JP2020110944A - Gas press injection molding machine - Google Patents

Abstract

To prevent a sink mark from occurring on a design surface of a resin molded product with a simple structure.SOLUTION: A gas press injection molding machine 10 includes: a stationary die core insert 30; a movable die core insert 32; a slit-equipped core insert 50 provided in the movable die core insert 32; and a gas supply part 70 that supplies high-pressure gas from the movable die core insert 32 side to a cavity 44 between the stationary die core insert 30 and the movable die core insert 32. The movable die core insert 32 has a housing part 38 connected to a gas flow path 74 of the gas supply part 70. The slit-equipped core insert 50 is a core insert that is stored in the housing part 38, further, has a groove 62 for molding a rib 94 on a non-design surface side of a resin 92, and a slit 64 for guiding a gas supplied to the housing part 38 to a groove defining part 54a surrounded by the groove 62.SELECTED DRAWING: Figure 1

Description

The present invention relates to a gas press injection molding apparatus for injecting a molten resin into a cavity of a mold and supplying a gas between the resin and the mold during injection molding of a resin molded product.

When a resin molded product is manufactured by injection molding, the molded product can be made thin by providing reinforcing ribs on the surface (non-designed surface) opposite to the designed surface of the molded product. However, sink marks may occur on the design surface of the thin molded product. In other words, in the portion of the molded product where the ribs are provided (particularly the intersection between the ribs), the solidification is delayed due to the difference in the volume shrinkage of the resin, so that a sink mark occurs on the design surface. In order to prevent the occurrence of sink marks in the molded product, there is a technology that injects molten resin into the cavity of the mold and supplies gas between the resin and the mold to press the resin toward the design surface side. .. In this specification, an apparatus for supplying a gas as well as injecting a resin is referred to as a gas press injection molding apparatus.

Patent Document 1 discloses a molding method using a gas press injection molding apparatus. The mold of the gas press injection molding device disclosed in Patent Document 1 has a groove for molding a rib and a gas injection pin for guiding gas to a molding surface surrounded by the groove. With this structure, sink marks can be concentrated on the non-designed surface of the resin, and as a result, sink marks do not occur on the designed surface of the resin molded product.

JP, 2004-223879, A

When the gas injection pin is provided as in the device of Patent Document 1, more gas injection pins are required as the number of portions surrounded by ribs in the molded product increases. However, since the mold is provided with a water channel for cooling the molten resin, the position where the gas injection pin is provided is limited. Also, if many gas injection pins are provided, the structure of the mold becomes complicated, and man-hours are required for designing and manufacturing the mold.

The present invention has been made in view of the above problems, and an object thereof is to provide a gas press injection molding apparatus that has a simple structure and prevents occurrence of sink marks on the design surface of a resin molded product. ..

Aspects of the invention include
A first mold for molding a design surface of a resin molded product;
A second mold for molding the non-designed surface of the resin molded product;
A rib forming portion provided on the second mold;
A gas press injection molding apparatus comprising: a gas supply unit configured to supply a gas having a pressure higher than atmospheric pressure from a side of the second mold into a cavity between the first mold and the second mold. ,
The second mold has a storage part connected to the gas flow path of the gas supply part,
The rib forming part is a nest housed in the housing part, and further includes a groove for forming a rib on the non-designed surface side of the resin, and the gas supplied to the housing part surrounded by the groove. And a slit for guiding the groove defining portion.

According to the present invention, it is possible to prevent the occurrence of sink marks on the design surface of a resin molded product with a simple structure.

FIG. 1 is a simplified diagram of a gas press injection molding apparatus according to this embodiment. FIG. 2 is an enlarged view of the insert with slit and the storage unit in FIG. FIG. 3 is a plan view of the insert with slit. FIG. 4 is a perspective view of the insert member. FIG. 5 is an explanatory diagram for explaining a state in which gas is supplied between the resin and the insert with slit.

Hereinafter, a gas press injection molding apparatus according to the present invention will be described in detail with reference to the accompanying drawings, with reference to preferred embodiments.

[1. Gas press injection molding machine 10]
The configuration of the gas press injection molding apparatus 10 will be described with reference to FIG. The gas press injection molding apparatus 10 is arranged between an injection unit (not shown) that injects and injects the molten resin 92 (FIG. 5) into the mold and a mold clamping unit (not shown) that opens and closes the mold. .. In this specification, for convenience of description, the direction from the mold clamping portion to the gas press injection molding device 10 and the injection portion (from the bottom to the top of the paper of FIG. 1) is the X direction. Further, the direction orthogonal to the X direction (from left to right in the plane of FIG. 1) is the Y direction, and the direction orthogonal to the X direction and the Y direction (front to back in the plane of FIG. 1) is the Z direction (FIG. 3). .. In addition, a minus (-) is added to the opposite direction of each direction.

