JP2009233975A - Injection mold and injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection mold suitable to manufacture a molded product with minimized distortion, high accuracy and minimized dispersion by absorbing a volume change associating the contraction of resin within a cavity by a mold structure in injection molding. <P>SOLUTION: In the injection mold for molding resin MD into a shape according to a cavity 11 by injecting the resin MD into the cavity 11 that is the inner part of the mold, the cavity 11 includes movable members CP<SB>1</SB>and CP<SB>2</SB>and back mechanisms SP<SB>1</SB>and SP<SB>2</SB>for moving the movable members CP<SB>1</SB>and CP<SB>2</SB>according to the pressure of the resin injected to the movable members CP<SB>1</SB>and CP<SB>2</SB>. The movable members CP<SB>1</SB>and CP<SB>2</SB>in the back mechanisms SP<SB>1</SB>and SP<SB>2</SB>are moved in the pressure direction when the resin MD is injection molded, and moved in a contracting direction when the resin MD contracts. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  In the present invention, the injection molding die suitable for manufacturing a molded product with less distortion, high accuracy and less variation by absorbing volume change accompanying resin shrinkage of the cavity in the injection molding, The present invention relates to the injection molding method.

  Generally, in the conventional injection molding, the resin is cooled and contracted in the process of injecting and filling the molten molding resin into the mold. For this reason, even after the resin has been filled into the mold, a method has been employed in which the pressure is maintained to replenish the resin corresponding to the volume decrease accompanying the resin shrinkage to prevent sink marks.

  Further, the pressure of the resin is efficiently applied in the vicinity of the gate (resin inlet), and it is difficult to apply a sufficient resin pressure to a place far away from the gate.

  For this reason, residual stress remains in the molded product due to differences in the cooling / shrinking location of the molded product, and in particular in molded products with uneven thickness, sink marks and distortion occur in the molded product, resulting in variations in accuracy of the molded product. Has occurred.

  Therefore, the conventional molding technology uses injection compression molding, in which the molding resin is injected with the mold temporarily clamped, the mold is clamped when filling is completed, and a uniform resin pressure is applied to the inside of the mold. It has been.

  Note that sink marks include the states described below. That is, in injection molding, a molten resin is injected into a cavity to form a molded product. However, the molded product taken out after cooling shrinks compared to the shape of the cavity. For this reason, the finished molded product does not have the shape of the inner surface of the cavity, but is dented or punctured. The defective state of the molded product due to the shrinkage of the resin.

See also Patent Document 1.
JP-A-7-178773

  However, the conventional method as described above has the following problems.

  That is, in injection compression molding, when the resin is filled, the mold is temporarily tightened, and the effect of removing air from the joint of the mold by the injection pressure of the resin, and by tightening the main mold when the resin filling is completed Since the pressure is uniformly applied to the inside of the mold (cavity), it is particularly effective for optical resin molding. However, in this method, it is necessary to control the timing of resin injection / filling and the timing of final mold clamping. In addition, there is a problem that a mold having a complicated shape having many fine core pins and a mold having many slide cores are likely to be damaged or have resin leakage, and are difficult to apply.

The invention according to claim 1 of the present invention is an injection mold in which the resin is molded into a shape corresponding to the cavity by injecting the resin into a cavity inside the mold.
An injection mold comprising: a movable member disposed on a surface forming the cavity; and a back mechanism configured to move the movable member in accordance with a pressure of resin applied to a predetermined portion of the movable member. It is desirable to be.

  In the invention according to claim 2, the back mechanism is an elastic body, the elastic body supports the movable member, the movable member is movable in a pressure direction when the resin is injection-molded, and the resin is When shrinking, an injection mold configured to move in the shrinking direction is desirable.

  The invention according to claim 3 is preferably an injection mold in which the movable member is arranged at a position corresponding to a thick portion where the resin filled in the cavity is highly contracted.

  The invention according to claim 4 is preferably an injection mold in which the movable member is disposed at a first position of the cavity and a second position opposite to the first position.

  The invention according to claim 5 includes a heating unit that heats the resin filled in the cavity and a control unit that controls the heating unit, and the control unit cools the resin once the temperature is increased. An injection mold that performs control is preferred.

  The invention according to claim 6 is an injection molding method in which the resin is molded into a shape corresponding to the cavity by injecting the resin into a cavity inside the mold, and the step of injecting the resin into the cavity; An injection molding method including a step of applying pressure to a predetermined portion of a movable member disposed on a surface forming the cavity and a step of moving the movable member according to the pressure is desirable.

