JP6373609B2 - Manufacturing method of resin molding - Google Patents

Description

The present invention relates to a resin molded body formed by injection molding of a synthetic resin. In particular, it is related with the resin molding which has a hollow cylindrical part.

A resin molded body having a hollow cylindrical portion is widely used as a connector member for connecting a pipe such as a resin pipe, a resin cap, a resin stopper, a resin cover, or a tube. The resin molded body having such a hollow cylindrical portion 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 hollow cylindrical portion is manufactured by injection molding, the cylindrical portion is usually a core mold that defines the inner peripheral shape of the cylindrical portion, and a cavity mold that defines the outer peripheral shape of the cylindrical portion. And formed. 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. 6, the molded body 9 is removed from the cavity mold 92 while leaving the molded body 9 in the core mold 91 (FIG. 6A), 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. 6B), as shown in FIG. 7, when the molded body 9 remains in the cavity mold 92 when the mold is opened ( FIG. 7 (a)), the molded product 9 can no longer be removed from the cavity die 92 even when the protruding pin 93 provided on the core die 91 side is operated, resulting in a so-called cavity remaining defect (FIG. 7). (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 a resin molded body having a shape that can prevent a defect in the remaining cavity and can adjust the demolding resistance from the core mold to an appropriate level.

As a result of intensive studies, the inventor divided the inner peripheral surface of the cylindrical portion of the resin molded body into a plurality of partial regions in a straight line along the demolding direction, and provided a step between adjacent partial regions, The inventors have found that the above object can be achieved when the step is set to a predetermined size, and the present invention has been completed.

The present invention is a resin molded body formed by injection molding of a synthetic resin and having a hollow cylindrical portion, and the inner peripheral surface of the cylindrical portion has no undercut in the demolding direction, and the inner In at least a part of the peripheral surface, the inner peripheral surface is divided into a plurality of partial regions extending linearly along the demolding direction so that adjacent partial regions are offset from each other in the radial direction of the cylindrical portion. A step is provided, the step extends linearly along the demolding direction, and the size of the step in the radial direction of the cylindrical portion is 0.5 to 20 of the thickness of the cylindrical portion. % Resin molded body (first invention).

In the first aspect of the invention, in the partial region of the cylindrical portion in the axial direction, the inner peripheral surface is divided into partial regions and provided with a step, while in the other region of the cylindrical portion in the axial direction, It is preferable that the inner peripheral surface be flat (second invention). Alternatively, in the first aspect of the present invention, on the inner peripheral surface of the tubular portion, a gap is formed between the partial region located on the radially inner side of the tubular portion and the partial region located on the radially outer side of the tubular portion. Are preferably different (third invention). Or in 1st invention, it is preferable that the cross-sectional shape of a cylindrical part is made into polygonal shape, oval shape, and ellipse shape (4th invention).

According to the resin molded body of the present invention (first invention), it is possible to prevent a defect in the cavity remaining at the time of taking out a molded product, and to adjust the demolding resistance from the core mold to an appropriate level. Further, if the second and third inventions are adopted, the degree of freedom in adjusting the mold release resistance is increased, and the cavity remaining defect prevention and the adjustment of the core mold release resistance can be more effectively performed. Can do. Moreover, if it is made like 4th invention, torque can be transmitted through a cylindrical part using the cross-sectional shape of a cylindrical part.

