Machining Tests of Wood with the Molder

Quality of wood finish and power consumption were studied as a function of feed rate, cutterhead speed, cutting angle, type of knife, and wood moisture content. Species evaluated were yellow birch, red gum, hard maple, white oak, yellow-poplar, Douglas-fir, ponderosa pine, and southern yellow pine. Quality comparisons were based on visible machining defects. Characteristic defects were raised grain in softwoods, fuzzy grain, chipped grain, and chip marks. Many defective pieces were only slightly defective. Hardwoods exhibited from 63 to 94 percent defect-free pierces; softwoods similarly had 20 to 77 percent defect-free pieces. Quality was most affected by number of knife cuts per inch, with quality increasing with increasing number of knife cuts up to about 16. For a constant number of knife cuts, feed rate and cutterhead speed had no effect on quality. With sharp knives, high-speed steel knives were superior to carbide tipped knives. Quality was better at 6 percent moisture content than at 20 percent moisture content. The relation between quality and depth of cut differed from one species to another. Quality increased with decreasing cutting angle. Power consumption increased with decreasing cutting angle, and with increasing moisture content, feed rate, and cutterhead speed.

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