JP2004052174A - Nozzle for conjugate spinning and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nozzle for conjugate spinning, having nozzle holes with high coaxiality. <P>SOLUTION: The nozzle for the conjugate spinning is obtained by accumulating and combining two or more single-layer nozzles so that the center axes of the nozzle holes may be positioned on the same axis line. The nozzle has a fitting part at the joining part of two single-layer nozzles to be joined to each other over the whole periphery, formed at the outer periphery at the joining side of one single-layer nozzle and the outer periphery at the joining side of the other single-layer nozzle, and the two single-layer nozzles to be joined are fixed at the fitting part by a fixing tool. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a composite spinning nozzle used for manufacturing an optical transmission body such as an optical fiber and a rod lens, and a method for manufacturing the same.
[0002]
[Prior art]
Composite spinning nozzles are used, for example, for manufacturing optical transmission bodies such as plastic optical fibers and plastic rod lenses having a refractive index distribution in which the refractive index decreases from the center to the outer periphery. This composite spinning nozzle is composed of a plurality of single-layer nozzles, and by using this composite spinning nozzle, a plurality of solutions or molten raw materials are arranged in such a manner that the refractive index after curing gradually decreases from the center to the outer periphery. (Hereinafter, referred to as “stock solution”) can be laminated in a concentric cylindrical shape and shaped (spun) into a thread shape.
[0003]
FIG. 1 shows the structure of a composite spinning nozzle composed of a plurality of single-layer nozzles. Each single-layer nozzle is arranged and fixed such that the nozzle hole center point on the vertical plane of the nozzle hole is located on a coaxial line. I have. FIG. 1A is a plan view of the composite spinning nozzle viewed from the side of the stock solution discharge side opening 110, and FIG. 1B is a cross-sectional view. The first-layer single-layer nozzle 101 supplies and discharges an undiluted solution for forming a central layer (first layer) of a cylindrical laminated structure of a formed filamentous material. A stock solution for forming a second layer around one layer is supplied and discharged. The flow path of the stock solution passing through the center of each single-layer nozzle and reaching the discharge-side opening 110 is a nozzle hole.
[0004]
Although FIG. 1 shows only the first-layer single-layer nozzle 101 and the second-layer single-layer nozzle 102, third-layer and subsequent single-layer nozzles are further arranged on the second-layer single-layer nozzle 102. In some cases. Also, in FIG. 1, the filament is formed while discharging the undiluted solution from the lower side to the upper side of the drawing. However, when the entire composite spinning nozzle is used in a different direction from FIG. There is also.
[0005]
After the filament formed by using such a composite spinning nozzle is subjected to a curing treatment, and then subjected to a stretching treatment or a heating treatment as necessary, an optical transmission body can be obtained. In the above-described composite spinning nozzle, the center point of the nozzle hole on a plane perpendicular to the longitudinal direction of the nozzle hole of each of the single-layer nozzles constituting the nozzle (hereinafter referred to as “nozzle hole center point”) is positioned as coaxially as possible. That is, high coaxiality of the nozzle hole is required. If the coaxiality of the nozzle hole is low, the composition distribution and shape in the cross-sectional direction of the obtained optical transmission body may fluctuate, or eccentricity may occur, thereby deteriorating the optical characteristics of the optical transmission body.
[0006]
As an example, a case of a plastic rod lens used for a sensor part of a copying machine, a facsimile, a scanner, a writing device of an LED printer, and the like will be described. In the production of this plastic rod lens, a plurality of stock solutions are arranged and shaped using a composite spinning nozzle so that the refractive index after curing gradually decreases from the center to the outer periphery, and the plurality of stock solutions are concentric. By forming a filament (precursor of a plastic rod lens) having a structure laminated in a cylindrical shape and further diffusing each layer component into adjacent layers, the refractive index is continuous from the center to the outer periphery in the cross-sectional direction. Thus, a refractive index distribution structure that gradually decreases is formed. A rod lens with such a refractive index distribution structure allows light incident from one end face to propagate to the other end face while drawing a sinusoidal curve, and accurately form an image on the image plane ahead. And high optical performance can be exhibited.
