Abstract:
A method of position-based integrated motion controlled curve sawing includes the steps of: transporting a curved workpiece in a downstream direction on a transfer, and monitoring position of the workpiece on the transfer, scanning the workpiece through an upstream scanner to measure workpiece profiles in spaced apart array, along a surface of the workpiece and communicating the workpiece profiles to a digital processor, computing by the digital processor, a high order polynomial smoothing curve fitted to the array of workpiece profiles of the curved workpiece, and adjusting the smoothing curve for cutting machine constraints of downstream motion controlled cutting devices to generate an adjusted curve generating unique position cams unique to the workpiece from the adjusted curve for optimized cutting by the cutting devices along a tool path corresponding to the position cams, sequencing the transfer and the workpiece with the cutting devices, and sequencing the unique position cams corresponding to the workpiece to match the position of the workpiece feeding the workpiece, on the transfer, longitudinally into cutting engagement with the cutting devices, and actively relatively positioning the workpiece and the cutting devices relative to each other according to a time-based servo loop updated recalculation, based on said workpiece position, of cutting engagement target position as the workpiece is fed longitudinally so as to position the cutting engagement of the cutting devices along the tool path.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]    This application is a divisional application of U.S. patent application Ser. No. 10/342,400 filed Jan. 15, 2000 which is a continuation of U.S. patent application Ser. No. 09/505,255 filed Feb. 15, 2000 which is a continuation of Ser. No. 09/211,047 filed Dec. 15, 1998, which is a division of U.S. patent application Ser. No. 08/822,947 filed Mar. 21, 1997 claims priority from U.S. Provisional Patent Application No. 60/013,803 filed Mar. 21, 1996, U.S. Provisional Patent Application No. 60/015,825 filed Apr. 17, 1996 and United States Provisional Patent Application No. 60/025,086 filed Aug. 30, 1996 entitled Position-Based Integrated Motion Controlled Curve Sawing. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    This invention relates to a method and a device for sawing lumber from workpieces such as cants, and in particular relates to a cant feeding system, for the breakdown of a two-sided cant according to an optimized profile.  
         BACKGROUND  
         [0003]    It is known that in today&#39;s competitive sawmill environment, it is desirable to quickly process non-straight lumber so as to recover the maximum volume of cut lumber possible from a log or cant. For non-straight lumber, volume optimization means that, with reference to a fixed frame of reference, either the non-straight lumber is moved relative to a gangsaw of circular saws, or the gangsaw is moved relative to the lumber, or a combination of both, so that the saws in the gangsaw may cut an optimized non-straight path along the lumber, so-called curve-sawing.  
           [0004]    Advances in digital processing technology and non-contact scanning technology have made possible in the present invention, an orchestrated approach to curve sawing involving a plurality of coordinated machine centers or devices for optimized curve sawing having benefits over the prior art.  
           [0005]    A canted log, or “cant”, by definition has first and second opposed cut planar faces. In the prior art, cants were fed linearly through a profiler or gang saw so as to produce at least a third planar face either approximately parallel to the center line of the cant, so called split taper sawing, or approximately parallel to one side of the cant, so called full taper sawing; or at a slope somewhere between split and full taper sawing. For straight cants, using these methods for volume recovery of the lumber can be close to optimal. However, logs often have a curvature and usually a curved log will be cut to a shorter length to minimize the loss of recovery due to this curvature. Consequently, in the prior art, various curve sawing techniques have been used to overcome this problem so that longer length lumber with higher recovery may be achieved.  
           [0006]    Curve sawing typically uses a mechanical centering system that guides a cant into a secondary break-down machine with chipping heads or saws. This centering action results in the cant following a path very closely parallel to the center line of the cant, thus resulting in split taper chipping or sawing of the cant. Cants that are curve sawn by this technique generally produce longer, wider and stronger boards than is typically possible with a straight sawing technique where the cant has significant curvature.  
           [0007]    Curve sawing techniques have also been applied to cut parallel to a curved face of a cant, i.e. full taper sawing. See for example Kenyan, U.S. Pat. No. 4,373,563 and Lundstrom, Canadian Patent No. 2,022,857. Both the Kenyan and Lundstrom devices use mechanical means to center the cant during curve sawing and thus disparities on the surface of the cant such as scars, knots, branch stubs and the like tend to disturb the machining operation and produce a “wave” in the cant. Also, cants subjected to these curve sawing techniques tend to have straight sections on each end of the cant. This results from the need to center the cant on more than one location through the machine. That is, when starting the cut the cant is centered by two or more centering assemblies until the cant engages anvils behind the chipping heads. When the cant has progressed to the point that the centering assemblies in front of the machine are no longer in contact, the cant is pulled through the remainder of the cut in a straight line. It has also been found that full taper curve sawing techniques, because the cut follows a line approximately parallel to the convex or concave surface of the cant, can only produce lumber that mimics these surfaces, and the shape produced may be unacceptably bowed.  
           [0008]    Thus in the prior art, so called arc-sawing was developed. See for example U.S. Pat. Nos. 5,148,847 and 5,320,153. Arc sawing was developed to saw irregular swept cants in a radial arc. The technique employs an electronic evaluation and control unit to determine the best semi-circular arc solution to machine the cant, based, in part, on the cant profile information. Arc sawing techniques solve the mechanical centering problems encountered with curve sawing but limit the recovery possible from a cant by constraining the cut solution to a radial form.  
           [0009]    Applicant is also aware of U.S. Pat. No. 4,373,563, U.S. Pat. No. 4,572,256, U.S. Pat. No. 4,690,188, U.S. Pat. No. 4,881,584, U.S. Pat. No. 5,320,153, U.S. Pat. No. 5,400,842 and U.S. Pat. No. 5,469,904; all designs that relate to the curve sawing of two-sided cants. Eklund, U.S. Pat. No. 4,548,247, teaches laterally translating chipping heads ahead of the gangsaws. Dutina, U.S. Pat. No. 4,599,929 teaches slewing and skewing of gangsaws for curve sawing. The U.S. Pat. Nos. 4,690,188 and 4,881,584 references teach a vertical arbor with an arching infeed having corresponding tilting saws and, in U.S. Pat. No. 4,881,584, non-active preset chip heads mounted to the sawbox.  
           [0010]    Applicant is aware of U.S. Pat. No. 4,144,782 which issued to Lindstrom on Mar. 20, 1979 for a device entitled “Apparatus for Curved Sawing of Timber”. Lindstrom teaches that when curve sawing a log, the log is positioned so as to feed the front end of the log into the saw with the center of the log exactly at the saw blade. In this manner the tangent of the curve line for the desired cut profile of the log extends, starting at the front end, parallel with the direction of the saw blade producing two blocks which are later dried to straighten and then re-sawn in a straight cutting gang.  
           [0011]    It has been found that optimized lumber recovery is best obtained for most if not all cants if a unique modified polynomial cutting solution is determined for every cant. Thus for each cant a “best” curve is determined, which in some instances is merely a straight line parallel to the center line of the cant, and in other instances a complex curve that is only vaguely related to the physical surfaces of the cant.  
           [0012]    Thus it is an object of the present invention to improve recovery of lumber from cants and in particular irregular or crooked cants by employing a “best” curve smoothing technique to produce a polynomial curve, which when modified according to machine constraints results in a unique cutting solution for each cant.  
           [0013]    To achieve this objective, in a first embodiment, a two sided cant is positioned and accurately driven straight into an active curve sawing gang, with active chip heads directly in front of the saws, to produce the “best” curve which includes smoothing technology. In one embodiment, a machining center in the form of a profiler cuts at least a third and potentially a fourth vertical face from a cant according to an optimized curve so that the newly profiled face(s) on the cant can be accurately guided or driven into a subsequent curve sawing gang. The profiled cant reflects the “best” curve which includes smoothing technology to limit excessive angles caused by scars, knots and branch stubs; while the gang saw products reflect the previously calculated optimized cutting solution.  
           [0014]    Due to an increased incidence of jamming of circular gang saw blades with curve sawing in general, it is another object of the present invention to orient the circular saw sawguides near the first contact point of the cant within the gang saw and still allow the sawguides to be rotated back away from the saw blades, thus allowing the saw blades to be removed more easily in the event of a cant becoming jammed than with other known curve sawing circular gang saws of the known type.  
