JP7262986B2 - Injection mold, injection mold manufacturing method, injection molding machine, and resin molded product manufacturing method - Google Patents

Description

The present invention relates to an injection mold for injection molding a resin material, a method for manufacturing an injection mold, an injection molding machine, and a method for manufacturing a resin molded product.

Conventionally, an injection molding method has been used to manufacture articles made of resin, in which a resin material is injected into a mold using an injection molding machine, cooled and solidified, and then the molded product is removed from the mold. In the injection molding of this resin material, it is necessary to inject the molten resin material into the mold with a high pressure that overcomes the resistance due to the viscosity of the molten resin. In addition, after the resin has been injected into the mold, the resin shrinks in the mold as it cools, and a relatively high constant pressure is applied to the resin material for a certain period of time so that the dimensional difference from the mold dimensions does not increase. A subsequent holding pressure step is required.

If the part size is large or the shape has a large change in thickness, the pressure from the molding machine may not reach the end of the mold evenly, causing variations in the contraction state of the resin inside the mold, resulting in warping. Defects such as sink marks were sometimes caused.

In view of the above circumstances, a molding method called "injection compression molding" is sometimes used in the injection molding of articles such as gears and lenses that require particularly high precision (Patent Document 1). In this injection compression molding, after injecting a resin material into a mold, a piece portion of the mold having a shape is moved by a hydraulic cylinder or the like, and pressure is applied from the piece to the resin in the mold. According to this injection compression molding, in addition to the pressure from the molding machine, direct pressure is applied from the pieces, which equalizes the pressure inside the shaped part and reduces the difference in shrinkage of the resin, making it possible to obtain high-precision molded products. .

JP-A-10-58502

In the above-mentioned injection compression molding, it is necessary to apply pressure by a hydraulic cylinder or the like from inside or outside the mold, and there is a problem that the cost increases due to the enlargement of the mold size and the installation of hydraulic control equipment. In addition, the mold requires a structure for applying pressure to partial bridges and sliding parts, and for varying the pressure at multiple parts of the molds. can not be secured and may not be implemented.

In addition, since the shrinkage behavior of resin is closely related to pressure (P), volume (V), temperature (T), and the glass transition temperature (Tg) of the material, the pressure from the molding machine and pieces is It is necessary to control along the PVT characteristic peculiar to . However, in the case of control by an external pressure device using oil pressure or the like, it may be difficult to perform desired pressure control with good responsiveness. Moreover, when different pressure controls are to be applied to a plurality of locations, there is a possibility that the control mode and the configuration of the pressure equipment will become extremely complicated. Due to these circumstances, injection compression molding has hitherto not been widely used in the manufacture of articles other than those having simple shapes such as gears and lenses. In addition, it is difficult to arrange cooling water passages and the like in the cylinder structure of the conventional bridge that is operated by hydraulic pressure, etc., and there is a problem that the cooling efficiency of the mold is reduced and the molding cycle is lengthened. .

An object of the present invention is to easily and inexpensively manufacture products that require relatively strict control of resin shrinkage, such as highly accurate mechanical parts with complex shapes and exterior parts that require high appearance quality. To enable injection molding accompanied by mold compression.

In order to solve the above problems, the present invention provides an injection molding die comprising a shaped piece having a transfer surface and a base for supporting the shaped piece, wherein the transfer surface of the shaped piece and the base , elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and is composed of an elastic structure that recovers its shape following the contraction of the resin accompanying cooling. and

With the above configuration, there is no need for a pressure control device such as a hydraulic cylinder, and in the manufacture of articles such as high-precision mechanical parts with complicated shapes and exterior parts that require high appearance quality, the mold can be easily and inexpensively compressed. Injection molding can be performed.

It is an explanatory view showing the section composition of the metallic mold concerning one embodiment of the present invention. FIG. 3 is an explanatory diagram showing PVT characteristics of general resins; It is explanatory drawing which showed the cross-sectional structure of the metal mold|die which concerns on one different embodiment of this invention. It is explanatory drawing which showed the cross-sectional structure of the metal mold|die which concerns on one different embodiment of this invention. FIG. 5 is an explanatory diagram showing the operation of the mold in FIG. 4; It is explanatory drawing which showed the cross-sectional structure of the metal mold|die which concerns on one different embodiment of this invention. It is an explanatory view showing the configuration of an injection compression molding mechanism. It is explanatory drawing which showed the cross-sectional structure of the metal mold|die which concerns on one different embodiment of this invention. 1(a) and 1(b) are explanatory diagrams showing a resin molded product molded in one embodiment of the present invention. FIG. It is explanatory drawing which showed the cross-sectional structure of the metal mold|die which concerns on one different embodiment of this invention. 11 is an explanatory view showing a cross-sectional configuration of the elastic member of FIG. 10; FIG. FIG. 11 is an explanatory diagram showing a modeling procedure of the elastic member in FIG. 10; FIG. 2 is an explanatory diagram showing a general configuration of a mold for molding gears; It is explanatory drawing which showed the cross-sectional structure of the metal mold|die which concerns on one different embodiment of this invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. The configuration shown below is merely an example, and, for example, details of the configuration can be changed as appropriate by those skilled in the art without departing from the scope of the present invention. Further, the numerical values taken up in the present embodiment are reference numerical values and do not limit the present invention.

