JP6282527B2 - Method for producing synthetic resin molding - Google Patents

Description

The present invention relates to an injection mold for forming a resin molded body by injection molding of a synthetic resin. In particular, the present invention relates to an injection mold for molding a bottomed cylindrical resin molded body having a hollow cylindrical portion and a bottom portion.

BACKGROUND ART A bottomed cylindrical resin molded body having a hollow cylindrical portion and a bottom portion provided so as to close one end thereof is widely used as a resin cap, a resin stopper, a resin cover, and the like. Such a bottomed cylindrical resin molded body can be formed by injection molding of a synthetic resin, preferably a thermoplastic resin. When these molded bodies are formed by injection molding, there is a merit that a resin molded body can be manufactured accurately and efficiently.

When a resin molded body having a cylindrical part is manufactured by injection molding, the cylindrical part is typically a core mold that defines the inner peripheral surface shape of the cylindrical part, and a cavity mold that defines the outer peripheral surface shape of the cylindrical part. It is formed by. When the mold is opened and the resin molded body is taken out, usually, the mold body is first removed from the cavity mold while leaving the molded body remaining in the core mold when the mold is opened, and then Then, the resin molded body is taken out so that the molded body is removed from the core mold using a protruding pin or the like provided on the core mold side.

For example, Patent Document 1 discloses a mold for forming a resin molded body having a pipe-shaped hollow cylindrical portion. In this mold, in order to improve the demoldability of the resin molded body, a highly slippery film is coated on the outer peripheral surface of the center pin (core mold) of the mold and the inner peripheral surface of the cavity mold. Is disclosed. And, regarding demolding of the molded body from the mold, it is disclosed that the molded body is first demolded from the cavity mold, and then the molded body is demolded from the center pin (core mold) (Patent Document 1). FIG. 3 etc.).

JP 2001-219451 A

As described above, in the injection mold, the order in which the molded bodies should be removed is determined. Therefore, if the actual order in which the molded bodies are removed is changed, the molded product cannot be removed. It will be a manufacturing defect. For example, as shown in FIG. 9, the molded body 9 is removed from the cavity mold 92 while leaving the core mold 91 in the core mold 91 (FIG. 9 (a)), and then the protruding pin 93 is operated to make the molded body into the core. When the mold is configured to be removed from the mold 91 (FIG. 9B), as shown in FIG. 10, when the molded body 9 remains in the cavity mold 92 when the mold is opened ( FIG. 10A), even if the protruding pin 93 provided on the core mold 91 side is no longer operated, the molded product 9 cannot be removed from the cavity mold 92, resulting in a so-called cavity remaining defect (FIG. 10). (B)). In the process of mass-producing resin moldings one after another, if such a defective take-out of a molded product occurs, it will be necessary to stop the series of injection molding processes and restore it to a normal state, and the mold may be broken. This is not preferable.

In order to ensure that the molded body remains on the core mold side when the mold is opened, the inner peripheral surface of the cylindrical portion of the molded body 99 may be shaped to cause an undercut in the demolding direction as shown in FIG. Conceivable. If the core mold 991 and the inner peripheral surface of the molded body have an undercut shape, the undercut meshes with each other and the core mold cannot be removed unless the molded body is forcibly deformed, and the core mold removal resistance is increased. Therefore, the molded body 99 can be reliably left on the core mold 991 side when the mold is opened.

However, according to the inventor's study, it has been found that providing an undercut on the inner peripheral surface of the molded body cylindrical portion may cause another adverse effect. The molded product 99 remaining on the core mold 991 side is then demolded from the core mold 991 by an extruding pin or the like, but since the demolding resistance at that time is large, the resin molded body is deformed by the force of the extruding pin. As a result, the predetermined shape accuracy may not be achieved, or pin marks may remain on the surface of the resin molded product, resulting in poor appearance. In particular, when the resin molded product is a precision resin molded product that requires high accuracy, this problem tends to appear remarkably. That is, it has been found that if an undercut is provided on the inner peripheral surface of the molded body cylindrical portion, the resistance to demolding from the core mold tends to be excessive.

An object of the present invention is to provide an injection mold capable of preventing and suppressing defects remaining in a cavity while forming a bottomed cylindrical resin molded body.

As a result of intensive studies, the inventor has found that the above-described object can be achieved by connecting the ridges in a specific form on the surface of the cavity mold that forms the bottom of the resin molded body, thereby completing the present invention.

