Note: Descriptions are shown in the official language in which they were submitted.
CONTOUR LINE SCANNER
BACKGROUND OF THE INVENTION
The present invention relates generally to
automation of the processing of logs, cants and other
wooden workpieces and more particularly to methods and
apparatus for scanning and dimensionally analyzing such
workpieces to maximize the yield of wood products there-
from. Although the invention is described in connection
with the processing of cants, it is also applicable to
sawing and turning logs.
Many modern lumber mills now employ some type
of automatic scanning equipment which feeds information
regarding workpiece dimensions to a data processing
device for analyzing the dimensional data to control
cutting mechanisms. Broadly, the prior systems suffer
from two disadvantages. First, such systems conven-
tionally seek to maximize the volume of salable wood
products from each log, but do not necessarily produce
the most economical mix of wood products. Second, the
prior systems obtain huge amounts of data about the
workpieces, necessitating very large memory and comput-
ing capacity to process. Consequently, such systems are
very expensive, often too expensive for small mills. It
would be preferable to have a method and apparatus for
controlling the processing of wooden workpieces which is
capable of maximizing the economic yield in salable wood
products, and yet is simpler and less expensive than
those systems provided by the prior art.
In edging a cant to produce dimension lumber,
any irregular margins of the cant, or wane, are cut off
and the cant is sawn lengthwise into boards of various
widths. A cant is typically trapezoidal in cross sec-
tion and has irregular side faces, but may be square
along one or both side faces, depending on how the cant
is sawn from a log. In the former case, the cant is
edged to square it up, by removing its irregular, tri-
angular cross-section margins or wane. Then, in both
9~3
cases, the cant is sawn lengthwise into boards of vary-
ing widths. Conventionally, the configuration of the
cant is analyzed to determine the widthwise positions of
several sawlines which will provide the combination of
board widths that maximizes the volume of lumber pro-
duced from the cant. Similar analytic techniques are
employed in sawing a log into cants.
However, the conventional optimization methods
do not take into account the economic value of the lum-
ber produced as a function of its dimensions. Also,they do not take into account the variations in value of
a board of a given dimension as a function of the grade
of the lumber. I'he grade of a given piece of lumber is
affected by a number of variables, including the pres-
ence or absence of knots, splits and rot in the wood.
The grade also varies with the amount of wane, or corner
truncation, remaining on the finished lumber. Conven-
tional optimization techniques largely ignore these
economic factors.
The customary approach to edging a cant is to
remove essentially all of the wane, ignoring variations
in the inherent grade of the wood due to knots, splits
and rot. If the cant is trapezoidal, the edging process
results in the loss of a triangular or trapezoidal cross
section strip of wood from each side of the cant suffi-
cient to square up the entire thickness of the cant over
its entire length. This approach, in effect, saws each
cant in a manner commensurate with producing the highest
grade of lumber, without taking into account inherent
characteristics of the wood that might prevent the
resultant lumber from achieving such high grade.
Thus, by ignoring economic value as a function
of both width and grade, significant amounts of other-
wise marketable wood are lost. If, due to variations in
market conditions, lumber of a certain dimension has a
higher value on a volumetric basis than lumber of other
dimensions, it is preferable to cut as much lumber as
S~3
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possible to the higher value dimension to maximize eco-
nGmic yield. However, the aggregate economic value of
the wood products produced from a cant or log is not
maximized by maximizing only the gross volume of lumber
produced from a cant of a given width, without regard
for the relative values of different dimensions of lum-
ber. And if, because of inherent characteristics of the
wood, the lumber produced could not possibly exceed a
given grade level, cutting off more wane than is com-
mensurate with that grade level wastes useful wood.
One of the most commonly-used system for scan-
ning a cant preparatory to edging, employs a method of
shadow scanning the cant as disclosed, for example, in
U.S. Pat. No. 3,970,128 to Kohlberg. This system pro-
vides for a pair of illumination sources positionedabove and to each side of a conveyor along which a cant
is conveyed to illuminate the sides of the cant at a
downward angle. A scanner is positioned directly above
the cant to receive light reflected upwardly from the
sides of the cant. The light sources are operated
alternately so that one side is shaded while the other
side is illuminated. In this way, the longitudinal
edges of the top of the cant surface are defined by dis-
tinct shadow lines which are readily detected by the
scanner. Scanning is synchronized with the alternate
lighting of the illumination sources. The scanning out-
puts are fed to a computer for calculation of an optimum
distance between two straight edging cuts and an optimum
orientation of those cuts to convert the cant to a stan-
dardized finished piece of lumber with minimum wastageof material. U.S. Pat. No. 3,806,253 to Denton applies
this technique to the scanning of logs.
A second technique, applied in U.S. Pat. No.
4,097,159 to Strandberg to scanning cants and in U.S.
Pat. No. 4,192,613 to Hammar to scanning logs, aligns
the light source and scanner on opposite sides of the
workpiece so that the workpiece interrupts the transmis-
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sion of light from the source to the scanner. The posi-
tion of the interruption is detected by the scanner and
provided to a data processor which analyzes the dimen-
sions of the silhouette of the workpiece to control its
processing.
A third scanning technique is disclosed in U.S.