It is a figure which shows the resin molding of 1st Embodiment. It is a schematic diagram which shows the structure of the metal mold | die for shape | molding the resin molding of 1st Embodiment in a mold closed state. It is a schematic diagram which shows the structure of the metal mold | die for shape | molding the resin molding of 1st Embodiment in a mold open state. It is a figure which shows typically the demolding process in the resin molding of 1st Embodiment. It is a figure which shows the resin molding of 2nd Embodiment. It is a figure which shows typically the demolding process in the conventional resin molding. It is a figure which shows typically the cavity remaining defect in the demolding process in the conventional resin molding. It is a figure which shows the form which provided the undercut in the cylindrical part inner peripheral surface of the 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 according to the first embodiment. The upper diagram in FIG. 1 is shown as a cross-sectional view along the axis of the cylindrical portion of the resin molded body, and the lower diagram is shown as an external view seen from the open end of the cylindrical portion. The resin molded body 1 is a synthetic resin member and is formed by injection molding. The resin molded body 1 has a hollow cylindrical portion 11. In the present embodiment, the resin molded body 1 is formed in a cup shape having an opening by the hollow cylindrical portion 11 and the bottom portion 12. In the present embodiment, the cylindrical portion 11 is formed in a cylindrical shape. In addition, a hole is provided in the bottom portion 12 to form a pipe-shaped through portion 12a.

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. A rod or string can be inserted into the hole of the penetrating portion 12a. 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 cylindrical space (cavity) between the core mold and the cavity mold, and along the axial direction of the cylindrical part, Demolded from the core mold.

The outer peripheral surface 11f of the cylindrical portion 11 of the resin molded body 1 is formed in a smooth cylindrical shape. And the outer peripheral surface 11f of a cylindrical part does not have the part which becomes an undercut in a demolding direction. Further, the outer peripheral surface 11f is formed as a flat curved surface having no step.

The inner peripheral surface of the cylindrical portion 11 of the resin molded body 1 is divided into a plurality of partial regions 11a, 11b, 11c, 11d,. And the level | step difference is provided in the boundary of the partial area so that the partial area | regions 11a, 11b, 11c, 11d ... which adjoin each other are offset in the radial direction of a cylindrical part. And the cylindrical part inner peripheral surface is comprised so that the part which becomes an undercut in a mold release direction may not arise in the inner peripheral surface of a cylindrical part.

In the present embodiment, the inner peripheral surface of the cylindrical portion 11 is a plurality of substantially straight lines extending along the direction of demolding the cylindrical portion at the opening side portion (B section) in the axial direction of the cylindrical portion. Are divided into a cylindrical partial region 11b, 11c, 11d... And a remaining region 11a excluding the partial region from the inner peripheral surface of the cylindrical part. The partial region 11a and the partial regions 11b, 11c, 11d,... Are formed so as to form a part of a smooth cylindrical surface. There is a step extending linearly along the demolding direction (axial direction) of the cylindrical portion between the partial region 11a and the partial region 11b. Similarly, there are steps extending linearly along the demolding direction of the cylindrical portion between the partial regions 11a and 11c and between the partial regions 11a and 11d.

The partial area 11a is arranged on the radially inner side of the cylindrical portion with respect to the partial areas 11b, 11c, 11d. And partial area | region 11b, 11c, 11d ... is arrange | positioned in the same position in the radial direction of a cylindrical part. That is, the inner peripheral surface of the cylindrical portion 31 of the resin molded body has a form in which grooves corresponding to the partial regions 11b, 11c, 11d,... Are provided on the cylindrical surface corresponding to the partial region 11a. It has become.

And an undercut is not produced in the mold releasing direction on the inner peripheral surface of the cylindrical portion. The partial area 11a is set with a draft gradient α, and the partial areas 11b, 11c, 11d,. In the present embodiment, the draft gradient α is larger than the draft gradient β.

The step between the partial region 11a and the partial regions 11b, 11c, 11d,... Is provided in such a form that the surface of the step is substantially along the radial direction of the cylindrical portion. Even if the surface of the step is provided to be inclined with respect to the radial direction of the cylindrical portion, and the concave groove appearing on the inner peripheral surface corresponding to the partial regions 11b, 11c, 11d,. good.