The present invention relates to a synthetic resin molding in which a bottomed cylindrical resin molded body having a hollow cylindrical portion and a bottom portion provided so as to close an end of the cylindrical portion is formed by injection molding of a synthetic resin. A body manufacturing method, comprising: a core mold that defines at least an inner peripheral surface shape of the tubular portion; and a cavity mold that defines at least an outer peripheral surface shape of the tubular portion; The surface for forming the outer surface of the injection molding gold is provided with a region in which ridges having a height of 1 to 10 μm and a width of 1 to 10 μm are continuously provided at intervals of 1 to 10 μm. A step of preparing a mold, and a thermoplastic resin in a molten state having a melt flow rate of 3 g / 10 min to 100 g / 10 min in the injection mold, and resin in a space between the continuous protrusions Does not penetrate completely, and the outer surface of the bottom of the molded body Injecting so that a linear space remains between the mold surfaces, forming a resin molded body in the mold, and after cooling and solidifying the injected resin, the mold is opened. Thus, the synthetic resin molded body thus formed remains on the core mold side and the resin molded body is taken out from the cavity mold (first invention).

In the first invention, the mold is prepared such that at least a part of the continuously provided ridges extends from the peripheral portion of the surface forming the outer surface of the bottom portion of the cavity mold toward the central portion of the surface. Is preferred (second invention). Alternatively, in the first invention, the mold is prepared such that at least a part of the continuously provided ridges extends in a direction substantially orthogonal to the flow direction of the resin injected from the gate into the mold. It is preferable (third invention). Alternatively, in the first invention, region, it is preferable to prepare so that mold cotton throughout the surfaces forming the outer surface of the bottom portion in the cavity mold (Fourth invention) which projections are continuously provided. Alternatively, in the first invention, it is preferable to prepare the mold so that the surface forming the inner peripheral surface of the bottom portion of the core mold is a smooth flat shape (fifth invention).

According to the method for producing a synthetic resin molded body of the present invention ( first invention), it is possible to prevent / suppress defects in the cavity remaining when a molded product is taken out. Moreover, if it is made like 2nd invention thru | or 5th invention, the defect prevention of a cavity remainder can be performed more effectively.

It is a figure which shows the example of the resin molding manufactured with the metal mold | die of 1st Embodiment. It is a schematic diagram which shows the structure of the metal mold | die of 1st Embodiment in a mold closing / mold opening state. It is a schematic diagram which shows the cavity type | mold of the metal mold | die of 1st Embodiment. It is a figure which shows typically a mode that the bottom part of a resin molding is formed with the metal mold | die of 1st Embodiment. It is a figure which shows typically the demolding process in the injection molding which uses the metal mold | die of 1st Embodiment. It is a figure which shows the example of another resin molding. It is a figure which shows the example of another resin molding. It is a figure which shows typically the example of the form of the protruding item | line provided in a metal mold | die. It is a figure which shows typically the demolding process in the injection molding of a bottomed cylindrical resin molding. It is a figure which shows typically the cavity remaining defect in the demolding process in the injection molding of a bottomed cylindrical resin molding. It is a figure which shows the example of a form which provided the undercut in the cylindrical part internal peripheral surface of a bottomed cylindrical resin molding.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking a resin cap attached to an end of a rod or pipe as an example. The present invention is not limited to the individual embodiments shown below, and can be carried out by changing the form.

FIG. 1 shows a resin molded body 1 formed by the mold of the first embodiment. The left view of FIG. 1 is shown as a cross-sectional view along the axis of the cylindrical portion of the resin molded body, and the right view is shown as an external view seen from the bottom side of the bottomed cylindrical shape. The resin molded body 1 is a synthetic resin member and is formed by injection molding. And the resin molding 1 has the hollow cylindrical part 11 and the bottom part 12 provided so that the edge part of the cylindrical part 11 might be closed. In the present embodiment, the resin molded body 1 is formed in a cup shape, that is, a bottomed cylindrical shape, by a square cylindrical hollow cylindrical portion 11 and a rectangular bottom portion 12. In this embodiment, the cylindrical part 11 is formed in the square cylinder shape of a square hollow cross section.

The resin molded body 1 of the present embodiment is a member used as a cap member attached to the tip of a bar or pipe. In addition, the specific use of a resin molding is not specifically limited.

