Thick-Slicing of Wood: Effects of Bar-Type and Speed of Cut on Quality of Slice

Red oak, yellow poplar and Douglas-fir flitches were sliced to 1/2 inch thickness at 140F with an experimental cutting machine allowing variation in speed of cut (5 and 200 feet per minute), pressure bar type (conventional, conventional-with-restraint, and round free-rolling bars), and compression settings (10 to 20% compression). Physical damage, thickness variation, and maximum knife and pressure bar forces were measured. As cutting speed increased, knife-side fractures increased in depth while the bar-side fractures decreased in depth. Cutting with the conventional-with-restraint bar produced the least depth of fracture on the knife-side but the greatest depth of fracture on the bar-side. Cutting with the round free-rolling bar produced the greatest depth of fracture on the knife-side and the least depth of fracture on the bar-side. As compression increased the depth of fracture decreased on the knife-side and increased on the bar-side. When both knife-side and bar-side fractures were considered, best results were obtained with a cutting speed of 5 feet per minute, with a conventional pressure bar set at 20% compression. The above variables had no apparent effect on thickness uniformity. Maximum parallel and perpendicular knife forces were 348 and 502 pounds per inch of length while maximum bar pressures were 288 and 871 pounds per inch of length respectively. The maximum combined parallel cutting force was 593 pounds per inch of length.

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