Abstract:
A cutting device for a mill plate including a cutting tool supported for movement in a Y-direction and cutting in a Z-direction, and a conveyor for conveying a mill plate in the X-direction. A measuring device is movable in the X-direction along one side of a mill plate supported on the conveyor to map the X-axis and Y-axis positions of the mill plate one side. Positioning guides adjacent one side of the conveyor are adjusted in the Y-direction to follow the mapped Y-axis position of the mill plate one side at the X-axis position of the mill plate one side aligned with the positioning guides as the mill plate is conveyed in the X-direction. A clamp on the side opposite the mill plate one side is adapted to push the mill plate opposite side in the Y-direction to maintain the mill plate one side in engagement with the positioning guides.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    Not Applicable. 
       FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       MICROFICHE/COPYRIGHT REFERENCE 
       [0003]    Not Applicable. 
       FIELD OF THE INVENTION 
       [0004]    The present invention relates to machining, and more particularly to machining mill plates. 
       BACKGROUND OF THE INVENTION 
       [0005]    It is well known to use machine tools to cut pieces of various required shapes from larger base or stock materials. 
         [0006]    In some cases, the pieces are cut from large (e.g., twenty feet long or longer), flat materials, such as mill plates, made of thick and heavy metal. That size makes such plates difficult to handle, and further can require a large footprint for the machine tool in a facility to provide the space needed for handling. Still further, given the complexity and size of the machine tools required to cut such materials, machine tools which have often heretofore been used in such applications provide a tool which will move in one axis of the plane of the plate (the Y-axis), in which case the mill plate itself is moved in a perpendicular axis (the X-axis). 
         [0007]    Mill plates such as mentioned above have generally rectangular shapes with generally flat sides or edges. However, the generally flat edges are typically formed with tolerances which can result in some curvature to the “flat” edges. 
         [0008]    Machining of such mill plates typically has been accomplished by moving the mill plate while it is being machined moved with one of its “flat” edges oriented in the one (X-axis) direction and maintained in that orientation by pressing the plate edge against one or more guides oriented in the direction of plate movement (the X-axis). However, particularly where high precision is required for the cut piece, mill plate tolerances resulting in some curvature in the edge of the large mill plate can result in undesirable curvature also in the cut piece, as illustrated in  FIGS. 1   a - 1   e  and  FIGS. 2   a - 2   e , which illustrate prior art methods of cutting of a rectangular piece from a mill plate  20 . (For illustration purposes, the curvature of the mill plate edges is greatly exaggerated in the Figures.). 
         [0009]    In the prior art method illustrated in  FIGS. 1   a - 1   e , a mill plate  20  is supported on an entry conveyor  24  having a plurality of datum rollers  28  pivotable about horizontal axes aligned in a horizontal plane, whereby the mill plate  20  will generally move in the horizontal direction perpendicular to the axes of the datum rollers  28 . 
         [0010]    A suitable cutting tool  30  is supported by a machine tool (not shown in  FIGS. 1   a - 1   e ) for selective lateral movement across the width of the mill plate  20  (i.e., in a vertical direction in  FIGS. 1   a - 1   e ). 
         [0011]    Adjacent the area of the cutting tool  30  are a plurality of vertical datum rollers  34  (pivotable about vertical axes) arranged in a vertical plane substantially perpendicular to the horizontal plane/axes of the entry conveyor rollers  28 . The vertical datum rollers  34  define a base position for the side of the mill plate  20  in the area of the cutting tool  30 . 
         [0012]    On the conveyor side opposite the vertical datum rollers  34  is a pusher  40  having a roller  44  (rotatable about a vertical axis) which is biased (e.g., by a piston  46 ) to engaging the other side or edge  48  of the mill plate  20 . The pusher  40  pushes the mill plate  20  into engagement with the vertical datum rollers  34  on the opposite side of the conveyor  24 . The mill plate  20  is thus essentially oriented so that the longitudinal direction of the mill plate  20  is considered to be the direction of the edge  50  of the mill plate  20  located at the vertical datum rollers  34 . 