As will be described later, the resin molded body 1 is formed by injection molding of a synthetic resin. In the injection molding process, the cylindrical part 11 of the resin molded body 1 is formed by a rectangular cylindrical space (cavity) between the core mold and the cavity mold, and is cavity type along the axial direction of the cylindrical part. Or removed from the core mold. Further, the bottom 12 of the resin molded body 1 is formed by a flat space (cavity) between the core mold and the cavity mold, and is peeled off in a direction perpendicular to the formation surface of the core mold or the cavity mold. Demolded.

The inner surface of the bottom 12 of the resin molded body 1 is formed on a smooth plane. Further, the outer surface 12f of the bottom portion 12 of the resin molded body 1 is formed to have a surface having a fine striped matte surface form. As will be described later, this surface shape of the bottom outer surface 12f is generated corresponding to the surface shape of the cavity mold.

In the resin molded body 1, an example in which the entire outer surface 12 f of the bottom portion 12 is a striped matte surface is shown, but only a part of the outer surface may be a striped matte surface.

Further, the resin molded body 1 has a gate mark GR, and at the time of injection molding, the resin flows from the position of the gate mark GR toward another part, but a striped matte surface provided on the bottom outer surface 12f. The direction in which the stripes extend is approximately perpendicular to the resin flow direction.

The inner peripheral surface and the outer peripheral surface of the cylindrical portion 11 of the resin molded body 1 are formed smoothly so that there is no undercut portion in the demolding direction.

The synthetic resin constituting the resin molded body 1 is not particularly limited as long as it is a resin that can be molded by injection molding. Preferably, an olefin resin such as a polypropylene resin, a thermoplastic resin such as a polyamide resin or an acrylonitrile butadiene styrene resin, a thermosetting resin such as a melamine resin, rubber, a thermoplastic elastomer, or the like can be used. Among these, a thermoplastic resin can be particularly preferably used. The resin molded body 1 is made of a polyamide resin.

The manufacturing method of the resin molding 1 and the metal mold | die used for manufacture are demonstrated. The resin molded body 1 is manufactured by resin injection molding. FIG. 2 shows a mold 2 used for injection molding of the resin molded body 1. FIG. 3 shows a cavity mold 22 among the molds. FIG. 2A schematically shows a state where the mold 2 is closed, and FIG. 2B schematically shows a state where the mold 2 is opened. FIG. 2 shows the cavity mold 22 and the core mold 21 in a cross-sectional view. Further, in the drawing of the cavity mold 22 in FIG. 3, an external view of the cavity mold 22 viewed from the left side is shown, and a sectional view of the cavity mold 22 is shown on the right side. In these drawings, the hatching of the cross section of the cavity mold 22 and the core mold 21 is omitted for easy understanding of the drawings.

The mold 2 has a core mold 21 and a cavity mold 22. The core mold 21 defines at least the inner peripheral surface of the cylindrical portion 11 of the resin molded body 1, and the cavity mold 22 defines at least the outer peripheral surface of the cylindrical portion 11 of the resin molded body 1. Therefore, the core mold 21 is provided with a smooth surface 21a corresponding to the inner peripheral surface shape of the cylindrical portion 11 of the resin molded body, and the cavity mold 22 has an outer periphery of the cylindrical portion 11 of the resin molded body. A smooth surface 22a corresponding to the surface shape is provided.

In the demolding process to be described later, the process is designed so that the molded body remains on the core mold side when the mold is opened. After the mold is opened, the core is formed in order to finally remove the resin molded body 1 from the core mold 21. The mold is provided with a protruding pin 23. From the viewpoint of configuring the protruding pin on the mold, it is preferable to configure the mold 2 such that the core mold 21 side is the movable mold side and the cavity mold 22 side is the fixed mold side.

As shown in FIG. 3, in the cavity mold 22, a plurality of ridges are provided in stripes on the surface 22 f that defines the outer surface 12 f of the bottom 12 of the resin molded body 1. On the other hand, in the core mold 21, the surface 21 f that defines the inner surface of the bottom portion 12 of the resin molded body 1 is formed in a smooth flat shape.

