Patent Description:
Embodiments of the disclosure relate to honeycomb extrusion dies, and in particular to honeycomb extrusion dies comprising slots with divots extending into side surfaces of the slots and methods of using such honeycomb extrusion dies to manufacture honeycomb structures.

Honeycomb extrusion dies can be used to extrude honeycomb structures from ceramic-forming batch materials, which after firing, may produce porous honeycomb structures that can be utilized in fluid treatment systems, such as catalytic converters and particulate filters, for example.

<CIT> discloses a honeycomb extrusion die including a die body with inlet and exit faces, feedholes comprising feedhole entrances at the inlet face terminating at feedhole outlets in the die body, and a plurality of die pins extending to the inlet face, the die pins including side surfaces defining a matrix of intersecting slots. <CIT> and <CIT> disclose additional prior art.

According to the invention, a honeycomb extrusion die according to claim <NUM> is provided. The honeycomb extrusion die comprises a die body comprising an inlet face and an exit face, the die body having feedholes with feedhole entrances at the inlet face and feedhole outlets, and a plurality of die pins extending to the exit face, the plurality of die pins comprising side surfaces configured to define a matrix of intersecting slots, at least some of the matrix of intersecting slots and the plurality of die pins further comprising: divots formed in the side surfaces of the die pins between the feedholes and the exit face, entrance slot portions of the matrix of intersecting slots between the feedhole outlets and the divots, the entrance slot portions having an entrance slot width WA, and exit slot portions of the matrix of intersecting slots between the divots and the exit face, the exit slot portions having an exit slot width WB, wherein WA > WB over an entire length from the feedhole outlets to the divots.

An example embodiment of the disclosure provides a honeycomb extrusion die. The honeycomb extrusion die comprises a die body comprising an inlet face and an exit face, the die body having feedholes with feedhole entrances at the inlet face and feedhole outlets, and a plurality of die pins extending to the exit face, the plurality of die pins comprising side surfaces configured to define a matrix of intersecting slots, at least some of the matrix of intersecting slots and the plurality of die pins further comprising: divots formed in the side surfaces of the die pins between the feedholes and the exit face, entrance slot portions of the matrix of intersecting slots between the feedhole outlets and the divots, the entrance slot portions having an entrance slot width WA, and exit slot portions of the matrix of intersecting slots between the divots and the exit face, the exit slot portions having an exit slot width WB, wherein WA > WB over an entire length from the feed hole exits to the divots, and wherein the at least some of the matrix of intersecting slots have SWCR of greater than or equal to <NUM>, wherein SWCR is a slot width contraction ratio defined as SWCR = WA/WB, and wherein the at least some of the entrance slot portions have an entrance length LA as measured between the feed hole outlets and the divots, and at least some of the exit slot portions have an exit length LB as measured between the divots and the exit face, and wherein LA > LB.

Another example embodiment of the disclosure provides a method of manufacturing a honeycomb structure. The method comprises providing a honeycomb extrusion die having a die body comprising: an inlet face and an exit face, the die body having feedholes with feedhole entrances at the inlet face and feedhole outlets, and a plurality of die pins extending to the exit face, the plurality of die pins comprising side surfaces configured to define a matrix of intersecting slots, at least some of the matrix of intersecting slots and the plurality of die pins further comprising: divots formed in the side surfaces of the die pins between the feedholes and the exit face, entrance slot portions of the matrix of intersecting slots between the feedhole outlets and the divots, the entrance slot portions having an entrance slot width WA, and exit slot portions of the matrix of intersecting slots between the divots and the exit face, the exit slot portions having an exit slot width WB, wherein WA > WB over an entire length from the feedhole outlets to the divots; and extruding a batch material through the feedholes and matrix of intersecting slots. A position of maximum die wear from the extrusion is located at the exit slot portions of the matrix of intersecting slots, regardless of the rheology of the batch material.

According to the invention, a method of fabricating a honeycomb extrusion die according to claim <NUM> is also provided.

Additional features of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the disclosure. It is to be understood that both the foregoing general description and the following detailed description are explanatory and are intended to provide further explanation of the disclosure.

The accompanying drawings, which are included to provide a further understanding of the disclosure are incorporated in and constitute a part of this specification, illustrate embodiments of the disclosure and together with the description serve to explain the disclosure. The drawings are not necessarily drawn to scale.

