6 OSB history Invented in 1949 by Armin Elmendorf Introduced as an alternative to traditionalwood products because of wood shortagesduring World War II.Patented by Elmendorf in 1965Waferboard appeared in markets in the early 1970’sThe OSB industry evolved from the waferboard industry in the late1970's as technology and investors embraced the concept.Waferboard consisted of randomly placed wood flakesOSB consists of specifically oriented wood strandsWaferboard was the parent product of what would evolve into Oriented Strand Board. Waferboard consisted of wood strands approximately 50mm in width and length placed and random and pressed together. As investors began to see a viable market for the product research and investment increased. This lead to new technologies allowing wood strands to be placed in patterns creating a product more structurally sound than waferboard.
7 OSB history In 1980 North America produced 751 million square feet of OSB panelBy 1990 the number had risen to7.6 billion square feetMid 1990’s OSB Began to rival traditionalplywood in production and sales in the panel marketIn 2001 OSB surpassed plywood in production and salesBy 2005 OSB accounted for more then 60% of the panel market with25 billion square feet producedWaferboard - It consisted of a random array of thin flakes about 50mm both in length and width
9 OSB MANUFACTORING Timber Harvesting Since OSB is manufactured from wood strips, the size of the timber used can be relatively small when compared to other wood products. This fact also increases the sustainability of the process. Since smaller timber can be utilized, less growing time is required for timber to be mature enough for the OSB production process. The smaller size requirement also means that nearly the entire tree can be used in the production process. Tree Limbs that would normally be excluded from other wood production processes can be used in OSB production. Fast growing aspen-poplar is used for OSB in the northern part of North America, while southern yellow pine from plantation stands or mixed hardwood species are used in the south. Other species, such as birch, maple or sweetgum are used in limited quantities to supplement the aspen or southern yellow pine resource.The timber used in OSB production comes primarily from young growth forests. This gives OSB manufacturers an advantage of using smaller timber that can be grown in a shorter period of time; making OSB more sustainable than other building products.
10 OSB MANUFACTORING Log Sorting Once logs arrive in the mill’s yard, they are sorted by size and species. This segregation helps to ensure more consistent properties in the final product.After harvest, whole logs are hauled to the mill's wood yard, then sorted.
11 OSB MANUFACTORING Log preparation After logs have been sorted they are soaked in a hot water ponds. This serves several purposes. First it serves to loosen the bark on the log to aid in the debarking process that will follow. In cold weather climates, these hot water ponds server to remove any frost from the log. The hot water ponds also server to increase the moisture content for the logs. This helps to achieve a more desirable wafer size during the stranding process. After the logs have soaked in the water bath that are lifted from the bath using a jackladder and transported via conveyor to the debarking machine.Logs are soaked to loosen bark and remove frost (where applicable) to prepare wood for debarking and stranding.
12 Soderhamn Eriksson Debarking Machine OSB MANUFACTORINGDEBARKINGSoderhamn Eriksson Debarking MachineThere are several methods used in the forest industry to debark sawn timbers. Given the size of the timber used in the OSB production process machines similar to the Soderhamn Eriksson debarker (shown above) are most commonly used. Logs are transported via conveyor to the circular opening at the mouth of the machine. Ridged rollers clamp the log and draw it through the circular mouth. As the long is drawn through spring loaded arms are held in tension around the outer diameter of the log. These arms rotate around the log as it is drawn through shearing the bark away similar to peeling an apple.Logs are run through the debarker to remove bark. Bark is later used as fuel in the mill's energy supply.
13 OSB MANUFACTORING Stranding The freshly debarked logs are then carried to the strander. The stander is effectively an industrial size cheese-grater. Logs are loaded in and pressed against a series of rotating blades. These rotating blades shred the logs into strands of wood approximately 6 inches long and 1 inch wide. These strands are the basis of the wood panels that will be produced.The strands are cut from whole logs into precise dimensions of up to six inches long.