The surface 22f of the cavity mold 22 will be described in detail. The plurality of ridges provided on the surface 22f defining the outer surface 12f of the bottom portion 12 of the resin molded body 1 are spaced apart from each other by a predetermined distance, for example, as shown in FIG. 8A. As shown in FIG. By providing a plurality of ridges in parallel, the surface of the surface 22f looks striped. The ridges on the surface 22f are connected to a predetermined region of the surface 22f so that the height of the ridges is 1 to 10 μm, the width of the ridges is 1 to 10 μm, and the interval between the ridges is 1 to 10 μm. It is installed. The height of the ridge is the dimension CC in FIG. 4A, the width of the ridge is the dimension AA in FIG. 4A, and the distance between the ridges is the dimension BB in FIG. 4A. is there. In the present embodiment, the ridges are connected to the entire area of the surface 22f. However, the ridges may be connected to only a part of the area of the surface 22f as necessary.

In the mold of the present embodiment, the ridges are provided in parallel with a height of 5 μm, a width of the ridges of 6 μm, and an interval between the ridges of 5 μm. The form in which the ridges are continuously provided is particularly preferably provided such that the height of the ridges is 2 to 8 μm, the width of the ridges is 2 to 8 μm, and the interval between the ridges is 2 to 8 μm. The height CC of the ridges and the interval BB between the ridges is preferably such that the ratio CC / BB satisfies 0.3 ≦ CC / BB ≦ 2.0, and 0.5 ≦ CC / BB ≦ A value of 1.5 is particularly preferable.

The mold 2 is manufactured by a known method. The portion of the surface 22f defining the outer surface of the bottom of the resin mold body of the cavity mold 22 can be formed by, for example, etching, laser processing, fine groove cutting, die-sinking electric discharge machining, or the like.

Hereinafter, the manufacturing process of the synthetic resin molding using the above-mentioned mold and the operation effect produced by injection molding using the mold of the present invention will be described.

In a state where the mold 2 is closed and a cavity is formed, resin is injected through a sprue, a runner, and a gate G provided in the mold, and the resin molded body 1 is formed. These details are omitted in FIGS. The kind of runner or gate is not particularly limited, and various types can be adopted. When forming a resin molded body from a thermoplastic resin, the resin is injected into the mold in a molten state.

The viscosity of the injected resin is usually about 2 g / 10 min to 170 g / 10 min in terms of melt flow rate. More preferably, it is about 3 g / 10 minutes to 100 g / 10 minutes.

FIG. 4 shows how the bottom 12 of the resin molded body is formed by filling the resin inside the mold 2. In FIG. 4A, molten resin flows into the space between the core mold 21 and the cavity mold 22 from the left side of the figure. Here, the surface 21f of the core mold 21 is a smooth surface, while the surface 22f of the cavity mold 22 is provided with ridges 22p, 22p,.

When the ridges are continuously provided in the above-described size, the resin cannot completely enter the space between the continuously provided ridges due to the viscosity of the molten resin. For this reason, as shown in FIG. 4B, in the state where the injection and filling of the resin are completed, the resin contacts the apex portion of the ridges on the surface 22f provided with the ridges 22p of the cavity mold 22. However, in the portion between the ridges, the resin does not contact the mold surface, and the mold surface and the resin surface are not completely adhered. That is, at the bottom 12 of the resin molded body 1 to be formed, the resin is not in close contact with the surface 22f of the cavity mold due to the presence of the continuous protrusions 22p and 22p, and the bottom 12 of the molded body and the cavity mold A linear space is left between the 22 surfaces 22f. On the other hand, the resin comes into close contact with the smooth molding surface 21f of the core mold 21, and the smooth shape of the surface 21f is faithfully transferred.

When the resin filling is completed in this state and the resin is solidified to complete the resin molded body 1, the outer surface 12 f of the bottom portion 12 of the resin molded body has a portion in contact with the top of the ridge provided in the cavity mold, and A mat-shaped molding surface having a striped surface form in which portions formed without contacting the mold surface between the ridges and the ridges are alternately arranged.

After injecting the resin, the resin molded body 1 is taken out from the mold 2 after the resin is solidified. FIG. 5 schematically shows the demolding process. When the resin molded body 1 is formed (FIG. 5A), first, the core mold 21 and the cavity mold 22 are opened. At this time, the resin molded body 1 remains on the core mold 21 side (FIG. 5B). Thereafter, the protrusion pin 23 provided in the core mold is operated to remove the resin molded body 1 from the core mold 21 (FIG. 5C). The resin molded body 1 taken out from the mold 2 is collected by a transport robot or the like.