Honeycomb bodies are used in many different applications. For example, exhaust after-treatment systems of exhaust gas from internal combustion engines may use one or more catalysts supported on high-surface area substrates (e.g., ceramic honeycomb bodies) to reduce exhaust pollutants such as CO, HC, NOx, SOx, for example. Similarly, high porosity honeycomb bodies may be end plugged to for use as wall-flow honeycomb filters. Porous ceramic bodies useful as catalyzed flow-through honeycomb substrates and wall-flow honeycomb filters can be manufactured utilizing the honeycomb extrusion dies according to the embodiments described herein.

In particular, a honeycomb structure of a honeycomb body can be formed by extruding from a honeycomb extrusion die, a ceramic-forming batch mixture, comprising ceramic-forming materials that may comprise ceramics or ceramic precursors, or both, an organic binder(s), a liquid vehicle, an optional pore former, and possibly other processing aids, lubricants, or sintering aids. After green honeycomb formation (e.g., via extrusion through the honeycomb extrusion die), the green honeycomb body can be dried and reacted and/or sintered into a porous ceramic honeycomb body. The porous ceramic honeycomb body can have open and interconnected porous ceramic honeycomb macro- and microstructure suitable for exhaust after-treatment or other fluid treatment purposes. The ceramic material may be, for example, cordierite, aluminum titanate, alumina, mullite, silicon carbide, silicon nitride, and the like, and combinations thereof. Other suitable extrudable batch materials may be used.

The extrusion can be performed using any suitable extruder, such as a hydraulic ram extrusion press, a two stage de-airing single auger extruder, a twin-screw extruder, and the like; each with a honeycomb extrusion die of an embodiment as described herein attached to the discharge end thereof, such as shown in <FIG>, for example.

As should be recognized, extrusion of such ceramic-forming batch mixtures through the honeycomb extrusion die subjects the honeycomb extrusion die to severe wear given the abrasive nature of the batch mixture being extruded. The amount of wear may be dependent on the properties and components of batch mixture and its corresponding liquid content. For example, more coarse batch mixtures (e.g., larger particle sizes) may cause more aggressive wear, and likewise dryer batches (containing less liquid) may cause more wear. Such honeycomb extrusion dies have tolerances and/or features that are desired be maintained during the useful life of the extrusion die. However at some point in the life of the extrusion die, these tolerances and/or features may become degraded to the point that desired honeycomb dimensions (e.g., honeycomb wall thickness) or features in the extruded bodies may no longer be obtained. Although honeycomb extrusion dies can be conventionally recoated with a suitable wear coating to extend their useful life, recoating can be expensive, and the extent of recoating is generally limited, as at some point the honeycomb extrusion die can no longer be used (e.g., once it has been excessively degraded from both use and the coating operations). Thus, extrusion die designs that assist in enabling improved wear characteristics and attributes may be effective in increasing the useful life of the honeycomb extrusion die. This can have significant impacts to the cost of manufacturing honeycomb bodies and to the quality of the resulting honeycomb bodies.

One goal in producing some honeycomb bodies is to minimize wall thickness variability, for example, as both the variance in the dimensions of the walls of a single honeycomb body, and also as variance in the dimensions of multiple honeycomb bodies made from the same die. For example, as an extrusion die wears, the width of the slots used to form the honeycomb walls can widen and become increasingly less uniform across the die. This variability, such as in the form of a slot width standard deviation, is one metric that may help to determine if a particular honeycomb extrusion die is still capable of producing a honeycomb body within acceptable dimensional tolerances or limits. In some cases, a honeycomb extrusion die may be rejected after extrusion of a certain linear footage of extruded green ware due to increases in slot width variability correlated to this linear footage. In other cases, the honeycomb extrusion die may be inspected by image-analysis software.

In addition to altering the dimensions, or the variability in the dimensions, of the extruded honeycomb, wearing of a die pin root (at the location where the feedholes insect with the slots) may significantly reduce the cross-sectional area of the attachment of the die pin to the die body, and thus reduce its area moment of inertia. This reduced area moment of inertia may lead to higher stresses when a die pin is subject to any bending moment, such as during extrusion, handling, and/or during die recoating. Particularly, non-uniform wear at the die pin root may lead to die pin movement during recoating due to the shape asymmetry of the coating and the die pin. Additionally, this asymmetry coupled with the difference in coefficient of thermal expansion (CTE) between the base material and wear coating, may cause further die pin deformation. This may result in even greater slot width variability.