As shown in FIG. 1, the gas press injection molding apparatus 10 includes a fixed side mounting plate 12, a fixed side template 14, a movable side mounting plate 16, a spacer block 18, a movable side template 20, and an ejector. It has a plate 22 and an ejector pin 24.

The fixed-side attachment plate 12 is attached to the injection part (not shown). The fixed-side template 14 is the main body of the cavity and is attached to the fixed-side mounting plate 12. The fixed side mounting plate 12 and the fixed side template 14 are provided with a resin injection passage 26 (a sprue, a runner, and a gate) connecting from the injection portion to the cavity 44 (FIG. 5). The movable side attachment plate 16 is attached to a mold clamping part (not shown). The movable side mold plate 20 is the main body of the core, and is attached to the movable side mounting plate 16 via the spacer block 18. The ejector plate 22 is attached to an ejector mechanism (not shown) of the mold clamping unit. The ejector pin 24 is attached to the ejector plate 22. The movable side mounting plate 16 and the movable side template 20 are movable in the X direction. The ejector plate 22 and the ejector pin 24 are movable along the X direction.

Further, the gas press injection molding apparatus 10 includes a fixed mold insert 30, a movable mold insert 32, a slit insert 50, and a gas supply unit 70. The fixed mold insert 30 is a mold (first mold) for molding the design surface of the molded product of the resin 92 by the first mold surface 34, and is attached to the fixed-side mold plate 14. The movable mold insert 32 is a mold (second mold) for molding the non-designed surface of the molded product of the resin 92 by the second mold surface 36, and is attached to the movable side mold plate 20. When the fixed mold insert 30 and the movable mold insert 32 are closed, a cavity 44 is formed between the first mold surface 34 and the second mold surface 36.

The movable mold insert 32 has a storage part 38 that is recessed from the second mold surface 36, for example, in the depth direction (−X direction). A slit insert 50 is stored inside the storage portion 38. The slit insert 50 is a mold (rib forming part) for forming the rib 94 (FIG. 5) on the non-designed surface of the resin 92 molded product. The slit insert 50 will be described in detail in the following [2].

The gas supply unit 70 includes a gas generator 72, a gas flow path 74, and a gas injection pin 78. The gas generator 72 has a pump, a valve, etc., and discharges gas (nitrogen gas, oxygen gas, carbon dioxide gas, etc.) at a pressure higher than atmospheric pressure. The gas flow path 74 guides the gas discharged from the gas generator 72 to the storage section 38. On the other hand, the gas injection pin 78 branches the gas flow path 74 and guides the gas discharged from the gas generator 72 to the cavity portion 44 other than the front surface of the slit insert 50.

[2. Insert 50 with slit and storage 38]
The configuration of the storage section 38 will be described with reference to FIG. A discharge port 76 of the gas flow path 74 is opened at the bottom portion 40 of the storage portion 38. Further, one or more spacers 42 are provided on the bottom portion 40 of the storage portion 38. The spacer 42 may be separate from or integral with the bottom portion 40. The positions of the spacer 42 in the Y direction and the Z direction may be any positions as long as they do not overlap the discharge port 76 and the slit 64 of the slit insert 50 described later.

The structure of the insert 50 with a slit will be described with reference to FIGS. The slit insert 50 is configured by combining a plurality of insert members 52, here four insert members 52. As shown in FIG. 3, the four nesting members 52 are arranged along the Y direction and are relatively arranged in the −Y direction with the nesting members 521 arranged relatively in the Y direction. The insert member 522 and the two insert members 523 arranged between the insert member 521 and the insert member 522. Each nesting member 52 has a rib forming surface 54 and a nesting bottom surface 56 that are parallel to the Y and Z directions, a pair of contact surfaces 58 and 58 that are parallel to the X and Z directions, and the X and Y directions. Is a hexahedron having a pair of side surfaces 60, 60 parallel to the.

On the rib molding surface 54 of each nesting member 52, a groove 62 for molding the rib 94 on the non-designed surface of the molded product of the resin 92, here, one groove 62Z parallel to the Z direction, and the Y direction. Four parallel grooves 62Y are provided. The groove 62Y provided in the insert member 521 is formed up to the contact surface 58 in the -Y direction. The groove 62Y provided in the insert member 522 is formed up to the contact surface 58 in the Y direction. The groove 62Y provided in the insert member 523 is formed from the contact surface 58 in the Y direction to the contact surface 58 in the -Y direction.