         SUMMARY OF THE INVENTION  
         [0015]    In all embodiments of the integrated motion controlled position-based curve sawing of the present invention, the method of position-based integrated motion controlled curve sawing includes the steps of: transporting a curved elongate workpiece, which may be a cant, in a downstream direction on a transfer means, monitoring, by monitoring means, the position of the workpiece on the transfer means, scanning the workpiece through an upstream scanner to measure workpiece profiles in spaced apart array along a surface of the workpiece, communicating, by communication means, the workpiece profiles to a digital processor, which may include an optimizer, a PLC and a motion controller, computing by the digital processor, a high order polynomial smoothing curve fitted to the array of workpiece profiles of the curved workpiece, adjusting the smoothing curve for cutting machine constraints of downstream motion controlled cutting devices to generate an adjusted curve, generating unique position cams unique to the workpiece from the adjusted curve for optimized cutting by the cutting devices along a tool path corresponding to the position cams, sequencing the transfer means and the workpiece with the cutting devices, sequencing the unique position cams corresponding to the workpiece to match the position of the workpiece, feeding the workpiece on the transfer means longitudinally into cutting engagement with the cutting devices, and actively relatively positioning, by selectively actuable positioning means, the workpiece and the cutting devices relative to each other according to a time-based servo loop updated recalculation, based on said workpiece position, of cutting engagement target position as the workpiece is fed longitudinally so as to position the cutting engagement of the cutting devices along the tool path.  
           [0016]    Advantageously, the high order polynomial smoothing curve is an n th  degree modified polynomial of the form f(x)=a n x n +a n−1 x n−1 +. . . +a 1 x+a 0 , having co-efficient a n  through a 0 , and where the coefficients a n  through a 0  are generated by numerical processing to correspond to, and for fitting a smoothing curve along, the corresponding workpiece profiles.  
           [0017]    In one aspect of the present invention, the method includes monitoring, by monitoring means cooperating with the digital processor, of loading of the cutting devices and actively adjusting the workpiece feed speed by a variable feed drive, so as to maximize the feed speed. In a further aspect, the method includes compensating for workpiece density in the adjusting of the feed speed or includes monitoring workpiece density, by a density monitor cooperating with the digital processor, and compensating for the density in the adjusting of the feed speed.  
           [0018]    Advantageously, the monitoring of the position of the workpiece includes encoding, by an encoder, translational motion of the transfer means and communicating the encoding information to the digital processor. Further advantageously, the monitoring of workpiece position includes communicating trigger signals from an opposed pair of photoeyes, opposed on opposed sides of the transfer means, to the digital processor.  
         SUMMARY OF THE FIRST MECHANICAL EMBODIMENT  
         [0019]    The first mechanical embodiment consists of, first, an indexing transfer which temporarily holds a cant in a stationary position by a row of retractable duckers or pin stops, for regulated release of the cant onto a sequencing transfer. The sequencing transfer feeds the cant through a scanner, where the scanner reads the profile of the cant and sends the data to an optimizer. The scanner may be transverse or lineal.  
           [0020]    An optimizing algorithm in the optimizer generates three dimensional models from the cant&#39;s measurements, calculates a complex “best” curve related to the intricate contours of the cant, and selects a breakdown solution including a cut description by position cams that represent the highest value combination of products which can be produced from the cant. Data is then transmitted to a programmable logic controller (PLC) that in turn sends motion control information related to the optimum breakdown solution to various machine centers to control the movement of the cant and the designated gangsaw products.  
           [0021]    Immediately following the scanner is a sequencing transfer that also includes a plurality of rows of retractable duckers and/or pin stops that hold the cants temporarily for timed queued release so as to queue the cants for release onto a positioning device. The positioning device may be merely positioning pins or a fence for roughly centering the cant in front of the gangsaw, or may be a positioning table including positioners having retractable pins that center the cant in front of the gangsaw. The positioner pins retract, the positioning table feeds the cant via sharpchains and driven press rolls, straight into the combination active chipper and saw box.  
           [0022]    The gangsaw uses a plurality of overhead pressrolls, and underside circulating sharpchain in the infeed area, with fixed split bedrolls in the infeed area and non-split bedrolls in the outfeed area. A plurality of overhead pressrolls hold the cant from the top and bottom by pressing down onto the flat surface of the cant thus pressing the cant between the lower infeed sharpchain (infeed only) and bedrolls and the overhead pressrolls, for feeding the cant straight into the gang saw. The chipping heads and the saws on the saw arbor may be actively skewed and translated, so as to follow the optimized curve sawing solution. In this fashion the cant moves in one direction only, and the chipping heads and the saws are actively motion controlled to cut along the curved path that has been determined by the optimizer. The chip heads move with the saws to create flat vertical sides on the cant so that there is no need to handle and chip slabs, and no need to install a curve forming canter before the gangsaw.  
           [0023]    The chipping heads may be retracted or relieved out away from the preferred curved face of the cant so as to keep the cutting forces equal in the event of a bulge or flare in the thickness of the cant or to reduce motor loading. The use of active chipping heads in this manner allows creating a side board in what would be waste material in the prior art between an outermost saw and a chipping head in the instance where the bulge or flare is substantial enough to contain enough material in thickness and length to create an extra side board. The optimizer would prepare the system to accept the extra side board.  
           [0024]    In summary, the active gangsaw of a first mechanical embodiment of the present invention comprises, in combination, an opposed pair of selectively translatable chipping heads co-operating with a gangsaw cluster, wherein the opposed pair of selectively translatable chipping heads are mounted to, and selectively translatable in a first direction relative to a selectively articulatable gangsaw carriage, wherein the first direction crosses a linear workpiece feed path wherealong workpieces may be linearly fed through the active gangsaw so as to pass between the opposed pair of selectively translatable chipping heads and through the gangsaw cluster, and wherein the gangsaw cluster is mounted to the gangsaw carriage and is selectively positionable linearly in the first direction and simultaneously rotatable about a generally vertical axis to thereby translate and skew the workpiece carriage relative to the workpiece feed path by selective positioning means acting on the gangsaw carriage.  
           [0025]    Advantageously, the gangsaw carriage is selectively positionable linearly in said first direction by means of translation of said gangsaw carriage along linear rails or the like translation means mounted to a base, and is simultaneously rotatable about said generally vertical axis by means of rotation of said gangsaw carriage about a generally vertical shaft extending between said gangsaw carriage and said base.  
         SUMMARY OF THE SECOND MECHANICAL EMBODIMENT  
         [0026]    The second mechanical embodiment consists of, first, an indexing transfer which temporarily holds a cant in a stationary position by a row of retractable duckers or pin stops, for regulated release onto a sequencing transfer. The sequencing transfer feeds the cant through a scanner, where the scanner measures the profile of the cant and sends the data to an optimizer.  
           [0027]    An optimizing algorithm in the optimizer generates three dimensional models from the cant&#39;s measurements, calculates a complex “best” curve related to the intricate contours of the cant, and selects a breakdown solution including a cut description by position cams that represents the highest value combination of products which can be produced from the cant. Data is then transmitted to a PLC that in turn sends motion control information related to the optimum breakdown solution to various machine centers to control the movement of the cant and the various devices hereinafter more fully described.  
           [0028]    Immediately following the scanner is a sequencing transfer that also includes a plurality of rows of retractable duckers and/or pin stops that hold the cants temporarily for timed queued release so as to queue the cants for release onto a positioning device. The positioning device positions the cant in front of the gangsaw, and in some cases positions the cant in front of selected gangsaw zones that have been determined by the optimizer decision processor to provide the optimum breakdown solution.  
           [0029]    A skew angle is calculated by the optimizer algorithm so that the positioning device presents the cant tangentially to the saws. If the positioning device is a skew bar, the skew bar pins retract, the rollcase feeds the cant into a pair of press rolls and then further into a chipper drum and an opposing chipper drum counter force roll. The chipper drum begins to chip and to form the optimized profile onto one side of the cant as the cant moves past it, while the opposing chipper drum roll counters the lateral force created by the chipper drum, to help to maintain the cants&#39; direction of feed. The cant is driven toward the saws and contacts a steering roll mechanism adjacent the chipper drum in the direction of flow. The steering roll comes into contact with the face that has just been created by the chipper drum. The steering roll has an opposing crowder roll that maintains a force against the steering roll while being active so as to move in and out to conform to the rough side of the cant as it moves toward the saws. A guide roll is positioned to allow the cant to move up to the saws in the intended position. The guide roll is adjustable, and also capable of steering when the configuration requires it to steer for different saw configuration and lumber sizes. The guide roll also has an opposing crowder roll that maintains a force against the guide roll while also being active so as to move in and out to conform to the rough side of the cant.  
           [0030]    The steering mechanism and the chipper drum are active as the cant proceeds through the saws and are controlled by controllers that use control information from the optimized curve decision, thus controlling the movements of the cant as it proceeds through the apparatus, profiling one face of the cant and cutting the cant into boards as defined in the cutting description.  
           [0031]    An alternate embodiment consists of two opposed chipper heads. In this embodiment a cant may be chipped from both sides, with the steering being done from one side or the other, depending on the cant being sawn. Air bags are provided on all steering rolls. The air bags may be locked so as to become solid when being used for steering, and may be unlocked to act as a crowding roll when the opposite side is doing the steering.  
           [0032]    Alternatively, a plurality of overhead press rolls, and underside fixed rolls hold the cant from the top and bottom by pressing down onto the flat surface of the cant thus pressing the cant between the lower rolls and the overhead press rolls. The cant is fed straight into the gang saw and the gangsaw translated and skewed so as to follow the optimized curve sawing solution.  
