Abstract:
Both a system and method for marking honeycomb structures is provided. The system includes a printing station having a print head moveable relative to a log that prints an identification mark for each structure to be cut from the log; an elevation mechanism that positions the log relative to the printing station, sensors for determining a distance between the print head and log; and a length measuring sensor. A processor is connected to the printing station, elevation mechanism, and length measuring sensor which (a) associates an identification code with the log, (b) generates a separate identification mark for each honeycomb structure to be cut from the log, (c) controls the elevation mechanism to place the log at a desired location relative to the print head of the printing station, and (d) receives length data from the length sensor. The processor then determines cut locations for the log that define the ends of the green body honeycomb structures to be cut, and directs the printing station to print one of the identification marks on a location along the length of said log corresponding to one of said structures defined between the cut locations. A method of associating the honeycomb structures with manufacturing data is also provided.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/001,270 filed Oct. 31, 2007, entitled “System and Method for Marking Honeycombs and Associating Manufacturing Data Therewith.” 
    
    
     FIELD 
     This invention generally relates to marking honeycomb structures, and is specifically concerned with a system and method for printing bar codes on honeycomb structures. 
     BACKGROUND 
     Ceramic honeycomb structures are widely used as anti-pollutant devices in the exhaust systems of automotive vehicles, both as catalytic converter substrates in automobiles, and diesel particulate filters in diesel-powered vehicles. In both applications, the ceramic honeycomb structures are formed from a matrix of thin ceramic webs which define a plurality of parallel, gas conducting channels. To reduce the pressure drop that the exhaust gases create when flowing through the honeycomb structure, the web walls are rendered quite thin, i.e. on the order 2-30 mils, depending upon whether the structures are to be used a catalytic converters or diesel particulate filters. In either case, the matrix of cells is surrounded by an outer skin which may be also quite thin. 
     In the first steps of manufacturing such substrates, generally the ceramic-forming ingredients are mixed together with a binder and liquid vehicle to form a paste-like substance which is extruded into a green body honeycomb “log.” These green body logs are next conveyed through a drying station where they are subjected to microwaves, radio-frequency waves or induction currents to set or gel the binder. The log-like honeycomb extrusion may then be cut into segments along its longitudinal axis to form individual green body honeycomb structures, which are then loaded into a kiln. The honeycomb structures are fired at temperatures of typically 1300° C. or higher in order to sinter the batch constituent particles present in the extruded material into a fired ceramic honeycomb structure. The resulting fired ceramic honeycomb structures may then be subjected to a number of other manufacturing steps (such as plugging, washcoating, further firing steps, and packaging) before being rendered into a final product. 
     Due to the thinness of the outer skin and the inner cell-forming webs, the honeycomb structures may be relatively fragile and subject to damage. This is particularly true in the first steps of manufacture, when the web matrix and outer skin is in a green body state, being formed from a dried “clay” of unfused, particulate ceramic-forming ingredients held together by an organic binder. However, certain irregularities can also occur to the substrates during subsequent manufacturing steps from the thermal stresses that the unfinished ceramic structures may undergo during the firing process, and the necessary subsequent mechanical handling of the fired bodies as they are converted into finished products. Such irregularities in the structures may take the form of internal cracks and voids, chips and dents, and separations between the outer skin and the inner matrix of webs. 
     To reduce the occurrence of such irregularities, it would be desirable to have a quality control procedure which allowed the manufacturer to reliably trace any defective ceramic honeycomb structure back to the specific factory, extruder, dryer, kiln, and batch ingredients that it originated from. Such a procedure would allow the manufacturer to review the particular manufacturing parameters used to fabricate the honeycomb structure and to modify its manufacturing operation in order to reduce the occurrence of such irregularities in future articles. Accordingly, it is a known procedure to mark, after the final firing or heating step, finished ceramic honeycomb structures with marks containing manufacturing information so that remedial manufacturing operations may be implemented in the event of irregularities. 
     Unfortunately, the applicants have observed that such a marking procedure does not reliably result in an accurate recovery of the manufacturing information associated with a particular ceramic honeycomb structure. In particular, the applicants have observed that subsequent to the manufacture of the green bodies of such structures, different batches of ceramic structures come from different kilns necessarily become mixed together in order to efficiently implement other stages of the fabrication process. Additionally, different unfinished ceramic structures may be removed from one or more manufacturing loops, put into storage, and then later reintroduced into another manufacturing loop. Hence a quality control process where manufacturing information is printed on the finished ceramic honeycomb structures may not accurately reflect the actual manufacturing conditions and history of the structures, as structures which end up adjacent to one another in the final stages of manufacturing might have quite different manufacturing histories. 