<Embodiment 1>
FIG. 1 shows a cross-sectional configuration of an injection molding machine for manufacturing a resin molded product 4, which is an article such as a gear, in this embodiment, particularly the injection mold portion thereof. Also, FIG. 13 shows the configuration of a conventional general mold for molding a similar resin molded product 52 .

In FIG. 1, 1 is an elastic structure with a high spring coefficient, 2 is an elastic structure with a low spring coefficient, 3 is a core piece as a shape piece whose part shape is processed, 4 is a resin molded product such as a gear, 5 is a rotating piece machined into a gear shape. Each piece is arranged between a fixed side mold 44 and a movable side mold 45 . Further, an ejector pin 6 for releasing the resin molded product 4 after mold opening is arranged on the side of the movable mold 45 .

On the other hand, in FIG. 13, the resin molded product 52 is a similar gear, and the tooth surface of the gear is transferred by the shaped pieces 53 and the core portion of the gear is transferred by the shaped pieces 54 . 13, each piece is arranged between the fixed mold 44 and the movable mold 45. The fixed mold 44 has a resin injection gate 441, and the movable mold 45 has an ejector pin. 55 are placed.

13, the elastic structures 1 and 2 are arranged between the core piece 3 and the movable side mold 45 that constitutes one of the bases of the mold. The difference is that the core piece 3 is supported by the elastic structures 1 and 2 .

In addition, in each attached drawing according to the embodiment of the present invention, including FIG. 1, the elastic structures 1 and 2 are illustrated as having a bow-shaped shape or a rod-shaped shape. However, the shape of the elastic structures 1, 2 is arbitrary and does not limit the invention. In addition, in each of the accompanying drawings, including FIG. 1, according to the embodiment of the present invention, the core piece, which is a shaped piece, and the elastic structure supporting it are illustrated as if they were separate bodies. However, the core piece and the elastic structure functionally constitute an elastic structure piece, and do not necessarily need to be separate bodies, and they may be integrally formed.

In the mold shown in FIG. 1, when resin is injected into the cavity from the gate 441 arranged on the side of the fixed mold 44, for example, the injection pressure of the resin pushes the core piece 3 downward in the figure, and the elastic structure 1 and 2 elastically deform. As a result, the elastic structures 1 and 2 apply an urging force to the core piece 3 according to the amount of deformation.

The amount of elastic deformation of the elastic structures 1 and 2 at this time (or the spring coefficient that determines it) is determined in advance according to the pressure distribution in the mold by resin flow analysis presumed by simulation. Then, for example, an elastic structure 1 with a high spring coefficient is arranged in a portion where the resin pressure is high, and an elastic structure 2 with a low spring coefficient is arranged near the end of the flow where the resin pressure is low.

The spring coefficient of each elastic structure is a simulation value of the resin injection pressure and pressure distribution in the mold, and a resin-specific characteristic value called PVT characteristics of pressure (P) - specific volume (V) - temperature (T) of the resin material. Use the value obtained by multiplying the amount of shrinkage calculated from by the calibration factor. This calibration coefficient is obtained by conducting an experiment in advance.

The reason why the calibration coefficient obtained by experiment is used is that the specific volume change due to PVT characteristics is the overall value including both the skin layer and the core layer of the resin, and the skin layer and the core layer change from time to time during cooling. This is because it is difficult to simulate changes in elastic modulus.

The calibration coefficient q and the PVT characteristic are related, for example, by the following formula (1).

q=ΔV/Δt (1)
In the above formula (1), ΔV is the change in specific volume of the PVT characteristics, and Δt is the contraction rate in the plate pressure direction of the resin molded product obtained by experiment. Moreover, the spring coefficient k can be calculated by the following formula (2), for example.

k=q ^-1 ×ΔV/P (2)
In the above equation (2), P corresponds to the internal pressure inside the mold according to flow analysis.

