Sawmill technology

A sawmill is a facility which processes raw timber into dimensional lumber for shipping and eventual sale. A sawmill’s basic operation is much like those of hundreds of years ago: a log enters on one end and dimensional lumber exits on the other end.

Prior to the development of the sawmill, people harvested timber and cut the resulting logs into planks by hand, an often painstaking process. Sawmills centralized timber processing in the 1600s, allowing a high volume of timber to be processed at a central location, which was initially powered by water and later by steam and electricity. Modern high-volume sawmills are dramatically different from 17th century sawmills, with highly automated systems which rely heavily on computers.

A sawmill may be equipped with planing, molding, tenoning, and other machines for finishing processes. The biggest mills are usually situated where timber can be brought by river or rail, and the design of the mill is affected by the mode of transportation. Waterborne logs float into the mill and are dragged out in turn by a winch. More space is necessary for storage in the rail-borne system; an overhead crane serves the stockyard and carries the logs to the machines.

Before being processed, lumber must be graded and sorted. Sometimes this is done on the site of a timber harvest, and at other times grading is handled at the sawmill itself. After grading, logs are debarked and then run through the head saw, also known as the primary rig. The head saw roughly splits the lumber into boards, which are finished with trimming, drying, and planing to ensure that they are evenly cut pieces of lumber. Once the lumber has fully dried, it can be packaged for shipping or stored on-site at the sawmill until there is a demand for it.

Cutting can be performed on various large machines such as reciprocating saws, band saws, or circular saws which cut the log into various thicknesses as it moves past the saw on a feeder table. The log frame is a machine with a set of vertically reciprocating blades, suitably spaced; it divides a log into boards at one pass of the table. The number of blades employed may be as few as 4 for cutting thick pieces or as many as 50 for thin boards. Resawing machines handle material partly broken up, such as flitches (longitudinal sections of log) and deals (boards).

Waste products like sawdust and woodchips may be pulped for papermaking, or burned to generate power; substantial quantities of these materials are now fabricated into particleboard and chipboard.

An entire workforce operates the mills that turn fresh trees into saleable lumber for the timber industry. This includes processors at the mills, mill operators, and support staff. Mill operations can be surprisingly dangerous, and so pay can be quite good, although the dangers have been reduced in recent years by a wave of technological advancements in the area of mill safety. Different sized mills may have different job requirements, with people needed to mill enormous redwoods into long lengths of lumber all the way down to those feeding excess wood into chippers or pulpers to make supplies for gardening or the paper industry.

The latest trend is the small portable sawmill for personal or semi professional use. Many different models have emerged with different designs and functions. They are especially suitable for producing limited volumes of boards, or specialty milling such as oversized timber. Portable mills can be trailered and set up on site, next to the trees being cut. The portable mills can cut lumber with speed and accuracy, though the subsequent steps of planing and drying must still be performed to produce finished lumber. Commodity lumber in standard sizes can be made this way. The more common use, however, is in the production of specialty timber products not readily available through lumber yards.

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