JP2006035630A - Injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a rapid rise of a mold inner pressure accompanying completion of the packing of a molten resin into cavities. <P>SOLUTION: In the injection process wherein a molding die 10 is equipped with cavities 11b, 12b, with a gate 12e which injects the molten resin into the cavities 11b, 12b and with a overflow portion 12h which is communicant with the resin final packing portions of the cavities 11b, 12b and wherein the molten resin is injected from the gate 12e into the cavities 11b, 12b, the injection process is ended, after the packing of the molten resin into the cavities 11b, 12b has been completed, at the point of time when the molten resin overflows by a predetermined ratio of volume based on the volume of the overflow portion 12h. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an injection molding method for molding a resin molded product by injecting molten resin into a cavity of a molding die at a predetermined pressure.

  Conventionally, in an injection molding method, an insert part is set in advance in a cavity of a molding die, and then a molten resin is injected into the cavity at a predetermined pressure, so that the insert part made of metal or the like is a resin molded part. An insert molding method for integrally molding is widely adopted.

  By the way, in the injection molding method, in the injection process of the molten resin, until the filling rate of the molten resin into the cavity rises to about 90%, the mold internal pressure is very low due to the presence of the space in the cavity. Is maintained.

  However, in the injection process, when the molten resin is almost completely filled into the cavity, the mold internal pressure rapidly increases as the space in the cavity disappears. As a result, an excessive pressure is applied to the insert part, causing damage to the insert part, or adversely affecting the durability of the molding die.

  In view of the above points, an object of the present invention is to suppress a rapid increase in mold internal pressure accompanying completion of filling of a molten resin into a cavity.

In order to achieve the above object, according to the first aspect of the present invention, in the molding die (10), the cavity (11b, 12b) and the gate (12e) for injecting molten resin into the cavity (11b, 12b) are provided. And an overflow part (12h) communicating with the resin final filling part of the cavity (11b, 12b),
In the injection step of injecting molten resin from the gate (12e) into the cavity (11b, 12b), after the filling of the molten resin into the cavity (11b, 12b) is completed, the overflow portion (12h) The injection process is terminated when the molten resin overflows by a predetermined volume relative to the volume.

  According to this, when the molten resin is injected into the molding die (10), the overflow part (12h) is in a state of insufficient filling (short shot), and the space part always remains in the overflow part (12h). Even when the resin filling into the cavities (11b, 12b) is completed, the internal pressure of the molding die (10) can be maintained at a very low state.

  Thereby, it can avoid that the durable life of a metal mold | die (10) is adversely affected by the mold internal pressure which is excessive.

  Further, since the overflow part (12h) communicates with the final resin filling part of the cavities (11b, 12b), the molten resin flows into the overflow part (12h before the resin filling into the cavities (11b, 12b) is completed. ) Will not overflow to the side. Therefore, even if the overflow part (12h) is added to the molding die (10), the molding of the resin molded product (14) is not hindered.

As in the invention according to claim 2, in the injection molding method according to claim 1, an injection amount necessary for the molten resin to overflow to a predetermined proportion of the volume of the overflow portion (12h) is set in advance. Every
When the injection amount in the injection process reaches the set injection amount, the injection process may be terminated.

  According to a third aspect of the present invention, in the injection molding method according to the first or second aspect, the overflow portion is formed by a small communication passage (12i) having a cross-sectional area smaller than a cross-sectional area of the overflow portion (12h). If (12h) is communicated with the resin final filling portion of the cavity (11b, 12b), the small communication path (12i) becomes a flow resistance of the flow of the molten resin, so that the resin into the cavity (11b, 12b) Filling can be performed more reliably.

  As in the invention according to claim 4, in the injection molding method according to any one of claims 1 to 3, an insert part (13) is set in the cavity (11b, 12b) in advance, Then, if the said injection process is performed, the resin molded product (14) shape | molded in a cavity (11b, 12b) and the insert component (13) can be integrally molded (insert molding).

  At the time of insert molding, by always leaving a space in the overflow portion (12h), the internal pressure of the molding die (10) can be maintained at a very low state, so the insert part (13) is damaged by excessive internal pressure of the die. Can be avoided.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a cross-sectional view of the molding die 10 of the present embodiment, FIG. 2 is a plan view of the movable die 11 of FIG. 1, and FIG. 3 is a plan view of the fixed die 12 of FIG. FIG. 4 is a perspective view showing a molded product immediately after molding.

  The molding die 10 according to this embodiment includes a movable die 11 and a fixed die 12. The movable mold 11 and the fixed mold 12 are provided with mold mounting plates 11a and 12a, respectively. The movable mold 11 is connected to a mold clamping device (not shown) of the injection molding apparatus via the mold mounting platen 11a, and can be moved in the horizontal direction in FIG. 1 by the driving force of the mold clamping apparatus.

  The fixed mold 12 is fixed and held on a fixed portion (not shown) of the injection molding apparatus via the mold mounting board 12a.

  In this embodiment, as shown in FIG. 4, the pipe-shaped insert part 13 is insert-molded so as to penetrate the central part of the rectangular parallelepiped resin block body 14. The insert part 13 is specifically a metal pipe formed of a metal such as aluminum, and the resin material of the resin block body 14 is 66 nylon of thermoplastic resin.

  Of the mating surfaces of the movable mold 11 and the fixed mold 12, a movable side cavity 11b and a fixed side cavity 12b forming a mold space for molding the resin block body 14 are formed at a substantially central portion in the vertical direction. A rectangular parallelepiped shape of the resin block body 14 is formed by combining both the cavities 11b and 12b.

