Patent Publication Number: US-2020298441-A1

Title: Method of modifying a honeycomb-structure-forming extrusion die and modified extrusion dies

Description:
This application claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application No. 62/819,879 filed on Mar. 18, 2019, the content of which is incorporated herein by reference in its entirety. 
    
    
     FIELD 
     Embodiments described herein generally relate to methods for modifying an extrusion die. Specifically, embodiments described herein relate to methods for modifying a honeycomb extrusion die in order to produce extruded articles having complex geometries. 
     BACKGROUND 
     Honeycomb extrusion dies are used to produce extruded honeycomb structures, such as to produce a honeycomb substrate for catalysts in catalytic converters. Known honeycomb extrusion dies can be formed by wire electrical discharge machining (EDM). In wire EDM, a current is passed through an electrically conductive wire which is used to cut slots in a face of an extrusion die bar stock. Wire EDM can be used to form linear slots. However, wire EDM cannot be used to form a extrusion patterns of more complex configurations, such as patterns with discontinuous slots. While more complex patterns may be prepared using plunge EDM in which an electrode is used to form the slots in the extrusion die to provide the extrusion die with the desired pattern, plunge EDM can be a relatively time-consuming and expensive method for producing an extrusion die. 
     Accordingly, there is a need in the art for a method for manufacturing an extrusion die to enable the extrusion die to produce extruded articles with more complex honeycomb patterns. 
     BRIEF SUMMARY OF THE INVENTION 
     In a first aspect, a method of manufacturing a honeycomb-structure-forming extrusion die having a plurality of slots includes inserting a die insert that includes a runner and a plurality of teeth into a slot of the plurality of slots of the extrusion die such that each of the plurality of teeth blocks at least a portion of the slot, and separating the runner from the plurality of teeth such that the plurality of teeth remain within the slot of the plurality of slots of the extrusion die. 
     In a second aspect according to the preceding paragraph, the plurality of teeth of the die insert are spaced from one another along a longitudinal axis of the runner. 
     In a third aspect according to either of the preceding paragraphs, the method further comprises forming the die insert that includes the runner and the plurality of teeth such that the plurality of teeth are arranged on the runner in a blocking configuration for blocking a plurality of portions of the slot. 
     In a fourth aspect according to the previous paragraph, forming the die insert comprises machining a stainless steel sheet. 
     In a fifth aspect according to the third paragraph, forming the die insert comprises photochemical machining of a metal sheet. 
     In a sixth aspect according to any of the three preceding paragraphs, forming the die insert comprises include coating the plurality of teeth of the die insert. 
     In a seventh aspect according to the preceding paragraph, the coating comprises plating. 
     In an eighth aspect according to the preceding paragraph, the plating comprises nickel plating. 
     In a ninth aspect according to any of the three preceding paragraphs, prior to coating, a thickness of each tooth is less than a width of the slot, and after coating the thickness of each tooth is at least as thick as the width of the slot. 
     In a tenth aspect according to any of the seven preceding paragraphs, forming the die insert comprises forming each of the plurality of teeth with a thickness corresponding to a width of a slot of the plurality of slots of the extrusion die. 
     In an eleventh aspect according to any of the eight preceding paragraphs, each of the plurality of teeth comprises a first end connected to the runner and a second end, and wherein forming the die insert includes preparing each of the plurality of teeth such that a thickness of the first end of each of the plurality of teeth is greater than a thickness of the second end of each of the plurality of teeth. 
     In a twelfth aspect according to any of the preceding paragraphs, the method further comprises inserting a shim into a slot of the plurality of slots prior to inserting the die insert into a slot of the plurality of slots of the extrusion die. 
     In a thirteenth aspect according to the preceding paragraph, the method comprises inserting the shim into a slot of the plurality of slots of the extrusion die in an orientation perpendicular to the die insert. 
     In a fourteenth aspect according to either of the two preceding paragraphs, the method comprises removing the shim and subsequently securing the plurality of teeth to the extrusion die. 