[0007]
In manufacturing such a plastic rod lens, the coaxiality of the nozzle hole of the composite spinning nozzle affects the center axis accuracy of the refractive index distribution in the cross-sectional direction of the finally obtained rod lens, that is, the optical axis accuracy. It greatly affects the optical performance of plastic rod lenses that require easy control of the refractive index distribution. Therefore, the composite spinning nozzle used for shaping the filamentous body is required to have high nozzle hole coaxiality.
[0008]
As a conventional composite spinning nozzle, one that fixes between single-layer nozzles with pins or bolts has been used. For example, in FIG. 1, each single-layer nozzle is provided with a knock pin 103, and the knock pin 103 is fitted into the fitting portion 104 of another single-layer nozzle, thereby fixing between the single-layer nozzles.
[0009]
[Problems to be solved by the invention]
However, in the conventional composite spinning nozzle, the position of the structural portion that is a fixed position reference of each single-layer nozzle due to limitations in the processing accuracy of the machine tool itself used for processing each single-layer nozzle and human errors of a processor. It was inevitable that the accuracy would deviate somewhat from its design value. In particular, in the single-layer nozzle fixing structure as shown in FIG. 1, the position of a structural portion (the center point of the knock pin 103 or the knock pin fitting portion 104) serving as a fixing position reference of each single-layer nozzle and its design value are determined. When the displacement occurs between the single-layer nozzles, even if the displacement is slight (for example, about several μm) per one layer of the single-layer nozzle, when they are assembled into a composite spinning nozzle, the size cannot be ignored (for example, several tens of micrometers). μm), which is directly reflected in the coaxiality of the nozzle hole as the composite spinning nozzle. The problem of such coaxial misalignment becomes even more serious as the number of single-layer nozzles constituting the composite spinning nozzle increases.
[0010]
As described above, in the conventional composite spinning nozzle, even when the center point of the nozzle hole of each single-layer nozzle is designed to be located on a coaxial line, actually, each center point is located on the coaxial line. It is not uncommon for the deviation to exceed several tens of μm.
[0011]
Therefore, an object of the present invention is to provide a composite spinning nozzle composed of a plurality of single-layer nozzles, which is suitable for manufacturing an optical transmission body having a refractive index distribution from the center in the cross-sectional direction to the outer peripheral portion, and has a high coaxial nozzle hole. It is an object of the present invention to provide a composite spinning nozzle having a property.
[0012]
[Means for Solving the Problems]
In view of the above-described problems, the present inventors have focused on processing individual raw material blocks for each single-layer nozzle in the prior art, and as a result of intensive studies, completed the present invention.
[0013]
That is, the present invention is a composite spinning nozzle in which a plurality of single-layer nozzles are stacked and combined so that the central axis of the nozzle hole is located on a coaxial line,
The joining portion between the two single-layer nozzles to be joined to each other has a fitting portion provided around the joining side outer periphery of one single-layer nozzle and the joining side outer periphery of the other single-layer nozzle over the periphery thereof. ,
The present invention relates to a composite spinning nozzle, wherein two single-layer nozzles to be joined are fixed by a fixing jig at the fitting portion.
[0014]
The present invention also provides a fitting recess, wherein the fitting portion is formed by a step portion provided on the outer periphery of the joining side of one single-layer nozzle and a step portion provided on the outer periphery of the joining side of the other single-layer nozzle. The present invention relates to the above-described composite spinning nozzle.
[0015]
Further, in the invention, it is preferable that the fixing jig has, at three or more locations on an inner peripheral surface thereof, support portions that come into contact with both step portions of the two single-layer nozzles forming the fitting concave portion. And a composite spinning nozzle.
[0016]
The present invention also relates to any one of the above-described composite spinning nozzles, wherein the fixing jig has a cylindrical shape.
[0017]
The present invention is also a method for producing the above-described composite spinning nozzle,
The present invention relates to a method for manufacturing a composite spinning nozzle, wherein at least two of the single-layer nozzles constituting the composite spinning nozzle are manufactured by processing one raw material block.
[0018]
The present invention is also a method for producing the above-described composite spinning nozzle,
A step of preparing a raw material block having a size capable of forming at least two of the single-layer nozzles constituting the composite spinning nozzle;
Forming a recess corresponding to the fitting recess on the outer periphery thereof while rotating the raw material block;
The present invention relates to a method for manufacturing a composite spinning nozzle including a step of cutting the raw material block at the concave portion and forming at least two of the single-layer nozzles constituting the composite spinning nozzle.