When the diameter of the cylindrical portion is 20 mm, the length is 10 mm, and the thickness is 1.0 mm, the size of the step (the size of the step in the radial direction of the cylindrical portion) is 0.005 to 0.2 mm. Provided in the range. The step is more preferably in the range of 0.01 to 0.1 mm. A level | step difference is provided so that it may become 0.5 to 20% of the thickness of a cylindrical part as a standard dimension. The ratio of the size of the step to the thickness of the cylindrical portion is more preferably set to be about 1 to 10%.

In the present embodiment, the tubular portion is divided into two regions in the axial direction, and one of the tubular portions divided in the axial direction is a region located on the far side from the opening of the tubular portion ( In section A in FIG. 1, the inner circumferential surface of the cylindrical portion is not divided into the partial areas described above, and in the section A, the collecting surface in the cylindrical section is a flat cylindrical surface having no step. ing. On the other hand, in the other region of the tubular portion divided in the axial direction, that is, in the region located on the opening side of the tubular portion (B section in FIG. 1), the inner peripheral surface of the tubular portion is the partial region 11a, 11b, 11c, 11d,... Are provided between these partial areas, and grooves corresponding to the partial areas 11b, 11c, 11d,. Yes.

As described above, in a partial region in the axial direction of the cylindrical portion, the inner peripheral surface is divided into partial regions and a step is provided, while in other regions in the axial direction of the cylindrical portion, the inner periphery The surface may be flat.
Note that the inner peripheral surface may be divided into partial regions over the entire length of the cylindrical portion in the axial direction, and a step may be provided. That is, only a part of the inner peripheral surface may be divided into partial regions to provide a step, or the entire inner peripheral surface may be divided into partial regions to provide a step.

In the resin molded body 1 of the first embodiment shown in FIG. 1, the example in which the inner peripheral surface is divided into 11 partial regions so that ten grooves appear on the inner peripheral surface of the cylindrical portion is shown. The number of partial areas may be changed as appropriate. Moreover, the through-hole provided in the bottom part 12 of the resin molding 1 does not need to be required.

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. The resin molded body 1 of this embodiment is formed 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. 2 and 3 show a mold 2 used for injection molding of the resin molded body 1. FIG. 2 schematically shows a state where the mold 2 is closed, and FIG. 3 schematically shows a state where the mold 2 is opened. 2 and 3 show the cavity mold 22 and the core mold 21 in cross-sectional views. 2 and 3, in order to make the drawings easier to see, the cross sections of the cavity mold 22 and the core mold 21 are not hatched, and a cavity portion formed by the cavity mold 22 and the core mold 21 when the mold is closed. Hatching is applied to the portion where the molded body is formed.

The mold 2 has a core mold 21 and a cavity mold 22. The core mold 21 forms the inner peripheral surface of the cylindrical portion 11 of the resin molded body 1, and the cavity mold 22 forms the outer peripheral surface of the cylindrical portion 11 of the resin molded body 1. Therefore, the core mold 21 is provided with shapes corresponding to the inner peripheral surface shapes 11a, 11b, 11c, 11d,... A shape corresponding to the outer peripheral surface shape 11 f of the cylindrical portion 11 is provided.

In the demolding process described later, the process is designed so that the molded body remains on the side of the core mold when the mold is opened. In order to finally remove the resin molded body 1 from the core mold 21, the core mold has a protruding pin. 23 is provided. 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.

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 provided in the mold, and the resin molded body 1 is formed. 2 to 4, these details are not shown. The kind of runner or gate is not particularly limited, and various types can be adopted. After injecting the resin, the resin molded body 1 is taken out from the mold 2 after the resin is solidified. FIG. 4 schematically shows the demolding process. When the resin molded body 1 is formed, 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. 4A). Then, the protrusion pin 23 provided in the core mold is operated to remove the resin molded body 1 from the core mold 21 (FIG. 4B). The resin molded body 1 taken out from the mold 2 is collected by a transport robot or the like.