     SUMMARY 
     Generally speaking, the invention is both a system and method for marking a honeycomb structure cut from an extruded log of ceramic-forming ingredients. To this end, the system of the invention comprises a printing station having a print head that is moveable relative to the log and that prints a separate identification mark for each green body structure to be cut from the log; a positioning station that positions the log relative to the printing station, and that includes sensors for determining a distance between the print head and the log; and a length measuring sensor that measures a length of the log. 
     A processor is connected to the printing station, positioning station, and length measuring sensor which (a) associates an identification code with the log, (b) generates a separate identification mark for each structure to be cut from the log, (c) controls the positioning station to place the log at a desired location relative to the print head of the printing station, and (d) receives length data from the length sensor. The processor then determines cut locations along the length of the log that define green body honeycomb structures to be cut, and directs the printing station to print one of the identification marks on a location along the length of said log corresponding to one of said structures defined between the cut locations. 
     The printing station preferably includes a non-contact ink jet type printer capable of printing a two-dimensional bar code in heat resistant ink on the side of the log. The print head is connected to a carriage assembly capable of moving it along the length of the log and adjusting the distance between the print head and the log. The length measuring sensor is preferably an optical sensor that is also connected to the carriage assembly, and the processor determines the length of the log by monitoring the distance that the carriage assembly moves the length measuring sensor from one end of the log to the other. Finally, the printing station includes a mark reader that optically scans the printed marks and relays the resulting image data to the processor, which compares the actual mark image with the mark intended to be printed, and determines whether the actual mark passes quality control. 
     The positioning station preferably includes a carrying tray coupled to an elevation mechanism. The carrying tray carries the log in a horizontal position. The elevation mechanism raises the tray and log into a printing position, and isolates it from vibration and other environmental influences that could adversely affect the printing of the bar code. The elevation mechanism has at least one optical sensor for monitoring the location of the log, and elevates the tray into a position where the apex of the log is at a desired distance from the print head and parallel to the path that the carriage assembly moves the print head. The carrying tray includes an identification code that is readable by an optical reader. An optical reader included within the printing station reads the identification code and transmits the identification code to the processor so that the particular log and its manufacturing history can be associated with the green body honeycomb structures ultimately cut from the log. 
     In another aspect, a method for marking a honeycomb log is provided, comprising the steps of associating an identification code with said log formed of ceramic-forming ingredients; determining multiple cut locations along a length of the log that define unfinished honeycomb structures that will result from cutting said log; generating a separate identification mark for each structure to be cut from said log, and printing one of said identification marks to a location along the longitudinal axis of said log corresponding to one of said structures. 
     By marking the log before the green body honeycomb structures are cut therefrom, the system and method of the invention advantageously produces individually marked green body honeycomb structures without the need for individually handling and marking them in their relatively fragile, pre-fired green body state. Additionally, the provision of an identification code on the carrying tray, and of an optical reader in the printing station capable of reading the identification code and transmitting it to the processor allows the processor to virtually track the initial manufacturing conditions of the log and to associate this early manufacturing history data with each of the green body honeycomb structures cut from the log. 
     According to another aspect, a method of manufacturing a honeycomb green body is provided, comprising the steps of extruding a honeycomb green body of ceramic-forming ingredients, placing the honeycomb green-body on a tray including an tray identification code, passing the honeycomb green-body on the tray through a dryer, and associating in a database, the tray identification code with manufacturing data selected from the group of batch data, extruder data, and dryer data. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  illustrate the application of the system of the invention prior to the marking of a green body log from which ceramic structures are ultimately cut from, wherein a plurality of sensors/inputs provided from the ceramic paste dispenser, the extruder, and/or the drying station relay the initial manufacturing history of the green body log to the digital processor of the system, and wherein the dried, green body log is loaded on to a conveyor tray of the system which has an optically readable identification tag that allows virtual identification of the extrusion upon arrival to the printing station of the system. 
         FIG. 2  is a simplified, perspective view of the printing station of the system, illustrating how the printing station determines the cut locations and mark locations (both of which are indicated in phantom) on the green body log prior to applying unique, identifying marks along the longitudinal axis of the log. 