If the mold 2 is used, as shown in FIG. 4B, the bottom outer surface 12f of the molded body 1 and the molding surface 22f of the cavity mold can be prevented from coming into close contact with each other, and both can be easily peeled off. Therefore, during the mold opening process illustrated in FIG. 5B, the bottom 12 of the molded body 1 and the bottom molding surface 22 f of the cavity mold 22 are easily peeled off, and the resin molded body 1 is more oriented toward the core mold 21. Can be prevented easily, and so-called cavity defects can be prevented and suppressed.

From the viewpoint of facilitating the release of the bottom 12 of the resin molded body from the cavity mold, at least a part of the continuously provided ridges forms the outer surface of the bottom with the cavity mold 22 as in this embodiment. It is preferable to provide a ridge from the peripheral portion to the central portion so as to extend from the peripheral portion of the surface 22f toward the central portion of the surface. If this is done, air can flow from the peripheral portion of the surface 22f toward the center of the surface through the space left between the ridges, so the outer surface 12f at the bottom of the resin molded body. Then, the cavity-type surface 22f is easily peeled even at the center of the surface 22f, and the effect of preventing and suppressing the remaining defects of the cavity is enhanced.

Further, as in the present embodiment, at least a part of the continuously provided ridges extends in a direction substantially orthogonal to the flow direction of the resin injected from the gate into the mold. In addition, the effect of preventing / suppressing remaining cavity problems is enhanced. When the extending direction of the ridges and the flow direction of the resin are substantially orthogonal, the molten resin is difficult to enter between the ridges and the ridges, and a space is likely to remain between the ridges. Here, the term “substantially orthogonal” does not have to be strictly 90 degrees, but may be about 60 degrees.

In addition, as in the present embodiment, the region where the ridges are continuously provided extends over the entire surface 22f of the cavity mold 22 forming the bottom outer surface 12f. This is a particularly preferable form from the viewpoint of easy release. In addition, the area | region which connects a protruding item | line does not need to cover the whole surface 12f which forms a bottom part outer surface, and may be a part of surface 12f.

Further, a resin molded body manufactured by the mold 2 is formed of a thermoplastic resin, and in the injection molding process, a molten thermoplastic resin is injected into the mold, and the injected resin is cooled and solidified to be a resin molded body. It is preferable to obtain When the injected thermoplastic resin in the molten state comes into contact with the top of the ridges provided in the mold, it is cooled from that part, the viscosity is further increased, and it is difficult to enter the space between the ridges. This is because adhesion between the outer surface of the bottom of the molded resin body and the cavity mold is more reliably prevented. Among thermoplastic resins, especially when injection molding is performed using polyphenylene sulfide (PPS) resin, polybutylene terephthalate (PBT) resin, polyphenylene ether (PPE) resin, etc. Effectively demonstrated.

The present invention is not limited to the above embodiment, and can be implemented with various modifications. Other embodiments of the present invention will be described below. However, in the following description, portions different from the above embodiments will be mainly described, and detailed descriptions of the same portions will be omitted. In addition, these embodiments can be implemented by combining some of them or replacing some of them.

In FIG. 6, the resin molding 3 of 2nd Embodiment is shown. In this embodiment, the form of the cylindrical part and bottom part of the resin molding 3 is different. In the present embodiment, the cylindrical portion 31 of the resin molded body is formed in a cylindrical shape, and the bottom portion 32 is formed in a disk shape. The entire bottom outer surface 32f has a striped matte shape, the direction of the resin flowing from the gate (corresponding to the gate mark GR in the molded product) during injection molding, and the striped pattern on the bottom outer surface. This is the same in that the directions are substantially orthogonal.

The mold for manufacturing the resin molded body of the present embodiment also has an effect of making it easy to release the bottom 32 of the resin molded body from the cavity mold, as in the mold of the first embodiment. That is, as long as it is a bottomed cylindrical molded body, the specific shape of the molded body is not particularly limited. Moreover, you may change suitably the cylindrical part form and the surface form of a cylindrical part.

Further, as in the resin molded body 4 of the third embodiment shown in FIG. 7, the outer surface of the bottom portion 42 may be a concentric striped matte shape. That is, the striped pattern provided on the bottom outer surface 42f and the form of the ridge connected to the cavity mold may be a form in which straight lines are connected in parallel, or may be concentric. Further, the ridges may be continuously provided in such a form that the ridges cross each other. Even in such a form, the effect of facilitating the release of the bottom 42 of the resin molded body from the cavity mold occurs.

