Plywood veneer moisture content can be very high if the wood is cut from a tree’s outer sapwood layer instead of its inner heartwood core. To maintain a good glue bond between plywood veneers and maximize veneer strength, plant operators must dry each sheet within a tightly controlled moisture range. A wet section of veneer in an otherwise dry heartwood sheet can make the sheet blow out inside the steam press, causing delamination of the plywood and resulting in lost production and increased costs.
Overdrying the veneer can make it brittle and cause it to lose its strength properties. Depending on the moisture profile, plant operators may either place wet veneers in ambient air to equilibrate or send them through a series of kilns at precisely controlled temperatures. The moisture sort system also uses feedback from the kilns to optimize the sort process, making it a key component in a plywood mill’s ability to maximize productivity and quality.