Table 1 below shows Examples 1 and 2 of making resin molded products by injection molding without using elastic structures 1 and 2 as shown in FIG. 13, and elastic structures 1 and 2 of the present embodiment shown in FIG. Production examples 3 and 4 of resin molded products by the injection mold used are shown. In Examples 1 to 4, polyacetal resin (Polyplastics Duracon M90) was used as the resin material, and molding was performed at a resin temperature of 220°C, a mold temperature of 80°C, and a filling time of 1.5 seconds. rice field. The holding pressure after injection is controlled to two stages of holding pressure 1 and holding pressure 2, but the pressure values of each of Preparation Examples 1 to 4 are different as shown. For example, the holding pressure 1 is the holding pressure until the resin reaches the glass transition temperature, and the holding pressure 2 is the holding pressure from the glass transition temperature to the room temperature.

For the PVT characteristics of the resin material used to calculate the spring coefficient k, data published in, for example, "Computer Aided Innovation of New Materials II" was used.

In Table 1 above, in Production Example 3, a molded product with an accuracy equivalent to that in Production Example 1 using a conventional mold can be obtained with approximately half the pressure. Moreover, in Example 3, a molded product with high precision was obtained at the same pressure as in Example 2. In addition, in Example 4, a molded product with the same precision can be obtained with approximately half the pressure of Example 2.

FIG. 2 shows the PVT characteristics of the resin based on data published in "Computer Aided Innovation of New Materials II". In FIG. 2, the three arrows along the vertical axis indicate the amount of change in specific volume from the resin melt state to cooling and solidification at pressures of 80 MPa, 40 MPa, and 20 MPa, respectively. As shown in the figure, the specific volume change is about 0.112 cm^3/g at 80 Mpa, the specific volume change is about 0.122 cm^3/g at 40 Mpa, and the specific volume change is about 0.2 cm at 20 Mpa. It is 124cm^3/g. As can be seen from FIG. 2, the specific volume varies depending on the pressure applied to the resin. In particular, as shown in FIG. 2, the lower the molding pressure, the greater the volume change and the greater the shrinkage during cooling.

Considering this point, in this embodiment, different spring coefficients are used according to the pressure acting on the resin in the mold. For example, as shown in Example 3 and Example 4, the spring coefficient is set large for the elastic structure in the portion where the amount of contraction is small under high pressure, and the spring coefficient is set small for the elastic structure in the portion where the amount of contraction is large under low pressure. set. This makes it possible to change the volume of the mold by following the volume change of the resin when the pressure is applied. As mentioned above, when a uniform pressure is applied by a conventional hydraulic cylinder, etc., if control is performed to follow the volume change of the high pressure part, a sufficient compression stroke can be applied to the low pressure part where the volume change is larger. can't call Therefore, in some cases, sufficient accuracy cannot be obtained in the low-pressure part of the mold. On the other hand, in the present embodiment, by setting the spring coefficient as described above, the elastic structure follows the volume change of the resin when the pressure acts on both the high pressure section and the low pressure section, and the mold is formed. Volume can vary. Therefore, the above-mentioned problems in active injection compression molding using a conventional pressure device do not occur.

When the volume of the mold is changed following the volume change of the resin when pressure is applied, it is preferable that the shrinkage amount ΔV and the deformation amount ΔD when the resin shrinks satisfy the following relationship. desirable.

For example, ΔV is the amount of shrinkage when the resin shrinks, which is obtained from the pressure (P)-volume (V)-temperature (T) characteristics of the mold pressure and resin generated by the load P of the holding pressure on the resin in the mold. do. In that case, the ratio Q between the contraction amount ΔV and the deformation amount ΔD when the load P is applied to the elastic structure is

ΔD=QΔV (1.0≦Q≦1.25) (3)
It is desirable to satisfy the range of

Also, when the holding pressure 1 is switched to, for example, the holding pressure until the resin reaches the glass transition temperature, and the holding pressure 2 is the holding pressure from the glass transition temperature to the room temperature, the following relationship is obtained. should be satisfied.

For example, the pressure in the mold generated by the load P1 of the holding pressure until the resin in the mold reaches the glass transition temperature from the molten state and the pressure (P) - volume (V) - temperature (T) characteristics of the resin Let ΔV1 be the amount of shrinkage of the resin from the state until it reaches the glass transition temperature. In that case, the ratio Q1 between the contraction amount ΔV1 and the deformation amount ΔD1 when the load P1 is applied to the elastic structure is

ΔD1=Q1ΔV1 (where 1.0≤Q1≤1.1) (4)
It is desirable to satisfy the range of Furthermore, the pressure in the mold generated by the load P2 of the holding pressure from the glass transition temperature of the resin to room temperature and the pressure (P) - volume (V) - temperature (T) characteristics of the resin obtained from the glass transition temperature to room temperature Let ΔV2 be the amount of shrinkage of the resin until it reaches . In that case, the ratio Q2 between the contraction amount ΔV2 and the deformation amount ΔD2 when the load P2 is applied to the elastic structure is

ΔD2=Q2ΔV2 (where 1.0≦Q2≦1.25) (5)
It is desirable to satisfy the range of

<Embodiment 2>
FIG. 3 shows a configuration example of a different elastic structure mold. In FIG. 3, 7 is a resin molded article, and 8 is a core piece as a first shape piece having a shape in the clamping direction. Further, 9 is a core piece as a second shape piece whose transfer surface direction is arranged not parallel to the mold closing direction, for example, in a vertical direction, and 10 is a slide piece. 11 is an elastic structure with a high spring coefficient, and 12 is an elastic structure with a low spring coefficient. To support.

