Extrusion molding die and its manufacturing method

Abstract

To provide technology that can reduce the manufacturing cost of extrusion molding dies.SOLUTION: The method of manufacturing a die for extrusion molding equipped with a discharge port forming portion, comprising: formation process S102 to form the base material of the outlet forming part into a predetermined shape, and cladding process S104 that forms an overlay layer on the surface of the base material that has been processed into a predetermined shape and that constitutes at least the edge region of the inner wall of the flow channel on the outlet side by laser cladding.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to an extrusion die and a method for making the same. [Background technology]

[0002] Patent Document 1 discloses an extrusion die used in an extrusion molding device. Patent Document 1 discloses that, in general, in an extrusion die, at least a resin flow path is subjected to a surface treatment by electroplating such as hard chrome plating in order to improve rust resistance, abrasion resistance, and mold releasability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2000-071311 A Summary of the Invention [Problem to be solved by the invention]

[0004] The plating described in Patent Document 1 often generates holes such as pits and pinholes. The holes that exist at least in the end region of the flow path on the discharge port side must be repaired, but the repair requires time and effort, which increases the manufacturing cost of the extrusion molding die.

[0005] The present invention has been made in light of these circumstances, and one exemplary purpose of an embodiment of the present invention is to provide a technique that can reduce the manufacturing costs of extrusion molding dies. [Means for solving the problem]

[0006] In order to solve the above problems, a manufacturing method of one embodiment of the present invention is a manufacturing method for an extrusion molding die having an outlet forming portion that forms an outlet, comprising: forming a base material of the outlet forming portion into a predetermined shape; and forming a buildup layer that constitutes at least the end region of the inner wall surface of the flow path on the outlet side by laser cladding on the surface of the base material processed into the predetermined shape.

[0007] Another aspect of the present invention is an extrusion die including an outlet forming portion for forming an outlet for a molten resin, the outlet forming portion including a base material and an overlay layer of a cobalt-based alloy that is overlaid on a surface of the base material and that constitutes at least an end region of a flow path surface on the outlet side.

[0008] Any combination of the above components, or mutual substitution of the components or expressions of the present invention between methods, devices, systems, etc. are also valid aspects of the present invention. Effect of the Invention

[0009] According to the present invention, a technique can be provided that can reduce the manufacturing costs of extrusion molding dies. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a schematic configuration of an inflation molding apparatus. [Diagram 2] FIG. 2 is a cross-sectional view of a die according to an embodiment. [Diagram 3] FIG. 2 is an enlarged cross-sectional view showing the periphery of the die discharge port. [Figure 4] 2A to 2C are schematic manufacturing process diagrams showing a manufacturing method of the die of FIG. 1. [Diagram 5] FIG. 5 is a schematic diagram showing the state of the build-up process in FIG. 4. [Figure 6] 5A to 5C are schematic manufacturing process diagrams showing a manufacturing method of a die of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the same or equivalent components, parts, and steps shown in each drawing will be given the same reference numerals, and duplicated explanations will be omitted as appropriate. Also, the dimensions of the parts in each drawing will be enlarged or reduced as appropriate to facilitate understanding. Also, some of the parts that are not important for explaining the embodiment will be omitted in each drawing.

[0012] In the embodiments, the extrusion molding die will be described as a round die, i.e., a die for an inflation molding apparatus, as an example. However, the technical ideas of the embodiments can also be applied to T-dies and other extrusion molding dies to the extent that they are not inconsistent.

[0013] 1 is a schematic diagram showing a schematic configuration of an inflation molding apparatus 1 including an extrusion die 2 (hereinafter simply referred to as "die 2") according to an embodiment. The inflation molding apparatus 1 includes the die 2, a cooling device 3, a pair of stabilizing plates 4, and a take-off machine 5.

[0014] Molten resin is supplied to the die 2 from an extruder (not shown). The resin is extruded from a ring-shaped discharge port 2a formed in the die 2. Air is ejected from an air ejection port 2b formed in the center of the die 2 into the inside of the extruded resin. This forms a thin resin film (hereinafter also referred to as a "bubble") that expands into a tube shape. A cooling device 3 is disposed above the die 2, and cools the bubble by blowing cooling air onto it.