  As described above, the present invention has an effect that the residual stress can be reduced and the distortion of the molded product can be reduced by absorbing the volume reduction due to the shrinkage of the resin by the movable member.

  In addition, since the part where the shape of the molded product changes due to resin shrinkage becomes a movable member, it is possible to control the appearance of the molded product by setting the movable member at a position shifted from the location where you want to prevent sink marks in advance. Become.

  Furthermore, since there is no fear of sinking, it is not necessary to apply an excessive holding pressure after completion of resin filling, so that damage to the mold is reduced and molding at a low pressure is possible. This has the effect that both the molding equipment and the mold can be reduced in size and energy can be saved.

  Cooling from reheating using a heater capable of rapid heating, such as an IH heater incorporated in a mold after filling with resin, has the effect of making the molding density uniform and achieving further high accuracy.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic view showing an embodiment of an injection molding machine according to the present invention. Since these injection molding machines are already known, the outline will be described.

  In general, the injection molding machine 1 has a structure in which a nozzle of an injection mechanism part is brought into contact with a joint (parting part) of a mold and pressed to form.

  In the injection molding machine 1, an upper platen 3 and a lower platen 5 are attached to four tie bars (only two are shown) 13 and 13 installed substantially vertically so as to be movable in the vertical direction.

  An upper mold 7 is installed below the upper platen 3, and a lower mold 9 is installed above the lower platen 5. A mold clamping force drive mechanism (not shown) clamps the upper platen 3 and the lower platen 5 in a direction in which they approach each other.

  In addition, an injection mechanism (parting injection mechanism) 17 is disposed substantially horizontally on the side of the joint portion (parting portion) between the upper mold 7 and the lower mold 9. The nozzle 19 of the injection mechanism 17 is pressed substantially horizontally from the side of the joint (parting part) between the upper mold 7 and the lower mold 9 by a pressing force driving mechanism (not shown). It is supposed to be attached. And resin MD which melt | dissolved the material in the replenishment part 15 (in this example, when resin MD is mentioned, molten resin is included) is inject | emitted. In addition, the injection molding machine 1 is not limited to the above-mentioned thing, It is natural that it applies to various things which attach a metal mold | die and inject resin.

  On the other hand, in this injection molding machine 1, a cavity 11 that is a space corresponding to the product shape inside the mold is formed by combining the upper mold 7 and the lower mold 9.

  The shape of the cavity 11 is represented by a rectangle as an example in order to represent it as a concept, but actually, it is formed in a necessary shape according to the shape of the molded product.

  In addition, the shapes of the upper and lower molds 7 and 9 are also represented as rectangles as an example in order to express them as a concept, but they can be formed into appropriate shapes as necessary.

  Please refer to FIG. 2 and FIG. FIG. 2 shows a cross section of the mold in FIG. 1 viewed from a direction perpendicular to the paper surface. Moreover, FIG. 3 has shown the case where a metal mold | die (the whole metal mold | die) is seen from the AA direction in FIG.

  As shown in FIG. 2, the injection molding machine 1 includes a cavity 11 (that is, an internal space 11a corresponding to the upper mold and an inner space corresponding to the lower mold 9) formed by the upper and lower molds 7 and 9. An injection mold for molding the resin MD into a shape corresponding to the cavity 11 by injecting the resin MD (including molten resin in this example) from the gate GT into the space 11b is provided. ing.

Then, according to the pressure of the movable member (movable piece) CP ₁ , CP ₂ arranged at a predetermined position on the surface forming the cavity 11 and the resin MD applied to the predetermined position of the movable member CP ₁ , CP _2. The movable members CP ₁ and CP ₂ are provided with a back mechanism configured to be movable.

Specifically, the back mechanism is formed of an elastic body _SP 1, SP ₂ holes _HL 1 of (springs, etc.) and cylindrical, HL _2, elastic body _SP 1, SP ₂ (such as a spring) is the The movable members CP ₁ and CP ₂ are supported by the cavity 11. That is, one end of each spring SP ₁ , SP ₂ as an elastic body is attached to the bottom of each cylindrical hole HL ₁ , HL ₂ processed on the surface forming the cavity 11, and the spring SP ₁ , The other end of SP ₂ is attached to the movable members CP ₁ and CP ₂ .

The cylindrical holes HL ₁ and HL ₂ and the movable members CP ₁ and CP ₂ are formed so as to slide together. Further, the movable members CP ₁ and CP ₂ protrude from the surface of the cavity 11 by the lengths D 1 and D 2, respectively, in a free state where no external pressure is applied. The lengths of D1 and D2 are desirably determined by conditions such as spring strength and resin pressure. Of course, the dimensional accuracy required for the molded product is taken into consideration.