Pat. Nos. 4,158,507 to Himmel; 4,264,208 to Haberl, et
al.; 4,294,149 to Olsson and 4,300,836 to Holmes, et
al. Generally speaking, this technique employs scanning
a beam across back and forth or lengthwise along the
workpiece, using a beam pivoting device, and measuring
the dimensions of the surfaces of objects scanned by
triangulation or reflected light intensity techniques.
A fourth technique disclosed in U.S. Pat. No.
4,188,544 to Chasson and various patents cited therein
uses a television camera and a fan-line laser projected
downwardly onto a workpiece at different acute angles
for detecting the intersection line of a plane of light
produced by the laser and the workpiece and calculating
dimensions of the workpiece surface by using known dis-
tances and geometric relationships. Systems similar to
that of Chasson are also disclosed in U.S. Pat. Nos.
4,086,496 to Berry; 4,186,310 to Maxey and 4,196,648 to
Jones, et al. These systems all use a separate set of
scanners and light source at each scanning interval
along the cant.
As mentioned above, all of the foregoing lumber
processing control systems analyze the dimensions of the
workpiece and control their processing to maximize the
30 volume of usable wood products to be produced from the
workpiece. None of them are known to take into con-
sideration the relative economic value or grade of the
products. For the most part, the analytic methods
employed in these systems involve mapping the entire
35 surface of the workpiece. Therefore, sufficent memory
(e.g., 256,000 bytes) must be provided in the data
processor to store three-dimensional spatial coordinates
~l~Z519S~;3
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of the workpiece. Substantial computing capacity, such
as i5 provided by a main frame or minicomputer, is
required.
Also, data acquisition time in such systems is
long, one second or more. This does not leave time for
much analysis when trying to edge 15 to 20 cants per
minute. Speed is especially important when handling
relatively narrow cants, under 16 inches, because of the
need for high volume throughput to economically edge
narrow cants. Long data acquisition processing time
virtually precludes application of prior automated scan-
ning and analysis techniques to small-log lumber mills.
Typically, edger operators in such mills, unaided by any
automated analysis, only have time to briefly view each
cant, make a snap decision and push a button. The
resultant decisions are typically not optimal.
Referring to the aforementioned Chasson patent,
the amount of memory and computing capacity required can
be reduced somewhat by sampling the dimensions of the
workpiece at intervals spaced along the length of the
workpiece. However, this approach sacrifices substan-
tial accuracy. It can miss significant variations in
the contours of the workpiece between sampling inter-
vals~ which are conventionally positioned six inches or
more apart. And the time and cost savings are too lit-
tle to enable use of low cost microcomputers for con-
du~ting extensive analysis of edging options.
Accordingly, there remains a need for a scan-
ning and analysis system which is capable of accurately
characterizing the dimensions of a workpiece, without
requiring storage and processing of vast amounts of
data, and controlling the processing of the workpiece so
as to maximize the economic value of the wood products
produced therefrom.
SUMMARY OF THE INVENTION
It is therefore one object of the invention to
provide an improved method and apparatus for scanning,
~2S1~63
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analyzing and controlling the processing of logs, cants
and the like for optimum yield.
A second object of the invention is to increase
the yield of salable wood products produced from wooden
workpieces.
A third object is to maximize the value of lum-
ber of a specified grade that can be cut from a work-
piece of a given size and wood quality.
Another object of the invention, as aforesaid,
is to simplify the scanning and analysis of the work-
pieces so that they can readily be carried out on a
microcomputer, yet obtain an accuracy commensurate with
sampling increments of less than one inch and speeds
commensurate with edging 15 to 20 or more cants per
minute.
A further object is to reduce the cost of
apparatus for scanning and analyzing wooden workpieces
to be processed into dimension lumber, yet improve the
analysis and increase the throughput over prior such
apparatus.
A more specific object of the invention is to
maximize the aggregate value of boards of different
sizes that can be cut from a cant of a given size.
Yet another object is to maximize the total
value of lumber that can be cut from an irregular-
ly-shaped cant containing wood of a given quality.
In accordance with the invention, the foregoing
objects are realized in a contour line scanning system
which projects coplanar lines of light onto opposite
sides of a wooden workpiece in a plane parallel to the
width of the workpiece to form a contour line along each
side. The contour lines define the width of the work-
piece in the aforementioned plane and characterize any
irregularities in the sides of the workpiece. A sensor
means is directed toward the workpiece for sensing the
contour lines and producing an output signal correspond-
ing to the position of such lines. This output signal
~2~19~3
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is input to a computer or other suitable means programed
for determining an optimum sawline through the work-
piece, as a function of stored values of lumber of
different dimensions, from the widthwise profile of the
workpiece as characterized by the contour lines.
In a preferred embodiment, such a system
adapted for edging a cant has beam-forming ~eans posi-
tioned to direct thin, coplanar sheets of light towards
the opposite narrow side faces of the cant in a plane
positioned between and parallel to the broad faces of
the cant. For processing trapezoidal cross section
cants, a single scanner can be used, positioned above or
below the cant and directed normal to the plane of the
sheets of light to sense both contour lines. I'he con-
tour lines are stored in memory as digitized lateralpositions and therefore require minimal memory, for
example, 1024 bytes per scanner. The elevation of the
contour lines on the side faces of the cant establishes
a specified grade line. The specified grade can be
varied by shifting one of the cant or the beam-forming
means up and down or by providing multiple beam-forming
means at different elevations, to be alternately
switched on to establish the grade line at different
elevations on the side faces of the cant. Elevating the
grade line, that is, moving it toward the narrower broad
face of the cant, improves the grade of lumber to be
produced from the cant as a function of amount of wane
or corner truncation while decreasing the volume of
salable lumber. The computer also includes memory for
storing values of lumber of different grades and
widths. An operator can specify a lumber grade based,
for example, on a visual inspection of the quality of
wood in the cant. From the spacing between the contour
lines at the specified grade line, the computer deter-
mines a useful width of the cant between the lines.Then, using the stored values of various widths of lum-
ber of the specified grade, the computer determines a
9~;3
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combination of board widths, totaling no more than the
previously-determined useful width, that will yield the
greatest economic value of dimension lumber capable of
being produced from the cant.