Another contributor to slot width variability can be wear of the die pin sides at the exit of the slots, at which location the width of the extruded honeycomb walls are determined. For abrasive batches with high wall drag, the wear of the die may occur at the highest rate at the die pin root at the intersection of feedhole and slot. In accordance with the above, wear at the die root can lead to a premature ending of the die's life, e.g., prior to its expected linear footage. While wear at the exits of the slots may eventually lead to unacceptably high slot width variability, extrusions processes are generally less sensitive to wear at the slot exits than to wear at the pin roots.

Although die wear is a generally unavoidable consequence of extrusion of abrasive batch materials, one advantage of the honeycomb extrusion die embodiments described herein is that the wear is reduced and the location of the wear is controlled so that it is in an area of the die that is less susceptible to corresponding dimensional variability in the extruded honeycomb bodies. That is, to improve honeycomb extrusion die life, in accordance with embodiments described herein, the die is arranged so that the highest rate of wear occurs at the slot exits, and this is accomplished regardless of batch mixture used, i.e., independent of the rheological characteristics of the batch mixture. For example, the inventors have discovered that less wall thickness variability occurs in the extruded honeycomb, and honeycomb extrusion die life can be extended, if the peak batch slip velocity (representing wear) at the intersection between the feedholes and slots is less than the batch slip velocity at the exit of the slots.

In addition to increased die life, the embodiments described herein also allow for lower die pressure due to less wear at the pin root enabling dies having comparatively wider slot widths at the intersections between the feedholes and the slots. In turn, lower die pressures may assist in enabling dies having longer feedhole lengths, which may reduce die crowning (and thus be particularly useful for larger diameter dies, which may undergo significant crowning during use). As described herein, the disclosed embodiments assist in providing a single design that yields consistent performance (e.g., location of highest wear) for all honeycomb extrusion dies regardless of batch rheology, e.g., regardless of whether the batch material is a so-called low wall-drag batch or a high wall-drag batch.

Referring now to <FIG>, a honeycomb extrusion die <NUM> is illustrated that comprises a die body <NUM>. The die body <NUM> comprises an inlet face <NUM> and an exit face <NUM>, which are axially opposite from each other. For example, in conjunction with <FIG> described in more detail below, the inlet face <NUM> receives batch material, such as the batch material <NUM>, via the action of an extruder, such as an extruder <NUM>, and the exit face <NUM> discharges the batch material <NUM> reformed as a honeycomb structure <NUM>.

Referring back to <FIG>, the die body <NUM> comprises feedholes <NUM> extending in the die body <NUM> with feedhole entrances 124A at the inlet face <NUM> and feedhole outlets 124B within the body <NUM>. A plurality of die pins <NUM> extend from the die body <NUM> to form the exit face <NUM>. The plurality of die pins <NUM> comprise side surfaces <NUM> (a few labeled) that define a matrix of intersecting slots <NUM>. The matrix of intersecting slots <NUM> corresponds to the extruded honeycomb structure <NUM>, as the walls of the honeycomb structure <NUM> are formed from the batch material <NUM> as the batch material <NUM> is discharged from the slots <NUM> at the exit face <NUM>.

At least some of the slots <NUM> in the matrix of intersecting slots (such as all of the slots <NUM>) comprise divots <NUM> formed in the side surfaces <NUM> of the die pins <NUM> at positions located between the outlets 124B of the feedholes <NUM> and the exit face <NUM>. Accordingly, these intersecting slots <NUM> comprise entrance slot portions <NUM> of the matrix of intersecting slots <NUM> extending from intersections of the slots with the feedhole exits 124B to the divots <NUM>. The entrance slot portions <NUM> have an entrance slot width WA measured transverse to the slot <NUM> as best shown in <FIG> and <FIG>. The intersecting slots <NUM> further comprise exit slot portions <NUM> located extending between the divots <NUM> and the exit face <NUM>. The exit slot portions <NUM> have an exit slot width WB, measured transverse to the slot <NUM> (perpendicular to the axial direction) as also shown in <FIG> and <FIG>. Since the batch material is discharged from the extrusion die <NUM> through the slots <NUM>, the exit slot width WB of the exit slot portions <NUM> corresponds to the thickness of the walls <NUM> of the resulting honeycomb structure <NUM> and honeycomb body <NUM>.