The movable members (movable pieces) CP ₁ and CP ₂ move in the pressure direction when the resin MD is injection-molded, and move in the contraction direction when the resin MD contracts. Thus, the volume reduction due to the shrinkage of the resin MD is absorbed by the movable members CP ₁ and CP ₂ , whereby the residual stress can be reduced and the distortion of the molded product is reduced.

On the other hand, it is desirable that the movable members CP ₁ and CP ₂ are disposed at positions corresponding to the thick portions where the shrinkage of the resin MD filled in the cavity 11 is large. For example, when the shape of the cavity 11 includes a thick part and a thin part, it is preferable to place the movable members CP ₁ and CP ₂ in preference to the thick part.

Further, the movable members CP ₁ and CP ₂ are disposed at a first position of the cavity 11 and a second position facing the first position. For example, as a cube or a rectangular parallelepiped, in the case of cavity 11 with symmetry, one of the movable member CP ₁ is disposed at a position of the center of the internal space 11a (first position), the position of the center of the internal space 11b it is preferable that (second position) to be arranged the other movable member CP _2.

For example, as shown in FIG. 3, the movable member CP ₁ (CP ₂ ) is disposed at a first position (second position) that is the center of the mold. Thereby, the arrangement positions of the movable members CP ₁ and CP ₂ face _{each other} in the cavity 11.

In addition, heating means IH ₁ and IH ₂ (for example, an IH heater) for heating the resin MD filled in the cavity 11 and control means (not shown) for controlling the heating of the heating means are provided. Furthermore, temperature detection sensors SR ₁ and SR ₂ for detecting the temperature of the upper and lower molds 7 and 9 heated by the heating means IH ₁ and IH ₂ (for example, IH heater or the like) are provided in the upper and lower molds 7 and 9, respectively. ing.

  Under the control of the control means, the heating means (IH heater or the like) once raises the temperature of the resin MD and then cools it. As a result, the density of the molded product can be further stabilized and the residual stress can be suppressed.

  Please refer to FIG. 4, FIG. 5, FIG. 6, and FIG. An injection molding method for molding the resin MD into a shape corresponding to the cavity 11 by injecting the resin MD into the cavity 11 inside the mold will be described.

That is, in the injection molding method of molding the resin MD into a shape corresponding to the cavity 11 by injecting the resin MD into the cavity 11 inside the mold, the step of injecting the resin MD into the cavity 11; A step in which the resin MD applies pressure to predetermined portions of the movable members (movable pieces) CP ₁ and CP ₂ disposed on the surface forming the cavity 11, and the movable members CP ₁ and CP ₂ are movable in accordance with the pressure. The process of carrying out.

Specifically, as shown in FIG. 4, first, in step S01, the movable members (movable pieces) CP ₁ and CP ₂ arranged on the surface forming the cavity 11 are elastic bodies SP ₁ and SP _{2 in} a free state. It protrudes from the surface of the cavity 11 by the force of (spring etc.).

  Subsequently, in step S03, injection is started in the state of step S01. That is, the nozzle 19 of the injection mechanism 17 is pressed substantially horizontally from the side against the joining portion (parting portion) between the upper die 7 and the lower die 9 by a pressing force driving mechanism (not shown). The resin MD in which the material in the replenishing part 15 is melted is injected.

In step S05, the resin MD flows into the cavity 11 from the gate GT (see FIG. 2) in the Ar1 direction. Please refer to FIG. Resin MD flows into the cavity 11. Kotonoki, resin MD movable member _CP 1, CP ₂ which be folded over the pressure to the movable member _CP 1, CP ₂ which flows are kept free.

  In step S07, the injection molding machine 1 determines whether or not the resin MD that has flowed into the cavity 11 is completely filled in the cavity 11. When filling is completed, the process proceeds to step S09. When the filling is not completed, the process returns to step S05 and the injection of the resin MD into the cavity 11 is continued.

In step S09, the movable members CP ₁ and CP ₂ are pushed by the resin MD and pressure is applied in the arrow direction Ar2. Then, the movable members CP ₁ and CP ₂ move in the directions of the arrows Ar3 and Ar4, respectively, and are pushed to the limit. (See Figure 6)
Further, as shown in FIG. 6, the filling of the resin MD is completed, the movable member _CP 1, CP ₂ pressure is applied to the movable member _CP 1, CP ₂ are movable to the same plane as the cavity 11.