[0015] A pair of stabilizing plates 4 is disposed above the cooling device 3 and guides the bubble to a take-up machine 5. The take-up machine 5 is disposed above the stabilizing plates 4. The take-up machine 5 includes a pair of pinch rolls 5a. The pair of pinch rolls 5a are driven to rotate by a motor (not shown) and pull up the guided bubble while folding it flat. A winding machine 6 winds up the folded resin film to form a film roll body 7.

[0016] 2 is a vertical cross-sectional view of the die 2. The die 2 includes a die body 10 and a discharge port forming portion 12 placed on the upper surface of the die body 10.

[0017] The configuration of the die body 10 is not particularly limited. The die body 10 has a flow path 50 for the resin. The flow path 50 of the die body 10 is connected to a flow path 18 (described later) of the discharge port forming portion 12. An arbitrary coating is applied to an inner wall surface 50a of the flow path 50 of the die body 10. The arbitrary coating may be hard chrome plating.

[0018] The outlet forming part 12 forms the outlet 2a. The outlet forming part 12 includes an inner peripheral member 14 and an outer peripheral member 16. The inner peripheral member 14 is a cylindrical member. The outer peripheral member 16 is an annular member and surrounds the inner peripheral member 14. A flow path 18, which is a cylindrical gap, is formed between the inner peripheral member 14 and the outer peripheral member 16. The molten resin flows upward through the flow path 18, and is extruded from the outlet 2a, which is the upper end opening of the flow path 18.

[0019] The inner peripheral member 14 includes a base material 20 and a buildup layer 22 as a coating layer formed on the surface of the base material 20. The base material 20 is made of a metal such as S45C. In this embodiment, the buildup layer 22 is formed on the entire outer peripheral surface 20a of the base material 20 and constitutes an inner wall surface 18a on the inner peripheral side of the flow path 18.

[0020] The outer peripheral member 16 includes a base material 30 and a buildup layer 32 as a coating layer formed on the surface of the base material 30. The base material 30 is formed of a metal such as S45C, similar to the base material 20. In this embodiment, the buildup layer 32 is formed on the entire inner peripheral surface 30a of the base material 30, and constitutes an inner wall surface 18b on the outer peripheral side of the flow path 18.

[0021] The build-up layers 22 and 32 are each formed by laser cladding. In general, the build-up layer 22 formed by laser cladding is relatively thick, and is thicker than, for example, hard chrome plating.

[0022] The build-up layers 22, 32 are formed of a material different from the base materials 20, 30, respectively, and are preferably formed of a material having relatively high toughness. The build-up layers 22, 32 may be formed of a material having higher toughness than hard chrome plating. The build-up layers 22, 32 may be formed of a cobalt-based alloy, which is a material having relatively high toughness, such as Stellite 6 (registered trademark).

[0023] Fig. 3 is an enlarged cross-sectional view showing the vicinity of the discharge port 2a in Fig. 2. The edge portions 22b, 32b of the buildup layers 22, 32 on the discharge port 2a side are chamfered. In other words, the buildup layers 22, 32 have chamfered portions on the edges on the discharge port 2a side. The chamfering may be a C-chamfer as shown in the figure, an R-chamfer, or other chamfering.

[0024] From the viewpoint of suppressing the generation of so-called "eye mucus", the edge portions 22b and 32b are sharp, in other words, the chamfering of the edge portions 22b and 32b is small, and further in other words, the emission line width W 22 ,W 32 However, if the edge portions 22b, 32b are too sharp, it is not economical because chipping of the edge portions 22b, 32b occurs more frequently during cleaning of the die 2. This must be taken into consideration when chamfering the edge portions 22b, 32b.

[0025] When the cladding layer 22 is formed of a cobalt-based alloy having relatively high toughness, such as Stellite 6 (registered trademark), the bright line width W of the edge portions 22b and 32b is 22 ,W 32 In this case, chipping of the edge portions 22b and 32b can be suppressed, and the generation of eye mucus can be suppressed.

[0026] The edge portions 20b, 30b of the base materials 20, 30 on the discharge port 2a side may be chamfered as shown by the dashed lines. In this case, it becomes easier to build up the material around the edge portions 20b, 30b.

[0027] Next, a method for manufacturing the above-mentioned die 2 will be described.

[0028] The manufacturing method of the die 2 includes a step of manufacturing components of the die 2 such as the die body 10 and the discharge port forming portion 12, a step of assembling the die 2 by combining the manufactured components, and a step of inspecting the appearance, function, etc. of the assembled die 2. The assembling step can be configured using a known assembly technique. The inspecting step can be configured using a known inspection technique.