     In a fifteenth aspect according to any of the preceding paragraphs, separating the runner from the plurality of teeth comprises separating the runner by wire electric discharge machining or plunge electric discharge machining. 
     In a sixteenth aspect according to any of the preceding paragraphs, the method further comprises securing the plurality of the teeth to the extrusion die by plating the plurality of teeth and the extrusion die. 
     In a seventeenth aspect according to the preceding paragraph, plating is performed using nickel or a nickel alloy. 
     In an eighteenth aspect according to any of the preceding paragraphs, the method further comprises preparing a plurality of die inserts and inserting the plurality of teeth of each of the plurality of die inserts into the plurality of slots of the extrusion die. 
     In a nineteenth aspect, some embodiments relate to an extrusion die formed by a method according to any of the preceding paragraphs. 
     In a twentieth aspect, a method of modifying a honeycomb-structure-forming extrusion die having a plurality of slots includes inserting a first die insert into a first slot of the plurality of slots of the extrusion die such that each of a first plurality of teeth of the first die insert blocks a portion of the first slot, the plurality of teeth extending from a first runner of the first die insert, separating the first runner from the first plurality of teeth of the first die insert, inserting a second die insert into a second slot extending perpendicularly to the first slot such that each of a second plurality of teeth of the second die insert blocks a portion of the second slot, and such that the second plurality of teeth of the second die insert mate with the first plurality of teeth of the first die insert, the second plurality of teeth extending from a second runner of the second die insert, and separating the second runner from the second plurality of teeth of the second die insert. 
     In a twenty-first aspect according to the previous paragraph, wherein each of the first plurality of teeth of the first die insert has a first end connected to the first runner and a second end opposite the first end, wherein each of the first plurality of teeth comprises a slit extending from the first end towards the second end; and wherein each of the second plurality of teeth of the second die insert has a first end connected to the second runner and a second end, wherein each of the second plurality of teeth comprises a slit extending from the second end towards the first end, such that the first die insert and the second die insert mate by engaging the slits on the plurality of teeth of the first die insert with the slits of the plurality of teeth of the second die insert. 
     In a twenty-second aspect according to the preceding paragraph, the method comprises inserting the first plurality of teeth of the first die insert into a slot of the plurality of slots such that the slit of each of the first plurality of teeth is arranged at an intersection of two slots. 
     In a twenty-third aspect, a method of modifying a honeycomb-structure-forming extrusion die having a plurality of slots includes forming a die insert that includes a runner and a plurality of teeth, wherein the plurality of teeth are spaced from one another along a longitudinal axis of the runner, inserting the die insert into a slot of the plurality of slots of the extrusion die so that a material cannot be extruded through the portions of the slot of the extrusion die in which the plurality of teeth are inserted, and separating the runner from the plurality of teeth such that the plurality of teeth remain within the slot of the plurality of slots of the extrusion die. 
     In a twenty-fourth aspect, an extrusion die includes a plurality of pins defining a plurality of intersecting slots therebetween with at least one slot extending in a first direction across an entire discharge face of the extrusion die and at least one slot extending in a second direction across the entire discharge face of the extrusion die, the second direction being transverse to the first direction; and a plurality of teeth located in a slot of the plurality of intersecting slots extending in the first direction so as to block a flow of material through at least a portion of the slot during extrusion. 
     In a twenty-fifth aspect according to the preceding paragraph, each of the plurality of teeth comprises a coating. 
     In a twenty-sixth aspect according to the preceding paragraph, the coating is a nickel plating. 
     In a twenty-seventh aspect according to any of the three preceding paragraphs, a thickness of each tooth of the plurality of teeth is at least as thick as a width of the slot of the plurality of intersecting slots. 
     In a twenty-eighth aspect according to any of the four preceding paragraphs, the plurality of teeth are further located in a slot extending in the second direction. 
     In a twenty-ninth aspect according to any of the five preceding paragraphs, the plurality of pins are arranged in a square grid. 
