Abstract:
Laser scanning systems and methods are disclosed herein that can provide quick and efficient measurement of extruded ceramic logs, particularly related to log shape, during manufacture. Two two-dimensional laser scans from respective laser scanners are performed and the resulting laser scan data is combined to form a three-dimensional surface shape measurement of the ceramic log. The systems and methods disclosed herein enable a non-contact measurement of the extruded ceramic log, which reduces the risk of physically damaging the log. The measurement results can be used to adjust the extrusion process of the extruder that forms the extruded ceramic logs.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. application Ser. No. 13/103,420, filed on May 9, 2011, and claims priority from and the benefit of U.S. Provisional Application No. 61/333,938, filed on May 12, 2010, both of which are hereby incorporated by reference for all purposes as if fully set forth herein. 
     
    
     FIELD 
       [0002]    This disclosure generally relates to measuring extruded ceramic logs, and in particular to laser scanning systems and methods for making three-dimensional measurements of extruded ceramic logs. 
       BACKGROUND 
       [0003]    Ceramic honeycomb structures are used in a variety of applications, and in particular plugged ceramic honeycomb structures can be used as filters in vehicular exhaust systems to reduce pollutants. The honeycomb structures can be formed by extruding a plasticized ceramic-forming precursor in the form of a log. The log has a network of interconnected web walls that form a matrix of elongated cells which may be, for example, square, octagonal or hexagonal in shape. The network of web walls is surrounded by a cylindrical outer wall or “skin” that is integrally connected to the outer edges of the web walls of the matrix to form a cylindrical structure having opposing inlet and outlet endfaces for receiving and expelling exhaust gases through the matrix of cells. 
         [0004]    The extruded log needs to be measured to ensure it meets specifications with respect to its size and shape, and in particular with respect to the amount of bow in an axial direction, in the direction of extrusion. 
       SUMMARY 
       [0005]    The systems and methods disclosed herein can provide quick and efficient measurement of extruded logs, particularly related to log shape, during manufacture. The systems and methods disclosed herein preferably provide a non-contact measurement of the extruded log, thereby also helping to reduce the risk of physically damaging the log. As used herein, a ceramic log refers to an extruded, generally cylindrical body comprised of a ceramic composition and/or a ceramic-forming composition, that can be sintered and/or reaction sintered, to form a ceramic article upon heating of the log. The ceramic log may vary from its generally cylindrical shape due to imperfections in the manufacturing process. 
         [0006]    It is to be understood that both the foregoing general description and the following detailed description present embodiments of the disclosure, and are intended to provide an overview or framework for understanding the nature and character of the disclosure as it is claimed. The accompanying drawings are included to provide a further understanding of the disclosure, and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the disclosure and, together with the description, serve to explain the principles and operations of the disclosure. In some of the Figures, Cartesian coordinates are shown for reference. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic diagram of an example extrusion system used to create fired ceramic articles from ceramic logs formed by extrusion, where the system includes two laser scanning systems for measuring the ceramic logs at different stages during the manufacturing process; 
           [0008]      FIG. 2  is a more detailed schematic diagram of the example extrusion system of  FIG. 1 ; 
           [0009]      FIG. 3  is a close-up, top-down view of the conveyor in the process of transporting ceramic logs supported by trays from the extruder unit to the drying unit; 
           [0010]      FIG. 4  is an isometric view of an example cylindrical extrudate formed by extrusion using the extrusion system of  FIG. 1  and  FIG. 2 , and also showing how the extrudate is cut into logs and then into smaller pieces (wares) prior to firing; 
           [0011]      FIG. 5  is a close-up, isometric view of an example ceramic log; 
           [0012]      FIG. 6  is a view the −Y-direction and  FIG. 7  is a view in the -X-direction of an example laser scanning system arranged relative to a ceramic log supported by a tray on a conveyor, where the tray needs to be lifted from the conveyor to place the ceramic log in the measurement position; 
           [0013]      FIG. 8  is a bottom-up view of an example support arm with the laser scanners attached at opposite ends, with the support arm attached to the central beam of the support structure; 
           [0014]      FIG. 9  and  FIG. 10  are similar to  FIG. 6  and  FIG. 7 , except that the lifting mechanism has been activated to place the ceramic log in the measurement position above the conveyor; 
           [0015]      FIG. 11  shows an embodiment of the laser scanning system similar to that shown in  FIG. 6 , except that the system is configured so that laser scanning measurements can be taken with the ceramic log and tray resting on an unmoving conveyor; 