According to embodiments described herein, in order to set the highest wear area in the honeycomb extrusion die <NUM> to occur at the location of the exit slot portions <NUM>, the configuration of the honeycomb extrusion die is made according to the invention such that WA > WB over an entire length of the slots <NUM>. In other words, the entrance slot width WA for any location along an entrance length LA of the entrance slot portions <NUM> (from the intersections with the feed hole exits 124B to the divots <NUM>, as shown in <FIG>) is greater than the exit slot width WB for all locations along an exit length LB of the exit slot portions <NUM> (from the divots <NUM> to the exit face <NUM>, as shown in <FIG>).

Reference is now made to <FIG>, which shows a cross-sectioned side view of a schematic example embodiment of an extruder <NUM> (e.g., a continuous twin-screw extruder). The extruder <NUM> includes the honeycomb extrusion die <NUM> according to embodiments of this disclosure mounted at a discharge end at a downstream side <NUM> of the extruder <NUM>. The extruder <NUM> comprises a barrel <NUM> comprising a chamber <NUM> formed therein. The barrel <NUM> can be monolithic or it can be formed from a plurality of barrel segments connected successively in the longitudinal (e.g., axial) direction <NUM>, which corresponds to the extrusion direction. The chamber <NUM> extends through the barrel <NUM> in the longitudinal direction <NUM> between an upstream side <NUM> and the downstream side <NUM>. At, or proximate to, the upstream side <NUM> of the barrel <NUM>, a material supply port <NUM> can be provided, which can comprise a hopper or other suitable material supply structure, for supplying a batch material <NUM> to the extruder <NUM>. The honeycomb extrusion die <NUM> is provided at, and coupled to, the downstream side <NUM> of the barrel <NUM> for extruding the batch material <NUM> into a desired shape, such as honeycomb structure <NUM> or the like. Thus, the honeycomb structure <NUM> is illustrated in <FIG> as a green extrudate that is in the process of being extruded through the die <NUM>. The honeycomb extrusion die <NUM> can be preceded by other extrusion components (not shown), such as one or more screen, orifices, homogenizers, flow control or bow control devices, or the like to facilitate the formation of desirable flow characteristics, such as a steady, uniform, and/or plug-type flow front before the batch material <NUM> reaches the honeycomb extrusion die <NUM>. <FIG> is a schematic perspective illustration also showing the end of the extruder <NUM> at the downstream side <NUM> and the honeycomb structure <NUM> (e.g., an extrudate) being extruded therefrom.

The extruder <NUM> can be of any type, such as a ram extruder or a twin-screw extruder. For example, as shown in <FIG> the extruder <NUM> is a twin-screw extruder comprising a pair of extruder screws <NUM> mounted in the barrel <NUM>. The first screw <NUM> and the second screw <NUM> may be arranged generally parallel to each other, as shown, although they may also be arranged at various angles relative to each other. The screws <NUM> can be coupled to a driving mechanism <NUM>, which can be located outside of the barrel <NUM>, for rotation in the same or different directions. Both the screws can be commonly coupled to a single driving mechanism <NUM> or, as shown, to individual driving mechanisms <NUM>. The screws <NUM>, ram, or other extrusion element moves the batch material <NUM> through the barrel <NUM> with pumping and/or mixing action in the axial direction <NUM>. As shown in <FIG>, an extruder assembly or cartridge located proximate the downstream end <NUM> can comprise extrusion hardware such as the honeycomb extrusion die <NUM>. A skin forming mask <NUM> can also be included for the honeycomb structure <NUM> with a peripheral outer skin. While extrusion is illustrated as being horizontally oriented in <FIG>, this disclosure is not so limited and extrusion can be horizontal, vertical, or at some incline thereto.