     In a thirtieth aspect according to any of the six preceding paragraphs, each of the plurality of teeth have a height that is the same as or greater than a depth of the slot of the plurality of slots. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         FIGS. 1A-1C  show examples of extruded articles having complex honeycomb patterns formed using extrusion dies produced by a method according to an embodiment disclosed herein. 
         FIG. 2  shows a close-up view of a portion of an unmodified extrusion die according to an embodiment. 
         FIG. 3  shows a plan view of a die insert according to some embodiments. 
         FIG. 4  shows a side view of the die insert of  FIG. 3 . 
         FIG. 5  shows a plurality of die inserts formed from a metal sheet by a machining process according to an embodiment. 
         FIG. 6  shows a perspective view of an extrusion die having a plurality of die inserts and shims inserted therein according to an embodiment. 
         FIG. 7  shows a perspective view of a modified extrusion die according to an embodiment. 
         FIG. 8  shows an isometric view of a portion of an extruded article forming using a modified extrusion die according to an embodiment. 
         FIG. 9  shows a plan view of a portion of a die insert according to an embodiment. 
         FIG. 10  shows a plan view of a portion of a die insert according to an embodiment. 
         FIG. 11  shows a perspective view of the mating of a first tooth with a second tooth according to an embodiment. 
         FIG. 12  shows a perspective view of a portion of a modified extrusion die according to an embodiment. 
         FIG. 13  shows a perspective view of a portion of an extruded article with a complex honeycomb pattern formed using a modified extrusion die according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention(s) will now be described in detail with reference to embodiments thereof as illustrated in the accompanying drawings. References to “one embodiment,” “an embodiment,” “an exemplary embodiment,” etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. 
     Honeycomb extrusion dies are used to produce extruded articles having a honeycomb pattern. Such extruded articles may be used in a variety of applications, such as substrates for catalysts in catalytic converters or as particulate filters. The honeycomb structure provides a large surface area on which the catalyst can be placed and/or particulate matter can be captured. However, it may be desirable to form a catalyst substrate or particulate filter with more complex geometry, which may result in improved performance of the honeycomb article, such as reduced pressure drop, increased ash storage capacity, filtration efficiency, and reduced sensitivity to plugging of the substrate, among others. Using known methods for forming extrusion dies, such as wire EDM or abrasive wheel slitting, extrusion dies can only be formed by a series of linear slots extending across an entirety of a discharge face of the die (e.g., from one side of the extrusion die to an opposing side and/or as a chord connected between two points on the circumference of a circular-shaped extrusion die), so as to form a conventional grid pattern. Extrusion dies so formed cannot be used produce extruded articles having more complex patterns, such as patterns including discontinuous sections, or extruded articles having openings of different sizes and shapes. 
     While other methods exist for forming honeycomb extrusion dies capable of producing complex extruded articles, other methods, such as plunge EDM, may be time consuming and expensive. Plunge EDM utilizes an electrode which is separately prepared. Further, the electrode may deteriorate after multiple uses and may need to be replaced. Wire EDM is used to form honeycomb extrusion dies, although for producing features of honeycomb structures which are relatively simple (e.g., having slots that each extend as a continuous straight line across the face of the die). 
     Embodiments disclosed herein comprise selectively blocking portions of otherwise straight and continuous slots of an extrusion die in order to create more complex honeycomb patterns for the article extruded by the extrusion die. The term “block” or “blocking” as used herein means stopping, hindering, preventing, reducing, or otherwise impeding. Examples of more complex honeycomb patterns that can result from the embodiments disclosed herein can be appreciated from  FIGS. 1A-1C . More particularly, the patterns of  FIGS. 1A-1C  resemble a square grid of alternating walls (corresponding to the slots of the extrusion die used to make the honeycomb structure) and channels (corresponding to the pins of the extrusion die used to make the honeycomb structure), but with a plurality of discontinuous sections  505  (some of which shown in dashed lines) at which the walls are discontinuously broken. In other words, absent the discontinuous sections  505 , the patterns of  FIGS. 1A-1C  would resemble a continuous grid of equally sized squares. It is to be appreciated that an extrusion die including only continuous straight slots can be utilized to create other honeycomb patterns, such as triangle- or parallelogram-shaped channels. 