In FIG. 3, the resin molded product 7 is, for example, an exterior part of an electronic device or the like, and has an L-shaped cross section as shown in the figure, and the core piece 9 molds the right part of the resin molded product 7 in the figure. are arranged like this.

In the mold structure as shown in FIG. 3, a core piece 9 controlled by a slide piece 10 is formed in a vertical direction with respect to the mold clamping direction (upper in the figure). A slide mechanism (not shown) for the slide piece 10 is arranged, and a gate is not provided near the core piece 9. Therefore, it is closer to the end of the flow than the portion in the clamping direction. Internal pressure tends to be low.

Therefore, in the present embodiment, the core piece 8 forming the part in the mold clamping direction is configured as an elastic structure piece with a high spring coefficient that can be biased by an elastic structure 11 with a high spring coefficient. Further, the core piece 9 forming a portion perpendicular to the clamping direction is configured as an elastic structure piece with a low spring coefficient that can be biased by an elastic structure 12 with a low spring coefficient.

Also, as shown in FIG. 3, between the elastic structure 11 with a high spring coefficient at the left end in the drawing and the core piece 9, there is an elastic structure with a low spring coefficient that is not parallel to each other, for example, with a different attitude of approximately 90°. A structure 12 is inserted. That is, in the present embodiment, an elastic piece (core piece 8) with a high spring coefficient and an elastic piece (core piece 9) with a low spring coefficient are brought into contact with each other, and loads applied to each other's deformation via the contact portions are applied. Communicate the two by With such a structure, the elastic forces associated with elastic deformation and shape recovery of the elastic structures 11 and 12 can be mutually accommodated efficiently.

Table 2 shows molding examples of resin moldings as exterior parts in the same format as Table 1. In Table 2, production example 5 is a mold with a conventional configuration without an elastic structure, and production example 6 is a mold of this embodiment with elastic structures 11 and 12 shown in FIG. . The mold of Preparation Example 5 substantially corresponds to the structure of FIG. 3 from which the elastic structures 11 and 12 are removed. The bottom row of Table 2 shows the amount of sink marks (mm) on the slide surface of the resin molded product molded by the core piece 9 .

In Production Example 6 according to the present embodiment, as compared with Production Example 5 using a mold having a conventional configuration, the amount of sink marks on the slide surface could be particularly reduced by the structure using the elastic pieces as shown in FIG. Thus, in this embodiment, by providing a structure with a low spring coefficient in the portion where the internal pressure in the direction perpendicular to the clamping direction is low, a good molded product without sink marks is obtained even in the portion where the specific volume change is large. I was able to

<Embodiment 3>
FIG. 4 shows the configuration of the main part of the elastic structure mold that differs from this embodiment. The entire mold can be constructed similarly to the structure shown in FIG. 1 or FIG. 3 above. In FIG. 4, 13 is a resin molded product, and 14 is a rib formed on the resin molded product. The shape of the lower surface of the resin molded product 13 in FIG. 4 is formed by core pieces 15 and 16 . The core piece 15 has a transfer surface for transferring the shape of the lower surface of the resin molded product 13 , and the core piece 16 has a transfer surface for transferring the shape of the rib 14 .

Even if the core pieces 15 and 16 are integrally formed, the same effect as described below can be expected by selecting the spring coefficient. However, in this embodiment, the core pieces 15 and 16 are separate bodies, and the core piece 16 is slidably supported in the opening of the core piece 15 . These core pieces 15 and 16 are supported from below by elastic structures 17 and 18, respectively.

The elastic structures 17 and 18 have a structure in which inclined rod-shaped structural members are combined in an X shape. Among them, the elastic structure 17 is an elastic structure with a high spring coefficient, and the elastic structure 18 is an elastic structure with a low spring coefficient. Such a combination of spring coefficients can be achieved, for example, by setting the diameter of the structural material of the elastic structure 17 smaller than the diameter of the structural material of the elastic structure 18, or by selecting materials for the elastic structures 17 and 18, respectively. It can be realized by

FIG. 5 shows a state in which resin pressure is applied to the core pieces 15 and 16 from the resin material forming the resin molded product 13 by injection of molten resin into the mold, for example, to the structure shown in FIG.