[0019]
Further, the present invention relates to the above-described method for producing a composite spinning nozzle, comprising a step of opening a hole serving as a nozzle hole along a rotation axis of the raw material block while rotating the raw material block before the cutting step.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
[0021]
FIG. 2 schematically shows the structure of an embodiment of the composite spinning nozzle of the present invention. FIG. 2A is a plan view of the stock solution as viewed from the discharge side opening 20, and FIG. 2B is a cross-sectional view.
[0022]
The present embodiment shown in FIG. 2 is a single-hole five-layer composite spinning nozzle (a composite spinning nozzle composed of five single-layer nozzles and capable of forming one filament by combining five types of stock solutions). This is an example.
[0023]
Reference numeral 1 denotes a first-layer single-layer nozzle that supplies and discharges an undiluted solution for forming a central layer (first layer) of a cylindrical laminated structure of a formed filamentous body, and reference numeral 2 denotes a first-layer nozzle around the first layer. A second-layer single-layer nozzle for supplying and discharging a stock solution forming two layers, and reference numeral 3 denotes a third-layer single-layer nozzle for supplying and discharging a stock solution forming a third layer around the second layer, Reference numeral 4 denotes a fourth-layer single-layer nozzle for supplying and discharging a stock solution forming a fourth layer around the third layer, and reference numeral 5 supplies and discharging a stock solution for forming a fifth layer around the fourth layer. This is a fifth-layer single-layer nozzle. The flow path of the stock solution passing through the center of each single-layer nozzle and reaching the discharge side opening 20 is a nozzle hole.
[0024]
In FIG. 2, the filament is formed while discharging the undiluted solution from the lower side to the upper side of the figure, but the direction of the composite spinning nozzle in use is not particularly limited.
[0025]
Reference numerals 11, 12, 13 and 14 denote cylindrical fixing jigs (hereinafter referred to as "cylindrical jigs") used to fix the single-layer nozzles and assemble them into a composite spinning nozzle. Reference numeral 11 denotes a cylindrical jig for fixing the first-layer single-layer nozzle and the second-layer single-layer nozzle, and reference numeral 12 denotes a cylinder for fixing the second-layer single-layer nozzle and the third-layer single-layer nozzle. Reference numeral 13 denotes a cylindrical jig for fixing the third-layer single-layer nozzle and the fourth-layer single-layer nozzle, and reference numeral 14 denotes a fourth-layer single-layer nozzle and a fifth-layer single-layer nozzle. This is a cylindrical jig for fixing.
[0026]
FIG. 3 shows a sectional view of the composite spinning nozzle in a state where all the cylindrical jigs 11 to 14 are removed from the structure shown in FIG.
[0027]
Reference numerals 21, 22, 23, and 24 denote concave fitting portions (hereinafter, referred to as "fitting recesses") for attaching the cylindrical jigs 11 to 14, respectively.
[0028]
Reference numeral 21A denotes a step portion of the first-layer single-layer nozzle, and reference numeral 21B denotes a step portion of the second-layer single-layer nozzle, and the fitting portions 21 are formed by the step portions 21A and 21B. . Reference numeral 22A denotes a step portion of the second-layer single-layer nozzle, and reference numeral 22B denotes a step portion of the third-layer single-layer nozzle. The fitting portions 22 are formed by the step portions 22A and 22B. Reference numeral 23A denotes a step portion of the third-layer single-layer nozzle, and reference numeral 23B denotes a step portion of the fourth-layer single-layer nozzle. The fitting portions 23 are formed by the step portions 23A and 23B. Reference numeral 24A is a step portion of the fourth-layer single-layer nozzle, and reference numeral 24B is a step portion of the fifth-layer single-layer nozzle. The fitting portions 24 are formed by the structural portions 24A and 24B.
[0029]
As shown in FIGS. 2 and 3, each of the cylindrical jigs described above is fitted into a fitting recess formed by a step portion of the upper single-layer nozzle and a step portion of the lower single-layer nozzle. That is, it is mounted so as to be sandwiched between the upper-layer single-layer nozzle and the lower-layer single-layer nozzle, so that the two upper-layer and lower-layer single-layer nozzles can be fixed.