           [0016]      FIG. 12  illustrates an example two-dimensional measured surface shape profile as determined by the controller from the two-dimensional scan data and displayed on the controller display; 
           [0017]      FIG. 13  illustrates an example three-dimensional image of the measured surface shape of a ceramic log as determined by the controller from the three-dimensional scan data and displayed on the controller display; and 
           [0018]      FIG. 14  plots an example of the “profile of the line” (POL) in inches versus the log position in inches based on hypothetical two-dimensional scan data. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Reference is now made in detail to embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, the same or like reference numbers are used throughout the drawings to refer to the same or like parts. 
         [0020]      FIG. 1  is a generalized schematic diagram and  FIG. 2  is a more detailed schematic diagram of an example embodiment of an extrusion system  10  used to create ceramic articles from ceramic logs formed by extruding a ceramic-forming extrusion material. Extrusion system  10  includes an extruder portion  12  that has a mixing stage or “wet tower”  20  having an input end  22  and an output end  24 . Wet tower  20  initially receives at input end  22  the various batch material constituents  30  in dry form from respective constituent sources  31 , and mixes them along with water (and optionally oil) to form an initial ceramic-forming batch material  34 . The aqueous-based ceramic precursor mixture formed in wet tower  20  preferably comprises a batch material mixture of ceramic (such as cordierite) forming inorganic precursor materials, an optional pore former such as graphite or starch, a binder, a lubricant, and a vehicle. The inorganic batch material components can be any combination of inorganic components (including one or more ceramics) which can, upon firing, provide a porous ceramic having primary sintered phase composition (such as a primary sintered phase composition of cordierite or aluminum titanate). 
         [0021]    Wet tower  20  includes, for example, a mixer  40  followed by a rotary cone  44 . Wet tower  20  also includes a water unit  50  configured to provide water to mixer  40  in select amounts, e.g., by weighing the amount of water added to the mixer. In an example embodiment, water unit  50  is controlled manually and/or automatically, as discussed below. Examples of batch material  34  are discussed below. 
         [0022]    Extruder portion  12  further includes a conveyer unit  60  arranged adjacent output end  24  of wet tower  20 . Conveyor unit  60  includes a conveyor belt  64  with an input end  66  and an output end  68 . Conveyor belt  64  rotates clockwise as shown. Conveyor unit  60  includes a protective cover  70 . 
         [0023]    Conveyor belt input end  66  is arranged at the output end  24  of wet tower  20  to receive batch material  34  therefrom. In an example embodiment, rotary cone  44  serves to deliver batch material  34  to conveyor belt input end  66  in a relatively uniform layer. Wet tower  20  is configured to adjust the thickness of the layer of batch material  34  carried by conveyor belt  64 . 
         [0024]    The extruder portion  12  of extrusion system  10  further includes a chute  80  and an extrusion unit  90 . Chute  80  is arranged between conveyor unit  60  and extrusion unit  90 . Chute  80  is configured to receive batch material  34  from the output end  68  of conveyor belt  64  and deliver it to extrusion unit  90 . Extrusion unit  90  is configured to receive batch material  34  and form billets therefrom, which are then pressed through an extrusion die  92  (e.g., by a twin-screw extruder) to form an extrudate  100 . In an example embodiment, extrusion unit  90  includes multiple extrusion dies that operate at once to simultaneously form multiple extrudates  100 . 
         [0025]    In an example embodiment, extrusion system  10  includes a pressure sensor  94  in extrusion unit  90  electrically connected to a master controller MC and configured to measure the pressure during extrusion. Pressure sensor generates an electrical signal S P  that is sent to and received by master controller MC, which processes and preferably displays the pressure measurements on a display (not shown). This feedback allows the master controller MC to control the extrusion process. 
         [0026]    Extrudate  100  is deposited onto a conveyor  110  arranged adjacent extrusion die  92 . In an example embodiment, extrudate  100  is cut into sections called “logs”  101 , as shown in  FIG. 4  and in  FIG. 5  The cross-sectional shape can be round or non-round, e.g., oval. Logs  101  are supported in trays  114 .  FIG. 3  is a top-down close-up view of conveyor  110  showing logs  101  supported in trays  114  being conveyed in the +X direction away from extrusion unit  90 . 
         [0027]    At this point, logs  101  are “green” and “wet”. The green and wet logs  101  are conveyed by conveyor  110  to a drying station (e.g., an oven or “applicator”)  120 . Drying station  120  has an interior  122  where logs  101  reside while drying. Drying station  110  may use, for example, radio-frequency (RF) radiation or microwave frequency (MF) radiation, to effectuate drying. 
