A Laboratory Wood Chipper for Chipping Under Realistic Conditions

Wood chipping is a critical component part of many pulp and paper making processes. In order to study the damage mechanisms, when wood chips are created through the wood chipping process, it is crucial to have access to an experimental equipment in which chips can be produced under realistic conditions. In this paper, a laboratory chipper is presented, which has been developed to admit chipping at rates that can be varied in a large interval, i.e. at rates ranging from 0 to 50 m/s. The chipper also makes it possible to study e.g. the influence of different cutting angles on the chip geometry. The knife used to cut the chips is mounted on a knife holder, which is instrumented in such a way that forces in three orthogonal directions can be measured. One reason for measuring the forces acting on the knife during chipping is that the average force in the cutting direction will give information about the wear of the knife over time. Since the actual force and the measured force differ due to inertia effects, a simple mathematical model is developed and used to evaluate the force acting on the knife. The results from the force measurements are presented and it is concluded that the laboratory chipper is a versatile tool in the process of increasing the understanding of the chipping process.