Lumber and Wood Products Industry
This group deals with the production of lumber and basic wood materials. It contains establishments engaged in manufacturing articles made mainly of wood. Its industries include:
-Logging
-Sawmills and Planning mills
-Millwork, Veneers Plywood, and Structural Wood Members
-Wood Containers
-Wood Buildings and Mobile Homes
-Miscellaneous Wood Products
Material Production: Wood must be converted into some basic material unit in order to be used further. It is the efforts of the first three industries listed that perform this task.
Wood cutting is considered to be any type of process that incorporates the removal of unwanted wood from a workpiece in the form of chips. In the case of logging, the standing tree is the workpiece and the cutting process is usually sawing. In SAWING, chips or "saw-dust" are produced by a succession of small cutting edges or teeth, arranged in a narrow line on a saw blade. Sawing tools in the logging industry range from simple hand held saws, to more powerful motorized chain saws. Tools in the milling industry include cut-off saws and table saws that debark and section the timber into rough lumber. Saws can be classified into three distinct types; reciprocating, band, and circular.
MILLING is a type of wood cutting process where a surface is generated progressively as it is fed to a rotating tool in a direction perpendicular to the tool motion. It differs from sawing in that the tool is much thicker than a narrow blade. Milling is often used to produce surfaced lumber and patterns of lumber. It can be used to reduce the thickness of timber as in debarking, and to section timber into lumber. Milling is faster than sawing, but it often leaves surfaces that are too rough for many applications.
SPLITTING is a simple process that is not considered to be a cutting process. It uses a sharp edge coupled with a quick blow to separate wood in a direction parallel to its grain. Much less force is required to break bonds between wood grains than to break the grains themselves. Splitting is used regularly in the production of wood for fuel and even fencing.
COMPRESSION MOLDING is one process by which composite wood is produced. Different pieces and type of wood are essentially pressed together to form some type of mold (usually a sheet). There are three types of composite material; laminar, particulate, and fiber reinforced. Plywood is an example of a laminar composite wood, and particle board is an example of particulate. Composite wood iS used in many applications where stronger, more dense wood is required.
CURING is a process which can protect lumber before it is used in further applications. Chemical protective curing can improve wood's resistance to water, weather, and wear while often increasing its strength. Kiln drying is done to dry the wood and produce decorative surface patterns. Curing is also required in compression molding to insure proper bonding between composite wood.
Machining: The first three industries deal primarily with producing raw lumber and basic wood materials. The last three industries deal with machining and using these basic materials to produce final goods. Machining deals with removing wood (usually in the form of chips) so as to obtain a finished product of desired size, shape, and finish. SAWING and MILLING were a part of Material Production and are considered a part of machining, too.
SHAPING is the simplest form of machining relative to motion. It uses a single point cutting tool that moves in a straight line across the wood. Types of shaping include horizontal push and pull, and vertical cutting. A variety of tool geometries can be used to create many different shapes.
PLANING has the wood move past a single point cutting tool (the opposite of shaping). It is a simple form of machining that has its limitations due to slow feed rates and low productivity. It can be used to produce shapes from different tool geometries and reduce thickness of wooden pieces when appropriate.
TURNING is a high speed process where the workpiece rotates and a longitudinally fed, single point tool does the cutting. Variations of wood turning include tapering, facing, and boring. Turning requires the use of a lathe except in some boring operations. Multiple diameter poles and rods are easily produced in a turning process.
DRILLING uses a rotating tool with two edges that is pressed into the wooden workpiece to produce a hole or void. Precision holes are required for the ultimate assembly of wood products. Types of drilling tools include; straight and taper shank, deep hole, combination, subland, and spade. Feed rates depend on the type and thickness of the wood. Drilling is often followed by counterboring or countersinking to accommodate fastening devices.
REAMING is a process that can only follow a drilling or drilling related process. It uses a multiedged cutting tool (often on the same machine used for drilling) to bring holes to a more exact size. Types of reamers include; hand, machine, shell, expansion, and adjustable. Common drilling machines used for reaming include; upright, radial, gang, deep-hole, and transfer.
FILING requires cutting teeth arranged in succession along the same plane on the surface of a file to remove wood chips. Types of files include; single-cut, double-cut, vixen-cut, and rasp-cut. Files are also classified by coarseness and construction. Filing is important to wood industries in easily removing sharp edges that could cause injury in finished products.
ABRASIVE machining uses very small cutting edges that are integral parts of abrasive particles to produce chips from wood. A good example is using sandpaper to smooth a rough surface. Types of abrasives include; quartz, aluminum oxide, silicon carbide, and diamond. Some common types of abrasive processes include grinding and lapping. Grinding uses a wheel of some shape on which abrasives are bonded. Lapping requires that fine particles be embedded into a soft material (like paper) which serves to finish the part. Abrasive machining is limited to small amounts of wood removal. However, it can provide extremely smooth surfaces.
Assembly: The actual putting together, joining, and additional finishing of components constitutes assembly. While this major group deals with wood, finished products that use non-wood material are included as long as the major portion of the product is wood. Not many processes define a fashion in which wood products are put together; it's just done in (hopefully) the fastest, most efficient manner. Once together, there has to be a means of joining the components.
ADHESIVE BONDING uses composite systems with several compounds to join two surfaces together. The bonding material may exist as liquids, pastes, solids, tapes, or films. Common types of adhesives include:
Wood can be joined to almost any type of material using the proper adhesive. The surfaces of both components must be clean and dry to insure proper bonding.
MECHANICAL FASTENING requires that a joint be formed by mechanically interlocking or interfering with no fusion or bonding present. Fastener types for wood include integral and discrete. Integral fasteners are machined areas of wood such as tabs and seams that fit into other parts. Discrete fasteners are separate pieces such as nails, bolts, screws, and wires.
COATING is performed to impart certain properties to wood surfaces such
as resistance to weather and wear, different colors, and smoother finishes. Coating is
different from curing in that it only deals with the surface of the wood, and that it is
usually performed after joining. Coatings can be classified into organic and inorganic
types. Common coatings for wood include paint, stain, varnish, and plastic laminations.
Inspection and Testing: Most of the processes already described in the Lumber and Wood Products major group occur at only one point in the overall manufacturing path. Inspecting and testing, however, are performed numerously throughout all processes. It can consist of a simple check to see if a piece is present, or a minute measurement of the surface of a finished part. Inspection and testing tell whether or not a particular process was performed adequately.
DESTRUCTIVE TESTING does not allow for use of the tested part after inspection because it imparts some type of mechanical deformation. An example of destructive testing in wood products would be stress testing a wooden structural member. This type of testing is done on a sampling basis. Other types of destructive testing for wood products include fatigue, impact, creep, torsion, and shearing.
NON-DESTRUCTIVE TESTING allows for use of the part after inspection. It includes a wide range of optical and mechanical techniques. Mechanical techniques using instruments such as calipers, micrometers, and scales may contact the part, but they leave no significant mechanical deformation. Optical techniques include structured light, triangulation, holography, and interferometry. An example of a NDT application to wood products would be testing for the presence and size of a drilled hole.