Method and apparatus for cutting lumber and the like

Abstract

An in-feed conveyor brings individual pieces of lumber to an examining area, where a carriage is movably mounted relative to the conveyor for movement along the piece of stock. A control on the carriage is triggered whenever the carriage is positioned in predetermined alignment with defects in the stock, including undesirable end portions as well as structural or quality defects intermediate the ends of the piece. Triggering such control sends an input to a computer, which controls the cutting of the stock by a saw located downstream from the examining station, by which the defects are cut out of the piece of stock. The computer completely controls the incremental movement of the piece of stock at the saw, automatically stopping the stock and causing the same to be cut, not only to remove defects, but also to produce an optimum yield of different pieces cut from the good stock between the defects. Such optimum yield is computed by the computer based on the stock defect information fed to the computer during examination of each piece of stock, as well as on the contents of a manifest or list of desired pieces entered into the computer as a preliminary step, and as a function of predetermined priorities, as for example the longest obtainable pieces. The computer has a variable waste allowability parameter, so that selection of different amounts of tolerable or allowable waste in cutting the stock can correspondingly vary the nature of the optimum yield computed by the computer. A clamping and feeding apparatus very securely holds the stock in position with respect to the saw, both during the actual cutting and also during the advancement of the stock with respect to the saw, so that the stock cannot inadvertantly move during either such operation.