         [0013]    Cutting of a rectangular cut piece  60  (see  FIG. 1   e ) according to this prior art method is illustrated by the sequence of views in  FIGS. 1   a - 1   e . The mill plate  20  is first positioned so that the cutting tool  30  is positioned over one corner of the piece to be cut ( FIG. 1   a ). The mill plate  20  is then moved horizontally by the conveyor  24  in the direction of arrow  62  ( FIG. 1   b ), with the cutting tool  30  cutting one side  60   a  of the piece  60  during that movement. During that movement, the mill plate  20  is positioned by the pusher  40  pushing one mill plate edge  48  to keep the other mill plate edge  50  in contact with the vertical datum rollers  34  (aligned with the cutting tool  30 ) to cut one side  60   a  of the piece  60 . 
         [0014]    When the next corner of the piece  60  is reached, the conveyor  24  stops and holds the mill plate  20  in position while the cutting tool  30  is moved laterally across the mill plate  20  (in the direction of arrow  64 ,  FIG. 1   c ) to cut a second side  60   b  of the piece  60 . 
         [0015]    The conveyor  24  then moves the mill plate  20  horizontally in a reverse direction (arrow  66 ,  FIG. 1   d ), with the cutting tool  30  cutting a third side  60   c  of the piece  60  during that movement. During that movement, the mill plate  20  is positioned by the pusher  40  pushing one mill plate edge  48  to keep the other mill plate edge  50  in contact with the vertical datum rollers  34  (aligned with the cutting tool  30 ) to cut one side  60   a  of the piece  60 . 
         [0016]    Finally, when the fourth corner of the rectangular piece  60  is reached, the conveyor  24  again stops and holds the mill plate  20  in position while the cutting tool  30  is moved laterally across the mill plate  20  (in the direction of arrow  68 ,  FIG. 1   e ) to cut the fourth side  60   d  of the piece  60 . 
         [0017]    It should be appreciated that two of the sides  60   a  and  60   c  will be essentially of the same orientation/shape as the longitudinally aligned edge  50  of the mill plate  20 . Thus, if the edge  50  is not precisely linear (e.g., due to tolerances or damage), then the sides  60   a  and  60   c  will be similarly and undesirably cut in a non-linear fashion. 
         [0018]      FIGS. 2   a - 2   e  illustrate a second prior art method of cutting large mill plates  20 , wherein elements identical to those illustrated in  FIGS. 1   a - 1   e  are given identical reference numerals and corresponding but different elements are given the same reference numerals with prime (“′”) added (e.g., vertical datum rollers  34 ′). 
         [0019]    With this second prior art method, the mill plate  20  is oriented during movement by having edge  50  pressed toward vertical datum rollers  34 ′ which are positioned over a longer distance (e.g., along the entire length of the conveyor  20 ′) than described above in connection with  FIGS. 1   a - 1   e . However, typically the entry conveyor  24 ′ ends substantially in the area of the cutting tool  30 , so that when the mill plate  20  is moved forward through the machine tool (as in  FIG. 2   b ), the forward edge may extend beyond the vertical datum rollers  34 ′. As a result, with this second method, when cutting a mill plate  20  having a concave edge  50  such as in the illustrated example, the longitudinal orientation of the mill plate  20  will be established by the back corner  20   a  of the mill plate  20  and the last (forward) vertical datum roller  34 ′ a . It should thus be appreciated that the mill plate  20  will not only move forward when cutting side  60   a ′ ( FIG. 2   b ) and backward when cutting side  60   c ′ ( FIG. 2   d ), but it will also slightly twist (due to the pusher  40  pushing the mill plate  20  laterally during forward and backward motion when the front corner of the mill plate  20  is beyond the last vertical datum roller  34 ′ a ). 
         [0020]    It should be appreciated that if the edge  50  is not precisely linear (e.g., due to tolerances or damage), two of the sides  60   a ′ and  60   c ′ of the cut piece  60 ′ (which in the example is intended to be rectangular) will be not be linear due to the twisting of the mill plate  20  during cutting of those sides with the second prior art method as well. 
         [0021]    The present invention is intended to overcome one or more of these problems. 
       SUMMARY OF THE INVENTION 
       [0022]    The present invention relates to a cutting tool and method whereby a mill plate can be precisely cut notwithstanding imperfections in the sides or edges of the mill plate. 