14 OSB MANUFACTORING Wetting and drying After the stranding process the resulting strands have a relatively low moisture content. The stands are placed into wet bins to increasing their moisture content and then they are removed and placed in large cylindrical dryers to removed excess moisture to achieve a desired moisture content between 3 and 7 percent. The stands are rotated very slowly in the dryer to minimize breakage and to ensure a consistent moisture content.Strands are deposited into wet bins and allowed to soak. They are then removed and placed in dryers until theappropriate moisture content is reached.
15 OSB MANUFACTORING Blending and forming Strands go through the forming line where cross-directional layers are formed.When dry, the strands or wafers proceed to the blender where they are mixed with resin and wax. The small quantity of hot wax (about 1.0 to 1.5 percent of the weight of wafers) sprayed on the wafers helps to distribute evenly the powdered or liquid phenol-formaldehyde resin or polyurethane binder (2.0 percent to 3.5 percent by weight or more). Resins or binders are of the thermosetting type, which means they can’t be softened by heat or moisture once fully cured.After blending the strands are sent to the forming machine. The forming machine arranges the strands or wafers in several layers to form a mat on stainless steel press sheets or on a continuous belt. For OSB, the strands for the faces are usually oriented parallel with the long direction of the panel (machine direction) and the core layers are either cross-oriented or laid random.Strands are blended with resin binders and a small amount of wax, which improves the efficiency of the resin binder and enhances the panel's resistance to moisture and water absorption.
16 OSB MANUFACTORING Blending and forming Unfinished OSB panels leaving the forming line
17 OSB MANUFACTORING pressing The size of the mats varies with the press size, but generally, one mat will be large enough to produce several standard sized panels.In multi-opening presses, the mats are placed in the press accommodating from 10 up to 24 sheets at a time. Each mat sits between a pair of heated platens. When all the mats have been inserted, the press is closed under heavy pressure. Typical press parameters include a temperature of 400 to 425oF and a pressure of 650 to 800 psi for approximately 4 to 6 minutes.Layers of cross-directional strands are pressed under intense heat and pressure to form a rigid, dense structural panels.
18 OSB MANUFACTORING pressing The layup of the mat and the press operation are important in ensuring proper panel thickness. The duration of the press cycle varies from plant to plant and with the desired thickness of the board. For example, a press cycle of 3-1/2 minutes might be required for 6.35mm (1/4") thick panels, and eight minutes for 15.5mm (5/8") panels. The heat and pressure polymerize the resin or binder glueing the strands or wafers together strongly into a rigid panel.In newer plants, some presses are long and continuous rather than the more conventional stacked multi-opening presses. In those presses a continuous mat enters the front end of the press. Finished board exits the rear end of the press, which is then cut to the required size with flying cross-cut saws.
19 OSB MANUFACTORING finishing Exposure 1 are waterproof and intended for exterior use. Exposure 2 lack the waterproofing agent and are to be used in interior applications. Pressed panels are removed from the press line and conditioned on a rotating cooler prior to cutting them into desired dimensions.The panels are later sanded to improve their surface roughness. Certain processes, such as profiling with tongue and groove edges or the raised screen pattern on one face to eliminate slipping in roof application, can also be applied to the surface of the panels for special applications. Similar to other wood products, OSB also is prone to decay when conditions are optimum for biological microorganisms, such as fungus. Zinc borate and oxine copper are sprayed as fungicides to enhance resistance of OSB to biological deterioration. In general, OSB is not used for applications where there is direct contact with a moisture source, such as soil.Panels are cooled, grade stamped, stacked in bundles and edge coated. All graded panels bear a mandatory certification agency stamp.
22 OSB applicationsWalls - excellent strength and rigidity under all types of siding.Waferboard - It consisted of a random array of thin flakes about 50mm both in length and widthRoof Panels - uniformly sound and extra rigid to handle snow and wind loads.
