Geometry

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASABE. 56(2): 363-369. (doi: 10.13031/2013.42661) @2013
Authors:   Jens Wegener, Tim Wegener
Keywords:   Auger Chip formation Chipper harvester Chipping Cone screw knife Helical chipper Machining technology Wood chip geometry Wood chips.
<italic>Abstract.</italic>

In experiments with conical helical chippers, it was found that the wood chips produced were always shorter than the chipper’s pitch. Until now, no explanation of this phenomenon has been given in the literature. This article considers theoretically the process of wood chip formation in a helical chipper with respect to its geometry and the length, thickness, and width of the resulting chips. Additionally, an approximation formula for the chip length has been derived using geometrical relationships. According to this approximation formula, the chip length is predominantly influenced by the cone angle of the rotor and the wedge angle of the blade. A comparison of the results of this approximation formula with wood chips made from three different types of wood produced with an experimental helical chipper showed that the calculated chip length correlated relatively well with the average length of the chips produced during the experiments. In addition, however, the experimental results revealed that the characteristics of the material also influenced the chip length and especially its thickness. The latter dimension appears to be negatively correlated with the material’s shear strength.

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