FPL Press-Lam Process: Fast, Efficient Conversion of Logs Into Products

Describes a complete log-to-product system that rotary cuts veneer up to 1/2 inch thick from logs, press dries the veneer sheets in less than 15 minutes, applies glue to the hot sheets, and laminates them into a thick structural material. Employing “woods-run” southern pine logs as the input raw material, the dry product yield from 12- to 18-inch logs averaged 60 percent. The structural performance was evaluated for three-, four-, and six-ply 1.5-inch-thick vertically laminated bending members, having unbonded butt joints between ends of plies. The three-ply beams performed too poorly (low stiffness and adequate bending strength) to justify their cost. For the four-ply construction, 75 members had a mean bending strength of 6,480 pounds per square inch (psi); 5 percent exclusion limit strength of 4,900 psi, mean bending stiffness (calculated gross modulus of elasticity) of 1,710,000 psi, and no failures in flexural shear despite shear stresses as high as 508 psi. This performance was as good as, or better than, that expected of grade No. 2 southern pine. Both four- and six-ply members exhibited greater uniformity, in strength than solid material while having superior strength and equivalent stiffness. Warp tendency of Press-Lam was found to be in the “very light” category of the southern pine grading rules. The cost to produce three- through eight-ply vertically laminated members was estimated. Amortizing the plant and equipment cost of 1.2 million over 10 years at 10 percent, and depreciating the equipment to zero in 25 years, yielded a fixed cost of $258,000 per year. Logs were estimated to cost $73 per 1,000 board feet (Herring, scale) and the adhesive cost was 28.5 cents per pound. Including the energy and labor to produce 4-footwide continuous sheets of 4-ply Press-Lam at a production rate of 18 million board feet per year, brought the cost estimate to $126 per 1,000 board feet. From this analysis, the selling price would be equivalent to the majority of sawn structural lumber used in joists for housing.

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