The apparatus and method employed in the fore-
going preferred embodiment can be readily adapted to
other aspects of wood processing. For example, it can
be used for edging cants that are square along one or
both sides by positioning two scanners above or below
the cant at acute angles to the coplanar beams of
light. In either case, the cant is sawn along sawlines
normal to the beams of light. In other words, the saw-
lines are aligned with the direction in which the beams
of light are raised or lowered to vary the position of
the contour lines on the side faces of the cant. The
scanning system employed in the preferred embodiment can
also be readily adapted to scanning of whole logs or
turn downs for cutting into cants. In such case, the
sawline is aligned parallel to the plane of the beams of
light and the positioning of the log normal to such
plane is controlled for sawing cants, each containing
lumber of the maximum possible value, from the log. I'he
system can also be programmed with tables of values
varying with length as well as width and grade of lumber
so that logs, cants or lumber can be bucked into
selected lengths of maximum value by cutting them cross-
wise along sawlines normal to their length.
One important advantage of the invention is
that it enables processing of a wooden workpiece to
produce a mix of wood products having the maximum
aggregate value, rather than merely a maximum volume of
wood. Another important advantage is that it enables
utilizing the greatest possible width of a cant to pro-
duce lumber. This advantage is enhanced by sawing
boards having a maximum predetermined amount of corner
truncation in accordance with the specified grade of the
lumber. In doing so, the amount of wane to be chipped
;3
or otherwise discarded can be substantially reduced from
that of prior wood processing control systems. A third
advantage is that the data processing can readily be
performed by a microcomputer. Thus, apparatus costs can
be nearly an order of magnitude less than in prior sys-
tems. A further advantage is that scanning analysis and
edging control can be performed quickly enough, even on
a microcomputer, for the system to meet the throughput
demands by small-log mills. The capability of sophis-
ticated analysis is thereby made available where it canprovide the greatest benefits.
The foregoing and other objects, features and
advantages of the invention will become more readily
apparent from a detailed description of a preferred
embodiment which proceeds with reference to the accompa-
nying drawings.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a top plan view of an edger system
with cants shown in phantom lines at various positions
in the system.
Fig. 2 is a perspective view of the system of
Fig. 1, including cant scanning and positioning elements
of a contour line scanner in accordance with the inven-
tion.
Fig. 3 is an alternative embodiment of the cant
scanner of Fig. 2, as seen in an end view of the cant.
Fig. 4 is a top plan view of portions of the
edger system and scanner of Figs. 1 and 2, including two
of the edging saws, alternate positions for the fan-line
laser elements being shown in phantom lines.
Fig. 5 is a series of cross-sectional views
taken at spaced intervals along the cant of Fig. 4.
Fig. 6 is an enlarged cross-sectional view of
the cant of Fig. 4 showing the relative elevations of
different grade lines along its side faces.
Fig. 7 is a block diagram of the contour line
scanning system of Figs. 1 and 2.
~2S1~63
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Fig. 8-11 are diagrams illustrating the princi-
pal data arrays used by the microcomputer of Fig. 7.
DEI'AILED DESCRIPTION OF A PREFERRED EMBODIMENT
Physical Arrangement of System
Referring to Fig. 1, an edger system 10 for
edging cants is positioned in a lumber mill downstream
from a headrig or similar sawing apparatus (not shown)
which saws a log into lengthwise slabs or cants 12. The
cants are conveyed sideways by transfer chains 14 to
stop pins 16, which temporarily hold the cant 12a while
a previous cant 12b is being processed. Downstream of
the stop pins are a pair of lift skids 18 positioned at
opposite ends of a first roller chain infeed conveyor
20. The infeed conveyor is oriented to convey the cants
at right angles to transfer chains 14. The lift skids
are raised to receive a cant from the transfer chains
and lowered tG place it on the first infeed conveyor.
Adjacent each of the lift skids, on the oppo-
site lateral side of infeed conveyor 20 from stop pins
16, is an infinite setting lineup pin 24. Such pins
have hydraulically or pneumatically powered rams 26
which are extended or retracted laterally of conveyor 20
to position the cant laterally on the lift skids for
infeeding to the saws, as next described. Downstream of
conveyor 20 is a second roller chain infeed conveyor 28
positioned to receive the cants from conveyor 20 and
convey them forwardly into an edger 30.
The edger comprises a series of parallel saws
32 spaced across the path of conveyor 28 and driven by a
drive motor 34 through shaft 36. The saws are movable
axially of shaft 36 and their position is controlled by
an edger saw setting system or set works 38. Downstream
of the edger saws is an outfeed conveyor 40. Details of
construction and operation of the mechanical elements
shown in Fig. 1 are known in the art and, not forming a
part of the present invention except insofar as they are
used in combination with the apparatus described herein-
9~
after, need not be further described.