The operation and effect of the invention will be described.
According to the resin molded body 1, the resin molded body 1 can easily remain on the core mold 21 during the mold opening process shown in FIG. 4A, and so-called cavity remaining defects can be prevented and suppressed. And it can adjust to an appropriate level, without making mold release resistance excessive so that the resin molding may not deform | transform in the process of removing the resin molding 1 from the core type | mold 21. FIG.

The resin molded body 1 includes a plurality of linear partial regions 11a, 11b, 11c, and 11d in which the inner peripheral surface of the cylindrical portion 11 has no undercut in the mold release direction and the inner peripheral surface is along the mold release direction. .. Are divided so that adjacent partial regions are offset from each other in the radial direction of the cylindrical portion. As described above, when the step is provided on the inner peripheral surface, the shape of the surface where the resin molded body and the mold surface are in contact with each other on the inner peripheral surface side becomes complicated, and the contact area increases. The demolding resistance on the core mold side) increases, and the resin molded body tends to remain on the core mold 21 side when the mold is opened.

From the viewpoint of increasing the demolding resistance on the inner peripheral surface side (core mold side), it is preferable to increase the number of partial regions and steps to make the inner peripheral surface more complicated. Further, it is preferable that the boundary between the partial region and the step is clearer, that is, the corner R and the corner R are small. In this case, the resin and the mold are formed at the corner R and the corner R. The mold release resistance can be easily increased, and the mold release resistance can be effectively increased.

And since the resin molding 1 does not have the part which becomes an undercut in a mold release direction on the internal peripheral surface of the cylindrical part 11, the resin molding formed when removing the resin molding 1 from a metal mold | die The body is not subject to forced deformation, and the demolding resistance is not excessive. Accordingly, it is possible to prevent / suppress deformation of the resin molded body during demolding. In the resin molded body 1, the division into the partial area of the inner circumferential surface of the cylindrical part is performed linearly along the mold release direction of the cylindrical part, or there is a step between the partial areas along the mold release direction. Doing does not make the mold release resistance excessive, and contributes to suppression and prevention of deformation of the resin molded body.

And when the magnitude | size of the cylindrical part radial direction of the said level | step difference is made into 0.5 to 20% of the thickness of a cylindrical part, without making the demolding resistance from a core type | mold excessively, It becomes possible to more reliably leave the resin molded body on the core mold side. If the level difference becomes too large, the demolding resistance becomes excessive, and the molded body tends to be deformed when the molded body is taken out by a protruding pin. Conversely, if the step is too small, the demolding resistance cannot be sufficiently increased.

In addition, as in the resin molded body 1 of the present embodiment, in a partial region in the axial direction of the cylindrical portion (B section in FIG. 1), the inner peripheral surface is divided into partial regions and provided with a step. In the other axial region of the cylindrical part (section A in FIG. 1), when the inner peripheral surface is flat without a step, it is easier to adjust the demolding resistance. Become. That is, if the core mold is additionally processed and the ratio between the A section and the B section is changed, the demolding resistance can be adjusted. That is, if the B section divided into partial areas is increased, the demolding resistance is increased, and if the A section that is not divided into partial areas is increased, the demolding resistance is decreased. In this way, the degree of freedom for adjusting the demolding resistance can be increased.

In addition, as in the resin molded body 1 of the present embodiment, on the inner peripheral surface of the tubular portion, a partial region located on the radially inner side of the tubular portion, and a partial region located on the radially outer side of the tubular portion, Also, the difference in the escape gradient between the two contributes to the ease of adjusting the demolding resistance. In many cases, the draft (α) of the partial region located radially inside the cylindrical part cannot be freely set due to the restriction of the shape of the inner peripheral surface of the molded body, but the part located radially outside the cylindrical part If the draft of the region (β) is different from the draft of the partial region located on the inside (α), the degree of freedom in setting the draft of the partial region located on the outside is increased, and the mold release resistance is increased. The adjustment range becomes larger. From the viewpoint of increasing the sensitivity of adjustment of the demolding resistance by dividing into partial areas, the escape gradient (β) of the partial area located on the radially outer side of the cylindrical portion is changed to the escape slope of the partial area located on the inner side (β). It is particularly preferable to make it smaller than α).

