Causes and Control of End Waviness During Drying of Veneer

End waviness is a common defect occurring during the drying of thin wood veneer sheets principally from hardwoods. This drying defect interferes with the application of a uniform glue spread and may cause splits and lapped veneer in plywood panels. Experiments at the U.S. Forest Products Laboratory indicate that the ends of the veneer sheet dry faster than the bulk of the sheet. Drying rates were determined on sheets of rotary-cut 1/16- and 1/8-inch yellow birch 2 feet wide and 4 feet long. These sheets were dried in a roller-conveyor drier at temperatures from 175 to 320?F. Drying rates were determined for the end inch of the 2 by 4 foot veneer sheets compared with the drying rates at the center of the sheets. A special mechanical device was constructed to measure end waviness. The experiments indicate that wavy ends in veneer are usually caused by faster drying at the ends than in the rest of the sheet. Adding moisture and lapping veneer ends are two practical aspects of controlling end waviness.

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