Analysis of the Lumber Planing Process. Part II

The article discusses cutterhead horsepower demand while cutting heartwood Douglas-fir in a series of six experiments outlined as follows: 1) Cutting circle diameter, number of jointed knives cutting, percent moisture content, and feed speed. 2) Specific gravity, depth of cut, and feed speed. 3) Angle between rotational axis of cutting head and direction of feed, and depth of cut. 4) Direction of cutterhead rotation with relation to direction of feed and depth of cut. 5) Knife extension beyond base of gib. 6) Width of joint and depth of cut. The significant results of all tests are as follows: 1) A 9.02 inch cutting-circle head requires 7.35 percent more power than the 7.63 inch head. 2) On green stock the larger head required 10.8 percent more power; on dry stock, the difference was only 3.37 percent. 3) Cutting green stock with two knives required 11 percent more power than cutting dry stock; with four knives,15.2 percent, more power; with eight knives, 28.8 percent more power. 4) Green specimens showed less percentage power penalty at 500 FPM than at 100 FPM feed speed. 5) Doubling the depth of cut for either of the two feed speeds, namely 150.5 FPM and 306.7 FPM by no means doubles the horsepower. 6}There is a tendency for the horsepower to approach zero as the depth of the cut approaches zero. 7) Surfaces produced by both up-milling and down-milling were satisfactory at all depths of cut, although chip marking was much less in down-milling 8) A knife extension of 0.152 inch uses 46.8 percent more than a knife extension of 0.344 inch. 9) For depths of cut up to and including 1/8 inch, the cutterhead mounting knives with 0.040 inch width joint took 19.3 percent more power than the cutterhead having an 0.007 inch width of joint. 10) The percentage of power penalty by greater joint width tends to decrease as the depth of cut increases, with a range from a high of 38.2 percent at 1/64 inch depth of cut to a low of 13.7 percent at a 1/8 inch depth of cut.

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