         FIG. 3A  illustrates the application of the system of the invention after the marking of the green body log, wherein sensors/inputs provided from the cutting station continue relay the manufacturing history of the log during and after the cutting of the marked log into individual, marked green body honeycomb structures. 
         FIG. 3B  is an enlarged perspective view of one of the marked, green body honeycomb structures that the system produces. 
     
    
    
     DETAILED DESCRIPTION 
     With reference now to  FIG. 1A , wherein like numerals designate like components throughout all of the several figures, the system  1  of the invention initially monitors and records the manufacturing history of the log  3 , which is typically an extrusion of ceramic-forming ingredients from which individual, green-body honeycomb structures are ultimately cut. However, it should be recognized that the present invention is applicable to log structures made by any method, such as casting, molding, etc. To this end, the system  1  includes a digital processor  5  connected to a data input point  7  associated with a dispenser  9  of ceramic precursor paste, and an additional data input point  11  located associated with the extruder  13  that forms the log  3 . In the first stages of manufacture of the log  3 , the dispenser  9  dispenses a preselected quantity of ceramic precursor paste in to an inlet  14  of the extruder. A mechanism (such as a ram or conveyor screw(s)) within the body of the extruder  13  forces the ceramic paste through a die assembly  15  having an extrusion die  16 . The extrusion die  16  has a large number of closely spaced intersecting slots surrounded by an opening that create an extrudate  17  that is initially supported by an air-bearing tray  18 . The resulting extrudate  17  includes a core formed from a honeycomb matrix of ceramic webs  19  surrounded by a skin  20  which may be, for example, cylindrical or elliptical (best seen in  FIG. 3B ). The air-bearing tray  18  supports the extrudate  17  as it is conveyed to a cutting station  21 , which periodically cuts the extrudate into green body logs  3 , which are individually loaded onto conveyor trays  22 . A suitable tray is described in U.S. Pat. No. 5,406,058. 
     During these initial stages of extrusion manufacture, the data input point  7  may relay to the processor  5  data concerning the specific recipe (type and amount) of particulate ceramic batch ingredients and particular type and amount of liquid vehicle, organic binder and other processing ingredients used to form the ceramic precursor paste, and may include such items as the date, time, and ambient humidity, temperature conditions, and/or other relevant manufacturing data. The data input point  11  may relay data to the processor  5  concerning the identity of the extruder  13 , the pressure of the ceramic precursor paste, extrusion rates, etc. as the batch is squeezed through the die assembly  15 , the date that the extruder  13  was last subjected to routine maintenance, the temperature of the ceramic-forming paste during the extrusion operation, and/or other relevant extruder data. The data input points  7 ,  11  may include monitoring sensors that continuously and automatically relay such manufacturing data to the processor  5 . Alternatively, such data may be manually inputted into the data input points  7 ,  11  by human operators or scanning operations. The processor records and associates the inputted batch manufacturing data with a particular batch of extrudate  17  via a time delay based on the extrusion rate. 
     With reference now to  FIG. 1B , a conveyor  25  having a moving belt  26  that transports the conveyor tray  22  that supports the newly formed green body log  3  to the drying station  30 . The drying station  30  may includes a plurality of radiation emitters  31  capable of emitting a type and frequency of radiation (i.e. microwave, or radio-frequency) or of inducing a heat-creating electrical current that promotes the setting/gelling of the binder in the green body log  3  and removal of at least a portion of the liquid vehicle therefrom. A data input point  27  is connected both to the processor  5  and the control circuitry of the drying station  30 . During the drying operation, the input  27  may relay data to the processor  5  concerning the drying conditions, type and frequency of drying radiation used in the drying station  30 , the power levels used, the duration of the drying operation, the ambient temperature, date, and time of day, and ambient humidity. The processor  5  records this dryer data and associates it with the data received from the batch and extrusion data from input points  7 ,  11 . 
     After the log  3  has been processed through the drying station  30 , the tray  22  and log  3  are transferred to the printing station  40  of the system  1 . The conveyor tray  22  includes a cradle portion  23  which has a semi-circular or semi-elliptical recess  34  (best seen in  FIG. 2 ) along its longitudinal center line that is complementary in shape to the rounded bottom contour of the log  3 . The tray may be isolated by a shock-absorbing material to isolate the log  3  from extraneous vibrations during the printing operation. Finally, the conveyor tray  22  includes an tray identification code  36  in the form of a tag or label on an end of the tray, and the drying station  30  includes a tray ID code reader  37  which allows the processor  5  to associate the manufacturing history generated from the data provided by the data input points  9 ,  11 , and sensor  27  with a the tray and a specific log  3 . Accordingly, the manufacturing data of at least one, and preferably all, selected from the group of the batch ingredient data, extruder data, and dryer data, may be associated in a database by the processor  5  to a specific log  3 . 
