Pre-Pressing Plywood Assemblies

Production rate increase of 10 to 15 percent, gluing cost reduction up to 10 percent, and increased veneer from 95 percent less grade rejects and a few percent reduction in veneer stock dimension make pre-pressing plywood assemblies worth consideration. Stand time prior to pre-pressing should be 10 to 20 percent of the permissible maximum assembly time. At least 2 minutes pre-pressing are necessary with the optimum range from 3 to 8 minutes. Pre-pressing pressure should be between 150 to 200 psi with 25 psi an absolute minimum. Veneer moisture content, if too high, causes overpenetration of the glue when the panel is pre-pressed. Hardwood veneer species require more press and stand times than softwood species. Almost any conventional hot-press plywood glue can be pre-pressed successfully under the proper conditions. Pre-pressing performance of a hot-press interior and a phenolic exterior plywood glue indicated increase in bond strength over non-pre-pressed panels.

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