         [0023]    In one aspect of the present invention, a cutting device for a mill plate is provided, including a cutting tool supported for movement in a Y-direction of an X-Y-Z orthogonal coordinate system, and a conveyor adapted to convey a supported mill plate in the X-direction. The cutting tool cuts in the Z-direction through a mill plate lying generally in an X-Y plane with a thickness in the Z-direction. A measuring device at a first portion of the conveyor is movable in the X-direction along one side of a supported mill plate to map the X-axis and Y-axis positions of the supported mill plate one side. A plurality of fixed guide rollers are along the one side of a second portion of the conveyor adjacent the cutting tool, with the rollers rotatable about axes oriented in the Z-direction wherein the axes lie in an X-Z plane. At least two positioning guides are adjacent the conveyor one side on opposite sides of the cutting tool in the X-direction, where the positioning guides adjust the rollers in the Y-direction to follow the mapped Y-axis position of the mill plate one side at the X-axis position of the mill plate one side aligned with the positioning guide as the mill plate is conveyed in the X-direction. At least two clamps on the side opposite the mill plate one side are adapted to push the mill plate opposite side in the Y-direction to maintain the mill plate one side in engagement with the positioning rollers. 
         [0024]    In one form of this aspect of the present invention, the positioning guide rollers are rotatable about axes oriented in the Z-direction, and the positioning guide roller axes are selectively movable in the Y-direction. 
         [0025]    In another form of this aspect of the present invention, the conveyor is adapted to control the position of the mill plate in the X-direction, and each positioning guide is selectively adjustable to position its roller in the mapped Y-axis position corresponding to the X-axis position of the mill plate one side engaging the positioning guide. 
         [0026]    In another aspect of the present invention, a cutting device for a mill plate is provided including a cutting tool supported for movement in a Y-direction of an X-Y-Z orthogonal coordinate system, and a conveyor adapted to convey a supported mill plate in the X-direction. The cutting tool cuts in the Z-direction through a mill plate lying generally in an X-Y plane with a thickness in the Z-direction. A measuring device at a first portion of the conveyor is movable in the X-direction along one side of a supported mill plate to map the X-axis and Y-axis positions of the supported mill plate one side. At least two positioning guides are adjacent the conveyor one side on opposite sides of the cutting tool in the X-direction, where the positioning guides are adjusted in the Y-direction to follow the mapped Y-axis position of the mill plate one side at the X-axis position of the mill plate one side aligned with the positioning guide as the mill plate is conveyed in the X-direction. A clamp on the side opposite the mill plate one side is adapted to push the mill plate opposite side in the Y-direction to maintain the mill plate one side in engagement with the positioning guides. 
         [0027]    In one form of this aspect of the present invention, the positioning guides include rollers rotatable about axes oriented in the Z-direction, and the positioning guide roller axes are selectively movable in the Y-direction. 
         [0028]    In another form of this aspect of the present invention, a plurality of fixed guide rollers is adjacent the one side of the mill plate on the conveyor, with the plurality of fixed guide rollers being rotatable about axes oriented in the Z-direction wherein the axes lie in a X-Z plane. 
         [0029]    In still another form of this aspect of the present invention, the conveyor is adapted to control the position of the mill plate in the X-direction, and each positioning guide is selectively adjustable to position its roller in the mapped Y-axis position corresponding to the X-axis position of the mill plate one side engaging the positioning guide. 
         [0030]    In still another aspect of the invention, a method of cutting a mill plate is provided, including the steps of (a) locating a mill plate on a conveyor with the mill plate substantially lying in an X-Y plane with a thickness in the Z-direction of an X-Y-Z orthogonal coordinate system, (b) mapping the X-axis and Y-axis positions of one side of a mill plate extending in generally the X-direction, (c) conveying the mill plate in the X-direction to a cutting tool supported for movement in the Y-direction and generally cutting in the Z-direction, (d) moving the mill plate in the X-direction and the cutting tool in the Y-direction and Z-direction while selectively cutting the mill plate, and (e) during the moving step, biasing the mill plate one side in the Y-direction against positioning guides spaced generally in the X-direction along the mill plate one side, wherein the positioning guides are adjusted in the Y-direction in accordance with mapped variations in the Y-axis positions at the X-axis positions of the mill plate one side aligned with the positioning guides to prevent twisting of the mill plate during moving of the mill plate in the X-direction. 
