One end portion of a resin tube kept in a diameter expanded state by a plurality of diameter expanding claws is disengaged from the diameter expanding claws and is shifted onto an outer peripheral surface of a die by applying a pressing force toward the other end portion of the resin tube to an end surface of the one end portion of the resin tube.

Issues with pleat walled honeycombs are solved by replacing polygonal creases with curved creases. As with a conventional straight-walled honeycomb, these strips can be combined into a space-filling honeycomb structure. The benefits of these curved creases are threefold. First, the stress concentrations mentioned above with pleat-walled honeycombs are mitigated. The stress due to finite material thickness is spread more evenly over the crease line, instead of being concentrated at a point, as with pleat walled honeycombs. As a result, the maximal value observed is lower and the adverse effects are reduced. Second, the curved creases also serve to give better control over material properties, and third, the curved crease honeycombs do not require any of the horizontally-running creases. The curves are typically mathematical curves that can be computed algebraically or by solving a differential equation.

Methods of manufacturing an extrusion die (100) having a plurality of pins (600a-c) and a plurality of slots (601) defined by the plurality of pins, each pin having a base, the method including applying a coating material (604) over side walls of the bases of the pins of the extrusion die and removing a portion of the coating material coated over the side walls of the bases of the plurality of pins with a cutting tool (650). In some embodiments, the cutting tool has a cutting width (652) equal to a target slot width (640) of the slots. In some embodiments, applying the coating material over the side walls of the bases of the pins includes overcoating a coating material to a thickness that is greater than a thickness needed to define a target slot width of the slots.

A manufacturing method of a honeycomb structure include a forming step of extruding a kneaded material including a forming raw material by use of a horizontal forming machine include a forming die in which latticed slits are formed in a kneaded material discharge surface, to obtain a round pillar-shaped honeycomb formed body having latticed partition walls; and a firing step of firing the obtained honeycomb formed body to prepare the honeycomb structure. In the forming step, there is used the forming die in which there are formed the slits different in lattice shape between a central portion and a circumferential portion in the kneaded material discharge surface, and the forming die is disposed in an orientation in which an inclination of one row of the latticed slits formed in the central portion is within an angle of 10 to a vertical direction, to extrude the kneaded material in a horizontal direction.

A mouthpiece (10) for extruding a molding compound into a formed body which has internal channels, comprises: a mouthpiece frame (14) with a frame opening (16); a first core retaining plate (22) which is fastened in the area of an upstream end of the frame opening (16) when viewed in the flow direction (15) of the molding compound; and a plurality of longitudinal cores (28) which are axially and laterally held by an upstream end section (26) on the first core retaining plate (22). It is proposed that, furthermore, it comprises a second core retaining plate (36) which is loosely arranged downstream of the first core retaining plate (22) relative to the mouthpiece frame (14) in the flow direction (15), and in which the areas (32) of the cores (28) farther from the upstream end section (26) are arranged to be radially fixed but axially loose.

A method of making a die body configured to extrude a honeycomb body, the method comprising the step (I) of manufacturing a die body and the step (II) of predetermining an upstream slot width W1 of the die body such that the upstream slot width W1 is optimized while a root of each die pin includes a section modulus within a predetermined section modulus range. The method still further comprises the step (III) of predetermining a slot length L such that a pin stress is within a predetermined pin stress range.

One end portion of a resin tube kept in a diameter expanded state by a plurality of diameter expanding claws is disengaged from the diameter expanding claws and is shifted onto an outer peripheral surface of a die by applying a pressing force toward the other end portion of the resin tube to an end surface of the one end portion of the resin tube.