When resin pressure is applied to the structure of FIG. 4, the elastic structures 17 and 18 are deformed according to their respective spring coefficients as shown in FIG. Since there is little difference in internal pressure in the vicinity of the rib 14 shown in FIGS. Here, in the conventional structure in which the core pieces 15 and 16 are rigidly supported without the elastic structures 17 and 18, a case where a uniform pressure is applied by normal molding or a hydraulic cylinder will be considered. In this case, even if the internal pressure is the same, the resin temperature of the rib portion is high, so the amount of shrinkage at the base of the rib 14 is large, so that there is a possibility that the appearance or sink marks near the base of the rib 14 differ from the surroundings.

On the other hand, in the present invention, as shown in FIG. 4, the root portion of the rib 14 is composed of a core piece 16 which is separate from the core piece 15, and the core piece 16 is connected to an elastic structure 18 having a low spring coefficient. there is Therefore, at the root portion of the rib 14, which shrinks significantly during cooling, the core piece 16 undergoes a stroke due to greater deformation as shown in FIG. Therefore, during the cooling and holding pressure period after the injection is completed, the holding pressure is applied while compensating for the amount of resin due to shrinkage.

<Embodiment 4>
FIG. 6 shows the configuration of the main part of the elastic structure mold that differs from this embodiment. In this embodiment, a structural example is shown in which passages or channels for a cooling fluid, such as cooling water, are formed in an elastic structure piece having a core piece and an elastic structure.

In FIG. 6, 20 is a resin molded product, 21 is a cabinet piece, 22 is a core piece having a core side shape and having a flow path inside, and 23 is a core piece having a cooling fluid flow path inside. . Reference numeral 24 denotes an elastic structure having a low spring coefficient and internally provided with a cooling fluid flow path; 25, an elastic structure having a high spring coefficient and internally provided with a cooling fluid flow path; The inlet of the channel, 27 is the outlet.

The core pieces 22, 23 and the elastic structures 24, 25 provided with cooling fluid flow paths can be modeled as pipe structures, for example, using a layered manufacturing method such as a 3D printer. With such a structure, the core pieces 22 and 23 each having a channel therein are connected by the elastic structures 24 and 25 also having a channel therein so that the cooling fluid can be circulated. As a result, efficient cooling of the mold using the elastic structures 24 and 25 of the present embodiment is possible in the mold functionally equivalent to or higher than that of injection compression.

Here, FIG. 7 shows the structure of an injection compression mold using a general hydraulic cylinder. In FIG. 7, reference numeral 28 denotes a core piece having a cooling flow path inside; 29, the flow path; 30, a mold piece containing the core piece and the hydraulic cylinder; 31, an inlet for cooling fluid; fluid outlet. 33 is a hydraulic cylinder, 34 is a shaft that connects the core piece and the hydraulic cylinder, 35 is a stopper that regulates the stroke of the hydraulic cylinder, 36 is a pressure space in which the hydraulic cylinder operates, and 37 is a hydraulic inlet/outlet.

As is clear from a comparison of the mold provided with the elastic structure piece according to the present embodiment in FIG. 6 and the conventional injection compression mold in FIG. Since the cylinder is mounted on the rear portion of the core piece, it is difficult to provide a cooling passage in this portion. Therefore, the general injection compression mechanism shown in FIG. 7 cannot efficiently cool the mold on the side where the hydraulic cylinder is arranged. On the other hand, in the mold provided with the elastic structure piece according to this embodiment of FIG. Efficient mold cooling is possible in all mold parts.

Naturally, in order to increase the productivity of injection molded articles, it is necessary to increase the cooling efficiency and shorten the cooling time. Also, in order to eliminate molding defects such as sink marks, it is necessary to strengthen cooling. Then, as shown in FIG. 6, the structure in which the cooling passages are arranged by using the elastic structure pieces greatly contributes to the improvement of the productivity of the injection molding die and the molding accuracy.

<Embodiment 5>
The structure of FIG. 6 can be further modified as shown in FIG. FIG. 8 shows a structure in which a heat sink structure is formed by using the elastic structural piece shown in FIG. In FIG. 8, a fin structure 38 forming a heat sink is formed on the surface of an elastic structure 25 having a pipe-like structure and having a cooling water path arranged therein. In the same manner as described above, the fin structure 38 can be formed on the surface of the pipe-shaped elastic structure 25 at the same time when the pipe-shaped elastic structure 25 is modeled using a layered manufacturing method such as a 3D printer.

As shown in FIG. 8, by molding the fin structure 38 on the surface of the elastic structure 25 in which the cooling water path is arranged, the heat dissipation efficiency of the mold can be improved more than the structure shown in FIG. As a result, the mold cooling time can be shortened, and the productivity and molding accuracy of the injection mold can be greatly improved.