Turning to Fig. 2, fan line lasers 42 are posi-
tioned on opposite sides of the conveyor 20 for project-
ing lines of light laterally toward the sides of the
cant, while it is supported on the lift skids. For
clarity, the lift skids and conveyors are omitted from
Fig. 2 and the remaining Figures. Alternatively, the
fan line lasers 42 can be positioned on opposite sides
of conveyor 20 at a distance from its ends, as shown in
phantom lines in Fig. 4. In either case, the fan line
lasers are positioned to project coplanar fan-like
sheets of light 44 in opposite directions across con-
veyor 20. These fans of light are mutually oriented
parallel to a plane defined by the upper surfaces of the
lift skids and thereby parallel to the broad upper and
lower faces 46, 48 of cant 12. When a cant is posi-
tioned between lasers 42, the light beams 44 project
lines of light 50 onto opposite side faces 52, 54 of the
cant.
As illustrated in Fig. 2, each fan line laser
42 contains two or more fan line laser elements 43 and
electrical circuitry for selectably switching on alter-
nate elements. Such elements are vertically spaced to
form grade lines at different selectable elevations on
the sides of the cant.
Centered above conveyor 20 is a television
camera 56. A second such camera (not shown) can be
positioned below conveyor 20 so that the cants need not
be turned over to position their narrower broad faces 46
facing upwardly. Camera 56 is aimed downwardly at the
cant with the centerline 58 of its field of view normal
to the plane of beams 44 and therefore substantially
normal to the upper face 46 of the cant. The field of
view of camera 56 is sufficient to cover the area indi-
cated by dashed lines 60, as discussed further below.The foregoing arrangement is used in lumber mills where-
in the cants are cut by a headrig and, therefore, have a
~s~g~3
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generally trapezoidal cross-sectional shape.
In some mills, cants are cut from a log by a
resaw machine in what is referred to in the art as a
turndown sawing procedure. Referring to Fig. 3, that
procedure produces cants 13 having a single triangular
profile edge face 51 and a rectangular or squared-off
edge face 53, or two squared-off edge faces. Since the
squared-off edge faces are parallel to the centerline 58
of the field of view of camera 56, it is necessary to
use two cameras 57 positioned above the cant at an acute
angle 59, for example, 45, from the plane of beams 44
for viewing the contour lines on the squared-off faces
of the cant.
Camera 56 is positioned at an elevation and
provided with lenses such that it has a field of view
sufficient to encompass the full width of the widest
cants that will normally be processed by the particular
mill in which the system is installed. For most mills,
a field of view of, for example, 60 inches, will suffice
for scanning cants up to 40-45 inches wide and up to 60
inches in length. For stud mills, which cut cants of
just 8 feet in length, a single set of lasers and
camera, positioned to scan the narrow end of each cant,
will suffice. For longer cants, multiple sets of fan
line lasers and cameras are ordinarily positioned at
overlapping intervals, for example, 4 feet apart,
lengthwise along the cant. The additional fan line
lasers (not shown) are aligned to project sheets of
light in the same plane as lasers 42. Alternatively, a
total of four fan line lasers, positioned as shown in
phantom lines in Fig. 4, are used, with as many addi-
tional cameras as are needed for the maximum length
cants that are to be edged. The additional cameras 56a,
56b (Fig. 7) are aimed at the cant in the same manner as
cameras 56, 57. Each camera is oriented with its hori-
zontal scanning direction across the cant. Each scan
line in a single frame (e.g., 512 lines per frame)
63
thereby corresponds to a lengthwise increment along the
cant of, for example, 3/32 inch.
Sensing and Control Apparatus
Referring to Fig. 7, sensing and analysis of
the cant and control of the edging process is accom-
plished by system 62. The central components of this
system are the aforementioned fan line lasers 42 and
cameras 56, a digital computer 64, a digitizer 66,
operationally connecting the cameras to the computer,
and various conventional mechanism actuation control
devices 68 operably connected to the computer. Periph-
eral devices connected to the computer include an oper-
ator input device 70, such as an alphanumeric keyboard,
a graphic cathode ray tube (CRT) display 72, a printer
74, and a data storage disk 76 or other suitable mass
memory device.
Computer 64 is preferably a commercially-avail-
able microcomputer, such as the APPLE 2+ microcomputer,
equipped with an integral operator keyboard 70 and com-
patible peripherals 72, 74, 76. A camera 56 and dig-
itizer 66 suitable for use with such microcomputer are
the SANYO VC1610X camera and the DITHERTIZER II video
digitizer, manufactured by Computer Stations, Inc., St.
Louis, Missouri. This digitizer converts the analog
output signal of the images detected by the camera into
digital signals which can be processed by the computer.
Software is described hereinafter for analyzing such
signals and generating and storing positions of the con-
tour lines in the computer memory.
Overview of Edging Operation
In general, this invention seeks to establish a
pair of grade lines on opposite sides of a cant, deter-
mine the maximum width of the cant between two parallel
sawlines positioned between the grade lines, and deter-
mine the optimum position of two or more sawlines
through the cant to produce the maximum total value of
lumber.