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. 5, the resin molding 3 of 2nd Embodiment is shown. In this embodiment, the form etc. of the cylindrical part inner peripheral surface of the resin molding 3 differ. In the present embodiment, the inner peripheral surface of the cylindrical portion 31 of the resin molded body is divided into partial regions 31a, 31b, 31c, 31d... Along the axial direction of the cylindrical portion. The partial areas 31a and the partial areas 31b, 31c, 31d,... Are alternately arranged in the circumferential direction, and the partial areas 31a are located radially outward from the partial areas 31b, 31c, 31d,. ing. And the level | step difference is provided in the boundary part of partial area | region 31a and partial area | regions 31b, 31c, 31d .... That is, the inner peripheral surface of the cylindrical portion 31 of the resin molded body is such that the ridges corresponding to the partial regions 31b, 31c, 31d,... Are provided on the rectangular cylindrical surface corresponding to the partial region 31a. It has a form.

Similar to the first embodiment, even in the configuration in which the partial regions are provided so that the ridges are formed on the inner peripheral surface corresponding to the partial regions 31b, 31c, 31d,. In addition, it is possible to prevent defects remaining in the cavity when the molded product is taken out, and the resistance to demolding from the core mold can be adjusted to an appropriate level.

Moreover, in this embodiment, the cylindrical part of the resin molding 3 is formed in the square cylinder shape. That is, the cylindrical portion may be cylindrical as in the first embodiment, but may be rectangular as in the present embodiment. Similarly, the cross-sectional shape of the cylindrical portion taken on a plane perpendicular to the axial direction of the cylindrical portion (that is, the demolding direction) is a polygonal shape (particularly, a triangular shape, a quadrangular shape, a pentagonal shape or a hexagonal shape) or a long shape. It may be circular, elliptical, or the like.
If the cross-sectional shape of the cylindrical part is polygonal, oval, or elliptical as in this embodiment, the cylindrical parts are combined using the cross-sectional shape of the cylindrical part. Torque can be transmitted to the mating member, and torque can be transmitted using the cylindrical portion.

In the present embodiment, the inner peripheral surface is divided into partial areas in the axially inner area (A section) from the opening of the cylindrical portion, and a step is provided at the boundary of the partial area. On the other hand, in the region (B section) on the side of the remaining opening in the axial direction of the cylindrical portion, the inner peripheral surface is a flat rectangular tube having no step.
In this way, the section where the inner peripheral surface of the tubular portion should be divided into partial regions and the step should be provided at the boundary of the partial region is a region on the back side from the opening of the tubular portion as in this embodiment (FIG. 5). It may also be a region on the opening side as in the first embodiment.
Moreover, you may make it provide a level | step difference in the boundary of a partial area | region by dividing | segmenting a cylindrical part internal peripheral surface into a partial region over the whole axial direction of the internal peripheral surface of a cylindrical part.

As in the present embodiment shown in FIG. 5, a region (A section) on the back side from the opening in the axial direction of the tubular portion is divided into partial regions, and a step is provided at the boundary of the partial region. When the portion corresponding to the divided partial regions 31b, 31c, 31d,... Is projected from the inner peripheral surface (31a) like a ridge in the section, Additional processing of the core mold when attempting to increase the demolding resistance is preferably performed efficiently.

Moreover, in the resin molded body of this embodiment, the part of the partial area | regions 31b, 31c, 31d ... of the part corresponded to the protruding item | line of the cylindrical part internal peripheral surface of the resin molded body 3 is the radial direction of a cylindrical part. As seen along the line, the width of the partial area 31b, 31c, 31d... On the inner side of the cylindrical part is larger than the width on the cylindrical part opening side. Has been. In this way, by giving the shape of the partial region viewed from the radial direction a taper in the pulling direction, it is possible to effectively prevent the demolding resistance from becoming excessive, and to optimize the demolding resistance more effectively. It can be planned.