     A portion of an extrusion die  300  is shown in  FIG. 2 , having a discharge face  310  comprising pins  315  defining a plurality of intersecting slots  320  therebetween. The slots  320  have a width w 2 , which can be consistent for every slot  320  in the die  300  or variable for different ones of the slots  320  or for different portions of the same slot. Each of the pins  315  has a width w 3 , which can also be consistent for every one of the pins  315  in the die  300  or variable for different ones of the pins  315 , or for different directions of the pins  315 . 
     Some embodiments herein relate to a method for manufacturing a honeycomb extrusion die by inserting a die insert  100  (as shown for example in  FIG. 3 ) having a runner  120  and a plurality of teeth  140  into one or more of the slots  320  of the extrusion die  300  so as to block a plurality of portions  324  of slot  320  to prevent material from extruding through the blocked portion of slot  320 . Once die insert  100  is inserted into slot  320  of extrusion die  300 , runner  120  can be separated from plurality of teeth  140  so that the teeth  140  remain in slot  320  when the runner  120  is removed. The teeth  140  can be secured to extrusion die  300 , such as by a friction or interference fit, welding, bonding, adhesives, etc. Thus, when the modified extrusion die is used to form an extruded article, extruded material is unable to flow through the portions  324  of the slots  320  that are blocked by teeth  140 , resulting in an extruded article having a complex honeycomb pattern with discontinuous walls, e.g., having the discontinuous sections  505 . In this way, even if the slots  320  are initially formed as continuous straight slots, the blocking effect of the teeth  140  effectively causes the slots  320  to extrude material in a pattern having discontinuous sections, i.e., as if the slots  320  did not extend fully across the discharge face from one side of the discharge face to an opposing side. 
     Some embodiments herein include a die insert  100  configured to block portions  324  of slots  320  of extrusion die  300 . By blocking a portion  324  of a slot  320  of an extrusion die  300 , an extruded article can be formed that corresponds to the shape of the portions of the slots  320  that are not blocked. That is, each of the portions  324  that is blocked by one of the teeth  140  will create a corresponding discontinuous section  505  in the extruded honeycomb pattern. Thus, extrusion die  300  can be arranged to produce extruded articles with more complex patterns, such as shown for example at  FIGS. 1A-1C  as extruded articles  500 ,  510 , and  520 . As shown in  FIGS. 1A-1C , the extruded articles  500 ,  510 ,  520  can be formed to have complex patterns other than a square grid pattern, and can have regions with larger openings or different shaped openings. 
     A plurality of feedholes are in communication with the plurality of slots  320  so as to supply extrudable material (e.g., a ceramic-forming mixture) to the slots  320 , which is extruded by the slots  320  at the discharge face  310 . As shown in  FIG. 3 , the plurality of slots  320  can include a plurality of spaced and parallel slots  320  extending in a first direction along or parallel to axis X, and a plurality of spaced and parallel slots  320  extending in a second direction along or parallel to axis Y. When the first direction is perpendicular to the second direction, the discharge face  310  resembles a grid of squares. However, other patterns formed by crisscrossing straight continuous slots are possible, such as with respect to triangular- or parallelogram-shaped pins. In some embodiments, the first direction is arranged at an angle other than perpendicular to the second direction so as to form a grid of parallelogram or diamond shapes, while slots arranged at various angles with respect to three different directions can be arranged to form a grid of triangles. Extrusion die  300  is configured to produce an extruded article by flowing an extrudable material through the slots  320 , so as to produce an article with a pattern of slots  320 . 
     As used herein, an “intersection”  328  of slots  320  of extrusion die  300  is defined as a location where two slots  320  of extrusion die  300  intersect. As used herein, a “portion”  324  of a slot  320  includes any length of a slot  320  that is less than the entire length of slot  320 . In some embodiments, the portion  324  comprises a length of a slot  320  between two adjacent intersections  328 . However, portion  324  can be a smaller or greater length in order to block the desired amount or length of slot  320 . 