When a desired length <NUM> is extruded, the green honeycomb structure <NUM> can be cut by any suitable means, such as via a wire, blade, saw, or the like to form a honeycomb body <NUM> as shown in <FIG>. After cutting from the structure <NUM>, the honeycomb body <NUM> is in a green state and can be dried and fired via conventional methods to form a porous ceramic honeycomb body. The resulting porous ceramic body can have generally the same shape and configuration as the green honeycomb body, e.g., subject to shrinkage (if any) or other dimensional changes during drying, firing, or other manufacturing steps. Thus, the honeycomb body <NUM> in <FIG> generally represents the honeycomb body in both the green state (before firing) and the ceramic state (after firing).

Upon exiting the extruder <NUM> in the axial direction <NUM>, the green honeycomb structure <NUM>, and therefore the honeycomb body <NUM> cut from the honeycomb structure <NUM>, comprises a honeycomb matrix <NUM> of axially extending and intersecting walls <NUM> that form a plurality of axially extending channels <NUM>. If the mask <NUM> is used, the honeycomb structure <NUM> can also comprise an axially extending outer peripheral surface <NUM> or the outer peripheral surface <NUM> can be applied to the honeycomb body <NUM> in a subsequent manufacturing step. The plurality of intersecting walls <NUM>, shown intersecting at perpendicular angles, form the channels <NUM> that extend in the axial direction <NUM>. For example, a representative channel 308R extending in the axial direction <NUM> is shown by dashed lines for illustration purposes. A cross-sectional shape of the green honeycomb structure <NUM> perpendicular to the axial direction <NUM> can be circular (as shown), square, elliptical, rectangular, triangular, hexagonal, octagonal, or any other polygonal shape. Similarly, the channels <NUM> can have any suitable cross-sectional shape, such as square (as shown), circular, elliptical, rectangular, triangular, hexagonal, octagonal, or any other polygonal shape. The channels <NUM> can be all of the same shape and/or size, or different shapes and/or sizes. Similarly, the walls <NUM> can be all of the same thickness or different thicknesses (set by the width of the slots of the extrusion die <NUM>).

Average cell density of the honeycomb body <NUM> when in the porous ceramic state after firing, can be any suitable value, such as between about <NUM> cells per square cm and about <NUM> cells per square cm (between about <NUM> cells per square inch (cpsi) and about <NUM> cpsi). The intersecting walls <NUM> can have any suitable transverse wall thickness, such as ranging from about <NUM> to <NUM> (about <NUM> mils to <NUM> mils). For example, the geometries of the porous ceramic honeycomb body may have an average cell density of <NUM> cells per square cm (<NUM> cpsi) with a wall thickness of about <NUM> ("<NUM>/<NUM>") (<NUM> mils ("<NUM>/<NUM>")) or with a wall thickness of about <NUM> ("<NUM>/<NUM>") (<NUM> mils ("<NUM>/<NUM>")). Other geometries of the porous ceramic honeycomb body can include, for example, combinations of (average cell density {in cells per square cm})/(wall thickness {in mm}) of <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM> ((average cell density {in cpsi})/(wall thickness {in mil}) of <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>, <NUM>/<NUM>), and the like.

Accordingly, referring back to <FIG> shows a partial, cross-sectional side view of a repeating structure of the honeycomb extrusion die <NUM> configured to form the intersecting
walls <NUM>. This repeating die structure can be repeated throughout the die body <NUM> of the honeycomb extrusion die <NUM> and/or arranged with areas having different slot widths, pin sizes, or pins per square inch.

<FIG> shows an enlarged front view of a portion of the exit face <NUM> of the honeycomb extrusion die <NUM>. For example, the view of <FIG> may be provided at a central region of the exit face <NUM> of the honeycomb extrusion die <NUM> and not necessarily at an area proximate to the periphery of the exit face <NUM> that is configured to form the outer peripheral surface <NUM>. The inlet face <NUM> is located opposite the exit face <NUM>. Die body <NUM> can be made from any suitable tool material, such as tool steel. Portions of the honeycomb extrusion die <NUM>, such as the pin surfaces <NUM> defining the slots <NUM>, can be coated with a wear-resistant coating material. As described generally above, batch material <NUM> (e.g., see <FIG>) enters the feedhole inlets 124A (e.g., see <FIG>) under pressure provided by the operation of the extruder <NUM> (e.g., see <FIG>) and is discharged into the slots <NUM> at the feedhole outlets 124B.