[0029] 4 is a schematic manufacturing process diagram showing the process of manufacturing the discharge port formation portion 12. The process of manufacturing the discharge port formation portion 12 includes a forming step S102, a padding step S104, a cutting step S106, a grinding step S108, and an inspection step S110.

[0030] In the following, each process will be described using the inner circumferential member 14 as an example. The outer circumferential member 16 may be manufactured in the same manner as the inner circumferential member 14.

[0031] In the forming step S102, the base material 20 is formed into a predetermined shape by, for example, lathe processing. The base material 20 has an outer shape obtained by excluding the thickness of the buildup layer 22 from the inner circumferential member 14 at the portion where the buildup layer 22 is to be formed.

[0032] In the deposition step S104, the deposition layer 22 is formed on the surface of the base material 20 by laser cladding. FIG. 5 is a schematic diagram showing the deposition step S104. In this example, the deposition layer 22 is formed on the outer peripheral surface 20a of the base material 20 by using a deposition device 40. The deposition device 40 includes a nozzle 44 for supplying the deposition material 42 and a head 48 for irradiating the laser light 46 for inputting heat to the deposition material 42. The deposition material 42 may be a powder of a cobalt-based alloy such as Stellite 6 (registered trademark). The deposition layer 22 is formed by the deposition device 40 by supplying the deposition material 42 from the nozzle 44 and melting the deposition material 42 with the laser light 46 irradiated from the head 48. The deposition layer 22 is formed continuously over the entire area where the deposition layer 22 is to be formed by continuously changing the relative positions of the deposition material 42 supply position and the irradiation position of the laser light 46 with respect to the base material 20.

[0033] 4, in the cutting step S106, the surface of the buildup layer 22 formed in the buildup step S104 is cut so that the inner circumferential member 14 has a generally desired shape. In the cutting step S106, the surface of the buildup layer 22 may be cut by lathe processing.

[0034] In the grinding step S108, the surface of the buildup layer 22 cut in the cutting step S106 is mechanically ground so that the inner circumferential member 14 has a desired shape. When a predetermined surface roughness is required for the inner wall surface 18a of the flow path 18, the surface of the buildup layer 22 is mechanically ground so as to obtain the inner wall surface 18a having that surface roughness.

[0035] In the grinding step S108, the edge portion 22b of the buildup layer 22 on the discharge port 2a side is chamfered. In other words, a chamfer is formed on the edge of the buildup layer 22 on the discharge port 2a side. When the buildup layer 22 is made of a cobalt-based alloy such as Stellite 6 (registered trademark), the edge portion 22b has an emission line width W of 50 μm or more and 100 μm or less. 22 The material may be processed to have the following structure.

[0036] In the inspection step S110, the inner circumferential member 14 is inspected. For example, in the inspection step S110, it is inspected whether the dimensions of each portion of the inner circumferential member 14 are within an allowable range.

[0037] Also, for example, in the inspection step S110, it is inspected that (i) there is no hole of a predetermined size (for example, a diameter of 0.2 mm) or more on the inner circumferential surface 22a of the buildup layer 22 constituting the inner wall surface 18a of the flow path 18, and (ii) there is no hole in the end region 22a_1 of the inner circumferential surface 22a of the buildup layer 22 constituting the end region 18a_1 on the discharge port 2a side of the inner wall surface 18a of the flow path 18. This is because if there is a hole in the end region 22a_1 of the buildup layer 22 constituting the end region 18a_1 of the inner wall surface 18a of the flow path 18, a die line may occur in the molded product. Also, if there is a hole of a predetermined size or more in the upstream region 22a_2 of the buildup layer 22 constituting the upstream region 18a_2 of the inner wall surface 18a of the flow path 18, a die line may occur in the molded product. The end regions 18a_1, 22a_1 may be, for example, a region 10 mm from the discharge port 2a. The end regions 18a_1 and 22a_1 may be determined in advance through experiments or the like.

[0038] In addition, when manufacturing the outer peripheral member 16, the “inner peripheral member 14”, “inner wall surface 18a”, “end region 18a_1”, “upstream region 18a_2”, “base material 20”, “outer peripheral surface 20a”, “buildup layer 22”, “end region 22a_1”, “upstream region 22a_2”, “edge portion 22b”, and “bright line width W 22 " are respectively referred to as "outer peripheral member 16", "inner wall surface 18b", "end region 18b_1", "upstream region 18b_2", "base material 30", "inner peripheral surface 30a", "buildup layer 32", "end region 32a_1", "upstream region 32a_2", "edge portion 32b", and "bright line width W 32 " should be read as follows:

[0039] Next, a manufacturing method according to a comparative example to be compared with the embodiment will be described.