         [0028]    Extrusion system  10  also includes a cutting station  130  for cutting dried logs  101  into smaller pieces or wares  102  (see  FIG. 4 ) and a firing station  134  downstream of drying station  120  for firing the smaller, dried wares. 
         [0029]    Extrusion system  10  further includes at least one laser scanning measurement system  200  disposed adjacent and above conveyor  110 . The example extrusion system  10  of  FIG. 1  and  FIG. 2  includes a first laser scanning system  200  disposed between extrusion unit  90  and drying station  120  and a second laser scanning system disposed between the drying station and firing station  134 . 
         [0030]      FIG. 5  is a close-up view of an example ceramic log  101 . Ceramic log  101  has a central axis A 1 , opposite endfaces  148  and a matrix of intersecting, thin, porous walls  150  that extend across and between the endfaces and that define longitudinally extending cells  152  that collectively form a honeycomb structure  154 . Honeycomb structure  154  is surrounded by an outer skin  156  that defines an outer surface  160 . Both endfaces  148  have the same general contour shape, such as circular or oval. 
         [0031]    The contours of outer skin  156  and endfaces  148  define an overall shape of outer surface  160 , and this shape is referred to as the “surface shape.” This shape can vary from being perfectly cylindrical due to imperfections in the extrusion process. The surface shape taken at a given cross-section perpendicular to axis Al is referred to as the “two-dimensional surface shape,” while the surface shape of an extended portion of outer surface  160  is referred to as the “three-dimensional surface shape.” 
         [0032]    In an example embodiment, master controller MC is operably connected to wet tower  20 , to conveyor units  60  and  110 , to extruder  90 , to drying station  120  and to the at least one laser scanning system  200 , and is configured to control the operation of these system components to control the overall operation of the extrusion system. 
         [0033]    When logs  101  are sufficiently dry (meaning that most or all of the liquid initially present in the logs has been removed so that the moisture content has been reduced to a level acceptable for cutting and firing), they are cut into smaller greenware pieces  102  (see  FIG. 4 ) at cutting station  130 . Greenware pieces  102  are then fired at firing station  134 , which includes for example a hot-air oven or kiln. The resultant heat transforms the relatively soft and fragile dried greenware pieces  102  into hardened, fired wares  102 ′ having a rigid honeycomb structure  154  and outer surface  160  with a fixed surface shape. In an example embodiment, fired wares  102 ′ are used to form ceramic filters wherein the ceramic is porous enough to allow fluid (gas and/or liquid) to flow therethrough. 
         [0034]    Exemplary AT-based ceramic materials are discussed in U.S. Pat. No. 7,001,861, U.S. Pat. No. 6,942,713, U.S. Pat. No. 6,620,751, and U.S. Pat. No. 7,259,120, which patents are incorporated by reference herein. Such AT-based bodies may be used as an alternative to cordierite and silicon carbide (SiC) bodies for high-temperature applications, such as automotive emissions control applications. The systems and methods disclosed herein apply to any type of extruded greenware. 
         [0035]    During the manufacturing process, the wet and dried green ceramic logs  101  preferably have a surface shape that conforms to a particular specification, for example as defined by a desired end product shape. For example, where the end product is a filter, ceramic logs  101  preferably have a surface shape consistent with that of the filter holder prior to firing the logs and fixing the surface shape. In some applications, a resultant filter might not sit properly in the filter holder if it has a surface shape that does not meet the filter specification. Thus, the measurement of the surface shape allows for out-of-spec ceramic logs to be rejected before they are processed into end products. Further, measurement of the surface shape provides feedback for the manufacturing process and allows the manufacturing process to be adjusted so that the surface shape deviations can be corrected. 
       Laser Scanning Measurement System 
       [0036]      FIG. 6  is a front-on view (i.e., in the −Y-direction) and  FIG. 7  is a side view (i.e., in the −X-direction) of an example embodiment of laser scanning system  200 , along with log  101  supported by tray  114 . Laser scanning system  200  includes a support frame  210  having vertical support columns  214  oriented in the Z-direction and mechanically connected to horizontal crossbeams  220  oriented in the X and Y directions. Support frame  210  is fixed to or solidly rests upon a floor FL. A central cross-beam  220 C runs in the Y direction in the center of the support frame. Central cross-beam  220 C supports a mounting fixture  230  in a manner that allows the mounting fixture to move in the Y-direction. In an example, central cross-beam  220 C includes a flanged section that runs in the Y-direction, and mounting fixture  230  includes a central channel configured to slidingly engage the central cross-beam at the flanged section so that the mounting fixture can move in the Y-direction. Other known movable mount configurations can also be used. 