         [0031]    In one form of this aspect of the invention, the mapped X-axis and Y-axis positions of the mill plate one side are stored, and each positioning guide is adjusted to match the Y-axis positions of the mill plate one side with the associated X-axis positions of the mill plate aligned in the X-direction with the aligned positioning guide. 
         [0032]    In still another form of this aspect of the invention, the positioning guides are positioned on opposite sides in the X-direction of the cutting tool, and the biasing is accomplished by pushing the mill plate side opposite the one mill plate side toward the positioning guides. 
         [0033]    Other objects, features, and advantages of the invention will become apparent from a review of the entire specification, including the appended claims and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIGS. 1   a - 1   e  illustrate the steps of a first Prior Art method used to cut a rectangular piece from a mill plate, where: 
           [0035]      FIG. 1   a  shows the mill plate to be cut with a tool at the initial cutting position, 
           [0036]      FIG. 1   b  shows the mill plate as moved to cut a first side of the rectangular piece, 
           [0037]      FIG. 1   c  shows the mill plate as the tool is moved to cut a second side of the rectangular piece, 
           [0038]      FIG. 1   d  shows the mill plate as moved to cut a third side of the rectangular piece, and 
           [0039]      FIG. 1   e  shows the mill plate as the tool is moved to cut the fourth, final side of the rectangular piece; 
           [0040]      FIGS. 2   a - 2   e  illustrate the steps of a second Prior Art method used to cut a rectangular piece from a mill plate, where: 
           [0041]      FIG. 2   a  shows the mill plate to be cut with a tool at the initial cutting position, 
           [0042]      FIG. 2   b  shows the mill plate as moved to cut a first side of the rectangular piece, 
           [0043]      FIG. 2   c  shows the mill plate as the tool is moved to cut a second side of the rectangular piece, 
           [0044]      FIG. 2   d  shows the mill plate as moved to cut a third side of the rectangular piece; and 
           [0045]      FIG. 2   e  shows the mill plate as the tool is moved to cut the fourth, final side of the rectangular piece; 
           [0046]      FIGS. 3   a - 3   j  illustrate the steps used to cut a rectangular piece from a mill plate according to the present invention, where: 
           [0047]      FIG. 3   a  shows the mill plate prior to being loaded onto an entry conveyor, 
           [0048]      FIG. 3   b  shows the mill plate as moved onto the entry conveyor, 
           [0049]      FIG. 3   c  shows the mill plate as it has one side mapped, 
           [0050]      FIG. 3   d  shows the mill plate as it is moved to a cutting tool for cutting a piece from the plate, 
           [0051]      FIG. 3   e  shows the mill plate positioned relative to a cutting tool for initiation of cutting, 
           [0052]      FIG. 3   f  shows positioning guides being engaged with the mapped side of the mill plate to initial cutting, 
           [0053]      FIG. 3   g  shows the mill plate as moved to cut a first side of the rectangular piece with the positioning guides adjusted to follow the mapped side of the mill plate as it moves past the guides, 
           [0054]      FIG. 3   h  shows the mill plate as the tool is moved to cut a second side of the rectangular piece, 
           [0055]      FIG. 3   i  shows the mill plate as moved to cut a third side of the rectangular piece with the positioning guides adjusted to follow the mapped side of the mill plate as it moves past the guides, and 
           [0056]      FIG. 3   j  shows the mill plate as the tool is moved to cut the fourth, final side of the rectangular piece; 
           [0057]      FIG. 4  illustrates a comparison of the pieces according to the methods of  FIGS. 1   a - 1   e ,  2   a - 2   e , and  3   a - 3   j;    
           [0058]      FIGS. 5-13  are top views of an exemplary machine tool and entry conveyor according to the present invention (with various portions of the machine tool broken away for illustration purposes), where: 
           [0059]      FIG. 5  shows a mill plate as moved onto the entry conveyor as illustrated in the step of  FIG. 3   b,    
           [0060]      FIG. 6  shows the mill plate as it has one side mapped as illustrated in the step of  FIG. 3   c,    
           [0061]      FIG. 7  shows the mill plate as it is moved to the machine tool, with the positioning guides moved into engagement with the mapped side of the mill plate, prior to cutting a piece from the plate as illustrated in the steps of  FIGS. 3   d - 3   f,    