The die pins <NUM> are arranged so that the side surfaces <NUM> (each pin <NUM> comprising four side surfaces <NUM> for square-shaped die pins <NUM> shown in <FIG>) form the plurality of slots <NUM> defined between the respective opposing side surfaces <NUM> of the die pins <NUM>. The slots <NUM> intersect with the feedhole outlets 124B of the feedholes <NUM> and extend axially to the exit face <NUM>. There may be overlap between the feedholes <NUM> and the slots <NUM>. During extrusion, the batch material <NUM> (e.g., see <FIG>) flows through the slots <NUM> and forms the intersecting walls <NUM> (e.g., see <FIG> and <FIG>) when the batch material <NUM> is extruded through the honeycomb extrusion die <NUM>.

In the embodiment depicted in <FIG>, <FIG> and <FIG>, the die pins <NUM> are square-shaped when viewed from the exit face <NUM>. The square-shaped die pins <NUM> form square-shaped channels <NUM> (as correspondingly shown in <FIG> and <FIG>). In other embodiments, the die pins <NUM> can have shapes other than square, such as circular, triangular, rectangular non-square, hexagonal, octagonal, diamond, combinations of the aforementioned, and the like and they can comprise filleted or radiused corners when viewed in transverse cross-section, e.g., to minimize stress in the final porous ceramic honeycomb body and/or reduce puddling of any catalyst coating applied thereto.

During use of the honeycomb extrusion die <NUM> in an extrusion process to form honeycomb green bodies, the batch material <NUM> is forced under pressure against the inlet face <NUM> and enters into the feedhole inlets 124A of the feedholes <NUM>. The batch material <NUM> further flows in the feedholes <NUM> to the feedhole exits 124B and transitions into the slots <NUM>. The structure of the slots <NUM> are defined by the plurality of die pins <NUM> extending to the exit face <NUM>, wherein the plurality of die pins <NUM> comprising side surfaces <NUM> configured to define the matrix of intersecting slots <NUM>.

At least some of the slots <NUM> of the matrix of intersecting slots <NUM> are made up of entrance slot portions <NUM>, divots <NUM>, and exit slot portions <NUM>. In some embodiments, substantially all of the center region of the extrusion die <NUM>, except for the skin-forming region, comprises the above structure. In some embodiments, even the skin-forming region at the periphery of the extrusion die <NUM> comprises the entrance slot portions <NUM>, divots <NUM>, and exit slot portions <NUM>. In some embodiments, all of the matrix of intersecting slots <NUM> that define the walls <NUM> of the extruded honeycomb structure <NUM> and/or honeycomb body <NUM> comprise entrance slot portions <NUM>, divots <NUM>, and exit slot portions <NUM>. In some embodiments, all of the matrix of intersecting slots <NUM> (thus, including any slots in a skin forming region of the die) comprise the entrance slot portions <NUM>, divots <NUM>, and exit slot portions <NUM>.

In more detail, the plurality of die pins <NUM> comprise divots <NUM> formed in the side surfaces <NUM> of the die pins <NUM> between the feedhole outlets 124B and the exit face <NUM>. Divots <NUM>, as defined herein, are recessed portions at a transition between the entrance slot portions <NUM> and exit slot potions <NUM>. In some embodiments of the honeycomb extrusion die <NUM>, the divots <NUM> formed in the side surfaces <NUM> of the die pins <NUM> may have a divot width DD of from <NUM> to <NUM> as measured from a centerline 135C of the entrance slot portions <NUM> to the deepest part of the divot <NUM> in a direction perpendicular to the axial direction. Since the divot width DD is measured from the centerline 135C of the slot portions <NUM>, the total or maximum width of the slots at the divots <NUM>, designated in <FIG> as divot slot width WD, is equal to twice the divot width DD. The divot slot width WD is wider than both the entrance slot width WA and the exit slot width WB. In some embodiments, the divots <NUM> have a divot length LD of from <NUM> to <NUM>. Divots <NUM> can have a bottom configuration with a compound radius such as shown in <FIG>. Other honeycomb dies can have other divot configurations, such as the extrusion die 120B having square-shaped divots 132B of the sides <NUM> of die pins <NUM> shown in <FIG>, such that the sides of the divot 132B is flat.