     According to some embodiments, one or more die inserts  100  are inserted into a slot  320  of an extrusion die  300  so as to block a plurality of portions  324  of slot  320 . Each of the plurality of teeth  140  includes a first end  142  connected to runner  120  and a second end  144  to be inserted into a slot  320 . Teeth  140  are configured to be inserted into a slot  320  of extrusion die  300  so as to block a portion  324  of slot  320  to prevent extruded material from flowing through that portion  324  of slot  320 . Teeth  140  are arranged on runner  120  in a configuration that corresponds to the arrangement of pins  315  and slots  320  for blocking a plurality of portions  324  of a slot  320  of extrusion die  300 . In this way, the extrusion die  300  can be used to produce an extruded article with a desired pattern comprising discontinuities (e.g., the discontinuous sections  505 ) corresponding to each of the portions  324  that are blocked by the teeth  140 . Teeth  140  are spaced from one another along a longitudinal axis Z of runner  120 . Teeth  140  can be arranged along runner  120  in a blocking configuration for blocking one or more portions of a slot  320 . In some embodiments, teeth  140  are arranged along runner  120  at a fixed interval. Thus, die insert  100  allows for a plurality of portions  324  of a slot  320  to be blocked at the same time by simultaneously inserting the plurality of teeth  140  into a slot  320  with a single one of the runners  120 , as opposed to individually placing a tooth in each portion of a slot to be blocked. 
     Each of the plurality of teeth  140  can have the same shape and dimensions, or different shapes and dimensions. Teeth  140  can have a height, h 1 , that is the same as or greater than a depth of a slot  320  of extrusion die  300  such that teeth  140  fill the depth of slot  320  and runner  120  is positioned above discharge face  310  of extrusion die  300  when teeth  140  are inserted into slot  320 . Each of the plurality of teeth  140  has a width w 1  measured in a direction parallel to longitudinal axis Z of die insert  100 . The width w 1  can be selected so as to block a desired portion  324  of a slot  320  of extrusion die  300 . For example, the width w 1  of the tooth  140  can be approximately the same as a width w 3  of the pins  315  so that the tooth spans between two adjacent intersections  328  of a slot  320 . In other embodiments, the width w 1  of the teeth  140  differs from width w 3  of pins  315 . In one embodiment, the width w 1  is greater than the width w 3  such that each tooth  140  extends in a slot  320  across multiple of the pins  315 . 
     Each tooth  140  has a thickness, t 1 , as best shown in  FIG. 4 , that is measured in a direction from a first surface  146  of tooth  140  to the opposing surface  147 . In some embodiments, the thickness t 1  of each tooth  140  is the approximately the same as, or slightly thicker than the width w 2  of a slot  320  such that the thickness t 1  corresponds to the width w 2  of slot  320 . In this way, each tooth  140  fills the entire width w 2  of the portion  324  of slot  320  so as to block extruded material from flowing through that portion  324  of slot  320  during extrusion. In some embodiments, a second end  144  of each of the plurality of teeth  140  has a thickness t 2  that is less than the thickness t 1  of the remainder of the tooth  140  so as to facilitate insertion of each tooth  140  into a slot  320  of extrusion die  300 . In some embodiments, thickness t 2  of second end  144  of each tooth  140  is about 40 to 60% less than the thickness t 1  of the remainder of tooth  140 . The teeth  140  can be tapered toward second end  144  and/or have a region  148  of reduced thickness. 
     Die insert  100  can be formed by machining a sheet of metal, such as stainless steel, to form runner  120  and teeth  140  in the desired arrangement on runner  120 . As shown in  FIG. 5 , a plurality of die inserts  100  are formed simultaneously from a sheet  105  of metal. Die insert  100  can be formed by any of various methods including, for example, photochemical machining of a metal sheet, wire EDM, or water jet machining, among other methods. 