           [0062]      FIG. 8  shows the mill plate as illustrated in  FIG. 7 , with the cutting tool moved to the starting point in preparation for cutting the piece, 
           [0063]      FIG. 9  shows the mill plate as moved to cut a first side of the rectangular piece with the positioning guides adjusted to follow the mapped side of the mill plate as it moves past the guides as illustrated in the step of  FIG. 3   g,    
           [0064]      FIG. 10  shows the mill plate as the tool is moved to cut a second side of the rectangular piece as illustrated in the step of  FIG. 3   h,    
           [0065]      FIG. 11  shows the mill plate as moved to cut a third side of the rectangular piece with the positioning guides adjusted to follow the mapped side of the mill plate as it moves past the guides as illustrated in the step of  FIG. 3   i , and 
           [0066]      FIG. 12  shows the mill plate as the tool is moved to cut the fourth, final side of the rectangular piece as illustrated in the step of  FIG. 3   j , and 
           [0067]      FIG. 13  shows the mill plate advanced through the machine tool to enable removal of the cut piece from the mill plate; 
           [0068]      FIG. 14  is a perspective view of the tool/exit side of a machine tool which may be used according to the present invention; and 
           [0069]      FIG. 15  is a perspective view of the entry side of the machine tool of  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0070]    The present invention is illustrated in  FIGS. 3   a - 15 , wherein  FIGS. 3   a - 3   j  illustrate the steps of the method of cutting a piece from a mill plate,  FIGS. 5-13  illustrate an exemplary machine tool and conveyor arrangement which may be used to practice the method, and  FIGS. 14-15  illustrate the exemplary machine tool. 
         [0071]    Referring first to the inventive method,  FIGS. 3   a - 3   j  illustrate the method of cutting a large mill plates  20 , wherein elements identical to those illustrated in  FIGS. 1   a - 1   e  are given identical reference numerals and corresponding but different elements are given the same reference numerals with double prime (“″”) added (e.g., vertical datum rollers  34 ″). 
         [0072]    With this novel method, the mill plate  20  is first located on the entry conveyor  24 ″ with at least two locations (e.g., corners at opposite ends) along the longitudinal edge  50  at known, base locations. For example, base plates  70  may be located at opposite ends of the entry conveyor  24 ″, with the two plates  70  aligned in the X-direction (i.e., along a horizontal line which is perpendicular to the axes of the fixed datum rollers  28 ). The base plates  70  may also be datum rollers. The mill plate  20  may be loaded onto the entry conveyor  24 ″ and then pushed horizontally in the Y-direction (i.e., the direction of the datum roller axes as illustrated by the arrow  72  in  FIG. 3   a ) so that its front and rear corners abut the base plates  70  in known positions in the X-Y plane (see  FIG. 3   b ). 
         [0073]    With the mill plate  20  in this known position (see  FIGS. 3   b - 3   d ), a mapping element or device  80  is moved in the X-direction (see arrows  82  in  FIG. 3   c ) adjacent the longitudinal edge  50  (the mapping device  80  is shown in three positions in  FIG. 3   c ). The mapping device  80  includes a follower  84  biased outwardly toward the mill plate edge  50  to follow the edge  50  as the mapping device  80  is moved, and the device  80  is connected to a suitable processor and memory for storing the position of the follower ( 84 ) at suitable increments (e.g., each inch) along the length of the edge  50 . The shape of the plate edge  50  is thus mapped in the X-Y plane according to the position of the mill plate  20  when mapped. 
         [0074]    The mill plate  20  is then moved in the X-direction (see arrow  86  in  FIGS. 3   d - 3   e ) toward the cutting tool  30 . In accordance with the present invention, in the area of the cutting tool  30  there are at least two positioning guides  90  spaced in the X-direction on the mapped edge/side  50  of the mill plate  20 . Advantageously, the positioning guides  90  may be all short of the Y-direction plane in which the tool  30  cuts (i.e., spaced in the X-direction toward the entry conveyor  24 ″ from the Y-Z plane of the tool  30 ), so that the guides will not interfere with cutting at the front corner of the plate  20 , allowing as much of the plate  20  to be used as possible during cutting operations. Those positioning guides  90  each include a roller  92  which is rotatable about a vertical axis (the Z-axis). 