12~ ;3
- 14 -
Referring to Figs. 4 and 7, the oper~tor visu-
ally grades the cant and inputs a selected grade via
keyboard 70, causing the computer 64 to switch on the
appropriate pair of fan line laser elements 43 to pro-
ject light beams 44 onto the cant and thereby establishcontour lines 50 at the selected elevation or grade
line. Referring to Fig. 6, the conventional grade
lines, in terms of permissible amounts of residual wane,
are Economy, Utility, Standard, Select and Clear.
Because the wane is generally triangular, selecting a
higher grade, and thereby elevating beams 44, increases
the amount of wane to be sawn from the cant and commen-
surately decreases the maximum available or usable board
width. For example, selecting l'Standardl' grade necessi-
tates cutt~ng the cant along lines 80, which removes anamount of wane from each side indicated by arrow 82 and
produces a maximum usable width, as indicated by arrow
84. Selecting IlClearl grade necessitates cutting along
line 86, nearer the center of the cant than lines 80,
thereby removing wane 88 and producing a narrower usable
width 90. If the inherent quality of the wood in the
cant is only IlStandardll grade, but the cant is cut for
IlClearll grade, as frequently happens in conventional
edging operations, the amount of material indicated by
arrows 92 is needlessly removed as wane. Such waste is
greatly reduced by varying the elevation of the grade
line in accordance with the grades of the cants and then
edging the cants at a lateral position determined by the
grade lines.
Once the grade lines are set and contour lines
50 thereby formed, sawlines are determined in two
steps. First, referring to Figs. 2 and 4, one sawline
94 is drawn (within the computer) along contour line
50a. Line 94 is positioned between the contour lines so
as to touch line 50a at two or more points, without
crossing it.
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Then, a second line 96 is drawn parallel to the
first sawline, along the second contour line 50b. The
second line touches contour line 50b at its closest
approach to sawline 94, that is, at the narrower end of
the cant. The spacing between the first and second
lines 94, 96 determines the maximum usable full-length
width of the cant, as indicated by end cross-section 100
in Fig. 5. The second line 96 is not necessarily the
second sawline. The second sawline (not shown) is
parallel to line 96 and may be positioned on it or to
either side of it, depending upon the results of subse-
quent computer analyses of the potential yield of the
cant and on any variations of width along the cant at
shorter lengths, as next described.
If the cant is less than a specified minimum
length, such as 10 feet, analysis of the best positions
to saw the cant for maximum yield is made only once, for
its maximum usable length--8 feet. If the cant is
longer than 10 feet, it is desirable to first determine
the maximum useful full length width and the best yield
for that width, and then analyze and compare potential
yields at different lengths less than its maximum
length. This analysis is performed at two foot inter-
vals, starting at the narrow end of the cant and pro-
ceeding toward the wide end, until the minimum usefullength is attained. This procedure is illustrated in
Fig. 4 by lines 96a, 96b, 96c, and in Fig. S, wherein
the maximum useful width for a selected grade, e.g.,
"Standard," is denoted at each interval of length by
arrows 100, 102, 104, 106, 108.
Typically, several possible combinations of
board widths can be cut from a cant of a given useful
width. For example, a 24 inch wide cant can be sawn
into four 6 inch, three 8 inch, or two 12 inch wide
boards, or any of a large number of combinations of
different board widths. Depending on current lumber
market conditions, the aggregate values of the possible
12~-~ g
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combinations for a given total width will typically
differ. AS further described below, the combination
yielding the maximum aggregate value is determined at
each usable width, and the length producing the greatest
value is selected. Then, the combination of widths pro-
ducing that greatest value for that length is identi-
fied. From that data, the positions of the second saw-
line and of any additional sawlines needed to cut the
cant into the identified combination of widths are
determined.
Referring back to Figs. 1 and 7, the first,
second and additional sawline positions are used by com-
puter 56 to control the positioning of the cant and the
edging saws. Through actuation controls 68, the com-
puter actuates the lineup pins 24 to angularly reposi-
tion the cant, supported on the lift skids 18, so that
the sawlines parallel saws 32. Simultaneously, the com-
puter actuates the saw setworks 38 to laterally position
the saws to cut the cant along the selected sawlines.
When this alignment procedure is completed, the computer
initiates a re-scan of the cant to verify its position
and adjust the position if necessary. Then, it causes
the lift skids to lower the cant onto conveyors 20, 28
and starts the conveyors (if not continuously running)
to feed the cant through the saws. Finally, the stop
pins 16 are actuated to allow the next cant to be infed
to the scanning station, so that it too can be scanned
and analyzed as discussed above.
This aligning procedure positions one of the
sawlines 94 in touching relation but not crossing con-
tour 50a. In general, this causes the sawlines to be at
an angle to the centerline of the cant, thus providing a
greater area of useful wood than if the sawlines were
parallel to the centerline of the cant. However, the
procedure may be deoptimized if it is desired to produce
nondiagonal grain lumber.
~S19~i~
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Following is a description of the software used
to implement the foregoing procedures.
Program Operation and Data
The foregoing process is controlled by a main
routine, which is set forth below. So that it can be
more readily understood, the main routine is listed in a
generalized flow chart form which can be readily imple-
mented in any desired programing language by a skilled
programer. In subsequent sections, the data arrays and
various subroutines used in the main routine are
described in further detail.