In step S11, the upper mold 7 and the lower mold 9 are heated by the heating means IH ₁ and IH ₂ (for example, IH heater). That is, when the upper and lower molds 7 and 9 are heated, the resin MD filled in the cavity 11 is heated.

In step S13, the control means provided in the injection molding machine 1 (not shown) the upper and lower molds 7 and 9 through the temperature detecting sensor SR _1, SR ₂ determines whether it is a predetermined temperature. When the upper and lower molds 7, 9 reach a predetermined temperature (temperature at which the resin MD is sufficiently melted), the process proceeds to step S15. When the upper and lower molds 7 and 9 are not at the predetermined temperature, the process returns to step S11, and heating is continued by the heating means IH ₁ and IH ₂ (for example, IH heater).

  In step S15, the heating process for the upper and lower molds 7 and 9 ends. This makes it possible to further stabilize the density of the molded product and suppress the residual stress after the resin MD is cooled in the subsequent processing.

  In step S17, the resin MD filled in the cavity 11 is cooled and contracted.

In step S19, as shown in FIG. 7, the movable members CP ₁ and CP ₂ move according to the shrinkage of the resin MD in the direction of the arrow Ar5. That is, the movable member CP ₁ is movable in the direction of the arrow Ar @ 6, the movable member CP ₂ is movable in the arrow Ar7 direction.

As described above, the present invention absorbs the volume reduction due to the shrinkage of the resin MD by the movable members CP ₁ and CP ₂ , thereby reducing the residual stress and reducing the distortion of the molded product.

Further, since the portion where the shape of the molded article due to resin MD shrinkage changes becomes movable member CP _1, CP _2, by setting the position shifted a movable member CP _1, CP ₂ from where you want to prevent pre-shrinkage It becomes possible to control the appearance of the molded product.

  Furthermore, since there is no fear of sinking, it is not necessary to apply an excessive holding pressure after completion of resin filling, so that damage to the mold is reduced and molding at a low pressure is possible. This has the effect that both the molding equipment and the mold can be reduced in size and energy can be saved.

  Cooling from reheating using a heater capable of rapid heating, such as an IH heater incorporated in a mold after filling with resin, has the effect of making the molding density uniform and achieving further high accuracy.

  Moreover, although what used the movable member in the above-mentioned injection-molding die demonstrated the example of injection molding, it can be utilized also for transfer molding etc., for example.

  The present invention is not limited to the embodiment of the invention described above, and can be implemented in other modes by making appropriate modifications.

It is the schematic which shows one Embodiment of an injection mold. It is explanatory drawing explaining a metal mold | die, a cavity, and a movable member. It is explanatory drawing explaining a metal mold | die, a cavity, and a movable member. It is a flowchart explaining an injection molding method. It is explanatory drawing explaining the movement of a movable member. It is explanatory drawing explaining the movement of a movable member. It is explanatory drawing explaining the movement of a movable member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding machine 3 Upper platen 5 Lower platen 7 Upper metal mold 9 Lower metal mold 11 Cavity 13 Tie bar 15 Replenishment part 17 Injection mechanism 19 Nozzle

Claims (6)

In an injection mold that molds the resin into a shape corresponding to the cavity by injecting the resin into the cavity inside the mold,
A movable member disposed on a surface forming the cavity, and a back mechanism configured to move the movable member in accordance with a pressure of resin applied to a predetermined portion of the movable member. Injection mold.   The back mechanism is an elastic body, and the elastic body supports the movable member. The movable member moves in the pressure direction when the resin is injection-molded, and moves in the contraction direction when the resin contracts. The injection mold according to claim 1, wherein the injection mold is configured as described above.   3. The injection mold according to claim 1, wherein the movable member is disposed at a position corresponding to a thick portion where shrinkage of the resin filled in the cavity is large.   The injection mold according to any one of claims 1 to 3, wherein the movable member is disposed at a first position of the cavity and a second position opposite to the first position. Heating means for heating the resin filled in the cavity, and control means for controlling the heating means,
The injection mold according to any one of claims 1 to 4, wherein the control means performs control of once raising the temperature of the resin and then cooling it. In the injection molding method of molding the resin into a shape corresponding to the cavity by injecting the resin into the cavity inside the mold,
Injecting the resin into the cavity;
Applying a pressure to a predetermined portion of a movable member disposed on a surface where the resin forms the cavity;
And a step of moving the movable member in response to the pressure.

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