A newly-developed model for predicting cutting power during wood sawing with circular saw blades
MADERAS : Ciencia y Tecnología
In the classical approach, cutting forces and cutting power in sawing processes of orthotropic materials such as wood are generally calculated on the basis of the specific cutting resistance k c (cutting force per unit area of cut). For every type of sawing kinematics (frame saws, band saws and circular sawing machines) different empirical values of specific cutting resistance k c have to be applied. It should be emphasised that sources in the scientific literature and handbooks do not provide
... oks do not provide any information about wood provenance, nor about cutting conditions in which cutting resistance had been determined. In analyses of sawing processes in which the offcut is formed by shear, Atkins's ideas that all cutting forms a branch of elastoplastic fracture mechanics can be applied. Thanks to this modern approach it was possible to reveal, using experimental results data of fracture toughness and shear yield stresses of Polish pine (Pinus sylvestris), the significant effect of the raw material provenance (source of wood) on cutting power. In the common model for circular sawing machine kinematics, which is similar to metal milling, the sum of all uncut chip thicknesses of the all the teeth simultaneously engaged represented the mean uncut chip thickness. In this work predictions of the newly-developed model for the circular sawing machine are presented. In the model, beside uncut chip thicknesses changes, appropriate changes in shear yield stress and toughness with tooth/grain orientation have been taken into account. The conducted analyses have demonstrated that values of RMS of cutting power obtained with the new developed model are slightly larger than experimental values. On the other hand computed values of cutting power with the use of the mean uncut chip thicknesses in the model are a bit lower from the empirical one. Dziemiany (Poland) for Scot pine wood samples used in the experiments and other data on the sawing process, and the firm Aspi Tech Sp. z o.o., Sp. k. Suwalki (Poland) for circular saw blades data. REFERENCES Altintas, Y. 2000. Modeling approaches and software for predicting the performance of milling operations at MAL-UBC. Machining Science and Technology 4(3):445-478. Ammar, A.A.; Bouaziz, Z.: Aghal, A. 2009. Modelling and simulation of the cutting forces for 2.5D pockets machining. Advances in Production Engineering & Management 4(4):163-176. Atkins, A.G. 2003. Modelling metal cutting using modern ductile fracture mechanics: quantitative explanations for some longstanding problems. Int J Mech Sci 45:373-396. Atkins, A.G. 2005. Toughness and cutting: A new way of simultaneously determining ductile fracture toughness and strength. Eng Fracture Mech 72:849-860. Atkins, A.G. 2009. The science and engineering of cutting. The mechanics and process of separating, scratching and puncturing biomaterials, metals and non-metals. Butterworth-Heinemann is an imprint of Elsevier, Oxford. Atkins, A.G. 2016. Slice-push, formation of grooves and the scale effect in cutting. Interface Focus 6(3): Beljo-Lučić, R.; Goglia, V.; Pervan, S.; Dukić, I.; Risović, S. 2004. The influence of wood moisture content on the process of circular rip sawing. Part I: Power requirements and specific cutting forces. Wood Res 49(1):41-49. Blackman, B.R.K.; Hoult, T.R.; Patel, Y.; Williams, J.G. 2013. Tool sharpness as a factor in machining tests to determine toughness. Eng Fracture Mech 101(2013):47-58. Böllinghaus, T.; Byrne, G.; Cherpakov, B.I.; Chlebus, E.; Cross, C.E.; Denkena, B.; Dilthey, U.; Hatsuzawa, T.; Herfurth, K.; Herold, H.