Analysis of Cutting Forces in Straight-Knife Peripheral Cutting of Wood

Effects of rake angle, wavelength, and depth of cut on cutting forces during straight-knife peripheral milling of sugar maple were determined. Progressions of normal (FN) and parallel (FP) force components during a typical up-milling cycle were determined. Results showed that at the initial step of the cut, FN was negative, ie the knife edge pushed the workpiece downward. The part of the knife path that remained visible on the machined surface was always created in such a situation. As the knife edge advanced in the cutting path, FN increased, reached a maximum negative value, then decreased to 0 N/mm, turned positive, and continued upward. FP was always positive and increased as chip thickness increased. Positive FN and FP reached a maximum just prior to emergence of the knife from the workpiece at about the maximum thickness position. However, when chip splitting occurred, the maximum positive FN and FP occurred before that maximum thickness position was reached. Maximum negative FN and FP increased as rake angle decreased and as wavelength increased. Maximum positive FN increased as rake angle and wavelength increased. Maximum positive FN and FP were also affected by depth of cut but to a lesser degree. Impact of these maximum cutting forces on production of defects was analyzed, and ways to decrease them were discussed