         [0075]    The rollers  92  are selectively moved in the Y-direction during operation. Specifically, as the mill plate  20  is moved over the entry conveyor  24 ″ in the X-direction, the mapped plate edge  50  also moves past the positioning guides  90 . Using the stored map of the edge  50  in the X-Y plane, each of the guides  90  are controlled so that their rollers  92  are extended out to the mapped Y-position of the plate edge  50  associated with the X-position of the plate edge  50  aligned with the guide  90 . 
         [0076]    On the opposite side  48  of the plate  20 , biasing clamps or pushers  94  are provided which push against that mill plate side  48  in the Y-direction toward the positioning guides  90 . These clamps  94  may advantageously include rollers  96  rotatable about vertical (Z) axes to allow the mill plate  20  to move past them in the X-direction without binding, and are suitably biased with a sufficient force (e.g., by a hydraulic piston configuration) to ensure that the mapped edge  50  of the plate  20  will be kept in contact with the positioning guide rollers  92  on the side opposite the biasing clamps  94 . 
         [0077]    It should thus be appreciated that, as shown in  FIGS. 3   f - 3   j , during cutting of the mill plate  20  by the tool  30 , the plate  20  will be moved only in the X-direction, without any twisting occurring around the Z-axis. 
         [0078]    Cutting of a rectangular cut piece  60 ″ (see  FIG. 3   j ) in accordance with the present invention thus occurs as illustrated in  FIGS. 3   f - 3   j.    
         [0079]    The mill plate  20  is first positioned so that the cutting tool  30  is positioned over one corner of the piece to be cut ( FIG. 3   f ). The mill plate  20  is then moved horizontally by the conveyor  24  in the X-direction (see arrow  62 ″ in  FIG. 3   g ), with the cutting tool  30  cutting one side  60   a ″ of the piece  60 ″ during that movement. During that movement, the mill plate  20  is pushed on one side  48  by the clamps  94  to keep the opposite, mapped, mill plate edge  50  in contact with the positioning guide rollers  92 . It should be appreciated that since the positioning guide rollers  92  will be adjusted to match the mapped shape of the mill plate edge  50  as the mill plate  20  moves past the rollers  92 , essentially every point in the mill plate  20  will move in only the X-direction during this operation (i.e., the plate  20  will not twist as can occur with the prior art operations illustrated in  FIGS. 1   a - 1   e  and  2   a - 2   e ). 
         [0080]    When the next corner of the piece  60 ″ is reached, the conveyor  24  stops and holds the mill plate  20  in position while the cutting tool  30  is moved laterally across the mill plate  20  (in the direction of arrow  64 ″,  FIG. 3   h ) to cut a second side  60   b ″ of the piece  60 ″. 
         [0081]    The conveyor  24  then moves the mill plate  20  horizontally in a reverse X-direction (arrow  66 ″,  FIG. 3   i ), with the cutting tool  30  cutting a third side  60   c ″ of the piece  60 ″ during that movement. During that movement, the mill plate  20  is positioned by the clamps  94  pushing on the side  48  to maintain the mapped side  50  in contact with the positioning guide rollers  92 . As with plate movement in the direction of arrow  62 ″ ( FIG. 3   g ), the positioning guide rollers  92  are adjusted to match the mapped shape of the mill plate edge  60 , with the rollers  92  positioned at the Y-axis positions mapped as being associated with the X-axis positions aligned with the rollers  92 . 
         [0082]    Finally, after the fourth corner is reached at the end of the step illustrated in  FIG. 3   i , the fourth side  60   d ″ of the piece  60 ″ is cut with the plate  20  held stationary and the tool  30  moved laterally across the mill plate  20  (in the direction of arrow  68 ″,  FIG. 3   j ). 
         [0083]    It should be appreciated that whereas two of the sides  60   a ,  60   a ′ and  60   c ,  60   c ′ could be neither precisely linear nor at right angles to sides  60   b ,  60   b ; and  60   d ,  60   d ′ (e.g., if tolerances or damage result in the plate side  50  not being linear) when the piece  60 ,  60 ′ is cut according to one of the described prior art procedures, the sides  60   a ″- 60   d ″ of a rectangular piece  60 ″ cut according to the present invention would all be straight and at right angles to each other. 
         [0084]    Of course, it should be appreciated that while the above described example of cutting a rectangular piece has been used for illustrative purposes, the present invention can be used to ensure that pieces are precisely cut to different desired shapes as well. 