<Embodiment 6>
FIG. 10 shows a configuration example of an elastic structure mold that can be used for injection molding a resin molded product 39 as shown in FIGS. 9(a) and 9(b).

FIG. 9 shows a box-shaped resin molded product 39 that can be molded with the mold of this embodiment, and the resin material is, for example, PC+ABS resin (for example, Multilon (trade name) TN7500MC manufactured by Teijin Kasei Co., Ltd.). The resin molded product 39 has a shape as shown in FIGS. 9(a) and 9(b). 9(a) and 9(b), for example, the resin molded product 39 has a disk shape with an outer diameter of φ46 mm as a whole, and has a circular top surface 40 with a thickness of 1.8 mm and a circular outer diameter portion with a thickness of 2.0 mm. , wall-like ribs 41 having a height of 6.0 mm and a draft angle of 3 degrees.

Further, as shown in FIG. 9B, the resin molded product 39 has a plurality of boss shapes 42 formed on the inner periphery of the rib 41 at different heights vertically from the circular top surface. Further, as shown in FIG. 9(a), the surface 43 of the resin molded product 39 is patterned with a texture by mold processing.

The fixed side mold 44 and the movable side mold 45 in FIG. 10 are manufactured using precipitation hardened pre-hardened steel. A plurality of elastic pieces 46 are erected on the movable side mold 45 for molding the boss shape 42 of the resin molded product 39 with their tip portions. The inside of the elastic piece 46 is composed of an aluminum alloy lattice structure as shown in FIGS. 11 and 12 below. The elastic pieces 46 can be manufactured by lamination molding using a powder bed type 3D printer (not shown) or the like.

FIG. 11 shows an example of the cross-sectional structure of the elastic pieces 46 used in the injection molding die of FIG. The elastic piece 46 of FIG. 11 has a lattice structure. This lattice structure is formed by forming lattice struts 47 made of aluminum alloy with a diameter of 0.5 mm, for example, as a lattice structure. The outer portion 48 of the elastic piece 46 has a thickness of 0.3 mm. In this example, the lattice spacing of the lattice support 47 is 1.2 mm in the horizontal direction, and the angle with respect to the bottom surface of the lattice support 47 as a reference plane is ±60 degrees.

FIG. 12 shows a modeling procedure when designing the lattice structure by the lattice support 47 of the elastic pieces 46 described above. FIG. 12 shows the lattice structure of the lattice struts 47 growing in the outer shell 50 forming the outer shape portion 48 of the elastic piece 46 as shown by 491, 492, 493, . . . However, this is for the sake of convenience to show the shape relationship with the outer shell 50 portion, and does not show the actual procedure of layered manufacturing.

In the modeling of FIG. 12, grid shapes 491, 492, 493, . In that case, the lattice shapes 491, 492, 493, . For example, the elastic piece 46 can be designed by such a design procedure based on modeling.

In addition, when the lattice structure by the lattice support 47 and the outer shell 50 part are integrally laminated, in practice, the lattice structures 491, 492, 493 . . . are laminated at the same time. Alternatively, a method may be adopted in which the lattice structure by the lattice support 47 is layered and manufactured separately from the outer shell 50 portion. In this case, the outer shell 50 portion of FIG. It may be manufactured by molding.

The elastic modulus of the elastic piece 46 is designed to be 63 GPa in the thickness direction of the top surface and 127 GPa in both the thickness and horizontal directions according to the shape of the boss of the resin molded product 39, for example. That is, the elastic structure of the elastic piece 46 can be designed and manufactured so that different parts thereof have different elastic moduli or spring coefficients. With such a design, the elastic piece 46 can be designed and manufactured so as to have an elastic modulus or a spring coefficient suitable for various injection pressures and holding pressures acting on the transfer surface supported by each part thereof. In the above description, the method of designing the lattice structure constituting the elastic structure of the elastic piece 46 by numerical calculation and manufacturing it by lamination molding was considered. However, a person skilled in the art may employ any design as long as it is a structure capable of imparting the desired elasticity to the elastic pieces 46 .

Table 3 below shows Example 7 of making a resin molded product using the injection molding die of this embodiment shown in FIG. FIG. 14 shows the amount of sink marks in Example 8 of the resin molded product according to (FIG. 14). The amount of sink marks in the table is the result of measurement with a digital microscope.

In the conventional injection molding die shown in FIG. 14 used in Preparation Example 8, the fixed side die 44 and the movable side die 45 are made of precipitation hardened pre-hardened steel. A steel material such as SKD51 is used for the core pin 51 forming the boss-shaped portion (42). The molding conditions for the resin molded product (39) of Preparation Examples 7 and 8 are, for example, injection filling time 0.5 sec, holding pressure time 3 sec, resin temperature 240°C, mold temperature 55°C, cooling time 15 s, and holding pressure 40 bar. bottom.