           [0033]    In summary, in a second mechanical embodiment of the present invention, a cant, having been scanned by a scanner, is transferred onto a positioning means such as a positioning roll case where the positioning means includes means for selectively skewed pre-positioning of a cant upstream of a selectively and actively positionable cant reducing means such as a chipper head for forming either a curved third face or curved third and fourth faces on the cant. The device further includes an upstream pair of opposed selectively actively positionable cant guides and a downstream pair of opposed selectively actively positionable cant guides, the upstream pair of guides being downstream of the cant reducing means and the downstream pair of guides being upstream of gang saws mounted on a saw arbor. The upstream and downstream pair of guides are aligned, with one guide of each pair of guides generally corresponding with the cant reducing means on a first side of the cant transfer path. The opposed guides in the two pairs of guides are in opposed relation on the opposing side of the cant transfer path and are generally aligned with a cant positioning means along the cant transfer path. The cant positioning means is in opposed relation to the cant reducing means, that is, laterally across the cant transfer path.  
           [0034]    In addition, either in combination with the above or independently, the gang saws and saw arbor may be selectively actively positionable both laterally across the cant transfer path and rotationally about an axis of rotation perpendicular to the cant transfer path so as to orient the gang saws to form the curved face on the rough face of the cant and to form a corresponding array of parallel cuts by the gang saws corresponding thereto.  
           [0035]    In a further aspect, the selectively actively positionable cant reducing means is an opposed pair of selectively actively positionable cant reducing means such as an opposed pair of chipper heads placed in spaced apart relation on either side laterally across the cant transfer path.  
           [0036]    In a further aspect, the pairs of selectively actively positionable cant guides include actively positionable cant guides on the side of the cant corresponding to the actively positionable cant reducing means and on the opposing side laterally across the cant transfer path, the cant guides on the side of the cant transfer path corresponding to the cant positioning means or, in the embodiment having opposed pairs of selectively actively positionable cant reducing means, the side of the cant transfer path corresponding to the cant reducing means which is selectively deactivated so as to become a passive guide.  
         SUMMARY OF THE THIRD MECHANICAL EMBODIMENT  
         [0037]    The third mechanical embodiment consists of, first, an indexing transfer which temporarily holds a cant in a stationary position by a row of retractable duckers or pin stops, for regulated release onto a sequencing transfer. The sequencing transfer feeds the cant through a scanner, where the scanner reads the profile of the cant and sends the data to an optimizer.  
           [0038]    An optimizing algorithm in the optimizer generates three dimensional models from the cant&#39;s measurements, calculates a complex “best” curve related to the intricate contours of the cant, and selects a breakdown solution including skew angles and a cut description by position cams that represents the highest value combination of products which can be produced from the cant. Data is then transmitted to a PLC that in turn sends motion control information related to the optimum breakdown solution to various machine centers to control the movement of the cant and the cutting of both a profiled cant and the designated gangsaw products.  
           [0039]    Immediately following the scanner is a sequencing transfer which feeds a profiler positioning table and subsequently a profiler. The sequencing transfer includes a plurality of rows of retractable duckers or pin stops perpendicular to the flow that hold the cant temporarily for timed release so as to queue the cant for delivery onto the profiler positioning table.  
           [0040]    The profiler positioning table locates and skews the cant to a calculated angle for proper orientation to the profiler and then feeds the cant linearly into the profiler whereby it removes the vertical side face(s). The newly profiled face or faces, used to steer the cant through the gang saws, follow the optimum curve calculated by the computer algorithm from the scanned image of the individual cant. The removal of superfluous wood from the vertical face(s) is achieved by the interdependent horizontal tandem movement of opposing chipping heads or bandsaws, substantially perpendicular to the direction of flow.  
           [0041]    On the outfeed of the profiler an outfeed rollcase has a jump chain that raises the cant off the rolls and then feeds the cant onto a cant turner were the cant is turned over laterally 180 degrees if necessary to the proper orientation for entry into the curve sawing gang. The jump chain includes a plurality of rows of retractable duckers or pin stops that hold the cant temporarily for timed release to the cant turner.  
           [0042]    A sequencing transfer, that also includes a plurality of rows of retractable duckers or pin stops, hold the cant temporarily for timed release so as to queue up the cant for release onto a positioning rollcase. The positioning rollcase includes a skew bar with retractable pins that pre-positions the profiled cant on the correct angle and in front of the selected gangsaw combination that has been determined by the optimizer to provide the optimum breakdown solution. The skew angle is calculated by the optimizer algorithm to present the profiled cant tangentially to the saws. The skew bar pins retract, the rollcase feeds the profiled cant into a steering mechanism, and the steering mechanism, using control information from the optimized curve decision, then controls the movement of the cant as it proceeds through the array of saws, cutting the profiled cant into the boards defined in its cutting description.  
           [0043]    In summary, the curve sawing device of a third mechanical embodiment of the present invention comprises a cant profiling means for opening at least a third longitudinal face on a cant, wherein the third face is generally perpendicular to first and second opposed generally parallel and planar faces of the cant, according to an optimized profile solution so as to form an optimized profile along the third face, cant transfer means for transferring the cant from the cant profiling means to a cant skewing and pre-positioning means for selectively and actively controllable positioning of the cant for selectively aligned feeding of the cant longitudinally into cant guiding means for selectively actively laterally guiding and longitudinally feeding the cant as the cant is translated between the cant skewing and pre-positioning means and a lateral array of generally vertically aligned spaced apart saws so as to position the third face of the cant for guiding engagement with cant positioning means, within the cant guiding means, for selectively actively applying lateral positioning force to the third face to selectively actively position the cant within the cant guiding means as the cant is fed longitudinally into the lateral array of generally vertically aligned spaced apart saws.  
           [0044]    The curve sawing method of the third mechanical embodiment of the present invention comprises the steps of:  
           [0045]    a) profiling a cant by a cant profiling means to open at least a third longitudinal face on a cant wherein the third face is generally perpendicular to the first and second opposed generally parallel and planar faces of the cant, the profiling according to an optimized profile solution generated for the cant so as to form an optimized profile along the third face,  
           [0046]    b) transferring the cant by cant transfer means from the cant profiling means to a cant skewing and prepositioning means,  
           [0047]    c) skewing and prepositioning the cant by the cant skewing and prepositioning means to selectively and actively controllably position the cant for selectively aligned feeding of the cant longitudinally into cant guiding means,  
           [0048]    d) guiding the cant by the cant guiding means for selectively actively laterally guiding and longitudinally feeding the cant as the cant is translated between the cant skewing prepositioning means and a lateral array of generally vertically aligned spaced apart saws,  
           [0049]    e) positioning the third face of the cant by cant positioning means within the cant guiding means so as to position the third face of the cant for guiding engagement with the cant positioning means, the cant positioning means for selectively actively applying lateral positioning force to the third face to selectively actively position the cant within the cant guiding means as the cant is fed longitudinally into the lateral array of generally vertically aligned spaced apart saws,  
           [0050]    f) feeding the cant longitudinally from the cant guiding means into the lateral array of generally vertically aligned spaced apart saws.  
           [0051]    In both the curve sawing device and the curve sawing method of the present invention the cant profiling means may open a third and fourth longitudinal face on the cant wherein the third and fourth faces are generally perpendicular to the first and second opposed generally parallel planar faces of the cant and are themselves generally opposed faces, and wherein within the cant guiding means the cant positioning means comprise laterally opposed first and second positioning force means corresponding to the third and fourth faces respectively to, respectively, actively applied lateral positioning force to selectively actively position the cant within the cant guiding means.  
           [0052]    In further aspects of the present invention, the first and second laterally opposed positioning force means each comprise a longitudinally spaced apart plurality of positioning force means. The first positioning force means may include, when in guiding engagement with the third face, longitudinal driving means for urging the cant longitudinally within the cant guiding means.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0053]    The invention will be better understood by reference to drawings, wherein:  
         [0054]    [0054]FIG. 1 is, in perspective view, a schematic representation of a typical integrated motion controlled curve sawing system of the present invention.  
         [0055]    [0055]FIG. 1 a  is, in perspective view, a scanned profile of a cant segment.  
         [0056]    [0056]FIG. 2 is a flow chart of a prior art time-based curve sawing method.  
         [0057]    [0057]FIG. 3 is a schematic block diagram representation of the integrated motion controlled curve sawing functions of the present invention.  
         [0058]    FIGS.  4  are, sequentially depicted in FIGS. 4 a - 4   e , representations illustrating the optimizer method of the integrated motion controlled curve sawing of the present invention.  
         [0059]    [0059]FIG. 5 a  is a flow chart of the servo loop updates of the position-based curve sawing of the present invention.  
         [0060]    [0060]FIG. 5 b  is a graphic representation of the sawbox set calculations of the curve sawing method of the present invention.  