The entrance slot portions <NUM> of the matrix of intersecting slots <NUM> are positioned between intersections with the feedhole outlets 124B and the divots <NUM>, whereas the exit slot portions <NUM> of the matrix of intersecting slots <NUM> are located between the divots <NUM> and the exit face <NUM>. As described above, the entrance slot portions <NUM> have the entrance slot width WA, and the exit slot portions <NUM> having the exit slot width WB. WA and WB can be measured as the dimensions of the slots as coated with a wear resistant coating.

A relationship between WA and WB can be set to control or influence the high wear area of the honeycomb extrusion die <NUM> to occur at the exit slot portions <NUM>, irrespective of the batch material used. According to the invention, the respective entrance slot portions <NUM>, and exit slot portions <NUM> are sized such that WA>WB over the entire length of the slots <NUM>. That is, the entrance slot width WA for any location along an entrance length LA of the entrance slot portions <NUM> (from the intersections with the feed hole exits 124B to the divots <NUM>, as shown in <FIG>) is greater than the exit slot width WB for all locations along an exit length LB of the exit slot portions <NUM> (from the divots <NUM> to the exit face <NUM>, as shown in <FIG>).

According to some embodiments, the relationship between WA and WB is further set or defined with respect to a slot width contraction ratio (SWCR), where the slot width contraction ratio is defined as SWCR = WA/WB. In some embodiments, at least some of the matrix of intersecting slots <NUM> have a SWCR that is greater than or equal to <NUM>. For example, the SWCR can be used to adjust the relative amounts of slip velocity of the batch material at a first location at the intersection of feedholes <NUM> and entrance slot portions <NUM>, and a second location at the exit slot portions <NUM>. In some embodiments of the honeycomb extrusion die <NUM>, the slot width contraction ratio (SWCR) is greater than <NUM>. In some embodiments, SWCR values less than or equal to <NUM> may result in unwanted wear at the die pin root for some batch materials, while values of SWCR greater than <NUM> may cause excessive wear at the exit slot portions and thus premature wearing out of the honeycomb extrusion die. In some embodiments of the honeycomb extrusion die <NUM>, the SWCR can be from <NUM> to <NUM>, such as from <NUM> to <NUM>. Adjusting the relative amounts of slip velocity in the honeycomb extrusion die <NUM> is useful in die designs wherein the exit slot width WB of individual slots is from <NUM> to <NUM>, although it may be useful on honeycomb extrusion dies with different exit slot widths.

Regarding further dimensions of the slots <NUM> of the honeycomb extrusion die <NUM>, at least some of the entrance slot portions <NUM> have the entrance length LA as measured between the intersections with the feed hole exits 124B and the divots <NUM> (e.g., see <FIG>), and at least some of the exit slot portions <NUM> have the exit length LB as measured between the divots <NUM> and the exit face <NUM> (e.g., see <FIG>), and wherein entrance length LA is greater than the exit length LB. Having an entrance length LA greater than the exit length LB may assist in some embodiments to provide a die pressure reduction. In some embodiments, the entrance length LA is greater than or equal to <NUM> times the exit length LB, or LA ≥ <NUM>B.

Furthermore, the entrance length LA of at least some of the entrance slot portions <NUM> in some embodiments is from <NUM> to <NUM>, as measured between the feedhole outlets 124B and the divots <NUM> as shown in <FIG>. In some embodiments, at least some of the exit slot portions <NUM> have an exit length LB from <NUM> to <NUM>, as measured between the divots <NUM> (downstream end thereof) and the exit face <NUM> as shown in <FIG>.

In some embodiments, the entrance slot width WA of the entrance slot portions <NUM> is a constant dimension along the entire length LA of the entrance slot portions <NUM>. Similarly, in some embodiments, the exit slot width WB of the exit slot portions <NUM> is a constant dimension along the entire length LB of the exit slot portions <NUM>. However, the width of the slots <NUM> along the entrance slot portions <NUM> and/or the exit slot portions <NUM> can be non-constant for some or all of slots <NUM>.