In particular, as in the embodiment of FIG. 7, a gate (a gate mark GR in the case of a resin molded body) is provided at substantially the center of the bottom portion 42 (provided by a ring gate in this embodiment) and injected from the gate. When the resin flows radially from the central portion of the bottom portion 42 toward the peripheral portion of the bottom portion 42, it is particularly preferable that the striped pattern of the bottom outer surface 42f is provided concentrically as in the present embodiment.

Various forms can be adopted as the form of the ridges connected to the cavity mold. The ridge may have a so-called mountain-shaped cross section, or the ridge may have a trapezoidal or square cross section. From the viewpoint of preventing the resin from entering the space between the ridges, it is preferable that the cross-sectional shape of the ridges is a cross-sectional shape that becomes a more prominent ridge, for example, a trapezoidal shape or a rectangular shape.

Various forms of the extending direction of the ridges can also be adopted. FIG. 8 shows a perspective view of one of the connected ridges taken out. As shown in FIG. 8A, the ridges may have a form that is continuous in the extending direction (indicated by an arrow). Alternatively, the ridge may be in a form intermittently provided in the extending direction. For example, as shown in FIG. 8B, the ridge is a kamaboko-shaped protrusion extending from the ridge. It may be in the form of being arranged at a predetermined interval in the current direction. Alternatively, as shown in FIG. 8C, the protrusion may have a shape in which protrusions are provided intermittently in the extending direction. For example, a pyramid-shaped protrusion (for example, a pyramid shape) protrudes. It may be in the form of being arranged at a predetermined interval along the extending direction of the strip.

Moreover, the specific application field in which a resin molding is used is not specifically limited. The present invention can be widely applied to fields where synthetic resin resin moldings are applicable. For example, the resin molded body of the present invention can be used for a resin cap, a resin stopper, a spacer, a cover, and the like. Furthermore, the resin molded body manufactured by the mold of the present invention can be used as a component part such as a resin case or a resin tank that can use a bottomed resin molded body having a cylindrical part and a bottom part, and a mechanical part. .

The injection mold of the present invention can efficiently produce a resin molded body by injection molding, and has high industrial utility value.

DESCRIPTION OF SYMBOLS 1 Resin molding 11 Tubular part 12 Bottom part 12f Bottom outer surface GR Gate trace 2 Mold 21 Core mold 22 Cavity mold 23 Extrusion pin 3, 4 Resin moldings 31, 41 Tubular part 32, 42 Bottom part 32f, 42f Bottom outer surface 9 Molded body 91 Core mold 92 Cavity mold 93 Extrusion pin

Claims (5)

A method for manufacturing a synthetic resin molded body, comprising forming a bottomed cylindrical resin molded body having a hollow cylindrical portion and a bottom portion provided so as to close an end of the cylindrical portion by injection molding of a synthetic resin. Because
And the core mold defining the inner peripheral surface shape of at least the cylindrical portion, as well as organic and cavity mold for defining the outer peripheral surface shape of at least the cylindrical portion,
In the cavity mold, the surface forming the outer surface of the bottom is provided with a region in which ridges having a height of 1 to 10 μm and a width of 1 to 10 μm are continuously provided at intervals of 1 to 10 μm. Preparing a mold for injection molding ,
A molten thermoplastic resin having a melt flow rate of 3 g / 10 min to 100 g / 10 min is added to the injection mold.
Resin is injected into the space between the continuous protrusions so that the resin does not completely enter, leaving a linear space between the outer surface of the bottom of the molded body and the surface of the cavity mold. Forming in a mold;
After the injected resin is cooled and solidified, the mold is opened, and the formed synthetic resin molded body remains on the core mold side, and the resin molded body is taken out from the cavity mold;
A method for producing a synthetic resin molded body comprising 2. An injection mold is prepared such that at least a part of the continuously provided ridges extends from a peripheral portion of a surface forming a bottom outer surface of the cavity mold toward a central portion of the surface. The manufacturing method of the synthetic resin molding as described in any one of. 2. The injection mold is prepared such that at least a part of the continuously provided ridges extends in a direction substantially perpendicular to the flow direction of the resin injected from the gate into the mold. The manufacturing method of the synthetic resin molding as described in any one of. Ridge area is continuously provided is method for producing a synthetic resin molded article according to claim 1 for preparing an injection mold in so that cotton throughout the surfaces forming the outer surface of the bottom portion in the cavity mold. The method for producing a synthetic resin molded body according to claim 1, wherein the mold for injection molding is prepared so that a surface of the core mold forming the inner peripheral surface of the bottom portion is a smooth flat surface.

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