         [0061]    [0061]FIG. 6 is a side section view according to a preferred embodiment of the invention, taken along section line  6 - 6  in FIG. 8;  
         [0062]    [0062]FIG. 7 is a end section view according to a preferred embodiment of the invention, taken along section line  7 - 7  in FIG. 6, with some parts not shown for clarity;  
         [0063]    [0063]FIG. 8 is a plan view showing the curve sawing system;  
         [0064]    [0064]FIG. 9 is a perspective views of a two sided curved cant;  
         [0065]    [0065]FIG. 9 a  is a perspective views of a four sided cant having been formed by the active chipping heads and sawn into boards by the active gangsaw;  
         [0066]    [0066]FIG. 10 is a side section view according to a preferred embodiment of the invention, along section line  10 - 10  in FIG. 12;  
         [0067]    [0067]FIG. 11 is a fragmentary end section view according to a preferred embodiment of the invention, along section line  11 - 11  in FIG. 10;  
         [0068]    [0068]FIG. 12 is a plan view showing the curve sawing system;  
         [0069]    [0069]FIG. 13 is an enlarged, fragmentary plan view of a chipping drum and the steering and guide rollers;  
         [0070]    [0070]FIG. 14 is an enlarged, fragmentary plan view of an alternate embodiment showing two chipping drums, with the steering and guide rollers operable from either side;  
         [0071]    [0071]FIG. 15 is an enlarged, fragmentary, diagrammatic plan view of a further alternate embodiment for skewing and translating saws and saw arbor;  
         [0072]    [0072]FIG. 16 is a perspective view of a two sided curved cant;  
         [0073]    [0073]FIG. 16 a  is a perspective view of a four-sided curved cant.  
         [0074]    [0074]FIG. 17 is a side elevation view according to a preferred embodiment of the invention;  
         [0075]    [0075]FIG. 18 is a plan view according to the preferred embodiment of FIG. 17;  
         [0076]    [0076]FIG. 19 is a plan view showing the profiler and curve sawing line;  
         [0077]    [0077]FIG. 20 is a perspective view of a two sided curved cant;  
         [0078]    [0078]FIG. 20 a  is a perspective view of a four sided cant with optimized curved vertical faces;  
         [0079]    [0079]FIG. 21 is an end elevation view according to the preferred embodiment of FIG. 18;  
         [0080]    [0080]FIG. 22 is an enlarged, fragmentary, side elevation view from FIG. 17. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0081]    [0081]FIG. 1 illustrates, schematically, a typical arrangement of the various machine centers and devices which are coordinated in the embodiments of the present invention to optimize the curve sawing of workpieces, such as cants, arriving in a mill flow direction A. Workpieces  12  are transferred through a non-contact scanner  14  for feeding thereafter through chipping heads and active saws. The position-based approach of the present invention relies on the scanner  14  first taking discrete laser, or other non-contact scanner measurement readings of a workpiece passing through the scanner so as to provide the measurement data from which the workpiece is mathematically modelled so that, if printed, might be depicted by way of example in FIG. 1 a . The scanner  14  is used to map the workpiece  12  passing therethrough so as to generate a profile of the workpiece along the length of the workpiece.  
         [0082]    The mathematical model of the workpiece  12  is processed in its entirety, or sufficiently much is processed so that the model may be optimized to produce a cutting solution unique for that workpiece. Optimizing generates a mathematical model of the entire cant and an optimized cutting solution. Position-cam data is then generated for the motion controllers.  
         [0083]    A position cam is the set of position data for the cutting devices at each of a longitudinal array of increments along the length of the workpiece profile. The position cams corresponding to the array of increments define, collectively, a table of position data or array of position data points for each linear positioner axis of the active cutting devices. In one sense the position cams may be thought of as virtual position location targets to which the cutting devices will be actively maneuvered to attain along the length of the workpiece, keeping in mind that the active cutting devices, such as an active sawbox  16 , may weigh in the order of 40,000 pounds.  
         [0084]    The position based method of the present invention provides advantages, as hereinafter described, over the inferior method of merely providing sequential, that is, time based point-to-point data so as to provide sequential curve sawing instructions for moving the saws dependent on constant feed speed, illustrated in the form of a flow chart in FIG. 2. A position based method rather than the point-to-point cutting method is preferred so that the orchestration and coordination of the various machine centers and devices is not reliant on, for example, a constant feed speed to provide X-axis data such as is the case in point-to-point time based motion instructions to the gangsaws where, if X-axis translation speed, i.e. feed speed, is varied, then the optimized cutting solution is spoiled because the location of the workpiece is no longer synchronized with the position of the saws.  
         [0085]    Orchestration of the machine centers and devices to take advantage of the position based method of the present invention is accomplished by a programmable logic controller (PLC)  18  and two motion controllers (MCs)  20  and  22 . In overview, schematically illustrated in the flow chart of FIG. 3, scanner  14  samples the workpiece  12  profile and provides the raw profile measurement information to a processor  24  known as an optimizer on local area network (LAN)  26 . The optimizer employs an optimizing algorithm to smooth the data and generate a mathematical model of the workpiece according to the procedure set out in Schedule A hereto and described below. The process of data smoothing and generation of a curve is depicted schematically in FIGS. 4 a - 4   e . The result is an optimized cutting solution decision by the optimizer  24  which is then communicated or handed off to the PLC  18  on communication link  27  and to the motion controllers  20  and  22 . The PLC may be an Allen-Bradley™ 5/40E PLC, and the two motion controllers may be Allen-Bradley™ IMC S-Class motion controllers.  
         [0086]    In one embodiment of first present invention, the PLC  18  directly controls all of the devices, with the exception that the two motion controllers  20  and  22  control four linear positioners  30 ,  32 ,  34  and  36 . The PLC buffers operator inputs for each workpiece and delivers these inputs to the scanner just prior to scanning. Optimizer decisions are sent from the optimizer to the PLC. The PLC uses the optimizer decision information to process the workpiece through the machine centers and devices. The PLC also buffers information exchange between the optimizer and the motion controllers.  
         [0087]    Of the two motion controllers, one motion controller  20  controls the linear positioners  30  and  32  used to move chipping heads  38  and  40 , and the other motion controller  22  controls the steering rolls in a gangsaw downstream of the chipping heads or the orientation of the sawbox in an active gangsaw  16  by positioners  34  and  36 . Given sufficient processing power, the two motion controllers may be combined into a single motion controller. The motion controllers operate on position cam data and sawbox set calculations as hereinafter described. The position cams use “X” and “Y”, or, alternatively, “master” and “servant” axes respectively to move the chipping heads and the saws as the workpiece passes through. Position cams operate on the principle that, for every point along the X axis (feed direction), there is a corresponding point, whether real or interpolated, on the Y axis. The X axis position is provided by the mill flow infeed devices such as transfer chains, sharp chains, belts, rolls, or the like generically referred to as feedworks  42 . The Y axis position is the target tool or cutting path for the chipping heads and saws. The target cutting or tool path may be made up of data points every 6 inches along the length of the workpiece  12 .  
         [0088]    The motion controllers are connected to the PLC as part of the remote input/output (I/O) system remotely controlling the machine centers and devices. The PLC communicates position cam data from the optimizer to the appropriate motion controller.  
         [0089]    The workpiece and the corresponding optimizer decision have to be sequenced and matched. Consequently, as the method of the present invention is position based, the position of the workpiece relative to the machine centers and devices has to be known. One method, and that employed in the present embodiments, is the use of an encoder  43  which, by means of a coupler  43   a , tracks the translation of a feed conveyor on feedworks  42 . Thus the longitudinal position of the workpiece  12  is tracked by the encoder  43 .  
         [0090]    The workpiece is fed longitudinally on the feedworks with its orientation maintained such as by press rolls while it is translated towards and through the sawbox. An infeed photoeye (I/F PE)  45  may be used to sense location of a workpiece  12  on the feedworks  42  to time raising and lowering of the press rolls into engagement with the workpiece so as to hold the workpiece against the feed conveyor to prevent lateral movement of the workpiece relative to the conveyor. The cutting machine centers, which may include, bandsaws, sash gangs, or the like, or chipping heads  38  and  40  and/or circular saws  52 , are actively preset to their starting positions to process the workpiece. The gap between subsequent workpieces may be adjusted if required, as is feed speed as hereinafter better described. Synchronization of the workpiece with the position cam data is facilitated by a synchronizer photoeye (SYNC PE)  46  which detects the longitudinal ends of the workpiece as it is being translated on the feedworks  42  in the mill flow direction. The workpiece is synchronized so that the position cam position targets for the cutting devices correspond to their intended locations on the workpiece. Cutting device motion is started prior to engaging a cutting device. The workpiece first enters the chipping heads, the position and motion of the chipping heads having been initiated and prelocated to encounter the anticipated position of the workpiece. The chipping head position feedback is read in a time-based servo loop and the motion velocity of the chipping head adjusted to correct the position of the chipping head to follow the position cams corresponding to the workpiece, so as to put the chipping heads on track with, or to as best as possible move the chipping heads towards coinciding with, the position cam position targets or tool path on the workpiece.  
