2568 Chapter 22 



program must develop the position of edging cuts, possible rip cut, trimming 

 cuts, and possible crosscut to yield a board or boards of highest quality and 

 value. 

 . Grading by computer therefore requires two developments: 



• A system that can scan a board and mathematically describe its shape and 

 defects. 



• A computer program that, from the mathematical description of the 

 board, can almost instantly give the grade and value of the board. 



The second problem seems easier to solve than the first, as computer capabilities 

 are advancing rapidly. Hallock and Galiger (1971) developed a program that 

 they believe to be nearly 100-percent accurate. Grades established by the pro- 

 gram should in all cases be correct, or at most one grade low; overgrading did not 

 appear to be possible. Programming language used was 3600 Fortran; process- 

 ing can be done on Control Data Corporation 3600, UNIVAC 1 108, or IBM 360 

 computers. 



The first problem, mathematical description of the board, seems more diffi- 

 cult. Progress in locating lumber defects by ultrasonics has been reported by 

 McDonald et al. (1969). In the opinion of some researchers digitized image 

 analysis seems a more promising route to board description. McMillin^ is study- 

 ing this possibility. 



Laminated lumber. — Lumber can be laminated for appearance or structural 

 grades. For structural purposes timbers can be built up into heavy sections by 

 flatwise lamination, narrow boards can be edgewise laminated and ripped to 

 standard wider widths, or rotary-cut veneers can be parallel-laminated to desired 

 thickness thereby randomizing strength-diminishing effects. These three proce- 

 dures are discussed in section 22-10. 



When appearance-grade dimension stock for furniture parts is cut from hard- 

 wood lumber, the removal of defects in the rough mill may result in loss of half 

 the lumber volume (see section 18-12). Future abundance of small-diameter 

 hardwood logs, and scarcity of large-diameter logs will increase these yield 

 losses unless alternative manufacturing procedures are developed. 



Suchsland (1980) proposed such an alternative procedure and observed that 

 most defects in a 4/4 hardwood board extend throughout its thickness and appear 

 on both faces so that a portion of the board is unusable. Manufacturing a 4/4 

 board from two laminae, randomly paired, would limit each defect to only one 

 face; in such laminated wood the defect in one face need not be removed because 

 the opposing face may be clear, allowing the manufacture of one-clear-face 

 cuttings. If, in addition, the defects in the laminae are repaired by plugging, the 

 entire board can be converted to furniture cuttings of three qualities, as follows: 



• Clear both sides 



• Clear one side, other side repaired (sound) 



• Repaired both sides (sound) 



"^McMillin, C. W. 1980. A problem analysis and research approach for cutting wood parts with a 

 laser under digital control of an optical image analyzer. Study Plan FS-SO-3201-17 dated June 1 . 

 1980 on file at the Southern Forest Experiment Station, Pineville. La. See also McMillin (1982) and 

 Huberet al. (1982). 



