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Force Relations and Dynamics of Cutting Knife in a Vertical Disc Mobile Wood Chipper

Author(s): Segun R. BELLO | Musiliu A. ONILUDE

Journal: Leonardo Electronic Journal of Practices and Technologies
ISSN 1583-1078

Volume: 10;
Issue: 18;
Start page: 17;
Date: 2011;
Original page

Keywords: Bending load | Capacity | Chipper efficiency | Chute | Cutting energy | Knife angle

The force relations and dynamics of cutting knife in a vertical disc wood chipper were investigated. The tool geometry determined include: rake angle (20 deg C); Shear angle, (fi= 52.15 deg C); the mean frictional angle, (t = 5.71 deg C). The analysis and comparison of the cutting forces has shown that the chips separated from the wood are being formed by off cutting, since normal applied force N is compressive in nature, the magnitude of the forces used by the knife on the wood is expected to increase as the cutting edge of the knife goes deeper into the wood until the value of the resisting force acting against the cut wood Ff is reached and exceeded. The evaluated forces acting on the knife and the chip are: F = 3.63Nmm^-1; N = 34.7 Nmm^-1; Fs= 27.45Nmm^-1; Fn =31.92 Nmm^-1; Ft = -8.46Nmm^-1; Fc = 33.85Nmm^-1. The resultant force acting on the tool face, Pr = 34.89Nmm^-1. The specific cutting pressure, Pc and cutting force needed to cut the timber, Fc, are 1.79 × 10^6 N/m2 and 644.84N respectively. The energy consumed in removing a unit volume of material is 69.96kJ/mm^-3 and the maximum power developed in cutting the chip is 3591.77W (4.82hp). The chipper efficiency (86.6%) was evaluated by the highest percentage of accepted chip sizes.
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