     In some embodiments, forming die insert  100  additionally includes coating, covering, or plating die insert  100 . Die insert  100  can be coated, e.g., plated, with any suitable material, such as nickel or a nickel alloy. Coating processes such as electroplating or other plating techniques can be used to adjust the thickness of die insert  100  so that the thickness of the coated die insert  100  is the same as or slightly greater than width w 2  of slots  320  to ensure that when die insert  100  is inserted to slot  320 , die insert  100  fits tightly within slot  320 . In some embodiments, coating, e.g., plating, results in the thickness t 1  of each tooth  140  being the same as w 2  or as much as 0.0003 inches larger than w 2 . In some embodiments, the thickness t 1  is about 0.001 to 0.002 inches thinner than the width w 2  of the slots  320  before the teeth are plated. In addition to setting the final dimensions (e.g., thickness t 1 ) of the teeth  140  to assist in frictionally securing teeth  140  to die  300 , the coating, e.g., plating, can be selected to provide an abrasion-resistant layer. 
     Die inserts  100  can be inserted into slots  320  on the face  310  of extrusion die  300  as shown in  FIG. 6 . In some embodiments, one or more shims  160  can be inserted into the slots  320  of extrusion die  300  to facilitate alignment of die inserts  100  within slots  320 , so that teeth  140  of die insert  100  block a desired portion of slot  320 . Shim  160  can be formed as a rectangular plate or strip and is configured to be inserted into a slot  320  along the length of the slot  320 . Shims  160  can be manually placed in the desired slots  320  for aligning die inserts  100 . Shims  160  can be loosely positioned within slots  320  or frictionally fit so that shims  160  can be removed once die inserts  100  are properly aligned within slots  320 . With die insert  100  inserted into a slot  320  extending in a first direction, shim  160  can be inserted into a slot  320  extending in a second direction so as to restrict the movement of die insert  100  and to help align the die insert  100 . For example, shim  160  can be inserted in a slot  320  that is transverse to slot  320  in which die insert  100  is positioned, e.g., perpendicular when slots  320  are arranged as squares. Shim  160  can be positioned in a space between teeth  140  of a die insert  100  such that shim  160  abuts a tooth  140  to prevent movement of a tooth  140  along slot  320 . In this way, after inserting the teeth  140  into the slot  320 , the insert  100  can be shifted within (e.g., slide along) the slot  320  until one or more of the teeth  140  encounter the shim  160 , thereby accurately setting the position for the teeth  140  of the die insert  100 . 
     Once die insert  100  is inserted into slot  320  and properly positioned and aligned, such as by use of shims  160 , runner  120  is separated from teeth  140  such that plurality of teeth  140  remain within slot  320 , as shown in  FIG. 7 . Shims  160  can be left in place within extrusion die  300  so as to prevent movement of teeth  140  during removal of runner  120 . Runner  120  can be separated from teeth  140  by any of various processes, including for example by a cutting tool, wire EDM, plunge EDM, etc. In some embodiments, the runner  120  includes a weakened section such as perforations, a groove, etc. to assist in separation from the teeth  140 . Runner  120  is removed so that runner  120  does not block or interfere with extruded material flowing through slots  320  when extrusion die  300  is in use to produce extruded articles. Once runner  120  is removed, shims  160  can then be removed from slots  320  if the shims  160  have not been removed previously. Shims  160  can be preferably removed by carefully withdrawing the shims  160  from the slots without moving teeth  140 . 
     As discussed above, teeth  140  can be dimensioned so that the teeth  140  fit closely within slots  320  and are frictionally secured therein. In some embodiments, however, teeth  140  are further secured to extrusion die  300  to prevent movement of teeth  140  when extrusion die  300  is used to produce extruded articles, during cleaning of the extrusion die  300  using high pressure water jets, etc. In some embodiments, the teeth  140  are secured in place using welding, bonding, or adhesives. In some embodiments, securing teeth  140  to slots  320  of extrusion die  300  comprises plating plurality of teeth  140  and extrusion die  300 . The securing can be performed before the shims  160  are removed and/or before the runner  120  is separated from the teeth. 