[0030]
As described above, the composite spinning nozzle of the present invention uses the cylindrical jig as described above to fix the single-layer nozzles in place of the conventional fixing portion such as a pin or a bolt. The fixing structure (the cylindrical jig and the concave portion for fitting) in the present invention can adopt a manufacturing method described later, and therefore has a nozzle hole coaxiality which is lower than that of the fixing structure (pins, bolts, etc.) in the prior art. Can be enhanced.
[0031]
In the present invention, the fitting portion is not limited to a concave shape, and may be, for example, a convex shape. However, when a manufacturing method of a composite spinning nozzle described later is used, the composite hole having a high coaxiality of the nozzle hole is easily used. It is preferable that the shape is concave because a spinning nozzle can be manufactured. When the fitting portion is formed in a convex shape, a fixing jig having, for example, a concave portion that can be fitted in the fitting portion can be used. Further, in the present invention, the fixing jig is not limited to a cylindrical jig. However, since the single-layer nozzle can be firmly fixed while maintaining the coaxiality of the nozzle hole, and is easy to manufacture, a cylindrical jig is used. Is preferred.
[0032]
Further, in the present embodiment, all the single-layer nozzles constituting the composite spinning nozzle have a structure in which the cylindrical jig is fitted and fixed in the fitting concave portion. It is also possible to use other methods for fixing between other single-layer nozzles, using for fixing between the nozzles.
[0033]
Hereinafter, a method for manufacturing the composite spinning nozzle of the present invention will be described with reference to FIG.
[0034]
First, one cylindrical raw material block having a size capable of processing all the single-layer nozzles constituting the composite spinning nozzle of the present invention is prepared (FIG. 4A).
[0035]
Next, recesses 31, 32, 33, and 34 serving as fitting recesses for attaching the cylindrical jig are cut on the outer periphery of the raw material block using a cutting machine tool such as a lathe (FIG. 4 (b)). The concave portions are formed in a number corresponding to the number of single-layer nozzles to be manufactured (a number one smaller than the number of single-layer nozzles).
[0036]
In FIG. 4B, the concave portion 31 corresponds to the fitting concave portion 21 (step portions 21A and 21B) for fixing the first-layer single-layer nozzle and the second-layer single-layer nozzle, and the concave portion 32 corresponds to the second-layer single-layer nozzle. The concave portion 33 corresponds to the fitting concave portion 22 (step portions 22A and 22B) for fixing the single-layer single-layer nozzle and the third-layer single-layer nozzle, and the concave portion 33 fixes the third-layer single-layer nozzle and the fourth-layer single-layer nozzle. Recesses 34 (steps 23A and 23B), and recesses 34 are fitting recesses 24 (steps 24A and 24B) for fixing the fourth-layer single-layer nozzle and the fifth-layer single-layer nozzle. Is equivalent to
[0037]
In the manufacturing method of the present invention, the concave portions 31, 32, 33, and 34 are rotated while rotating the raw material block itself around the center axis as the rotation axis Z (the direction g in FIG. 4B or the reverse direction). Is preferably processed. Thereby, in each of the finally obtained single-layer nozzles, the center point of the outer shape of the step portion (the center point of the outer shape of the step portion on the XY plane perpendicular to the rotation axis Z), which is a position reference fixed by the cylindrical jig, is set. , Can be strictly adjusted to Z on the rotation axis at the time of processing.
[0038]
Further, in the case of a single-hole composite spinning nozzle, it is desirable that the holes 30 serving as nozzle holes are simultaneously opened while rotating the raw material block. Thus, the center of the outer shape of the stepped portion of each single-layer nozzle and the center axis of the nozzle hole, which form the fitting concave portion for mounting the cylindrical jig, can be easily aligned with the rotation axis Z during the above-described processing. .
[0039]
Finally, as shown in FIG. 4 (c), the raw material block subjected to the above processing is divided at each of the recesses 31 to 34 using a cutting machine tool such as a wire cutter, and processing and finishing of details are performed. To complete the single-layer nozzles 1 to 5.
