Development of a Method for Rapid Laminating of Lumber Without the Use of High-Frequency Heat

Laminated lumber with typical exterior-type adhesive bonds is produced without high-frequency heat and with pressure-time reduced to seconds. The basic principle consists of preheating surfaces to be laminated, applying phenolic resin or resorcinol-phenol combination, and pressing. Although the process was developed for laminated 2 by 4s, press times for larger beams would be the same as for two-member assemblies and application of the method to such products as laminated beams for home construction, with marked cost reductions is an imminent possibility. Preliminary experiments of the technique of heating one member only and applying adhesive to the other were abandoned owing to the fact that a number of assemblies delaminated at the ends, probably because of poor temperature control of the hot plate. Further experiments showed that the heat stored when both surfaces are preheated is considerably greater than when only one surface is preheated. The double preheat results in a balance of the thermal effects about midpoint of the completed assembly. This balance eliminates the tendency to bow. A pilot plant was used to produce 2 by 4’s laminated by the double preheat method with a capacity of 7,500 bd ft. per day. These 2 by 4’s are dressed with corners relieved, then trimmed, after which they are end treated. The result is a product of considerable customer appeal.

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