As shown in Table 3 below, the amount of sink marks in the resin molded product of Preparation Example 7 using the injection molding mold of this embodiment is 8 μm, and the sink mark amount in the resin molded product of Preparation Example 8 using the injection molding mold of the conventional configuration shown in FIG. The volume was 23 μm. Thus, by using the elastic piece (46) of the present embodiment, good molding performance can be obtained with a small amount of sink marks.

As described above for the injection molding dies of the above-described embodiments, the portion between the transfer surface of the shape piece and the base of the mold is an elastic structure that conforms to the PVT contraction of the resin. There is an advantage that a special pressurizing device such as a cylinder and a control device are not required.

Further, by being supported by the elastic structure, the shaped piece elastically deforms following the contraction of the resin, and also operates to recover its shape. As a result, excess pressure is not applied to the resin, and as a result, the residual stress in the molded product is reduced, and the precision of the resin molded product can be improved.

In addition, by arranging elastic pieces with different spring coefficients based on prediction of the pressure distribution in the mold, mold compression control adapted to each pressure distribution and shrinkage distribution becomes possible. As a result, excess residual stress can be reduced and the amount of deformation of the entire mold can be reduced compared to when the same pressure is applied to the entire mold by a hydraulic mechanism or the like. At the same time, it is possible to obtain parts with good precision without occurrence of sink marks even in parts where resin pressure is partially low and shrinkage is large, which has been difficult to control conventionally.

In addition, by means of elastic pieces having elastic structural parts such as those shown in the above embodiments, appropriate pressure can be individually applied even to small localized parts where sink marks or the like are likely to occur due to changes in wall thickness due to rib structures or the like. be able to. As a result, it is possible to greatly improve the appearance quality and component precision of the resin molded product. In addition, it is possible to effectively reduce sink marks on the back side of the boss, which tend to occur due to thinning. Therefore, it is possible to injection-mold a high-quality resin molded product while realizing material reduction by thinning.

In addition, in the elastic pieces having the parts of the elastic structure described above, the spring coefficient of each part depends on the characteristics of each part, such as the cross-sectional area of the elastic structure, the three-dimensional shape, and the shape in which the parts are discontinuously combined. Varied structures may be used accordingly. In addition, by setting uneven and discontinuous spring coefficients at each part, it is possible to follow the phenomenon in which the proportional relationship between pressure and volume changes with the glass transition temperature (Tg) as a boundary, and the elastic piece can be accurately adjusted. It can follow the shrinkage of the resin, and good molding accuracy can be obtained.

By arranging a flow path for cooling fluid inside the elastic structure, or by making the surface of the elastic structure into a heat sink structure, it is possible to efficiently cool the mold and manufacture resin articles by injection molding. can be performed very efficiently. In addition, the injection mold provided with the elastic piece having the elastic structure portion shown in the above-described embodiment can be easily manufactured by a layered manufacturing method using a 3D printer or the like.

In the above, the term "mold" is used, and metal is often exemplified as the material of each member constituting the injection molding die, including the elastic piece having the elastic structural body. However, the material of each member that constitutes the injection molding die is not limited to metal, and even if the constituent members of the injection molding die are made of a material other than metal, such as resin or ceramic, the configuration of the present invention can be applied. It can be implemented similarly.

1, 2, 11, 12... Elastic structure 3, 8, 9, 16, 22, 23... Core piece 4, 7, 39, 52... Resin molded product 5... Rotary piece 6... Ejector pin 10 41: Rib 42: Boss shape 44: Fixed side mold 45: Movable side mold 46: Elastic piece 47: Lattice support 50: Outer shell.

Claims (18)