     With reference now to  FIG. 2 , the log  3  is transported in the conveyor tray  22  to the elevation mechanism  56  of the printing station  40  of the system  1 . The printing station  40  includes a non-contact print head  42 , which is preferably an ink-jet print head capable of printing the combination of a two dimensional bar code and alphanumeric code on the side of the log  3 . The ink is preferably a heat resistant ink. An example of a suitable print head is the XenJet QX500 printer available form Xennia Technology, Inc., having an office located in San Antonio, Tex. The print head  42  is mounted on a conveyor assembly  44  comprising a frame  45  and a carriage  46 . The carriage  46  is movable along a rail aligned with an X-axis. The carriage  46  includes adjustably-movable, orthogonally disposed arms  48   a ,  48   b  connected to the printed head  42  and oriented along Y and Z axes, respectively. The carriage  46  further includes three electric servo-motors mechanically connected to the rail  47  and arms  48   a ,  48   b  via appropriate mechanical linkages (not shown), and electrically connected to a power source (also not shown) that is controlled by the processor  5 , such that the processor  5  is able to actuate the servo-motors to position the print head  42  at a selected position along the X, Y and Z axes. While the printing operation is generally carried out along the X axis, the carriage  26  is capable of moving the print head  42  along the Y axis to maintain the printing along the apex  38  of the log  3  by compensating for any slight bending of the log  3 . 
     Also mounted on the movable carriage  46  are a length measuring sensor  50 , an identification mark camera  52 , and a mark blotter  54 . Each of these components is electrically connected to the processor  5 . The length measuring sensor  50  enables the processor  5  to measures a length of the log  3 , while the identification mark camera  52  determines whether the marks printed on the side of the log  3  by the print head  42  are machine legible and pass quality control standards. In the preferred embodiment, the length measuring sensor may be a simple photosensor capable of generating a signal indicating the presence or absence of a log directly under the carriage  46  from variations in the amplitude of light received, and the processor may to programmed to determine the length of the log  3  by scanning the sensor  50  along the X-axis rail  47  and noting the X-axis locations where the sensor commences a “log present” signal and a subsequent “log absent” signal. The identification mark camera  52  electronically photographs the actual marks printed by the print head  42 , and transmits the resulting image signal to the processor  5 . The processor  5  compares the image of the actual printed mark to an image of the mark intended to be printed and determines whether the printed mark passes or fails quality control standards. If the processor  5  determines that the printed mark fails quality control standards, it actuates the mark blotter  54 , which prints over the defective mark. 
     The elevation mechanism  56  of the printing station  40  raises and orients the conveyor tray  22  such that the log  3  is in a horizontal position parallel to the X-axis rail  47  with its apex  38  directly under the print head  42 . For this purpose, the elevation mechanism  56  includes a lift which lifts the tray off from a pair of slides  57   a ,  57   b , wherein the lift is operated by a hydraulically powered units  56   a  which affords a smooth and easily controlled lifting action which allows the station operator to accurately place the log  3  in a printing position. The elevation mechanism  56  further includes shock and vibration-absorbing support  56   b  for isolating the log  3  from vibration present in the floor of the factory during the printing operation. Such supports may take the form of rubber or silicone pads between the lift and the tray. Log height sensors  58   a ,  58   b  are mounted on the frame  45  of the printing station in opposing relationship, while a position camera  60  is mounted at a middle point between the position sensors. Like the previously described length sensor  50 , the log height sensors may be simple optical sensors that transmit a “log present” or “log not present” signal to the microprocessor, while the position camera  60  transmits a signal to the processor  5  indicative of the distance between the apex  38  of the log  3  and the print head  42 . The station operator monitors the log position output of the processor  5  while operating the hydraulic unit that controls the elevation mechanism  56  in order to precisely place the log  3  in a printing position. Finally, the printing station  40  includes an optical reader  62  for reading the identification code  36  on the tray  22  and transmitting this code via an electric signal to the processor  5 . 
