If you want detailed information about OSB, the ideal scenario would be to sit in a room with Alex Kuchar, Weyerhaeuser’s OSB Technical Manager. After more than 13 years at Weyerhaeuser, Alex knows a great deal about OSB.
Since we can’t sit everyone in the room with Alex, we’re doing the next best thing. Here are his insights into how Weyerhaeuser manufactures OSB products at its six mills in Canada and throughout the USA.
Q: Most people have never seen trees being harvested. What are the first steps?
A: Contract or Weyerhaeuser loggers come into a designated area to select and cut down trees that are ready to be harvested. Branches are taken off and the trees are transported to an OSB mill.
Q: What’s the first step at the OSB mill?
A: Trees are de-barked (with the bark and any remaining limbs being burned for fuel), then placed on a “strander” that has a set of knives within a circular wheel. The knives spin as the wood goes through a ring, cutting the tree into individual strands with specific target width, thickness and length.
Q: What happens to the wood strands?
A: They’re dried at high temperatures. Then, in a separate operation, they are passed over mesh screening to filter out different sizes. Larger strands are selected for the surface layers of OSB panels while smaller strands are used for the core layers.
Q: What’s next?
A: The different strand sizes are blended in a rotating drum with resins and wax. Strands with resin and wax are then transported to the orienters. The orienters align the strands so that strands for the top and bottom surfaces of the panel go one way while the interior strands go in the opposite direction. This adds stability to the panels.
Q: How large is the OSB panel at this point?
A: Before it goes into the press, the mat can be up to eight inches thick. After the mats go into the press, they are pressed at about 600 PSI, at up to 425 degrees Fahrenheit. Pressure brings the strands into close contact with one another and the heat cures the resin. Pressed mats come out from 3/8-inch to over an inch tall, depending on the product we’re manufacturing at the time.
Q: What is the curing process that takes place in the press?
A: Each press opening has platens and the press platens are heated with a hot oil system. It’s the combination of pressure and heat applied in the closed press process that cures the resins. When the OSB panels come out, they can be more than 300 degrees F.
Q: What are the final steps?
A: Panels go from the press to the finishing line where they are cut to the length and width needed. Depending on which product we’re creating there may be additional steps. For example, at the facilities where flooring panels get tongue and grooved, or EdgeGold has the DownPore system cut in, these final steps are taken. All products are sampled and tested for quality.
After putting single panels into unites, the product goes into the paint booth for edge sealant to be applied to ends and edges. After that the units get strapped and they’re prepared for shipping. Bar codes and unit information are added. From start to finish, the entire process generally takes less than an hour to complete.
Watch the video below to see the OSB manufacturing operations at Weyerhaeuser.