     After removal of the runner  120 , extrusion die  300  can be used to produce extruded articles  530  with more complex geometry, namely, by selectively blocking flow through the extrusion die with teeth  140 .  FIG. 8  shows a portion of an extruded article produced by an extrusion die having a continuous grid of square pins modified in accordance with the above so as to comprise square openings  532  (i.e., formed by a single square pin) and larger rectangular openings  534 . The larger rectangular openings  534  are formed as the result of a tooth of the die insert blocking a portion of a slot (i.e., the portion of the slot located between an adjacent pair of square pins) such that no material is extruded through that portion of the slot, resulting in a discontinuous or empty portion (e.g., the discontinuous sections  505  discussed above). Alternatively stated, a portion of the grid pattern defining the extruded article  530  that would otherwise be filled by a wall is empty due to the use of a tooth of the die insert to block extrusion of material through that portion of the slot. 
     In some embodiments, it is desirable to block one or more intersections  328  of slots  320  in extrusion die  300 . To block an intersection  328 , a first die insert  200  can be positioned in a slot  320  extending in a first direction (e.g., with respect to the axis X), and a second die insert  250  can be positioned in a slot  320  extending in a second direction (e.g., with respect to the axis Y). As discussed in more detail below, the first plurality of teeth  240  of first die insert  200  are configured to mate with second plurality of teeth  290  of second die insert  250  so that teeth  240 ,  290  of first and second die inserts  200 ,  250  form a plus-sign or X-shape to block an intersection  328  of extrusion die  300 . 
     The first die insert  200 , as shown in  FIG. 9 , is formed in substantially the same manner as the die insert  100  of  FIG. 3 , and can have the same general shape and configuration. Thus, first die insert  200  comprises a first runner  220  with the first plurality of teeth  240  extending from the first runner  220 . However, first die insert  200  differs from die insert  100  of  FIG. 3 , in that first die insert  200  further comprises a slit  246  on each tooth  240 . Slit  246  extends from first end  242  toward second end  244  of each tooth  240 . Slit  246  is shown as having a generally rectangular configuration, but may be formed with other shapes. Further, slit  246  can be centrally positioned on each tooth  240  if it is desired to center the teeth  240  in the intersections  328 . When first die insert  200  is inserted into a slot  320 , first runner  220  can be separated from first plurality of teeth  240  along line C such that the slit  246  is open at the first end  242  of each tooth  240 . First die insert  200  can be inserted into extrusion die  300  such that slit  246  of each tooth  240  is positioned at an intersection  328  of two slots  320 . 
     Second die insert  250  configured to mate with first die insert  200  is shown in  FIG. 10 . Second die insert  250  is formed substantially the same as first die insert  200  (and also die insert  100  of  FIG. 3 ), and comprises a second runner  270  with the second plurality of teeth  290  extending from second runner  270 . Second die insert  250  also comprises a slit  296 , however, slit  296  of second die insert  250  extends from second end  294  of each tooth  290  toward first end  292 . Thus, slit  296  is open at second end  294  of each tooth  290 . 
     As shown in  FIG. 11 , the teeth of first and second die inserts  200 ,  250  are configured to mate with one another. By aligning and engaging slits  246 ,  296  of teeth  240 ,  290 , the teeth  240 ,  290  of the first and second die inserts  200 ,  250  mate to form a plus-sign or X-shape that can fill an intersection  328  of a slot  320  and adjacent slot portions  324 . After mating the teeth  240  and  290  together by aligning and engaging the slits  246  and  296 , the second runner  270  can be separated from the second plurality of teeth  290  by cutting along line C in  FIG. 10 . 
     In order to form an extrusion die having blocked intersections as shown in  FIG. 12 , the teeth  240  of first die insert  200  are inserted into a slot  320  so that each tooth  240  of first die insert  200  is positioned at an intersection  328  of extrusion die  300 . First runner  220  is separated from the teeth  240  so that slit  246  is open at first end  242  of tooth  240  as discussed above. Since engagement of the slits  246  with the slits  296  is required to mate the teeth  240  and  290  together, first runner  220  of first die insert  200  must be removed prior to placing second die insert  250 . Second die insert  250  is then positioned in a slot  320  extending in a different direction than first die insert  200 , e.g., positioned perpendicularly with respect to first die insert  200  for an extrusion die having square pins and perpendicular slots. Slit  296  of each tooth  290  of second die insert  250  is open at second end  294  of tooth  290 . Thus, slit  296  of each tooth  290  of second die insert  250  can be engaged with slit  246  of each tooth  240  of first die insert  200 . Once second die insert  250  is inserted into slot  320 , second runner  270  of second die insert  250  can also be removed (e.g., by cutting along line C shown in  FIG. 10 ). 