         [0091]    In one embodiment, the position of the gangsaw is actively preset and the gangsaw motion initiated as the workpiece approaches the saws. The gangsaw position feedback is read in a time-based servo loop and the gangsaw motion velocity is adjusted to again correct the position of the gangsaw to follow the position cam data.  
         [0092]    The workpiece feed speed may be adjusted in response to anticipated loading or instantaneous loading of the cutting devices, whether chipping heads or gangsaw circular sawblades. The workpiece feed speed may be varied by a variable frequency drive (VFD)  44  according to instructions from the PLC  18 . Feed speed may be reduced in the event of binding of the workpiece or high motor loadings of the cutting devices. In an alternative embodiment, the feed may be reduced or reversed, in response to binding or high motor loadings of the cutting devices. In the case of chipping heads, the chipping heads may be disengaged or relieved if their corresponding motor loading becomes high. In one embodiment the RPM of the chipping heads and sawblades is maintained constant. Advantageously, to equal lateral cutting forces of the chipping heads, the bus load, that is, amperage to the chipping head motors, may be differentially varied. In an alternative embodiment, to avoid chip fines, the RPM may be adjusted to maintain chip quality, for example, reduced if chip fines are being produced. RPM may be adjusted also to compensate for the volume of material being removed from the cant, the density of the material, and any density varying anomalies such as burls, or knots, or the like.  
         [0093]    Position feedback to the motion controllers is provided by Temposonic™ actuator position sensors  48 . Advantageously, time-based feedback is provided to the motion controllers every {fraction (60/1000)} inch (approximately {fraction (1/16)} inch) of feed travel at 300 feet per minute, that is, approximately every one milli-second, as seen in the flow chart in FIG. 5 a , where the supervisory code initiates the sequence for every servo loop update.  
         [0094]    The workpiece feed speed may be matched to the material density, as determined, for example, by an x-ray lumber gauge, and/or to the saw design and cutting device loading, blade sharpness, etc. The workpiece feed speed may be adjusted to compensate for material volume to be removed, material density and workpiece anomalies such as burls, knots or the like. Feed speed and RPM of the chipping heads may be adjusted to mutually compensate. The feed speed may be preset for the anticipated loading or adjusted to compensate for monitored load levels on the cutting device motors  45  (for example by monitoring amperage). The use of position cam data allows for corresponding coordination of active cutting devices to keep a correspondence between the desired cutting solution along the position cams or tool paths with the actual position of the workpiece.  
         [0095]    The workpiece feed speed is varied as part of the orchestration of the machine centers and devices to maximize performance of the overall system. Variation of feed speed so as to maximize the feed speed assists in providing enhanced throughput in terms of lumber volume. In particular, feed speed maximization allows the machine centers to operate at their limitations for the length of the workpiece, and reduces stalling and slipping of the workpiece, resulting in cutting off the desired tool path, when held down onto the feedworks  42  by, for example, press rolls. As a result, wear on chipping heads and saw arbor assemblies may be reduced. The frequency of saw arbor motor overload conditions or chipping head motor overload conditions may be reduced. Further, as mentioned above, active and dynamic control of the feed speed may compensate for changes in sharpness in saw blades or chipping knives or for variations in wood density from an average value used in the optimizer for its volume calculations.  
         [0096]    The average wood density used by the optimizer is used to calculate the approximate horse power required to remove the wood necessary to generate or attain the cutting decision. The optimizer compares the required horse power to the horse power limitations of the cutting devices. This comparison is used to derive an optimized feed speed profile at approximately two foot increments along the workpiece.  
         [0097]    The PLC logic code uses the optimizer profile as a set point. Actual motor current is monitored by sensor  50  to provide feedback to the PLC  18 . The set point and feedback signals are used to create a speed reference for the variable frequency drive  44  using a proportional internal derivative(PID)-like algorithm. The current feedback signals are only valid and relied upon when the workpiece  12  is mechanically engaged by the cutting devices such as the chipping heads  38  and  40  or saws  52 .  
         [0098]    As seen in FIG. 1, optimizer  24  and associated network server  54 , man-machine interface  56 , PLC  18  and primary work station  58  communicate across a common Ethernet™ LAN  60 , which is available as a connection point to existing mill networks. This connection point allows workstations within the existing mill offices (with appropriate software) access to all cant optimization functions. A dedicated communications link  27  may exist between optimizer  32  and PLC  18 . All workstations and the network server  54  use applications which provide mill personnel the tools they require to define their environment, such as scanner, optimizer, machine centers, products, and shift schedules reports relative to the cant optimizer system; pre-generate various start-up configurations; start, stop and load the system; visually monitor the cant as it proceeds through the machine centers; and monitor the operation for unusual conditions.  
         [0099]    A modem  62  attached to the network server  54 , and the primary workstation  58  using remote access software and appropriate controls, allows remote dial-up access to the mill site for software reprogramming and remote operation of almost every application and function as well as retrieval of statistics and cant summaries for off-site service analysis. The man-machine interface  56  provides operator input and allows the operator access to various levels of machine operation and control. The PLC  18  and motion controllers  20  and  22 , share the task of monitoring speed and position of the cant and controlling positioners.  
         [0100]    The above position-based integrated motion control method for curve sawing is employed in the coordination of the three mechanical embodiments of the chipping heads and saws as set out below.  
         [0101]    In embodiments of the present invention where an opposed pair of chipping heads are mounted to an articulatable sawbox containing a saw cluster on a saw arbor, so that translating and skewing the sawbox also correspondingly translates and skews, about a common axis of rotation, the chipping heads, a geometric problem is encountered due to the instantaneous chipping location of the chipping heads being spaced apart, for example in front of, the instantaneous cutting location of the laterally outermost saw on the saw arbor. If it is desired to accurately cut a so-called jacket board, that is, a side board, from the cant material between the outermost saw and the corresponding chipping head, the spacing between, and the locations of, the instantaneous cutting locations must be known and accounted for.  
         [0102]    An inferior method entails linear approximation methods. However, cutting accuracy, where skewing approaches the order of six degrees, suffers where linear approximations are used. A better method, and that employed in the curve sawing of the present invention, requires use of non-linear equations of motion, referred to as sawbox set calculations, for both the chipping heads and for the saws.  
         [0103]    Saw box set calculations are graphically depicted in FIG. 5 b , where a chipping line is seen spaced apart from the sawline (the solution line). A jacket board is manufactured between the saw line and the chipping line. It is desirable to have an accuracy in the order of 5-10 thousand&#39;s of an inch in sawing variations in the thickness dimension. To achieve that accuracy an equation of motion for both the rotation and translation of the sawbox arbor and, independent of that, the chip head equation of motion is required. This is because the sawbox is on a base that translates, and, overlaid, is a skewing, that is, rotating, member whose axis of rotation, that is, the pivot point for the skewing, is not in alignment with the instantaneous sawing point on the saws, as the pivot point for the skewing is generally in the center of the saw arbor. In addition, the chip heads are further displaced from the pivot point so, as the sawbox is skewed, the chip heads swing through an arc and so also the corresponding instantaneous saw center swings through an arc. These mis-alignments both affect the saw line and chipping line, the difference between the saw line and the chipping line being the thickness of the recovered jacket board.  
         [0104]    In the inferior approximation method above noted, the assumption is made that the mis-alignments are all linear and that a ratio based on the radius or the lever arm between the chip head and the pivot point and between the instantaneous saw center and the pivot point is a sufficient approximation. In fact, as the skew angle approaches zero the approximation is a linear problem. However, if the skew angle approaches five or six degrees the approximation no longer is linear, that is, the small angle approximation no longer holds, and the actual geometry must be accommodated.  
         [0105]    In interpreting FIG. 5 b , the cant may be visualized as remaining fixed in space and the sawbox travelling relative to it. In FIG. 5 b , the Y axis is the offset line, meaning that this is the distance from the pivot line. The pivot line, the X axis in FIG. 5 b , is the path travelled by the sawbox pivot point, that is, the axis of rotation for skewing of the sawbox along the length of the cant. The position tracking is done along the pivot line. Because the chipping heads are mounted on the common sawbox assembly, the chipping head axes share a common travel path, that is, the chipping head axes are parallel to the saw arbor and at the same distance from it. The solution line is a smooth path defining the curve to be followed as the sawing line. It may be chosen to minimize the solution line distance from the pivot line. The chipping head lines on either side of the solution line outline the paths to be taken by the center of the chipping heads. They are related to the solution line but are not parallel. Note that the cutting points of the chipping heads varies along the length of the head and is not dependent on the angle θ as defined in FIG. 5 b . Angle θ is the required angle of the sawbox to keep the saws tangent to the solution line. The saw line is the line projecting along the cutting points of the saws. It&#39;s distance from the pivot point may be dependent on the cant thickness. It is not the position of the saw arbors. The chord u defines the distance in FIG. 5 b  from the saw line to the pivot point axis. The chord v defines the distance from the pivot point axis to the chipping head axis, that is, the centerline of the chipping heads.  