         [0037]    Laser scanning system  200  also includes a drive unit  240  operably connected to mounting fixture  230  to move the mounting fixture. Drive unit  240  is operably connected to a controller  250  that controls the movement of mounting fixture  230  along central cross-beam  220 C via drive unit  240 , including stepping the mounting fixture in the Y-direction in select increments (e.g., 1 mm). In an example embodiment, drive unit  240  includes a motor, such as a stepping motor or servomotor. In one example, drive unit  240  is incorporated into movable mount  230 . In another example, drive unit  240 , mounting fixture  230  and central cross-beam  220 C may comprise a servo motor and a servo slide mechanism. 
         [0038]    In an example embodiment, controller  250  is part of main controller MC. Also in an example embodiment, controller  250  is or includes a computer  252  (e.g., a personal computer (PC), workstation, etc.) with processor  254  and a memory unit (“memory”)  256 , and includes an operating system such as Microsoft WINDOWS® or LINUX. In an example embodiment, processor  254  is or includes any processor or device capable of executing a series of software instructions and includes, without limitation, a general- or special-purpose microprocessor, finite state machine, controller, computer, central-processing unit (CPU), field-programmable gate array (FPGA), or digital signal processor. Also, memory  256  includes refers to any processor-readable medium, including but not limited to RAM, ROM, EPROM, PROM, EEPROM, disk, floppy disk, hard disk, CD-ROM, DVD, or the like, on which may be stored a series of instructions executable by processor  254 . 
         [0039]    The surface shape measurement methods described herein may be implemented in various embodiments via a set of machine readable instructions (e.g., computer programs and/or software modules) stored in memory  256  and operable in processor  254  for causing controller  250  to operate laser scanning system  200  to perform the measurement methods described herein. In an example embodiment, the computer programs run on image processor  254  out of memory  256 , and may be transferred to main memory from permanent storage via a disk drive or port  257  when stored on removable media  116 , or via a network connection or modem connection when stored outside of controller  250 , or via other types of computer or machine-readable media from which it can be read and utilized. 
         [0040]    The computer programs and/or software modules may comprise multiple modules or objects to perform the various methods described herein, and control the operation and function of the various components in laser scanning system  200 . The type of computer programming languages used for the code may vary between procedural code-type languages to object-oriented languages. The files or objects need not have a one-to-one correspondence to the modules or method steps described. Further, the method and apparatus may comprise combinations of software, hardware and firmware. Firmware can be downloaded into processor  254  for implementing the various example embodiments described herein. 
         [0041]    Controller  250  optionally includes a data-entry device  258 , such as a keyboard, that allows a user of laser scanning system  200  to input information into controller  250  (e.g., the part number), and to manually control the operation of the laser scanning system. Controller  250  further optionally includes a display  259  that can be used to display information using a wide variety of alphanumeric and graphical representations. For example, display  259  is useful for displaying the measured three-dimensional surface shape, as well as any of individual two-dimensional surface shapes, as discussed below. 
         [0042]    Laser scanning system  200  also includes a support arm  260  attached to mounting fixture  230 .  FIG. 8  is a bottom-up view of an example support arm  260  and mounting fixture  230  as attached to central beam  220 C. An electrical cable  262  that connects controller  250  (not shown in  FIG. 8 ) to laser scanners  270 L and  270 R is shown in  FIG. 8 . Support arm  260  includes opposite ends  264 L and  264 R to which are attached respective laser scanners  270 L and  270 R. 
         [0043]    With reference again to  FIG. 6 , laser scanners  270 L and  270  have, when activated, respective two-dimensional laser scan paths  272 L and  272 R that include respective central axes A L  and A R  and that subtend respective scanning angles θ L  and θ R . Central axes A L  and A R  intersect at a location  280  and define a central angle φ between laser scan paths  272 L and  272 R. Location  280  serves as a reference for defining a measurement position MP, which is the position where ceramic log  101  can be scanned by laser scanners  270 L and  270 R. An exemplary measurement position is when ceramic log central axis A 1  coincides with location  280 . In an example embodiment, scan paths  272 L and  272 R overlap on ceramic log outer surface  160  when ceramic log  101  is in the measurement position. Laser scanners  270  suitable for use in laser scanning system  200  are available, for example, from Sick AG, Waldkirch, Germany, model no. IVC-3D  100 . 