For example, in one alternative embodiment of the extrusion die <NUM>, designated as the extrusion die 120A and shown in <FIG>, the entrance slot width WA of the entrance slot portion <NUM> is non-constant along its length LA from the feedhole exits 124B to the upstream side of the divot <NUM>. As such, the entrance slot portion <NUM> has tapered walls forming a wedge shape in plan view shown in <FIG>. Others of the slots <NUM> can also have tapered walls and a wedge shaped configuration. A taper angle <NUM> measured between the walls as shown in <FIG> can be from about <NUM> degrees to <NUM> degrees, for example. The other dimensions of WB and LA, LB, and LD and DD can be the same as described above. In this embodiment, WA> WB at each location along the length LA, and thus, even the minimum dimension of WA is greater than the width WB at any location along the exit slot portion <NUM>.

The honeycomb extrusion die <NUM>, comprising the slot configurations with entrance slot portion <NUM>, divots <NUM>, and exit slot portions <NUM> can be manufactured in any suitable manner. In some embodiments, the die <NUM> is manufactured by a wire-electrical discharge machining (wire-EDM) technique and thereafter coated with a suitable wear coating to achieve the desired dimensions of WA and WB.

In another aspect, a method of manufacturing a honeycomb body (e.g., honeycomb body <NUM>) is disclosed. Reference is made to <FIG>, which shows a flowchart of the manufacturing method <NUM>. In particular, <FIG> describes a method of manufacturing a honeycomb structure (e.g., honeycomb structure <NUM>) using a honeycomb extrusion die (e.g., any of the honeycomb extrusion dies <NUM>, including the honeycomb extrusion dies 120A, 120B of <FIG>).

The method <NUM> comprises, in block <NUM>, providing a honeycomb extrusion die <NUM> comprising a die body (e.g., die body <NUM>) comprising an inlet face (e.g., inlet face <NUM>) and an exit face (e.g., exit face <NUM>), the die body having feedholes (e.g., feedholes <NUM>) with feedhole entrances (e.g., feedhole entrances 124A) located at the inlet face and feedhole outlets (e.g., feedhole outlets 124B), and a plurality of die pins (e.g., die pins <NUM>) extending a distance into the exit face, the plurality of die pins comprising side surfaces (e.g., side surfaces <NUM>) configured to define a matrix of intersecting slots (e.g., intersecting slots <NUM>), at least some of the matrix of intersecting slots and the plurality of die pins further comprising divots (e.g., divots <NUM>) formed in the side surfaces of the die pins between the feedholes and the exit face, entrance slot portions (e.g., entrance slot portions <NUM>) of the matrix of intersecting slots between the feedhole outlets and the divots, the entrance slot portions having an entrance slot width WA, and exit slot portions (e.g., exit slot portions <NUM>) of the matrix of intersecting slots between the divots and the exit face, the exit slot portions having an exit slot width WB, wherein WA > WB over an entire length of the slots <NUM>.

The method <NUM> further comprises, in block <NUM>, extruding a batch material (e.g., batch material <NUM>) through the feedholes and matrix of intersecting slots. According to the method <NUM>, a position of maximum die wear from the extruding of the batch material is located at the exit slot portions of the matrix of intersecting slots, and this occurs regardless of the rheology of the batch material, i.e., whether the batch material is a high die wear batch mixture or a low die wear batch mixture.

Claim 1:
A honeycomb extrusion die (<NUM>), comprising:
a die body (<NUM>) comprising:
an inlet face (<NUM>) and an exit face (<NUM>) axially opposite from the inlet face (<NUM>);
feedholes (<NUM>) with feedhole entrances (124A) at the inlet face (<NUM>) that terminate at feedhole outlets (124B) within the die body (<NUM>); and
a plurality of die pins (<NUM>) extending to the exit face (<NUM>), the plurality of die pins (<NUM>) comprising side surfaces (<NUM>) that define a matrix of intersecting slots (<NUM>),
wherein at least some of the intersecting slots (<NUM>) in the matrix of intersecting slots (<NUM>) comprise:
divots (<NUM>) formed in the side surfaces (<NUM>) of the die pins (<NUM>) at positions located axially between the feedhole outlets (124B) and the exit face (<NUM>),
entrance slot portions (<NUM>) extending from intersections with the feedhole outlets (124B) to the divots (<NUM>), the entrance slot portions (<NUM>) having an entrance slot width WA, and
exit slot portions (<NUM>) extending from the divots (<NUM>) to the exit face (<NUM>), the exit slot portions (<NUM>) having an exit slot width WB,
wherein WA > WB over an entire slot length from the feedhole outlets (124B) to the exit face (<NUM>).