         [0106]    In FIG. 5 b , the point labelled as X s , Y s , is the desired cutting point of the saw at the sampling point x s  along the pivot line. Thus, y s =p(x s ). The point labelled as x s  is the x coordinate of the position cam data. It will fluctuate from the sampling point x s  by a small amount that can be ignored if the solution line is kept close to and a small angular deviation from the pivot line. The point X pr  defines the pivot point of the saw box at the sample point x s . It is about this point that the saw box assembly rotates. The point X p , Y p  in FIG. 5 b  is the intersection point of the saw box center line and the pivot axis. The point X h , Y p  in FIG. 5 b  is the intersection of the saw box center line and the chipping head axis. The points in FIG. 5 b  labelled X 1 , Y 1  and X 2 , Y 2  are the required position of the center of the chipping heads for the sample point x s . They are the intersection points between the chipping head lines and the chipping head axes.  
       FIRST MECHANICAL EMBODIMENT  
       [0107]    The gang saw apparatus of the first mechanical embodiment is generally indicated by the reference numeral  110  and is best seen in FIGS. 6 and 7.  
         [0108]    As best seen in FIG. 8, an even ending roll case  112  with a live fence  112   a  receives the cant from the mill (direction A) and then transfers the cants to a cant indexing transfer  114  (direction B). Transfer  114  includes a ducker A 116  which receives the first cant  118 . When ducker B 120  on the cant indexing transfer  114  becomes available the cant  118  is sequenced from ducker A 116  to ducker B 120 .  
         [0109]    Cant  118  advances from ducker B 120  to pin stops  114   a  on cant indexing transfer  114  when pin stops  122   a  become available. Cant turner  122 , not used with a dual chipper drum system, see FIG. 14, orients the cant for entering into gang saw  110 . An operator may elect to turn the cant  118  with the cant turner  122  before advancing cant  118  to ducker C 124  on the scanner transfer  126 . Cant turner  122  includes cant turner arms  122   a  and  122   b . If the cant  118  does not require turning then cant  118  will be sequenced from ducker B 120  to ducker C 124 , when ducker C 124  becomes available. Ducker C 124  is mounted on a scanner transfer  126 . Operator entries are entered via an operator console  128  and communicated to PLC  18  and, in turn, to optimizer  24 .  
         [0110]    When ducker D 134  on the scanner transfer  126  becomes available cant  118  is sequenced from ducker C 124  to ducker D 134 . Scanner  136  scans cant  118  as it passes through the scanner. When ducker E 138  on the scanner transfer  126  becomes available cant  118  is sequenced from ducker D 134  to ducker E 138 . On cant sequencing transfer  140 , cant  118  is sequenced to duckers F 142 , G 144 , and H 146  as they become available.  
         [0111]    In one alternative embodiment, although not necessary if the cant is scanned lineally, a positioning table is provided for positioning or centering, whether it be approximate positioning or accurate centering, of cant  118  on feedworks  42 , which may be sharpchain  154 . Positioning table  148  has park zone pins  150 . When park zone pins  150  become available cant  118  is sequenced from ducker H 146  to park zone pins  150  on the positioning table  148 . When positioning table  148  becomes available park zone pins  150  lower and a plurality of table positioners  152  having positioners pins (not shown) move out over cant  118  and draw cant  118  back over to center of sharpchain  154  on positioning table  148  for feeding to gangsaw  110 .  
         [0112]    As best seen in FIG. 6, a plurality of driven pressrolls  156 , each having a corresponding pressroll cylinder  156   a , press down to hold cant  118  against sharpchain  154  and bedrolls  158 . Driven pressrolls  156  and sharpchain  154  drive cant  118  in direction C into the active gangsaw  110 . As cant  118  enters the active gangsaw  110  active chipping heads  160  and  162  begin to chip two opposing vertical faces  118   b  and  118   c  on cant  118 . Chipping heads  160  and  162  are positionable along guide shafts  160   a  and  162   a . Drive shafts  160   c  and  162   c  are journalled in bearing mounts  160   b  and  162   b . Chipping heads  160  and  162  are driven by motor means (not shown) and are selectively, slidingly positioned along guide shafts  160   a  and  162   a  by positioning means such as actuators known in the art (also not shown). Chipping heads  160  and  162  may have anvils (not shown) for diverting chips, the anvils such as shown in FIG. 13 as anvil  278 .  
         [0113]    The vertical faces  118   b  and  118   c  are created so vertical faces  118   b  and  118   c  align optimally with the saws  164   a  of the gangsaw saw cluster  164 , whereby the saws  164   a  then begin to cut the cant  118 , as cant  118  is fed in direction C. As best seen in FIG. 7 and  8 , the saw cluster  164  rotates about vertical axis along shaft  166  in direction D, and translates in direction E as cant  118  moves through gangsaw  110 . Saws  164   a  within gangsaw saw cluster  164  are stabilized by saw guides  164   b . Saw guides  164   b  contact both sides of saws  164   a  to provide stability to the saws  164   a  as cant  118  passes through gang saw cluster  164 . Gangsaw saw cluster  164  are slidingly mounted on splined saw arbors  164   c.    
         [0114]    Gangsaw  110  translates in direction E, on guide bearings  168   a  along guides rails  168   b , and gangsaw  110  skews in direction D along guides  170 . Positioning cylinder  168   c  positions gangsaw  110  by selectively sliding gangsaw  110  on guide bearings  168   a  along guide rails  168   b  for translation in direction E. Positioning cylinder  170   a  selectively skews gangsaw  110  in direction D on guides  170 .  
         [0115]    Driven pressrolls  156  lift up as the trailing end  118   d  of the cant  118  passes in direction C onto outfeed roll case  164 . The cant  118  (now boards) moves through and out of the gangsaw  110 , and onto the gangsaw outfeed rollcase  164 .  
       SECOND MECHANICAL EMBODIMENT  
       [0116]    The gang saw apparatus of the second mechanical embodiment is generally indicated by the reference numeral  210  and is best seen in FIGS. 10 and 11.  
         [0117]    As seen in FIG. 12, an ending roll case  212 , having a live fence  212   a  receives cant  216  from the mill (direction A′). Cant  218  is transferred to a cant indexing transfer  214  (direction B′). Cant  218  is sequentially indexed by duckers A 216 , B 220 , C 224 , D 234 , and E 238  on cant sequencing transfer  214 , and by duckers F 242 , G 244 , and H 246  on cant sequencing transfer  240 . By way of illustration of the sequencing: ducker A 216  first receives cant  218 , then, when a ducker B 220  becomes available, cant  218  is sequenced from ducker A 216  to ducker B 220 . Cant advances from ducker B 220  to pin stops  214   a  when pin stops  214   a  become available. Cant turner  222  (not used with dual chipper drum system, see FIG. 14) is used to orient the cant for steering into the gang saw  210 , if needed where the operator may elect to turn cant  218  with cant turner  222  before advancing cant  218  to ducker C 224  on the scanner transfer  226 . Cant turner  222  includes cant turner arms  222   a  and  222   b . If cant  218  requires turning, then cant  218  is sequenced from ducker B 220  to ducker C 224 , when ducker C 224  becomes available. Ducker C 224  is mounted on a scanner transfer  226 . Scanner  236  scans cant  218  as it passes through the scanner.  
         [0118]    When park zone pins  250  on positioning table  248  become available, cant  218  is sequenced from ducker H 246  to park zone pins  250 . When positioning table  248  becomes available, park zone pins  250  lower and a set of gangsaw table jumpchains  252  raise and move cant  218  from park zone pins  250  and position cant  218  over positioning table rolls  254  against a plurality of raised skew bar pins  256   a  on skew bar  256 . Skew bar  256  is positioned according to the optimized profile to skew cant  218  for feeding in to gangsaw  210 .  
         [0119]    Driven pressroll  258   a  is actuated by corresponding pressroll cylinder  258   c . Driven pressroll  258   b  is actuated by corresponding pressroll cylinder  258   d . Pressrolls  258  press down to hold cant  218  against positioning table rolls  254 . Skew bar pins  256   a  are lowered out of the path of cant  218  so that driven pressrolls  258   a  and  258   b  can drive cant  218  in direction C′ between chipping drum  260  and opposing stabilizing roll  262 . With reference to the travel path of cant  218  direction C′ is the direction in which cant  218  moves from an upstream position, for example on the gangsaw positioning table, to a downstream position, for example, at chipping drum  260 . Cant  218  continues in direction C′ to engage driven steering roll  264  and driven guide roll  266  so as to pass between driven steering roll  264  and opposing non-driven crowding roll  268  and between driven guide roll  266  and crowding roll  270 , whereby the leading end  218   a  of cant  218  is grasped between the powered steering roll  264  and the non-driven crowding roll  268 .  
         [0120]    Chipper drum  260  and the non-driven chipper stabilizing roll  262  are guided on guide shafts  260   a  and  262   a , and selectively positioned by positioning cylinders  260   b  and  262   b . Air bag  262   c  absorbs deviations on cant  218 . Chipper stabilizing roll  262  helps to create a consistent pressure on the non chipping side of cant  218 . This helps to prevent the chipper head  260 &#39;s chipping directional forces from moving cant  218  in a different path than is desired.  