Main Routine
The main routine is presented in the form of a
functional description of program operation in the fol-
lowing listing. Each step in the operation is describedin a statement which is not specific to any particular
programing language, but can readily be implemented in
any desired computer language by a programer ordinarily
skilled in such language. Variables and data arrays
generated by each operation are identified after a colon
following each statement. Parenthesized variables indi-
cate dimensions of arrays of variables, as further dis-
cussed in the following section with reference to Figs.
8-11. Further explanation of each step is provided as
needing in a comment following the statement, or in a
detailed explanation in subsequent sections.
100 START MAIN ROUTINE
105 STORE CURRENT LUMBER PRICES: VAL (I, J, K)
107 GENERATE POSSIBLE COMBINATIONS OF BOARD
WIDTHS AND TOTAL WIDTH OF EACH COMBINA-
TION: COMB (J, R), TW (R)
108 DETERMINE TOTAL VALUES OF ABOVE BOARD COM-
BINATIONS AND SORT ROWS (R) BY DESCENDING
VALUE: TV (I, COMB, K)
Comment: Steps 105, 107, 108 are
explained in the following section "Data
Arrays."
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l l O I NFEED CAN T
Comment: This step actuates the stop pins
to allow next cant to be conveyed onto the
lift skids.
112 INPUT GRADE OF CANT: K - ?
Comment: This step determines the beam
elevation required to form contour lines
at a selected level or grade line as shown
in Fig. 6.
113 POSITION GRADE LINE
Comment: This step actuates positioning
of the light beam to the predetermined
elevation corresponding to maximum allow-
able corner truncation for a selected
grade.
115 SCAN CANT/ DIGITIZE AND STORE COUNT DATA
CORRESPONDING TO POSITIONS OF CONTOUR
LINES AT EACH SCAN: CL (M, N)
Comment: This step is explained in the
following section "Scanning and Digitizing
Contour Lines."
120 SMOOTH CONTOUR LINES
Comment: This step eliminates contour
line data points that deviate sufficiently
from adjoining points to indicate a prob-
able error.
125 DETERMINE MAXIMUM USABLE LENGTH OF CANT:
I = ML
Comment: Length is determined by finding
and subtracting the incremental positions
of the first and last nonzero values of CL
in the N dimension; maximum usable length
is the next shorter multiple of 2 feet
130 DETERMINE FIRST SAWLINE TOUCHING FIRST
CONTOUR LINE: SL (1, N)
Comment: The first sawline is determined
by any desired method. Array SL is an
array like array CL.
i3
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132 DETERMINE NARROWEST END OF CANT.
Comment: This is done by finding the
lengthwise position of the minimum differ-
ence between the first and second contour
lines.
135 STARTING AT NARROWEST END OF CANT, DETER-
MINE SECOND STRAIGHT LINE PARALLEL TO
FIRSI' SAWLINE AND TOUCHING SECOND CONTOUR
LINE AT A LENGTH I: SL t2, N(I))
Comment: Since this line is parallel to
the first line, it can be defined by iden-
tifying the point N(I) on the second con-
tour line nearest the first sawline
between length I and I - 2 feet.
140 DETERMINE MAXIMUM USABLE CANT WIDTH
BETWEEN FIRST AND SECOND STRAIGHT LINES AT
LENGTH I: CW (I)
Comment: Initially, this width is the
minimum full length width determined in
step 132. At shorter lengths, it is the
distance between the first contour line
and the point identified in step 135.
145 FIND TOTAL WIDTH TW LESS THAN CW(I) HAVING
MAXIMUM TOTAL VALUE TV(I): MTV(I)
Comment: This step is explained in the
following section "Data Arrays."
150 REPEAT STEPS 135, 140, 145, DECREASING L
IN 2 FOOT INCREMENTS UNTIL LENGTH I = 8
FEET
Comment: In stud mill operations, this
operation is only performed once because
the cants are typically about 8 feet long.
155 FIND GREATEST MTV(I)
160 LOOK UP ASSOCIATED COMBINATION OF BOARD
WIDTHS AND TOTAL WIDTH: MCOMB, MTW
165 ACTUATE LINEUP PINS TO POSITION CANT WITH
FIRST SAWLINE AT A PREDETERMINED ORIENTA-
TION (E.G., PARALLEL) TO EDGING SAWS
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170 RESCAN CANT FOR FIRST CONTOUR LINE, RE-
DET~RMI~ FIRST SAWLINB, AND REPOSITION
CANT IF FIRST ORIENTATION IS NOT CORRECT
Comment: This step provides feedback to
make sure that the lineup pins actually
position the cant as desired. It essen-
tially repeats steps 115 through 130.
175 ACTUATE SBTWORKS TO ALIGN E'IRST SAW
LATERALLY WITH FIRST SAWLINE, TO POSITION
SECOND SAW AT A SECOND SAWLINE AT DISTANCE
OF TOTAL WIDTH MTW AND TO POSITION ADDI-
TIONAL SAWS BETWEEN FIRST AND SECOND SAWS
TO SAW BOARD WIDTHS IN ACCORDANCE WIT~
SELECTED COMBINATION
185 ACTUATE LIFT SKIDS TO LOWER CANT ONTO IN-
FEED CONVEYORS
190 RETURN TO STEP 110
In the foregoing flow chart listing, various data arrays
and variables are identified. Following is a further0 description of such arrays and how they are developed.
