Maintenance of Quality in the Manufacture of Molded Plywood

The author describes the manufacture of molded plywood chair panels as practiced by the Brunswick Blake Callender Company. It is stated that the production of molded plywood panels with compound-curved surfaces is greatly dependent upon veneer quality. Thus, it is important to secure a reliable source for supplying quality veneer, particularly the face stock. All veneer shipments axe inspected in accordance with statistical sampling methods before being formally received. Unnecessary handling is eliminated to reduce damage. The moisture content specified is 6 to 10 percent. The supplier’s method of packaging the veneer must insure against damage in transit and permit efficient handling. In molding multiple-curved surfaces, it is assumed that the generated compressive stresses are small, thus showing no effects. Not so with tensile stresses. The veneers, as a result, must be tight cut (lathe checks limited to 30 percent of thickness of the veneer). To avoid “over-sanding” the high portions of the curved panels, presanding the veneer was instituted, which was done by a single drum precision sander developed for the leather industry. Only the tight side of veneer is sanded. In the case of wavy veneer, stock is flattened in a R.F. heated press. The molding is done in two three-opening hot presses using urea resin. The panels are cured in 4-1/2 to 6 minutes depending on contour; moisture content, and catalyst. The blanks receive pre-conditioning before being shaped. High speed belt sanders do the sanding of the blanks. The production line for preparing the back panels resembles, to a great extent, the one described for the seats.

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