         [0121]    Positioning guides  271  and  272  are actuated by hydraulic positioning cylinders  271   a  and  272   a . Positioning guides  271  and  272  are situated just upstream of chipper drum  260  and opposing chipper stabilizing roll  262  respectively (or alternately chipper drum  274 , as seen in FIG. 14). Positioning guides  271  and  272  are positioned to ensure precise positioning of the cant  218  just before cant  218  contacts chipper drum  260  and opposing chipper stabilizing roll  262 . Positioning guides  271  and  272  are retracted once cant leading end  218   a  contacts steering roll  264 . The positioning guides, chipping heads and steering rolls are actively positioned to attain the optimized cut profile.  
         [0122]    Guide plate  278 , which also acts as a chip deflector, is situated between and slidably attached to, chipping drum  260  and first steering roll  264 . Guide plate  278  inhibits cant  218  from being gouged while the cant&#39;s leading end  218   a  is moving past chipping drum  260  and up to the first steering roll  264  and before cant  218  contacts guide roll  266 . Chipping drum  260  is actively positioned to cut a modified polynomial curve as the third face of the cant according to the method depicted graphically in FIG. 4.  
         [0123]    Driven pressrolls  258   a  and  258   b  lift up after the leading end  218   a  of cant  218  contacts the guide roll  266 , and driven press roll  280 , actuated by pressroll cylinder  280   a , mounted above the path of cant  218  between steering roll  264  and guide roll  266  takes over to press cant  218  onto bed rolls  282  as the cant is grasped between guide roll  266  and crowding roll  270 . Press roll  280  presses down on to cant  218  to keep cant  218  down on to bed rolls  282  as the leading end  218   a  of cant  218  enters saws  284 . Saws  284  are mounted on splined saw arbors  286 . Saws  284  are held in position by saw guides  284   a.    
         [0124]    Driven steering rolls  264  and driven guide roll  266  are guided by guide shafts  264   a  and  266   a . Non-driven crowding rolls  268  and  270  are guided by guide shafts  268   a  and  270   a . Driven steering roll  264  and driven guide roll  266  are driven by drive motors (not shown), and positioned by linear positioning cylinders  288  and  290  respectively. Non-driven crowding rolls  268  and  270  are positioned by linear positioning cylinders  292  and  294  respectively. Air bags  292   a  and  294   a  are provided to absorb shape anomalies on cant  218 .  
         [0125]    Cant  218 , in the form of boards being cut from cant  218  by saws  284 , is transported through gangsaw  210 , driven and held by driven press rolls  296 , and driven press roll  298 , actuated by pressroll cylinders  296   a  and  298   a , respectively, mounted near the outfeed end of the gangsaw  210 . These press rolls may be fluted, that is, have friction means, to provide traction while still allowing some sideways movement of cant  218  (now boards) as cant  218  moves through and out of the gangsaw  210 , and thence onto outfeed rollcase  299 .  
         [0126]    In an alternative embodiment, as seen in FIG. 14, chipper  260  and steering side mechanism ( 264 ,  266 ) could be duplicated on the opposing side of the cant transfer path. An opposed second chipper drum  274  permits chipping and steering from both sides of cant  218 . This eliminates a cant turner before the scanner. Air bags would advantageously be provided on all positioning cylinders. The air bags would be disengageable so as to become solid cylinder rams on the opposite side of the rolls that are steering at any given time.  
         [0127]    A further alternative embodiment, seen in FIG. 15, has skewing and translating saws and saw arbor. Bed rolls  282  and overhead press rolls (not shown) hold the cant down onto bed rolls  282  and move cant  218  in a straight line all the way through the gangsaw while the saws  284  and arbor  286  move to create the curved optimized profile.  
       THIRD MECHANICAL EMBODIMENT  
       [0128]    The gang saw apparatus of the third mechanical embodiment is generally indicated by the reference numeral  310  and is seen in FIGS. 17 and 19.  
         [0129]    As illustrated in FIG. 19, a cant  316  is indexed along cant indexing transfer  312 , scanner transfer  322 ,jump chain transfer  358 , and cant sequencing transfer  368  by duckers A  314 , B 318 , C 320 , D 330 , E 334 , F 360 , G 362 , H 370 , I 372 , and J 374 . Then when a ducker B  318  on the cant indexing transfer  312  becomes available the cant  316  is sequenced from ducker A  314  to ducker B  318 .  
         [0130]    Following ducker B  318 , a cant turner  319 , which includes cant turner ducker  319   a , is located where an operator may elect to turn cant  316  before advancing the cant to ducker C  320  on the scanner transfer  322 . Scanner  332  is located between duckers C  320  and D  330  on the scanner transfer  322 . Profile positioning table  336  has park zone pins  338 . When park zone pins  338  become available on profiler positioning table  336 , cant  316  is sequenced from ducker E  334  to park zone pins  338 . Profiler positioning table  336  takes cant  316  from park zone pins  338  and positions the cant for feeding to profiler  340 . A plurality of jump chains  342  on profiler positioning table  336  run substantially perpendicular to the flow through profiler  340 . Positioners  344  extend, also substantially perpendicular to the profiler flow, to align cant  316  for passing through the profiler  340 . As cant  316  enters profiler positioning table  336  selected crowder arms  346  are activated as required to ensure cant  316  is in position against positioners  344 .  
         [0131]    Holddown rolls  348  hold cant  316  onto a sharp chain  350 . As the leading end  316   a  of cant  316  enters profiler  340 , pressrolls  352  lower in sequence to hold cant  316 . Opposed chip heads  340   a  cut vertical faces  316   b  and/or  316   c.    
         [0132]    Cant  316  leaves profiler  340  on profiler outfeed rollcase  354 . Rollcase  354  has ending bumper  356 . Cant  316  leaves profiler outfeed rollcase  354  to cant jumpchain transfer  358 . Cant turner arms  364   a  and  364   b  are provided downstream of jumpchain transfer  358 . If cant  316  requires turning, cant turner arms  364   a  and  364   b  rotate, turning the cant  316 . From the cant turner, cant  316  is transferred along cant sequencing transfer  368 .  
         [0133]    Gangsaw positioning table  376  includes park zone pins  380  and positioning table rolls  376   a . When park zone pins  380  become available, cant  316  is sequenced from ducker J  374  to park zone pins  380 . Park pins  380  are lowered and a set of gangsaw table jumpchains  382  take cant  316  from park zone pins  380  and position the cant against a plurality of raised skew bar pins  384   a  on skew bar  384 . Skew bar  384  skews cant  316  into alignment for feeding to gangsaw  310 .  
         [0134]    Cant  316  moves in direction B″ on positioning rolls  376   a  to a position between a set of driven steering rolls  386 ,  388  and a set of non-driven crowding rolls  392  and  394  as seen in FIG. 18. As the leading end  316   a  of cant  316  enters gangsaw  310 , pressrolls  378 , by means of pressroll cylinders  378   a , press down to hold cant  316  as cant  316  passes into the saw blades  424  mounted on saw arbors  424   b . The lateral position of the two driven steering rolls  386  and  388  are guided by guide shafts  386   a  and  388   a.  The two non-driven crowding rolls  392  and  394  are similarly laterally guided on guide shafts  392   a  and  394   a . The two steering rolls  386  and  388  are rotatably driven on shafts  386   b  and  388   b  by drive motors  396  and  398  for driving the rotation of steering rolls  386  and  388  via drive shafts  386   b  and  388   b , and laterally selectively positioned by positioning cylinders  400  and  402 . The two non-driven crowding rolls  392  and  394  are mounted on idler shafts  392   b  and  394   b  and are laterally positioned by positioning cylinders  404  and  406 . Air bags  408  are provided to absorb anomalies in the profiled face. The gangsaw  310  includes bedrolls  410 . The cant  316  (now sawed into boards) leaves the gangsaw  310  on the gangsaw outfeed rollcase  412 .  
         [0135]    The method of operation is seen in FIGS. 1 and 19. In operation, cant  316  such as depicted in FIG. 34 enters the system from a headrig rollcase (not shown), is ended against a bumper (not shown) and is then transferred in direction A″ to ducker A  314 . When ducker B  318  becomes available cant  316  is sequenced from ducker A  314  to ducker B  318  on the cant indexing transfer  312 . Ducker B  318  is normally down.  
         [0136]    The cant will advance from ducker B  318  to cant turner  319  (the cant turner ducker  319   a  is normally up) where an operator may elect to turn the cant  316 , before advancing the cant to ducker C  320  on the scanner transfer  322 . Ducker C  320  is normally up. Any operator entries relating to the cant about to be scanned must be made before the cant leaves ducker C  320 . Just before ducker C  320  is lowered to advance the cant, the operator inputs (specification choices, grade choices, straight cut &amp; test cant if needed) are entered on the operator console  128  passed to the PLC  18  and then communicated to the optimizer  24  over communications link  27 .  