23 OSB applicationsUnderlayment - uniformly thin, yet strong and finely sanded, OSB provides a smooth base for vinyl or tile.Single-Layer Floors - great for use directly under carpet, light-weight concrete or hardwood flooring.Subfloors - strong, rigid and impact-resistant for underlayment, carpet or tile.
24 OSB applicationsStructural Insulated Panels - OSB foam-core panels offer high strength, R-value, and easy installation.Structural insulated panels (SIPs), are a composite building materials. They consist of an insulating layer of rigid polymer foam sandwiched between two layers of structural board, usually OSB. SIPs share the same structural properties as an I-beam or I-column. The rigid insulation core of the SIP acts as a web, while the OSB sheathing exhibits the same properties as the flanges. SIPs combine several components of conventional building, such as studs and joists, insulation, vapor barrier and air barrier. They can be used for many different applications, such as exterior wall, roof, floor and foundation systems.
25 OSB applicationsFloor Joists - OSB I-joists provide a high-quality support system.Floor joist are basically wooden I-beams constructed using OSB as the beams web and finger jointed sawn lumber sandwiched on either end to create the flanges. Engineered Wood I-beams have several major advantages. First, they are much stronger, straighter and stiffer than conventional sawn lumber. Data indicates that they are 50% stiffer than sawn lumber. Consequently they provide less deflection, which translates into better floor construction. As a result of their strength, wood I-beams can be used to cover larger spans and can be separated on wider on-center spacings, thus reducing construction cost.OSB Rim Board is fabricated from oriented strand board, which is precision cut to match the depths of OSB FloorjoistsRimboards - OSB rimboards add strength and rigidity to the floor system.
27 OSB benefitsPriceOSB can be $3 to $5 a panel less expensive than plywood. For a typical 2400 square foot home, OSB will save about $700 if used as the subfloor, sheathing, and roof decking instead of plywood.Engineered for Applications and StrengthThe strands can be cut to different lengths, oriented in different directions and assembled with various amounts of adhesives for customized purposes.Recognized as a Structural Panel in the Model CodesOSB is recognized as an equivalent to plywood in all North Americanmodel codes for structural sheathing applications in dry service conditions.Wide Availability and Size-VarietyOSB provides wood products in dimensions that other structural panels do not offer, including panels from 4 feet by 8 feet to 8 feet by 24 feet in many thicknesses for multiple span ratings.PriceOSB panels can be produces cheaper largely due to highly automated and computerized manufacturing methods.Engineered for Applications and StrengthThe strands can be cut to different lengths, oriented in different directionsand assembled with various amounts of adhesives for customizedpurposes. Longer strands provide more flexibility. Directional orientationof strands contributes to strength. Additional resin develops durability.Recognized as a Structural Panel in the Model CodesOSB is recognized as an equivalent to plywood in all North Americanmodel codes for structural sheathing applications in dry service conditions.
28 OSB benefits High Consistency Because its quality is not dependent on the size of harvested trees, but on a manufacturing method , each OSB panel can be manufactured with the same uniformity and consistency.Environmentally AdvantageousOSB is processed mainly from fast-growing small diameter trees, avoiding the need to log old-growth timber. OSB is a resource-efficient product, maximizing yields from a fast-growing renewable resource.Wide Availability and Size-VarietyOSB is available in all home improvement retail outlets in North Americaselling wood in dimensions that other structural panels do not offer,including panels from 4 feet by 8 feet to 8 feet by 24 feet in more than halfa dozen thicknesses for multiple span ratings.High ConsistencyBecause its quality is not dependent on the size of harvested trees, but on amanufacturing method employing strands cut from trees, each OSB panelis manufactured with the same uniformity and consistency, with no voidsand allowing for reliable workability. OSB is easy to saw, drill, nail,plane, file and sand.Environmentally AdvantageousOSB is processed mainly from fast-growing small diameter trees, avoidingthe need to log old-growth timber. OSB is an extremely resource-efficientproduct, maximizing yields from a fast-growing renewable resource.
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