[0040] 6 is a schematic diagram showing the steps of manufacturing the discharge port forming part according to the comparative example. The steps of manufacturing the discharge port forming part according to the comparative example include a forming step S202, a rough polishing step S204, a grinding step S206, a pre-plating inspection step S208, a pre-plating polishing step S210, a plating step S212, a post-plating polishing step S214, and an inspection step S216.

[0041] The forming step S202 corresponds to the forming step 102.

[0042] In the rough polishing step S204, the outer peripheral surface of the base material of the inner peripheral member is buffed, i.e., polished by hand, to remove machining marks on the outer peripheral surface of the base material in the forming step S202. There is a risk that the shape of the outer peripheral surface of the base material will be distorted by hand polishing. The same applies to the steps described below.

[0043] In the manufacturing method of this embodiment, since a relatively thick build-up layer 22 is formed by laser cladding, the influence of machining marks on the outer peripheral surface 20a of the base material 20 is absorbed by the build-up layer 22. Therefore, in the manufacturing method of this embodiment, a step equivalent to the rough polishing step S204 is not required.

[0044] In the lapping step S206, the upper surface of the die body 10 and the lower surface of the discharge port forming portion 12 are finished flat to prevent resin from leaking between the die body 10 and the discharge port forming portion 12. In this embodiment, since it is sufficient to finish them flat in the grinding step S108, a step equivalent to the lapping step S206 is not necessary.

[0045] In the pre-plating inspection step S208, the dimensions of the base material are inspected to see if they are within an allowable range.

[0046] In the pre-plating polishing step S210, the outer peripheral surface of the base material is buffed, i.e., hand-polished, so as to meet a standard value for surface roughness, because a rough surface of the base material is prone to pits and pinholes.

[0047] In the plating step S212, the base material is plated with hard chrome.

[0048] In the post-plating polishing step S214, the surface of the hard chrome plating is buffed, i.e., hand polished.

[0049] The inspection step S216 corresponds to the inspection step S110.

[0050] Next, effects achieved by the embodiment will be described.

[0051] In the hard chrome plating of the comparative example, pits and pinholes are often generated. Even if a certain pit is removed by scraping the surface of the hard chrome plating, other pits and pinholes are often exposed as a result of evenly scraping the surface. In addition, in the process of scraping the hard chrome plating until the pits and pinholes are not exposed, the thickness of the hard chrome plating may become thinner than the allowable thickness, in which case the plating must be redone. In contrast, according to the present embodiment, the buildup layers 22, 32 constituting the inner wall surfaces 18a, 18b of the flow path 18 are formed by laser cladding. In the buildup layers 22, 32 formed by laser cladding, holes corresponding to the pits and pinholes in the hard chrome plating are rarely generated. In addition, since the buildup layers 22, 32 formed by laser cladding are relatively thick, there is a large amount of correction, and therefore even if holes exist on the surfaces of the buildup layers 22, 32, they can be easily repaired within the range of the correction amount.

[0052] The outer peripheral surface of the inner peripheral member 14 and the inner peripheral surface of the outer peripheral member 16 are required to have high shape accuracy in order to form the flow path 18. Here, in the manufacturing method according to the comparative example, the outer peripheral surface of the inner peripheral member 14 and the inner peripheral surface of the outer peripheral member 16 are formed by hard chrome plating. Since the hard chrome plating is relatively brittle, when the hard chrome plating is mechanically ground, cracks and chips may occur at the edges. Therefore, in the post-plating polishing step S214, the hard chrome plating is buffed, i.e., hand-polished. In addition, since pits and pinholes are easily generated in the base material on which the hard chrome plating is formed if the surface is rough, the base material is also buffed, i.e., hand-polished in the pre-plating polishing step S210. Furthermore, the base material is also buffed, i.e., hand-polished in the post-plating polishing step S214. Therefore, in the manufacturing method according to the comparative example, it is difficult even for an expert to manufacture the inner peripheral member 14 and the outer peripheral member 16 with high shape accuracy. It is even more difficult for an unexpert. In contrast, in the present embodiment, the surface of the buildup layer 22, which is the outer peripheral surface of the inner circumferential component 14, and the surface of the buildup layer 32, which is the inner peripheral surface of the outer peripheral component 16, are mechanically ground. Therefore, the inner circumferential component 14 and the outer circumferential component 16 can be manufactured with high shape accuracy regardless of the level of skill.