The contact surface 58 in the Y direction of each insert member 52 is provided with five slits 64 extending from the insert bottom surface 56 toward the rib forming surface 54 in a manner parallel to the X direction. In the rib molding surface 54, the slits 64 are provided between the grooves 62Y adjacent to each other. That is, at the boundary between the rib molding surface 54 and the contact surface 58 in the Y direction, the slits 64 and the grooves 62Y are alternately provided along the Z direction. It should be noted that only the insert member 522 is provided with the five slits 64 on the contact surface 58 in the −Y direction.

Each nesting member 52 is provided with two or more through holes 66 penetrating from the contact surface 58 in the Y direction to the contact surface 58 in the −Y direction. By inserting the connecting rod 68 into the through hole 66 of each nesting member 52, each nesting member 52 is coupled while being positioned with respect to each other. The contact surfaces 58 of the respective nesting members 52 adjacent to each other contact each other. In this state, the slit 64 provided on the contact surface 58 of the insert member 52 located in the −Y direction is covered by the contact surface 58 of the insert member 52 located in the Y direction. In this way, in the state where each of the insert members 52 is in contact, a group of passages is formed in the slit insert 50 by the plurality of slits 64 connected from the insert bottom surface 56 to the rib forming surface 54.

The rib forming surface 54 of the slit insert 50 is configured by arranging the rib forming surfaces 54 of the respective insert members 52 along the Y direction. In this state, the four grooves 62Y provided on the rib forming surface 54 of each nesting member 52 are connected. As a result, a lattice is formed by the four grooves 62Y and the four grooves 62Z on the rib forming surface 54 of the slit insert 50, and nine portions surrounded by the grooves 62Z and 62Y are defined. This portion is referred to as a groove defining portion 54a. A seam parallel to the Z direction, that is, an abutting portion of the abutting surfaces 58, 58 of the insert members 52, 52 adjacent to each other is located in each groove defining portion 54a. The slit 64 is located at this joint.

The slit insert 50 is press-fitted into the storage portion 38. Then, as shown in FIG. 2, the slit 64 located on the outer peripheral surface of the slit-equipped insert 50 is covered by the inner peripheral surface of the storage section 38. Further, the insert bottom surface 56 of one of the insert members 52 contacts the spacer 42 provided on the bottom portion 40 of the storage portion 38. In this state, the rib molding surface 54 of the slit insert 50 and the second mold surface 36 are flush with each other. Further, a space 80 is formed between the insert bottom surface 56 of the insert member 52 and the bottom portion 40 of the storage section 38. The space 80 and the slit 64 connect the gas flow path 74 and the cavity 44. That is, each slit 64 has a function of supplying the gas supplied from the gas supply unit 70 to the space 80 to the cavity 44, similarly to the gas injection pin 78.

The depth of the slit 64 in the −Y direction (width of the slit 64) is such that the resin 92 injected into the cavity portion 44 does not flow from the rib molding surface 54 side, and a sufficient amount of gas in the cavity portion 44. Can be supplied. For example, it is preferably 0.05 mm or more and less than 0.1 mm.

[3. Molding of resin 92]
A method of molding the resin 92 using the gas press injection molding apparatus 10 will be described with reference to FIGS. 1, 2, and 5. After the fixed mold insert 30 and the movable mold insert 32 are closed, the molten resin 92 is injected into the cavity 44 from an injection part (not shown). Simultaneously with or after the injection of the resin 92, the gas generator 72 is operated. The gas discharged from the gas generator 72 passes through the gas flow path 74 and flows into the gas injection pin 78. Further, the gas passes through the gas injection pin 78 and is supplied between the resin 92 and the movable mold insert 32.

Further, the gas discharged from the gas generator 72 passes through the gas flow path 74 and flows into the space 80 inside the storage section 38. The gas flows from the space 80 into each slit 64, passes through the slit 64, and is supplied between the resin 92 and each groove defining portion 54a. The gas presses the resin 92, as indicated by the arrow 96 in FIG. Therefore, the resin 92 is pressed against the fixed mold insert 30. At this time, a sufficient amount of gas is supplied between each groove defining portion 54a and the resin 92 from the slit 64 provided in each groove defining portion 54a. As a result, sink marks due to the contraction of the resin are generated on the non-designed surface of the resin 92 and are not generated on the designed surface.

[4. Modification]
In the above-described embodiment, the insert with slit 50 including the plurality of insert members 52 has been described. Instead of this, the slit insert 50 in which a plurality of slits 64 are provided in a single member may be used. However, the insert with slit 50 configured by the plurality of insert members 52 is easier to manufacture than the insert with slit 50 alone.