         [0085]      FIGS. 5-15  illustrate in greater detail a machine which may be used to practice the present invention, with  FIGS. 14-15  illustrating an exemplary machine tool  100  with which the present invention may be advantageously used. 
         [0086]    Specifically, the machine tool  100  of  FIGS. 14-15  includes a carriage  104  which supports a tool spindle  108  for movement in the Y-direction along a cable track  112 , where the tool in the tool spindle  108  may be moved in the Z-direction along a vertical rail  114  for cutting into an underlying mill plate. A rotary tool changer  116  is also provided adjacent the tool spindle  108  for allowing different tools to be loaded into the spindle for use in different cutting. Additionally, gas and plasma torches  120  may also be secured on the carriage  104  for movement in the Y-direction for still further forms of cutting as needed. 
         [0087]    On the exit side of the machine tool  100 , a dump table  130  is provided to facilitate handling of scrap and cut pieces after cutting. As is known, the dump table  130  may be moved up and down and tilted to facilitate dumping of scrap into a scrap hopper  134  disposed beneath the dump table  130 . The scrap hopper  134  may be rolled from beneath the dump table  130  to allow it to be emptied. An exit conveyor  140  with suitable rollers  142  (not shown in  FIG. 14 ; see  FIGS. 5-13 ) may also be provided, if desired, on the exit side of the machine tool  100  to provide suitable support for the mill plate and/or cut pieces if necessary. 
         [0088]    Wheels or rollers  150  (see  FIG. 15 ) are variously located on the entry side of the machine tool  100  and are controlled by a X-axis drive  152  ( FIG. 14 ). The wheels  150  engage the bottom of a mill plate which enters the machine tool  100 , and are controllably rotated to move the mill plate in the X-direction as required for cutting. A suitable control  156 , with a processor and memory, is provided to control the machine tool  100 , as well as controlling the entry conveyor  24 . The control  156  may also control the mapping device  80  during mapping of the longitudinal edge  50  of the mill plate  20  and store the mapped X-Y coordinates of the edge  50  for use during cutting as previously described. However, a separate control, such as a programmable logic controller (PLC), could be used for the mapping device  80  and/or positioning guides  90 , which may run in the background without affecting the machine control logic (whereby a pre-made part program can be used without requiring updating to compensate for the mapped plate side  50 ). 
         [0089]    It should be appreciated that machine tools of a variety of designs, and having a variety of features, can be used with the present invention including, for example, High Speed Plate Systems (e.g., the High Speed FDB-2500) available from Peddinghaus Corporation (300 North Washington Avenue, Bradley, Ill. 60915) and its related companies. 
         [0090]    Operation of a machine tool  100  such as described above with the present invention is illustrated in  FIGS. 5-13  (wherein various portions of the overlying machine tool  100  are broken away for illustration purposes). 
         [0091]    As illustrated in  FIG. 5 , a mill plate  20  is first moved onto the entry conveyor  24  and biased in the Y-direction so that it is oriented in a fixed position (e.g., with two points, the front and rear corners of a concave longitudinal side  50 , against base plates/datum rollers  70 ). 
         [0092]    While held in that position, the mill plate longitudinal edge  50  is mapped by movement of the mapping device  80  which moves along the length of the side (arrow  80 ) and follows and measures the Y-direction position of the side  50  at selected intervals (e.g., each inch). The mapped positions of the longitudinal side  50  are stored in the control  156 . 
         [0093]    While mapping of the mill plate longitudinal edge  50  is being done, the machine tool  100  may also be prepared for the desired cutting of the mill plate  20 . For example, the rotary tool changer  116  may be moved (see arrow  160  in  FIG. 6 ) to the tool spindle  108  for loading of the appropriate tool. 
         [0094]    The mill plate  20  is then advanced into the machine tool  100  along the entry conveyor  24  (see arrow  86  in  FIG. 7 ) so that the leading end of the mill plate  20  is disposed between the positioning guides  90  and clamps  94 . Advancing of the mill plate  20  may be accomplished in any suitable manner. For example, the rollers  28 ″ of the entry conveyor  24 ″ may be driven until the plate  20  is suitably engaged by the entry wheels  150  (see  FIG. 15 ) at which point the conveyor rollers  28 ″ may be released to spin freely with more precise movement of the plate  20  thereafter being controlled by the entry wheels  150 . It should also be appreciated, however, that movement of the plate  20  in the X-direction could be suitably driven in a variety of manners, including driven rollers engaging the sides of the plate  20 . 