[0040]
4 (c) corresponds to the first-layer single-layer nozzle 1 of FIG. 2 (b), and FIG. 4 (c) member 2 corresponds to the second-layer single-layer nozzle 2 of FIG. 2 (b). The member 3 in FIG. 4C corresponds to the third-layer single-layer nozzle 3 in FIG. 2B, and the member 4 in FIG. 4C corresponds to the fourth-layer single-layer nozzle 4 in FIG. 4 (c) corresponds to the fifth-layer single-layer nozzle 5 in FIG. 2 (b).
[0041]
Each single-layer nozzle according to the prior art is manufactured by processing an individual raw material block for each single-layer nozzle, whereas in the manufacturing method of the present invention, one raw material block is divided and processed into a single-layer nozzle. All the nozzles are manufactured, and at this time, all the step portions of the single-layer nozzles forming the fitting concave portion for attaching the cylindrical jig are formed at the stage of the raw material block (before the division processing). Therefore, the deviation of the fixed position reference (step portion) of each single-layer nozzle finally obtained can be suppressed, and the coaxiality of the nozzle hole can be improved.
[0042]
The material of the raw material block is not particularly limited, but stainless steel (SUS) is preferably used in consideration of strength, corrosion resistance, workability, cost, and the like.
[0043]
In the present embodiment, the step corresponding to the fitting recess for attaching the cylindrical jig of each completed single-layer nozzle is formed by processing the raw material block while rotating the raw material block. Although the cross-sectional shape perpendicular to the rotation axis direction Z is circular, the other portions are not limited to a circular cross-sectional shape, and may have any shape such as a triangle, a quadrangle, or a polygon such as a polygon. can do. When the step portion is formed by using another method, the step portion may have another shape. In the case where the fitting portion has, for example, a convex shape, the fitting portion can be formed by cutting a portion other than the fitting portion while rotating the raw material block.
[0044]
In the above, the present invention has been described by exemplifying a single-hole composite spinning nozzle. However, the present invention relates to a porous composite spinning nozzle (a single-layer single-layer nozzle has a plurality of nozzle holes, and one set includes a plurality of nozzle holes. The present invention can also be applied to a composite spinning nozzle capable of shaping the thread of the present invention) and a method for producing the same. When a plurality of nozzle holes are formed, for example, at the stage before dividing the raw material block, the raw material block may be separately processed before or after processing the concave portion corresponding to the fitting concave portion without rotating the raw material block.
[0045]
Further, there is no particular limitation on the number of single-layer nozzles constituting one composite spinning nozzle.
[0046]
In order to assemble each single-layer nozzle manufactured as described above as a composite spinning nozzle, a cylindrical jig as shown in FIG. 5 can be used. FIG. 5A is a plan view of the cylindrical jig, and FIG. 5B is a side view.
[0047]
The tubular jig in FIG. 5 corresponds to the members indicated by reference numerals 11 to 14 in FIG.
[0048]
Each cylindrical jig has, on its inner peripheral surface, support portions 41, 42, and 43 for fixing two single-layer nozzles. These supporting portions come into contact with the step portions (21A and 21B, 22A and 22B, 23A and 23B, or 24A and 24B) of the single-layer nozzle forming the fitting concave portion for mounting the cylindrical jig. Fix between single layer nozzles.
[0049]
The cylindrical jig illustrated in FIG. 5 has a circular shape on both the outer circumferential side and the inner circumferential side, but has a circular shape as long as it has a support portion for contacting and fixing the step portion of each single-layer nozzle. There is no limitation, and both the outer peripheral side and the inner peripheral side may be triangular, quadrangular or more polygonal or any shape, and the outer peripheral side and the inner peripheral side may have different shapes.
[0050]
The cylindrical jig of the present invention has, on its inner peripheral surface, preferably three or more supporting portions for fixing between the single-layer nozzles from the viewpoint of stably fixing the nozzles. In order to give a uniform force in the direction of the center 40 of each of the nozzles and to make it easier to arrange the central axis of each single-layer nozzle more coaxially, it is better that the number of contact points between the support portion and each single-layer nozzle is small. . Further, it is preferable that the support portions are arranged at equal angular intervals when viewed from the center 40 of the nozzle. In the example shown in FIG. 5, three supporting portions are formed on the inner peripheral surface of the cylindrical jig at equal intervals of a central angle of 120 °.
