What Happens At A Lumber Mill
In a lumber mill a tree becomes many things as it journeys through saw blades and other machinery until it finally ends up in a door or window.
Since the great frontier of America began to experience the whittling away of its great forests and woodlands, technology has also swept through the sawmills over the last century. Many tree species of the world are harvested for various uses. Whether it’s for building materials, furniture, musical instruments or decorations, a lot goes on in the sawmill in order to manufacture the finished product.
As raw logs are hauled out of the forest, still covered with moss and homes for insects and other critters, usually the first step is to be sent to a lumber sawmill. Here the logs are cut or ripped into specific widths. However, before this ripping process takes place, the logs are graded for defects by ways of a laser beam that sends a signal through a computer as to how much wood, in particular lengths, can be yielded. By eliminating some of the unwanted wood in the rough sawmill, the cut stock mill can utilize more wood and less waste during the finishing process.
Upon arrival at the cutstock mill, where the finished (end) product is manufactured, the boards must be dried and treated in a kiln. A kiln is essentially a large oven used to dry the wood and destroy any wood-damaging insects. This drying process also helps eliminate bowing of the wood and any moisture trapped in the wood fibers, which can damage the machinery, used to create the finish product. After a thorough drying the boards are again ripped for specified widths. The circular blades rip the lineal boards, which are then sent down a conveyor belt. The excess wood that is shaved off the desired boards is also sent down another conveyor belt into what is usually known as the “hog”. The hog is a machine that pulverizes and grinds up the wasted wood, which is actually not waste. The result is a pulp, used for particle board and fiberboard. The monetary value of this product is substantially less than solid wood. The remaining sound boards are then sent to chop saws known as the cutline.
Here, the boards are again cut only to specific lengths, not widths. The boards are now the unfinished structural parts of doors and window frames. A door consists of two stiles and two rails. The stiles are the long sides and the rails are the top and bottom. These parts, however, need to be shaped in order to fit flush with the profile of the door. Beveling the edge of the stile and rail so that the two adjoining pieces lock in place creates a profile. This beveling is created in a machine called a moulder, which is a series of rotating blades designed to cut notches in the edge of the board.
When the board’s relative thickness is less than desired for rails and stiles, the wood is again beveled for creating panel. The panel is shaped in order to fit between the gaps in the stiles and rails. When defects in the wood are present, such as pitch pockets, knots and insect holes, there is less desire to use the pieces for stiles and rails and panels. These defects on the long boards will force a cutter to chop them out and the shorter boards that don’t make the required length for a solid part are used for finger joint. These blocks are essentially glued back together with industrial strength wood glue and are then produced to the original desired length.
The bottom line is: every effort possible is made to do more with less. No inch of wood is ever thrown away.