Further, if the gas once flows into the space 80 inside the storage portion 38, is branched from the space 80 to the plurality of slits 64, and is supplied from each slit 64 between the groove defining portion 54 a and the resin 92. The position of the slit 64 may be anywhere.

When the rib 94 is provided in a wide area of the resin 92, a plurality of slit inserts 50 may be used. In that case, the shape and structure of each insert 50 with a slit may differ.

[5. Technical idea obtained from the embodiment]
The technical idea that can be understood from the above embodiment will be described below.

Aspects of the invention include
A first mold (fixed mold insert 30) for molding the design surface of a molded product of resin 92;
A second mold (movable mold insert 32) for molding the non-designed surface of the molded product of the resin 92;
A rib forming portion (slit insert 50) provided in the second mold;
A gas press injection molding apparatus 10 comprising: a gas supply unit 70 that supplies a gas having a pressure higher than atmospheric pressure from the second mold side into a cavity 44 between the first mold and the second mold. And
The second mold has a storage section 38 connected to the gas flow path 74 of the gas supply section 70,
The rib molding portion is a nest housed in the housing portion 38, and further includes a groove 62 for molding the rib 94 on the non-design surface side of the resin 92, and the gas supplied to the housing portion 38. And a slit 64 for guiding the groove defining portion 54a surrounded by the groove 62.

By using the slit insert 50 provided with the plurality of slits 64 as in the above configuration, it is not necessary to use a plurality of gas injection pins. That is, at least one gas flow path 74 guides the gas to one storage part 38, and the gas is diverted from the space 80 inside the storage part 38 to each slit 64 of the slit-equipped insert 50, and each groove demarcation part. Gas can be supplied between 54a and the resin 92. As described above, according to the above configuration, since it is not necessary to use a plurality of gas injection pins, even if the movable side mold plate 20 or the movable mold insert 32 is provided with a water channel or the like, the gas flow path 74 can be easily formed. Can be provided. Therefore, it is possible to prevent sink marks from being generated on the design surface of the molded product of the resin 92 with a simple structure.

In the present invention,
The nest includes a plurality of nest members 52 that abut each other,
The slit 64 may be provided at a joint between two adjacent nesting members 52.

According to the above configuration, the slit 64 may be formed on the contact surface 58 of the insert member 52, and the slit 64 can be easily formed.

In the present invention,
A spacer 42 that supports the rib forming portion (slit 50) is provided on a bottom portion 40 of the storage portion 38, and an exhaust port 76 of the gas flow path 74 is opened.
The slit 64 may communicate the space 80 surrounded by the storage portion 38 and the rib forming portion with the hollow portion 44.

According to the above configuration, the gas may be diverted from the space 80 to the plurality of slits 64, so that the number of gas flow paths 74 provided in the movable mold plate 20 or the movable mold insert 32 can be reduced.

The gas press injection molding apparatus according to the present invention is not limited to the above-described embodiment, and can of course have various configurations without departing from the gist of the present invention.

10... Gas press injection molding device 30... Fixed mold insert (first mold)
32... Movable mold insert (second mold) 38... Storage part 40... Bottom part 42... Spacer 44... Cavity part 50... Slit insert (rib forming part)
52, 521, 522, 523... Nesting member 54a... Groove defining portion 62, 62Y, 62Z... Groove 64... Slit 70... Gas supply portion 74... Gas flow passage 76... Discharge port 80... Space 92... Resin 94... Rib

Claims (3)

A first mold for molding a design surface of a resin molded product;
A second mold for molding the non-designed surface of the resin molded product;
A rib forming portion provided on the second mold;
A gas press injection molding apparatus comprising: a gas supply unit configured to supply a gas having a pressure higher than atmospheric pressure from a side of the second mold into a cavity between the first mold and the second mold. ,
The second mold has a storage part connected to the gas flow path of the gas supply part,
The rib forming part is a nest housed in the housing part, and further includes a groove for forming a rib on the non-designed surface side of the resin, and the gas supplied to the housing part surrounded by the groove. And a slit that guides to the groove demarcation portion. The gas press injection molding apparatus according to claim 1, wherein
The nest comprises a plurality of nest members abutting each other,
The said press is a gas press injection molding apparatus provided in the joint of two said nest members which adjoin each other. The gas press injection molding apparatus according to claim 1, wherein
A spacer that supports the rib forming portion is provided at the bottom of the storage portion, and an outlet of the gas flow path is opened,
The gas press injection molding apparatus, wherein the slit communicates a space surrounded by the storage portion and the rib molding portion with the hollow portion.

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