2950 Chapter 24 



uniform properties in all directions which can be cut into smaller panels without 

 regard to major or minor panel axes. This can be advantageous, especially when 

 panels are pressed to 8- by 16- or 8- by 24-foot size. Also, delamination stresses 

 between panel layers are probably less in panels with random flake placement 

 than where flakes in face layers are aligned at 90 degrees to those in the core (fig. 

 24-2). 



FLAKE ALIGNMENT 



Fabrication of oriented-strand boards (fig. 24-2 bottom) requires a method of 

 aligning flakes or strands in face layers parallel to the major panel axis, and at 

 right angles to this direction in core layers. Maximum-strength panels are fabri- 

 cated from long flakes — e.g., 3 inches in length. Sweetgum face flakes may be 

 nearly square, hickory flakes tube-shaped, and oak flakes splintery and incom- 

 pletely separated into strands (figs. 18-102 and 18-274 ABC). Processing flakes 

 of all these species through a flake splitter makes them more uniform in width, 

 but substantial variation will remain. Oak flakes in particular retain characteris- 

 tic incomplete separation so that individual strands may be semi-attached to one 

 another. This lack of discreteness combined with 3-inch length makes alignment 

 difficult on some equipment. 



Mechanical alignment. — Laboratory- and industrial-scale equipment is 

 available that aligns flakes by means of vibrating parallel plates (fig. 24-22 A 

 top). Readers interested in the degree of alignment attainable with vibrating 

 parallel plates are referred to Geimer (1976). Finned rolls (figs. 24-22 A bottom 

 and 24-22B) also effectively align flakes, are in service in several plants, and are 

 mechanically simple devices. 



Electrical alignment. — Maloney (1980) reported that equipment based on 

 Talbot's (1974) concept, and now available to the industy, can effectively align 

 and cross-align most flakes (fig. 24-23). Industrial-scale demonstration on 3- 

 inch-long white and red oak flakes had not been reported in the literature by early 

 1981. Earlier demonstrations in some southern laboratories Indicated additional 

 development was needed. 



FORMING MACHINES 



The alignment mechanisms just described, if incorporated in the production 

 line, are part of the forming equipment. It seems likely that most structural 

 flakeboard plants built to utilize southern hardwoods will have multi-opening 

 presses with perhaps 16 openings and platens measuring 8 by 16 feet or 8 by 24 

 feet. Forming machines for such presses are essentially wide-belt distribution 

 bins designed to discharge a uniform volume of material to the orientation 

 devices (fig. 24-223). Forming machines typically consist of one bottom-face 

 forming head, two core heads, and one top-face forming head. 