Data Arrays
Referring to step 105 in "Main Routine," cur-
rent lumber values are input to the computer whenever
they change, ordinarily on a weekly basis. Such values
are conventionally available from market reports pub-
lished in the form of tables of prices organized with
columns for each length and rows for each width of a
given type, thickness and grade of lumber. The prices
are given in dollars per thousand board feet. In a
typical edging operation the type and thickness of the
lumber are constants, so only length, width, grade need
be considered in organizing a data array for a single
edger. Referring to Fig. 8, a three dimensional array
VAL (I, J, K) is created in the computer memory to
receive lumber price data as a function of length (I) in
two foot increments from 8 to 20 or more feet; width (J)
in two inch increments from 3.625 inches to 11.625
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- 21 -
inches; and grade (K), such as Standard, Select, Clear,
Utility and Economy. The raw prices are input and then
column-wise divided by the number of boards of each
length per 1,000 feet to convert them to value per piece
of lumber.
Depending on lumber conditions, only a few
grades might be used, for example, just Standard and
Select grades. Similarly, only a few widths and lengths
might be used. For example, a small log stud mill would
only use 8 foot lengths and might cut only up to ~ inch
widths.
Next, referring to step 107 and Fig. 9, a
two-dimensional array COMB (J, R) is generated, listing
in rows (R), each combination of board widths (J) having
a total width less than the width of the edger, for
example, 40 inches. Also, since each edger has a fixed
number of saws, only combinations containing fewer
boards than the number of saws are listed. For each
combination, a total width TW(R) is generated by multi-
plying the number of boards of each width by such widthand summing the products. This data is added as a
column to the COMB(J,R) array.
Then, step 108 causes a three-dimensional array
of total values of lumber of board widths and for each
length and grade, for each combination to be generated,
as illustrated in Fig. 10. This array, TV (I, COMB, K),
is generated by multiplying, for each length and grade,
the number of boards of each width in a combination by
price VAL (I, J, K) and summing the product. This array
will have as many columns as there are different lengths
and grades in the VAL (I, J, K). In the aforementioned
example of a stud mill which cuts only Standard and
Select grade studs, array TV would consist of only two
columns.
The arrays of Figs. 9 and 10 can now be used to
economically optimize the edging of a cant. However, to
execute selection of the best combination more quickly,
12519~3
- 22 -
it is preferable to rearrange the rows of such arrays in
order of descending total width and value. It is also
desirable to delete combinations which utilize the same
total width but yield less total value than other com-
5 binations, retaining the latter. It should be under-
stood that, as market values change, the relative total
values for different combinations may change, so the
foregoing rearranging and deleting steps should be per-
formed each time lumber values change. The following
table lists small portions of an example of the combina-
tion and total value arrays, COMB (J, R) and TV (I,
COMB, K), for Standard grade, nominally two inch
(actually 1.625") thick, 16 feet long lumber.
TABLE 1
(40" Width Edger, 5 saws, 0.125" Kerf)
RowNominal Board Widths Total Total
No. 4 6 8 10 12 Width Value
1 1 0 0 0 3 39 26.83
2 0 1 0 1 2 39 26.41
3 0 0 0 4 0 39 25.64
4 0 0 1 2 1 39 25.54
0 0 2 0 2 39 25.48
6 1 0 0 1 2 37 25.08
7 0 1 0 2 1 37 24.66
8 0 1 1 0 2 37 24.58
9 0 0 0 0 3 35.25 24.48
30 10 0 0 1 3 0 37 23.81
11 0 0 2 1 1 37 23.73
12 0 2 0 0 2 35 23.68
13 1 0 0 2 1 35 23.33
14 1 0 1 0 2 35 23.25
35 15 0 1 0 3 0 35 22.91
. . .
~251~3t~3
The foregoing table is arranged in descending
order of total values, but no rows are deleted in order
to show the various combinations at a given total
width. In practice, only the best total value at each
total width--rows 1, 6, 9 and 12 in the portion shown
above--would be retained, thereby greatly reducing com-
puter memory requirements and average execution time.
Alternatively, the best two or three combinations at a
given total width could be displayed so that the oper-
ator has the option of selecting a non-optimal combina-
tion (as determined automatically) based on, for exam-
ple, visually observable grade-related criteria such as
location of defects.
~or purposes of illustration, Table 1 combines
the array of Fig. 9 with a single column of the array of
Fig. 10. In practice, the rightmost column "I'otal
Value" may be but one of many columns of the three-di-
mensional array of Fig. 10. Referring to Figs. 9 and
10, it will be observed that each array contains num-
bered rows. The row numbers are included in array TV(Fig. 10) so that they can be used as an index to aid in
looking up the combination in array COMB (Fig. 9) that
is associated with each row of total values in array TV.
When the rows in array TV are rearranged in
order of descending value, the row numbers are likewise
rearranged. The rows in array COMB are preferably
initially arranged in order of descending total width.
Using row numbers R as an index, step 145 in "Main Rou-
tine" can thus be performed in the following steps:
200 START
210 IN ARRAY COMB (J, R) SEARCH DOWN TW (R)
COLUMN FOR FIRST TW (R = Rl) LESS THAN CW
(I = Il)
220 IN ARRAY TV SEARCH DOWN THE ROW COLUMN AT
GRADE K = Kl, FOR FIRST ROW NUMBER R EQUAL
TO OR GREATER THAN Rl.