Further, as in the present embodiment, the partial region (31a) located on the radially outer side of the cylindrical part and the partial region (31b, 31c, 31d,...) Located on the radially inner side of the cylindrical part are The surfaces may have substantially the same draft angle. If the draft is the same, additional machining of the core mold becomes efficient.

In addition, in the said embodiment, although embodiment which does not have a level | step difference at all in the outer peripheral surface (11f) of a cylindrical part was demonstrated, invention is not limited to this, The shape of the outer peripheral surface of a cylindrical part can be set suitably. .

Moreover, in the resin molding 3 of this embodiment, there is no hole in the bottom part 32 of the molding, and it is formed in a disk shape. In this invention, as long as it has a hollow cylindrical part, it does not specifically limit about the shape of parts other than the cylindrical part of a resin molded object, The resin molded object is other parts, for example, a hollow cylindrical part, for example. The end portion may be provided with a flange portion or the like.

Moreover, the resin molded body may have a plurality of cylindrical portions arranged in parallel to each other. In this case, at least one of the plurality of cylindrical portions has no undercut in the demolding direction on the inner peripheral surface of the cylindrical portion as in the above embodiment, and the inner peripheral surface is The step is divided into a plurality of partial regions extending in the mold releasing direction, and a step is provided so that adjacent partial regions are offset from each other in the radial direction of the cylindrical portion, so that the step has a predetermined size. If so, the same effect can be obtained.

The specific application field in which the resin molded body is used is not particularly 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 of the present invention can be used as a component such as a resin case or a resin tank, a seal member, a mechanism part, or the like that can use a resin molded body having a cylindrical portion.

The resin molding of the present invention can be efficiently produced by resin injection molding and has high industrial utility value.

DESCRIPTION OF SYMBOLS 1 Resin molding 11 Cylindrical part 11a, 11b, 11c, 11d Partial area | region 11f Outer peripheral surface 12 Bottom part 2 Mold 21 Core mold 22 Cavity mold 23 Extrusion pin 3 Resin molding 31 Cylindrical part 31a, 31b, 31c, 31d, Partial region 32 Bottom 9 Molded body 91 Core mold 92 Cavity mold 93 Extrusion pin

Claims (4)

Using a mold having a core mold and a cavity mold, a manufacturing method for forming a resin molded body having a hollow cylindrical portion by injection molding of a synthetic resin ,
Including a step of preparing a mold configured such that the resin molded body remains in the core mold when the mold is opened;
The resin molded body has no undercut in the demolding direction of the inner peripheral surface of the cylindrical part,
And in at least a part of the inner peripheral surface, the inner peripheral surface is divided into a plurality of partial regions extending linearly along the demolding direction, and the adjacent partial regions are mutually in the radial direction of the cylindrical portion. There is a step to offset,
The step extends linearly along the demolding direction, and the size of the cylindrical portion in the radial direction of the step is 1 to 10% of the thickness of the cylindrical portion ,
The core mold has a shape corresponding to the shape of the inner peripheral surface of the resin molded body.
Manufacturing method of resin molding . In the resin molded body, in the partial region in the axial direction of the cylindrical portion, the inner peripheral surface is divided into partial regions and provided with a step,
The method for producing a resin molded body according to claim 1, wherein the inner peripheral surface is flat in another axial region of the cylindrical portion. In the resin molded body, on the inner peripheral surface of the cylindrical portion, the escape gradient differs between a partial region located on the radially inner side of the cylindrical portion and a partial region located on the radially outer side of the cylindrical portion. The manufacturing method of the resin molding of Claim 1 made . The method for producing a resin molded body according to claim 1, wherein a cross-sectional shape of the cylindrical portion is a polygonal shape, an oval shape, or an elliptical shape.

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