         [0044]    Support frame  210  is arranged relative to conveyor  110  so that the conveyor can move trays  114  into place below laser scanners  270 L and  270 R, thereby allowing for an in situ measurement of ceramic log  101 . In the example embodiment illustrated in  FIGS. 6 ,  7 ,  9  and  10  (and also shown in one of the laser scanning systems  200  in  FIG. 1  and  FIG. 2 ), laser scanning system  200  includes a lifting mechanism  300  configured to lift tray  114  and the ceramic log  101  supported thereby so that ceramic log  101  is placed at the measurement position. This allows for scan paths  272 L and  272 R to be incident upon ceramic log outer surface  160  at a particular axial location, i.e., at a given Y-position, as discussed in greater detail below. 
         [0045]    Lifting mechanism  300  allows for ceramic log  101  and tray  114  to be physically isolated from conveyor  110  when the ceramic log is being measured so that vibrations caused by the movement of the conveyor do not adversely affect the laser scanning measurements. 
         [0046]    In an alternative embodiment illustrated in  FIG. 10  and  FIG. 11 , ceramic log  101  and tray  114  remain on conveyor  110  and the conveyor is stopped while laser scanning measurements are taken. In this case, support structure  210  is configured so that laser scanning measurements can be taken when ceramic log  101  is conveyed by conveyor  110  to the measurement position while tray  114  resides on the conveyor. 
         [0047]    In the operation of laser scanning system  200 , once ceramic log  101  is disposed in the measurement position, controller  250  sends a control signal S 1  to drive unit  240  to move mount  230  and thus laser scanners  270 L and  270 R into an initial Y position PI ( FIG. 10 ) for scanning the ceramic log. In one example, initial position PI is such that the laser scan paths  272 L and  272 R are adjacent endface  148  so that they are not incident upon outer surface  160  but are incident upon tray  114 . Controller  250  then sends control signals S 1  to driver unit  240  to move mount  230  and thus laser scanners  270 L and  270 R in the −Y-direction in small increments, e.g., about 1 mm. For each Y-position, controller  250  activates laser scanners  270 L and  270 R with an activation signal SA so that they perform a two-dimensional scan of outer surface  160  of ceramic log  101 . For a tray  114  having a length of 1000 mm, performing two-dimensional scans in 1 mm increments results in 1000 two-dimensional surface-shape measurements. 
         [0048]      FIG. 10  also shows an intermediate or middle Y-position PM at about the middle of ceramic log  101 , and an end position PE just adjacent the opposite endface  148  from initial position PI. The raw scan data from each Y-position is sent to controller  250  via respective scan signals S 2 L and S 2 R, thereby forming two sets of raw two-dimensional scans (“two-dimensional scan data”) that are stored in memory  256 . The two sets of two-dimensional scan data are then combined by processor  254  to form a single set of raw three-dimensional scan data for ceramic log  101 . Note that since scan paths  272 L and  272 R can include portions of tray  114 , the two-dimensional scan data and the three-dimensional scan data can also include tray information (tray scan data). 
         [0049]    The raw scan data are stored in memory  256  and can be analyzed by processor  254  in a variety of ways to establish measurement information about ceramic log  101 . A preliminary data processing step includes finding the ceramic log ends (i.e., the axial locations of endfaces  148 ) by comparing adjacent scan data and finding where the tray measurements end and the outer surface measurements begin. This also provides a measurement of the log length. Once the ceramic logs ends are established, the raw scan data can be separated into log scan data and tray scan data. 
         [0050]    Another preliminary data processing step includes combining the two sets of two-dimensional scan data from laser scanners  270 L and  270 R to obtain a composite two-dimensional scan for each Y-position. This combining step can be carried out in processor  254  based on instructions stored in memory  256 . In an example embodiment, the information from the overlap of scan paths  272 L and  272 R is used to stitch the two two-dimensional scans together to establish a single two-dimensional surface shape for each Y-position.  FIG. 12  illustrates an example two-dimensional measured surface shape  160 ′ as determined by controller  250  from the two-dimensional scan data and displayed on controller display  259 . Major and minor axes MA and MI are shown for reference. Note that an image  101 ′ of ceramic log  101  is displayed as well, showing the Y-position YP at which the scan was taken. 
         [0051]    Once the log scan data is obtained, then the two-dimensional log data can be combined (e.g., in processor  254 ) to form the three-dimensional surface shape.  FIG. 13  illustrates an example three-dimensional image  101 ′ of the measured surface shape of ceramic log  101  as displayed on controller display  259 . Parameters relating to the surface shape can also be calculated and displayed with image  101 ′, such as the measured log length, the amount of bow along the major and minor axes, the maximum amount of bow, bow limit, etc. An example of the measurement values that can be displayed in a window  261  on controller display  259 , along with the three-dimensional image  101 ′, is shown in Table 1 below: 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 EXAMPLE LOG MEASUREMENT VALUES 
               