230 SHIFT ALONG ROW R2 TO COLUMN TV (I = Il)
63
-- 24 --
240 SET MTV (Il) = TV (Il)
In performing step 150, the row number R for
each MTV (I) is stored. The stored row number associ-
ated with the greatest MTV(I) found in step 155 (e.g.,
row number ~2) is then used in step 160 to look up the
combination MCOMB (J, R2) and total width MTW (R2).
Once the foregoing data arrays are stored, the
system is ready to scan cants and for analysis and edg-
ing in accordance with the above-described programs.
Scanning and Digit_zing Contour Lines
Referring to step 112 of the Main Routine, the
operator initiates scanning of a cant positioned in the
scanning station by visually observing the cant, judging
its quality independently of amount of wane, and input-
ting into the computer a grade based on that quality.Step 113 causes the computer to switch on one of the
pairs of fan line laser elements 43, to position the
beams 44 so as to delineate, by contour lines 50, the
maximum permissible wane for the selected grade. For
example, if the cant is judged to be of Standard grade,
then the operater keys in K = 1. Referring to Fig. 6,
the computer responds by switching on the elements 43
whose beams 44 are positioned to form contour lines 50
at the Standard line, one-fourth of the thickness of the
cant from its narrower broad face, as indicated by arrow
98. The variable K = 1 is then stored by the computer
for application to all subsequent steps of the Main Rou-
tine which are affected by grade K.
Next, in step 115, the computer actuates the
camera 56 and digitizer 66 and branches to subroutine
LINES which, in general terms, stores the positions of
the images of the contour lines in the computer memory
in array CL (M, N). The camera scans the cant in hori-
zontal scan lines oriented normal to the length of the
cant. Each scan produces an analog signal which
includes signal levels corresponding to the contour
lines. The digitizer 66 divides each scan line in the
1~51963
- 25 -
analog output signal from the camera 56 into, for exam-
ple, 512 segments or pixels and assigns a digital value
to each pixel corresponding to its analog value. The
digital value expresses these values in numerical levels
of gray scale, for example, from binary 0000 (zero) for
the darkest level to binary 1111 (15) for the lightest
level. The contour lines are, therefore, expressed as
relative light levels and can be sensed by comparing
each pixel value to a predetermined threshold between
levels corresponding to the background light and the
contour lines. The subroutine LINES then create a
numerical description of the contour lines 50, based on
their lateral position relative to, for example, one
side of the field of view of camera 56. Following is a
functional listing of subroutine LINES, in which N
identifies each scan line, M identifies each contour
line, and P is the count for each pixel.
300 START LINES
305 START CAMERA AND DIGITIZER
310 SET N = 1
Comment: This step identifies the first scan
line.
320 SET M = 1, P = O
Comment: This step identifies the first con-
tour line and starts the pixel count.
325 SET P = P+1
330 GET PIXEL (P)
Comment: This step accesses subroutine CONTOUR
to read the Pth pixel.
340 IF PIXEL tP) IS GREATER THAN THRESHOLD,
SET CL (M, N) = P; M = 2
Comment: This step compares the pixel value
with the threshold and, if such value corre-
sponds to the level of a contour line, stores
the position of the first pixel in the first
contour line memory location M = 1 at scan line
N and identifies second contour line.
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- 26 -
350 IF P LESS T~AN 512, GO TO STEP 325
Comment: This step repeats steps 325-350 for
scan line N until all pixels in the line have
been tested and both contour line positions
have been stored for scan line N.
360 SET N = N+l
Comment: This step increments to next scan
1 lne .
370 IF N LESS THAN 512, GO TO STEP 320
Comment: This step restarts procedure for next
scan line until last scan in field is completed.
380 RETURN TO MAIN ROUTI~E (STEP 120)
The foregoing listing illustrates the procedure
for a single camera. It is readily applied to multiple
cameras. E'or storing contour lines from additional cam-
eras steps 305 and 380 are modified so as to serially
repeat the entire procedure for each camera.
Operational Performance
In off-line testing, using actual market prices
and cants of varying dimensions, the above-described
system has demonstrated results consistently superior to
those obtainable by prior art edger optimization sys-
tems. It should be readily apparent from Table 1 that
merely selecting the board width combination which
utilizes the maximum usable width of a slab does not
necessarily yield the maximum value of lumber. For
example, Row 9 produces greater value from a width of
35.25 inches than does Row 10 from a width of 37
inches. For a given maximum usable cant width, there
can also be several possible combinations of the same
total width, each producing a different total value of
lumber, for example, as shown in Rows 6-11 of Table 1.
These differences in total values become un-
expectedly large when edging small cants. In wide
cants, over 20 inches wide, the differences in total
values of the best five combinations typically vary
around 5-10%. However, for cants under 16 inches wide,
12~
this variation increases greatly, to as much as 40-50
for 10-inch wide cants.
When using the above-described syste~, elimina-
tion of these variables translates into commensurate
increases in economic value of lumber recovered from a
cant. Similar increases can accrue from the ability to
maximize the useful width of each cant by adjusting the
grade line to match the actual grade of the wood in the
cant. Thus~ the foregoing system enables substantial
increases in productivity where there is the greatest
unmet need, namely, in small log mills.
Having illustrated and described the principles
of my invention with reference to one preferred embodi-
ment, it should be apparent to persons skilled in the
art that the invention may be modified in arrangement
and detail without departing from such principles. I
claim as my invention all such modifications as come
within the spirit and scope of the following claims.