     An example of an extruded article  540  formed by an extrusion die having blocked intersections is shown in  FIG. 13 . By blocking one or more intersections of extrusion die, and optionally adjacent slot portions, extrusion die can be selectively modified to produce extruded articles having a comparatively more complex honeycomb pattern. For example, extruded article  540  of  FIG. 13  comprises first openings  542  of a first size (i.e., created by blocking an intersection between two slots and one pin width of the slot on each side of the intersection), and second openings  544  of a second size that is smaller than the first size (e.g., corresponding to the size of square pins of the extrusion die). 
     An extrusion die can be produced using any combination of die inserts having a plurality of teeth extending from a runner. For example, an extrusion die can be produced using one or more die inserts  100  as shown in  FIG. 3 , one or more of first and second die inserts  200 ,  250 , or a combination thereof with or without additional die inserts having other dimensions. The die inserts are selected so as to block portions of slots of an extrusion die so as to enable the extrusion die to create honeycomb structures with a desired pattern in which walls of the honeycomb structures have discontinuities (e.g., discontinuous sections  505 ) corresponding to the locations of the blocked portions of the slots of the extrusion die. The die inserts can be placed and arranged on the extrusion die as necessary to create the desired honeycomb pattern. 
     Unless otherwise expressly stated, it is in no way intended that any method set forth herein be construed as requiring that its steps be performed in a specific order. Accordingly, where a method claim does not actually recite an order to be followed by its steps or it is not otherwise specifically stated in the claims or descriptions that the steps are to be limited to a specific order, it is in no way intended that any particular order be inferred. In addition, as used herein, the article “a” is intended to include one or more than one component or element, and is not intended to be construed as meaning only one. 
     It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the disclosed embodiments. Since modifications, combinations, sub-combinations and variations of the disclosed embodiments incorporating the spirit and substance of the embodiments may occur to persons skilled in the art, the disclosed embodiments should be construed to include everything within the scope of the appended claims and their equivalents. 
     The indefinite articles “a” and “an” to describe an element or component means that one or at least one of these elements or components is present. Although these articles are conventionally employed to signify that the modified noun is a singular noun, as used herein the articles “a” and “an” also include the plural, unless otherwise stated in specific instances. Similarly, the definite article “the,” as used herein, also signifies that the modified noun may be singular or plural, again unless otherwise stated in specific instances. 
     Where a range of numerical values is recited herein, comprising upper and lower values, unless otherwise stated in specific circumstances, the range is intended to include the endpoints thereof, and all integers and fractions within the range. It is not intended that the scope of the claims be limited to the specific values recited when defining a range. Further, when an amount, concentration, or other value or parameter is given as a range, one or more preferred ranges or a list of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether such pairs are separately disclosed. Finally, when the term “about” is used in describing a value or an end-point of a range, the disclosure should be understood to include the specific value or end-point referred to. 
     As used herein, the term “about” means that amounts, sizes, ranges, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. 
     The terms “substantial,” “substantially,” and variations thereof as used herein are intended to note that a described feature is equal or approximately equal to a value or description. For example, a “substantially planar” surface is intended to denote a surface that is planar or approximately planar. Moreover, “substantially” is intended to denote that two values are equal or approximately equal. 
     The present embodiment(s) have been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. 
     It is to be understood that the phraseology or terminology used herein is for the purpose of description and not of limitation. The breadth and scope of the present disclosure should not be limited by any of the above-described exemplary embodiments, but should be defined in accordance with the following claims and their equivalents.