An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
ΔV is the specific volume change when the resin shrinks, which is determined based on the pressure (P)-volume (V)-temperature (T) characteristics of the resin, P is the internal pressure in the mold, and deformation of the elastic structure at that time. Δt is the shrinkage rate of the resin along the direction of , and the calibration coefficient q is
q=ΔV/Δt (1)
and the spring coefficient k of the elastic structure is
k=q−1×ΔV/P (2)
injection mold. An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
A shrinkage amount ΔV when the resin shrinks, which is obtained from the pressure (P)-volume (V)-temperature (T) characteristics of the mold pressure generated by the load P of the holding pressure on the resin in the mold, The relationship between the deformation amount ΔD when the load P is applied to the elastic structure and
ΔD=QΔV (1.0≦Q≦1.25) (3)
injection mold. An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
From the melted state obtained from the pressure (P)-volume (V)-temperature (T) characteristics of the mold and the pressure inside the mold generated by the load P1 of the holding pressure until the resin in the mold reaches the glass transition temperature from the molten state The relationship between the shrinkage amount ΔV1 of the resin until it reaches the glass transition temperature and the deformation amount ΔD1 when the load P1 is applied to the elastic structure is
ΔD1=Q1ΔV1 (where 1.0≤Q1≤1.1) (4)
And the glass transition obtained from the pressure (P)-volume (V)-temperature (T) characteristics of the mold and the pressure inside the mold caused by the load P2 of the holding pressure from the glass transition temperature of the resin to room temperature The relationship between the shrinkage amount ΔV2 of the resin from temperature to room temperature and the deformation amount ΔD2 when the load P2 is applied to the elastic structure is
ΔD2=Q2ΔV2 (where 1.0≦Q2≦1.25) (5)
injection mold. An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
The elastic structure has a plurality of portions having elastic moduli or spring coefficients different from each other , and the plurality of portions support different portions of the transfer surface . An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
a second shape piece having a first shape piece as the shape piece, a first shape piece as the elastic structure, and a transfer surface not parallel to the transfer surface of the first shape piece; An injection molding die comprising a second elastic structure that elastically supports the second shape piece and has a direction of elastic deformation different from that of the first elastic structure. 6. The injection mold of claim 5, wherein the first elastic structure and the second elastic structure have different spring coefficients. 7. The injection molding die according to claim 5, wherein the first elastic structure and the second elastic structure have abutment portions that abut against each other, and apply elastic force to each other via the abutment portions. Injection molds that communicate with each other. An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
An injection mold in which a passage for circulating a cooling fluid is arranged inside the elastic structure. An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
An injection mold wherein the surface of said resilient structure comprises a heat sink structure. An injection molding die comprising a shaped piece having a transfer surface, a base supporting the shaped piece, and an elastic structure provided between the shaped piece and the base in a mold clamping direction,
The elastic structure elastically deforms according to the injection pressure and holding pressure of the resin injected into the mold, and recovers its shape following the contraction of the resin accompanying cooling,
The elastic structure is an injection mold having a lattice structure. In the injection mold according to any one of claims 2 to 10, the specific volume change during shrinkage of the resin determined based on the pressure (P) - volume (V) - temperature (T) characteristics of the resin ΔV, the internal pressure in the mold is P, the contraction rate of the resin along the direction of deformation of the elastic structure at that time is Δt, and the calibration coefficient q is q=ΔV/Δt (1)
and the spring coefficient k of the elastic structure is k=q−1×ΔV/P (2)
injection mold. In the injection mold according to any one of claims 1 or 3 to 11, the pressure in the mold caused by the load P of the holding pressure on the resin in the mold and the pressure (P) of the resin - volume ( The relationship between the amount of shrinkage ΔV when the resin shrinks, which is obtained from V)-temperature (T) characteristics, and the amount of deformation ΔD when the load P is applied to the elastic structure is ΔD=QΔV (1. 0≤Q≤1.25) (3)
injection mold. 13. In the injection mold according to any one of claims 1 , 2, or 4 to 12, the pressure in the mold caused by the holding pressure load P1 until the resin in the mold reaches the glass transition temperature from the molten state And the shrinkage amount ΔV1 of the resin until it reaches the glass transition temperature from the molten state obtained from the pressure (P)-volume (V)-temperature (T) characteristics of the resin, and when the load P1 is applied to the elastic structure and the deformation amount ΔD1 is ΔD1=Q1ΔV1 (where 1.0≦Q1≦1.1) (4)
And the glass transition obtained from the pressure (P)-volume (V)-temperature (T) characteristics of the mold and the pressure inside the mold caused by the load P2 of the holding pressure from the glass transition temperature of the resin to room temperature The relationship between the shrinkage amount ΔV2 of the resin from temperature to room temperature and the deformation amount ΔD2 when the load P2 is applied to the elastic structure is ΔD2=Q2ΔV2 (where 1.0≦Q2≦1.25). …(5)
injection mold. 14. The injection molding apparatus according to claim 1, wherein said elastic structure applies an urging force to said shaped piece according to the amount of deformation of said elastic structure. 15. The injection molding apparatus according to any one of claims 1 to 14, wherein said shape piece elastically deforms following contraction of resin. 16. A method of manufacturing an injection mold according to any one of claims 1 to 15 , comprising the step of forming the elastic structure by lamination molding. An injection molding machine comprising: the injection molding die according to any one of claims 1 to 15 ; and an injection device for injecting molten resin into the injection molding die. 16. A method of manufacturing a resin molded product, comprising injecting a molten resin into the injection molding die according to any one of claims 1 to 15 by means of an injection device, and injection molding the resin molded product.

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