         [0095]    At that point, operation continues as generally described herein in connection with  FIGS. 3   f - 3   j  (with the illustration, again, being of cutting a rectangular piece  60 ″ for simplicity). 
         [0096]    That is, the rollers  92  of the positioning guides  90  are selectively moved in the Y-direction as the mill plate  20  is moved over the entry conveyor  24 ″ in the X-direction. Using the stored map of the edge  50  in the X-Y plane, each of the guides  90  are controlled so that their rollers  92  are extended out to the mapped Y-position of the plate edge  50  associated with the X-position of the plate edge  50  aligned with the guide  90 . 
         [0097]    On the opposite side  48  of the plate  20 , biasing clamps  94  push against that mill plate side  48  in the Y-direction toward the positioning guides  90  to ensure that the mapped edge  50  of the plate  20  will be kept in contact with the positioning guide rollers  92  on the side opposite the biasing clamps  94 . Therefore, during cutting of the mill plate  20  by the tool  30  in the tool spindle  108 , the plate  20  will be moved only in the X-direction, without any twisting occurring around the Z-axis. 
         [0098]    To cut a rectangular cut piece  60 ″ (see  FIGS. 12-13 ), the mill plate  20  and machine tool  100  are first positioned as shown in  FIG. 8 , with the tool spindle  108  and tool  30  moved (see arrow  170  in  FIG. 8 ) over one corner of the piece to be cut. The mill plate  20  is then moved horizontally by the conveyor  24  in the X-direction (see arrow  62 ″ in  FIG. 9 ), with the cutting tool  30  cutting one side  60   a ″ of the piece  60 ″ during that movement. During that movement, the mill plate  20  is pushed on one side  48  by the clamps  94  to keep the opposite, mapped, mill plate edge  50  in contact with the positioning guide rollers  92 . Since the positioning guide rollers  92  are adjusted to match the mapped shape of the mill plate edge  50  as the mill plate  20  moves past the rollers  92 , essentially every point in the mill plate  20  will move in only the X-direction during this operation (i.e., the plate  20  will not twist as can occur with the prior art operations illustrated in  FIGS. 1   a - 1   e  and  2   a - 2   e ). 
         [0099]    When the next corner of the piece  60 ″ is reached, the mill plate  20  is held in a fixed position while the tool spindle  108  and tool  30  is moved laterally across the mill plate  20  (in the direction of arrow  64 ″,  FIG. 10 ) to cut a second side  60   b ″ of the piece  60 ″. 
         [0100]    The conveyor  24  then moves the mill plate  20  horizontally in a reverse X-direction (arrow  66 ″,  FIG. 11 ), with the tool spindle  108  and tool  30  cutting a third side  60   c ″ of the piece  60 ″ during that movement. During that movement, the mill plate  20  is positioned by the clamps  94  pushing on the side  48  to maintain the mapped side  50  in contact with the positioning guide rollers  92 . As with plate movement in the direction of arrow  62 ″ ( FIG. 9 ), the positioning guide rollers  92  are adjusted to match the mapped shape of the mill plate edge  60 , with the rollers  92  positioned at the Y-axis positions mapped as being associated with the X-axis positions aligned with the rollers  92 . 
         [0101]    After the fourth corner is reached at the end of the step illustrated in  FIG. 11 , the fourth side  60   d ″ of the piece  60 ″ is cut with the plate  20  held stationary and the tool spindle  108  and tool  30  moved laterally across the mill plate  20  (in the direction of arrow  68 ″,  FIG. 12 ). 
         [0102]    After the piece  60 ″ is fully cut, the mill plate  20  may be suitably advanced (in the direction of arrow  176 ,  FIG. 13 ) to clear the cut piece  60 ″ from the machine tool  100  so that it may be suitably removed and taken where needed. 
         [0103]    It should be appreciated that the present invention will allow precise cutting of a piece from a mill plate, even where the mill plate has an irregular side. This will enable cut pieces to meet the smallest of tolerances despite such plate irregularities.