[0053] In this embodiment, for example, the cladding layer 22 is formed of a cobalt-based alloy such as Stellite 6 (registered trademark), and the emission line width W 22 ,W 32 is finished to 50 μm or more and 100 μm or less. In this case, chipping of the edge portions 22b, 32b can be suppressed, and the generation of eye mucus can be suppressed. In order to prevent the generation of eye mucus, the bright line width can be narrowed, for example, to 20 μm or less, but as mentioned above, there is a concern about edge chipping during cleaning, and the cost of maintaining accuracy also increases, so it is preferable to ensure a bright line width of 20 μm or more. In contrast, in the manufacturing method according to the comparative example, the edge portions are made of chrome plating, which has a relatively low toughness, so in order to suppress chipping of the edge portions, it is necessary to finish the bright line width of the edge portions to 150 μm or more. Therefore, eye mucus is more likely to be generated than in this embodiment.

[0054] The present invention has been described above based on an embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications are possible in the combination of each component and each treatment process, and that such modifications are also within the scope of the present invention.

[0055] (Variation 1) Although not specifically mentioned in the embodiment, the build-up layer 22 by laser cladding may be formed at least in the end region 20a_1 on the discharge port 2a side of the outer peripheral surface 20a of the base material 20. That is, the build-up layer 22 by laser cladding may be formed so as to constitute at least the end region 18a_1 on the discharge port 2a side of the inner wall surface 18a on the inner peripheral side of the flow path 18. Therefore, for example, the build-up layer 22 by laser cladding may be formed only in the end region 20a_1 of the outer peripheral surface 20a of the base material 20. In this case, another coating, for example, hard chrome plating, may be applied to the upstream region 20a_2.

[0056] Similarly, the build-up layer 32 by laser cladding may be formed at least in the end region 30a_1 on the discharge port 2a side of the inner circumferential surface 30a of the base material 30. That is, the build-up layer 32 by laser cladding may be formed so as to constitute at least the end region 18b_1 on the discharge port 2a side of the inner wall surface 18b on the outer circumferential side of the flow path 18. Therefore, for example, the build-up layer 32 by laser cladding may be formed only in the end region 30a_1 of the inner circumferential surface 30a of the base material 30. In this case, another coating, for example, hard chrome plating, may be applied to the upstream region 30a_2.

[0057] Any combination of the above-mentioned embodiments and modifications is also useful as an embodiment of the present invention. A new embodiment resulting from the combination has the effects of the combined embodiments and modifications. It will also be understood by those skilled in the art that the functions to be performed by each component recited in the claims can be realized by each component shown in the embodiments and modifications alone or in cooperation with each other. [Explanation of symbols]

[0058] 2 die, 2a discharge port, 12 discharge port forming portion, 14 inner peripheral member, 16 outer peripheral member, 18 flow path, 18a, 18b inner wall surface, 20 base material, 22 build-up layer, 30 base material, 32 build-up layer.

Claims

1. A method for manufacturing an extrusion die having a discharge port forming part that forms a discharge port, comprising: forming a base material of the discharge port forming portion into a predetermined shape; forming a build-up layer by laser cladding on a surface of a base material processed into a predetermined shape, the build-up layer constituting at least an end region of an inner wall surface of the flow path on a discharge port side; A method for manufacturing an extrusion die comprising:

2. The method of claim 1 further comprising mechanically grinding a surface of the buildup layer.

3. The build-up layer is a layer of a cobalt-based alloy, The method for manufacturing an extrusion die according to claim 2, wherein mechanical grinding of the surface of the buildup layer includes finishing the edge portion of the buildup layer on the outlet side to a bright line width of 20 μm or more and 100 μm or less.

4. An extrusion molding die having a discharge port forming part that forms a discharge port for a molten resin, The discharge port forming portion is A base material; A build-up layer of a cobalt-based alloy is built up on the surface of the base material and constitutes at least an end region of the flow path surface on the discharge port side; 1. An extrusion die comprising:

5. 5. The extrusion molding die according to claim 4, wherein the edge portion of the buildup layer on the discharge port side has a bright line width of 100 μm or less.

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