             
          
           
               
                   
                 PARAMETER 
                 VALUE (INCHES) 
               
               
                   
                   
               
             
          
           
               
                   
                 TOTAL LOG LENGTH 
                 33.51 
               
               
                   
                 BOW - MAJOR AXIS 
                 0.034 
               
               
                   
                 BOW - MINOR AXIS 
                 0.038 
               
               
                   
                 BOW - MAXIMUM 
                 0.041 
               
               
                   
                   
               
             
          
         
       
     
         [0052]    In an example, the amount of bow is established by deducing from the two-dimensional scan data relative height measurements of outer surface  160  at three spaced-apart locations (e.g., at the middle and the respective ends) of ceramic log  101  in analogous fashion to a contact measurement. 
         [0053]      FIG. 14  plots an example of the “profile of the line” (POL) in inches versus the log position (i.e., the Y position along the log) in inches based on hypothetical laser scan data. The plot shows substantial variation in the POL at the ceramic log ends with smaller variations in between. The POL plots can also be displayed on controller display  259 . 
         [0054]    In an example, the results of processing the log scan data and/or the tray scan data in controller  250  to obtain a ceramic log measurement is used to adjust the extrusion process for forming ceramic logs  101 . Because the surface shape of ceramic log outer surface  160  is determined by the extrusion process, and the extrusion process includes many variables such as die shape, flow rate, pressure, moisture content of the batch material, etc., one or more of the extrusion process parameters can be adjusted based on the ceramic log measurements obtained by laser scanning system  200 . 
         [0055]    In one case, if the measured log length is out of specification, then this information can be used to adjust the cutting of extrudate  100  into green ceramic logs at the exit of extrusion unit  90 . In another example, impedance plate  95  in extrusion unit  90  is adjusted to adjust the flow of batch material  34  through die  92  when forming extrudate  100 . For example, when a ceramic log  101  has a “banana” type bow, it is indicative of different flow rates of batch material  34  through die  92 . Thus, when an upward banana-type of bow is measured, impedance plate  95  in extrusion unit  90  is adjusted to reduce the rate of flow through the bottom of the die to reduce or remove the bow. Also, as discussed above, in an example, one or more ceramic log measurements, such as bow and log length, are compared to corresponding limits, such as a bow limit and a log-length limit, to reject ceramic logs  101  that are out of specification. 
         [0056]    In an example, the tray scan data is processed to determine if the tray  114  carrying ceramic log  101  has any shape variations that are being imparted to the ceramic log. The processing of tray scan data by controller  250  can also be used to compare to at least one tray standard to determine which if any trays are non-conforming and, removing the non-conforming trays from the manufacturing process. 
         [0057]    While the disclosure has been described with respect to several preferred embodiments, various modifications and additions will become evident to persons of skill in the art. All such additions, variations and modifications are encompassed within the scope of the disclosure, which is limited only by the appended claims, and equivalents thereto.