     In operation, a log  3  is transported to the printing station  40  via the previously described tray  22 . The lift of the elevation mechanism  56  are positioned under the tray  22 . The optical reader  62  is scans the identification code  36  of the cradle portion, and the processor  5  assigns an identification number to the log  3  in the cradle, and relates the manufacturing history previously relayed to it from the data input points  7 ,  11 , sensor  27  and  37  to the log  3 . The station operator raises the elevator  56  via the previously mentioned hydraulic unit to raise the tray  22  until the log  3  is properly oriented within the station  40 . During this step, the station operator monitors the output of the log height sensors  58   a ,  58   b  and position camera  60  via the processor  5  until the log is properly aligned with the X,Y and Z axes of the station  40  with the log apex  38  a proper distance from the print head  42 . 
     The processor  5  next determines a length of the log  3  in the manner previously described by scanning the length measuring sensor  50  over the X-axis of the log  3  via the carriage  56 . The processor  5  then determines the cut locations  64  along the X-axis of the log, and further computes mark locations  65  along the X-axis. The mark locations  65  are selected to be between the cut locations  64 , and are preferably nearer one end of the green body honeycomb structures to be cut from the log  3 . The processor  5  then assigns a unique identification mark  75  to each of the mark locations  65  (which, as shown in  FIG. 3B , preferably comprises a combination of a two dimensional bar code  76  and an alphanumeric code  77 ). At the same time, the processor associates and records these unique identification marks  75  with the manufacturing history data of the log  3  in the data base. 
     The processor  5  next executes a printing operation by moving the print head  42  along the X-axis of the log  3  and printing a unique identification mark  75  at every mark location  65 , for example, in a heat resistant ink. After each mark is printed, it is inspected by the identification mark camera  52 . If the processor determines that the mark fails quality control, the mark blotter  54  is positioned over the defective mark and prints over it. The processor  5  then positions the print head  42  in a different position between the cut locations  64  defining the green body to be cut from the log  3 , and re-actuates the print head to re-print the mark, which is re-inspected by the identification mark camera  52 . Advantageously, the shock-absorbing characteristics of the isolator of the conveyor tray  22  effectively isolate the log from vibration during printing, which could otherwise result in the marring of the resulting printed identification marks  75 . 
     After the log  3  is printed, it is transported to a cutting station  66  as illustrated in  FIG. 3A . Cutting station  66  has a rotary saw blade  67  that is oriented orthogonally to the longitudinal axis of the log as shown. The saw blade  67  is rotated by a motor  68  mounted on a lifting and lowering assembly  69 . The system  1  includes a sensor  70  that continues to relay manufacturing history data to the digital processor  5 , such as the blade ID, number of cuts the blade  67  has made, its rotational speed, ambient humidity conditions, etc. The log  3  is transferred to a pair of supports  71   a ,  71   b  that allow the saw blade  67  to cut completely through the log  3  at a cut location  64  disposed between the V-chuck supports  71   a ,  71   b . In operation the marked log  3  is fed in the direction of arrow  72  until a cut location  64  is aligned with the saw blade  67 . The saw blade  67  is lowered into the position shown in phantom, thereby cutting the log  3 , and forming an individual green body honeycomb structure  74  bearing a unique identification mark  75 . The processor  5  records all of the cutting data generated by the data transmitted by the sensor  70  as well as any other cutting data input from the cutting step, and associates it the log  3  and with each of the resulting individual cut green body honeycomb structures  74 . The structures  74  are then transported away from the cutting station  66  such as by conveyor unit  73  to either storage or other manufacturing stations. 
       FIG. 3B  illustrates an example of an individually marked green body honeycomb structure  74  produced by the marking system  1 . As previously indicated, the mark  75  preferably formed from a combination of a two dimensional bar code  76  and an alphanumeric code  77  that uniquely identifies the structure so that the manufacturing history data stored a database by the processor  5  can be associated with it. A two dimensional bar code  77  can be used instead of a one dimensional bar code as a substantial portion of a two dimensional bar code can be obliterated without losing the identification code embedded within it. The provision of an alphanumeric code  77  in the mark  75  that stores the identifying code in human readable form can be convenient for use by human handlers. 
     Different modifications, additions, and variations of this invention may become evident to the persons in the art. All such variations, additions, and modifications are encompassed within the scope of this invention, which is limited only by the appended claims, and the equivalents thereto.