         [0137]    Between ducker C  320  and ducker D  330  scanner  332  (labelled as scanner  14  in FIG. 1) will scan the cant and transmit measurement data over local area network  26  to optimizer  24  for use in the modelling and optimization process. Encoder  43  on the scanner transfer  322  provides timing pulses to track both forward and backward movement of the cant.  
         [0138]    Three dimensional modelling and real-time optimization processing takes place in the optimizer  24  as the cant is moving through the scanner and prior to its delivery to profiler  340 . In FIG. 1, active chip heads  38  and  40  in sawbox  16 , immediately upstream of saws  52  are substituted for profiler  340 , although an additional upstream cant reducer may be provided to remove butt flare. A curve sawing algorithm, using measurement data from the processed scanner data models the cant and plots a complex “best” curve related to the contours of the wood, smooths surface irregularities in the plotted curve (see FIG. 4), selects an optimum cut description based on product value, operator input and mill specifications and generates control information to effect the cutting solution. Various parameters, such as minimum radius and maximum angle from center line are provided to conform to physical constraints. Control information relating to the positioning and movement of the cant is communicated back to PLC  18  for implementation at the various downstream machine centers which will both profile the cant according to the optimized curve and cut the cant into the products of the selected cut description.  
         [0139]    Ducker D  330  is normally down. When ducker E  334  becomes available the cant is sequenced from ducker D  330  to ducker E  334  on the scanner transfer  322 . Ducker  334  is normally down. Curve, skew and cutting description control data is transferred with the cant as it moves through the various stages. When the profiler positioning table park zone becomes available, the cant is sequenced from ducker E  334  to the park zone pins  338 . The park zone pins  338  are normally up.  
         [0140]    The profiler positioning table park pins  338  lower and the profiler positioning table  336  takes the cant from the park zone pins  338  and positions the cant for feeding to the profiler  340 . PLC  18  communicates the decision information to the profiler motion controller  20 . The jump chains  342  run forward and PLC  18  controls selected positioners  344  which extend to align the cant according to its predetermined location and skew angle control data. As the cant enters the profiler positioning table  336  the selected crowder arms  346  activate to ensure the cant&#39;s position against the positioners  344 , and the park pins  338  raise.  
         [0141]    The cant is detected against the positioners  344  and the holddown rolls  348  lower and the jump chains  342  stop. The crowder arms  346  and positioners  344  retract and the jump chains  342  lower the cant onto the sharp chain  350 .  
         [0142]    As the leading end of the cant enters the profiler  340 , the pressrolls  352  lower in sequence to hold the cant firmly in position as it passes each respective pressroll  352 . Once the cant is sensed to be within the cutting vicinity, the motion controller  20  begins to execute the PLC commands to create the optimum profile. As the cant moves in a straight path through the profiler  340 , the chipping heads  340   a  move horizontally and interdependently in tandem, substantially perpendicular to the direction of flow. The position of the cant is sensed by synchronization photoeye  46  and tracked by encoder  43 . As the trailing end of the cant leaves the profiler positioning table  336 , the holddown rolls  348  raise and jumpchains  342  raise. Also, as the trailing end of the cant leaves the profiler  340 , the pressrolls  352  raise and the motion controller  20  ends its profile.  
         [0143]    The cant leaves the profiler  340  on the profiler outfeed rollcase  354  with at least one of the “profiled” vertical surfaces  316   b  and  316   c  (shown in FIG. 20 a ) that conform to the calculated best curve. The cant is ended against the ending bumper  356  and if ducker F  360  is available the appropriate cant transfer jumpchains  358   a  are raised (based oil scanned length) to carry the cant from the profiler outfeed rollcase  354  to ducker F  360  on the cant jumpchain transfer  358 . Ducker F  360  is normally down. When ducker G  362  becomes available the cant is sequenced from ducker F  360  to ducker G  362  on the cant jumpchain transfer. Ducker G  362  is normally up.  
         [0144]    When the cant turner transfer  366  becomes available the cant is sequenced from ducker G  362  to the cant turner transfer  366 . If the cant requires turning in order to place the appropriate side of the cant (either  316   b  or  316   c ) against the skew bar  384 , the cant turner arms  364   a  and  364   b  will move to the mid-position (arms just above chain level), the cant will advance to the cant turner arms  364   a  and  364   b  and the cant turned acknowledge lamp and buzzer (not shown) will come on to request the operator to observe the actual turning of the cant. The operator pushes the cant turned acknowledge push-button (not shown) and the cant turner arms  364   a  and  364   b  will turn the cant.  
         [0145]    When the turn is complete the cant turner transfer  366  will be stopped and the cant turn acknowledge lamp and buzzer (not shown) will again enunciate. The operator pushes the cant turned acknowledge push-button (not shown) again and the cant turner transfer  366  will re-start and advance the cant to ducker H  370  if that ducker is available. If the cant does not require turning, the cant will advance to the photoeyes and then the cant turner transfer  366  will stop. When ducker H  370  becomes available the cant turner transfer  366  re-starts and advances the cant to ducker H  370 . Ducker H  370  is normally down. When ducker I  372  becomes available the cant will be sequenced from ducker H  370  to ducker I  372  on the cant sequencing transfer  368 . Ducker I  372  is normally down. When ducker J  374  becomes available the cant will be sequenced from ducker I  372  to ducker J  374  on the cant sequencing transfer  368 . Ducker J  374  is normally down.  
         [0146]    When the gangsaw positioning table park zone pins  380  become available the cant will be sequenced from ducker J  374  to the park zone pins  380 . The park zone pins  380  are normally up. The park pins  380  lower and the gangsaw table jumpchains  382  take the cant from the park zone pins  380  and position it against the skew bar pins  384 . The gangsaw table jumpchains  382  are controlled by PLC  18  to position the skew bar pins  384  on the correct optimized skew angle and place the skewed cant in front of the saw combination in the gangsaw that was selected to give the optimum cutting combination. This is a pre-positioning stage for presenting the cant to the steering rolls  386  and  388  and crowding rolls  392  and  394 . Steering rolls  386  and  388  and crowding rolls  392  and  394  are pre-positioned with a slightly larger gap between them than the known width of leading edge of the cant to facilitate loading the cant.  
         [0147]    The gangsaw table jumpchains  382  stop, the skew bar pins  384  retract and PLC  18  communicates decision information to the gangsaw motion controller  22 . As the leading end of the cant enters the gangsaw  310  (gangsaw  16  in FIG. 1), the pressrolls  378  lower in sequence to hold the cant as it passes under each pressroll  378 . As the cant approaches the saws  424  (saws  52  in FIG. 1) the motion controller  22  closes the gap in direction C″, between the steering and crowding rolls, and positions the two driven steering rolls  386  and  388  according to the profile determined by optimizer  24 . The two non-driven crowding rolls  392  and  394  now engage into a pressure mode and are applied to provide a counter force on the cant opposing the two powered steering rolls  386  and  388 . The pressure applied by the crowding rolls  392  and  394  follows a profile determined by optimizer  24 . The pressure mode ensures that the cant  16  remains in contact with the steering rolls  386  and  388  while allowing for anomalies in the cant surface  316   c  and  316   b  by means of airbags  408  (see FIG. 21). The position of the cant as it passes through the gangsaw is sensed by a photoeye and encoder  43 .  
         [0148]    With a curved cant the steering rolls  386  and  388  and the two non-driven crowding rolls  392  and  394  adjust their position as the cant is being fed into the gangsaw. This position follows the profile that is sent to the motion controller  22  from optimizer  24  so as to feed the cant into the saw blades with the cant&#39;s vertical face  316   c  remaining substantially laterally stationary relative to the gangsaw at the saw blade&#39;s first contact point  424   a  (see FIG. 18, looking in direction B″). While the cant&#39;s face  316   c  remains substantially stationary relative to a horizontal direction perpendicular to direction B″ at the saw blade&#39;s first contact point  424   a , the rear portion of the cant is in longitudinal motion and in lateral motion depending on the curve of the cant as the cant is being fed into and cut by the saw blades. The boards being formed begin to follow a slightly different path than the cant allowing the saw blades  424  to remain in a fixed position held by the gangsaw guides  428 . As the trailing end of the cant leaves the gangsaw positioning table  376 , the jumpchains  382  raise. As the trailing end of the cant passes under each pressroll  378 , each will raise in sequence so as not to roll off the end of the cant. Also, as the trailing end of the cant(now boards) leaves the gangsaw, the motion controller  22  ends its profile. The crowder rolls  392  and  394  and the steering rolls  386  and  388  retract so as not to run off the end of the cant. The boards (not shown), which now match the optimized cutting solution that was generated as the cant was being scanned, leave the gangsaw on the gangsaw outfeed rollcase  41   0 . The boards are transported by these rolls to the gang outfeed landing table (not shown).  
         [0149]    As will be apparent to those skilled in the art in the light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof. Accordingly, the scope of the invention is to be construed in accordance with the substance defined by the following claims.