[0051]
The material of the cylindrical jig is not particularly limited. However, in consideration of strength, corrosion resistance, workability, cost, and the like, it is preferable to use stainless steel (SUS).
[0052]
In this embodiment, all the single-layer nozzles are manufactured by processing one raw material block, but a plurality of single-layer nozzles manufactured by such a method and a single-layer nozzle manufactured by another method are manufactured. Can be combined to produce a composite spinning nozzle.
[0053]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the composite spinning nozzle which has high coaxiality of a nozzle hole can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view of a conventional composite spinning nozzle.
FIG. 2 is a schematic view of a composite spinning nozzle of the present invention.
FIG. 3 is a schematic sectional view showing a state in which a cylindrical jig is not attached to the composite spinning nozzle of the present invention.
FIG. 4 is a schematic diagram for explaining a method of manufacturing a composite spinning nozzle according to the present invention.
FIG. 5 is a schematic view showing a cylindrical jig constituting the composite spinning nozzle of the present invention.
[Explanation of symbols]
101: first layer single layer nozzle 102: second layer single layer nozzle 103: knock pin 104: knock pin fitting portion 110: nozzle hole discharge side opening 1: first layer single layer nozzle 2: second layer single layer nozzle 3: first Three-layer single-layer nozzle 4: Fourth-layer single-layer nozzle 5: Fifth-layer single-layer nozzle 11: A cylindrical jig 12 for fixing the first-layer single-layer nozzle and the second-layer single-layer nozzle 12: Second-layer single A cylindrical jig 13 for fixing the layer nozzle and the third layer single layer nozzle: a cylindrical jig 14 for fixing the third layer single layer nozzle and the fourth layer single layer nozzle 14: a fourth layer single layer nozzle and the fourth Cylindrical jig 20 for fixing the five-layer single-layer nozzle: nozzle hole discharge side openings 21, 22, 23, 24: fitting recesses 21A and 21B for mounting the cylindrical jig: fitting recess 21 is formed. Step portions 22A, 22B: Step portions 23A, 23B forming the fitting recess 22: Fitting Steps 24A, 24B forming the part 23: Steps 30 forming the fitting recess 24: Holes 31, 32, 33, 34 provided in the raw material block before division: provided in the raw material block before division. Recess 40: center 41, 42, 43 of nozzle hole: support provided on inner peripheral surface of cylindrical jig

Claims (7)

A plurality of single-layer nozzles are combined spinning nozzles that are stacked and combined so that the central axis of the nozzle hole is located on a coaxial line,
The joining portion between the two single-layer nozzles to be joined to each other has a fitting portion provided around the joining side outer periphery of one single-layer nozzle and the joining side outer periphery of the other single-layer nozzle over the periphery thereof,
In the fitting section, the two single-layer nozzles to be joined are fixed by a fixing jig. The fitting portion is a fitting concave portion formed by a step portion provided on the outer periphery of the joining side of one single-layer nozzle and a step portion provided on the outer periphery of the joining side of the other single-layer nozzle. The composite spinning nozzle according to claim 1, wherein 3. The fixing jig according to claim 2, wherein the fixing jig has, at three or more locations on an inner peripheral surface thereof, support portions that come into contact with both step portions of the two single-layer nozzles forming the fitting recess. 4. Composite spinning nozzle. The composite spinning nozzle according to any one of claims 1 to 3, wherein the fixing jig has a cylindrical shape. It is a manufacturing method of the composite spinning nozzle according to any one of claims 1 to 4,
A method of manufacturing a composite spinning nozzle, wherein at least two of the single-layer nozzles constituting the composite spinning nozzle are manufactured by processing one raw material block. It is a manufacturing method of the compound spinning nozzle according to claim 2 or 3,
A step of preparing a raw material block having a size capable of forming at least two of the single-layer nozzles constituting the composite spinning nozzle;
Forming a recess corresponding to the fitting recess on the outer periphery thereof while rotating the raw material block;
A method for manufacturing a composite spinning nozzle, comprising a step of cutting the raw material block at the concave portion and forming at least two of the single-layer nozzles constituting the composite spinning nozzle. The method according to claim 6, further comprising, before the cutting step, a step of opening a hole serving as a nozzle hole along a rotation axis of the raw material block while rotating the raw material block.

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