  Further, as shown in FIGS. 2 and 3, a semi-cylindrical movable side accommodating portion 11c and a stationary side accommodating portion 12c for accommodating the insert part 13 are formed on both sides of both cavities 11b and 12b. A cylindrical shape corresponding to the pipe-shaped insert part 13 is formed by combining both the accommodating portions 11c and 12c.

  The diameter dimension d1 of the movable side accommodating part 11c and the fixed side accommodating part 12c is larger than the outer diameter d2 of the pipe-shaped insert part 13 by a predetermined amount. On the other hand, between the movable side accommodating part 11c and the movable side cavity 11b, and between the fixed side accommodating part 12c and the fixed side cavity 12b, the movable side die-cutting that is in close contact with the outer peripheral surface of the pipe-shaped insert part 13 respectively. A portion 11d and a fixed-side die cutting portion 12d are formed.

  In the fixed mold 12, a gate 12e for injecting molten resin into the cavities 11b and 12b is formed at one end (the lower end in FIG. 1) of the fixed cavity 12b.

  A passage of a sprue (pouring gate) 12f communicates with the gate 12e, and a spherical nozzle touch portion 12g is formed at an upstream end portion of the sprue 12f. The injection device 13 is connected to the nozzle touch portion 12g. By bringing the tip spherical surface of the nozzle portion 13a into contact, the molten resin passes from the nozzle portion 13a of the injection device 13 through the passage of the sprue 12f and is supplied to the gate 12e.

  On the other hand, the other end portion (upper end portion in FIG. 1) of the fixed-side cavity 12b is located on the opposite side to the formation portion of the gate 12e, and thus becomes a resin final filling portion for the cavity. The other end portion of the fixed side cavity 12b, that is, an overflow portion 12h communicating with the resin final filling portion is formed in the fixed mold 12. Here, the overflow portion 12h communicates with the other end portion (resin final filling portion) of the fixed-side cavity 12b through a small communication passage 12i having a cross-sectional area significantly smaller than the cross-sectional area.

  The overflow portion 12h has a rectangular parallelepiped shape in this example, but may have a shape other than the rectangular parallelepiped shape. The volume of the overflow portion 12h is designed to have a size that can absorb the variation in the injection amount of the molten resin into the molding die 10 as will be described later.

  Next, the injection molding method of this embodiment will be described. Since FIG. 1 shows the mold clamping state of the molding die 10, first, the movable mold 11 is moved from the mold clamping state of FIG. 1 to the left side in the figure, and the movable mold 11 is shifted to the mold open state.

  Next, the pipe-shaped insert component 13 is set inside the accommodating portion 11c, the die pressing portion 11d, and the cavity 11b of the movable die 11. At this time, the pipe-shaped insert part 13 can be kept in the set state by inserting the pipe-shaped insert part 13 into the inside of the die-cutting portions 11d and 12d.

  Next, the movable mold 11 is moved in the right direction in FIG. 1 from the mold open state to abut against the fixed mold 12, and a predetermined mold clamping force is applied to the movable mold 11. As a result, the movable mold 11 is brought into pressure contact with the fixed mold 12 to obtain the mold clamping state shown in FIG.

  When the mold clamping is completed, the injection device 13 then moves forward toward the fixed die 12, and the tip spherical surface portion of the nozzle portion 13a of the injection device 13 is brought into contact with the nozzle touch portion 12g of the sprue 12f of the fixed die 12. Thereby, the internal passage of the nozzle portion 13a communicates with the passage of the sprue 12f. With the completion of this nozzle touch, a screw (not shown) inside the injection device 13 moves forward to inject molten resin inside the injection device 13 from the nozzle portion 13a into the passage of the sprue 12f.

  Further, the molten resin is injected into the cavities 11b and 12b through the passage of the sprue 12f and the gate 12e.

  The molten resin is sequentially filled from one end side (lower end portion) to the other end side (upper end portion) of the cavities 11b and 12b, and is melted after filling of the resin into the inner space of the cavities 11b and 12b is completed. The resin overflows into the overflow part 12h.

  Here, the volume of the overflow portion 12h and the injection amount of the molten resin into the molding die 10 are set so as to satisfy the following matters. That is, even when the injection amount reaches the maximum amount within the variation range, a space portion of a predetermined ratio with respect to the entire volume of the overflow portion 12h always remains and the molten resin is not sufficiently filled (short shot). The volume of the overflow part 12h is set so as to be in a state.

  Even when the injection amount of the molten resin into the molding die 10 becomes the minimum amount within the variation range, a part of the molten resin injected into the cavities 11b and 12b is always in the overflow portion 12h. Set the injection quantity so that it overflows. Thus, even when the injection amount becomes the minimum amount in the variation range, the filling of the molten resin into the cavities 11b and 12b can be completed with certainty.

  Even after the injection process is completed by injecting the molten resin into the molding die 10 in a preset amount, the advancement state of the screw inside the injection device 13 is maintained for a predetermined time to maintain the resin injection pressure. . This process is generally called a pressure holding process.

  When the time of the pressure holding process reaches a predetermined time, the screw inside the injection device 13 is retracted to lower the resin injection pressure, and the pressure holding process is ended.

  Next, after cooling the molding die 10 for a predetermined time, the movable die 11 is moved from the mold-clamped state of FIG. 1 to the left side in the figure, and the molding die 10 is opened to form the molded product. Remove from the mold 10.

  FIG. 4 shows the molded product immediately after being taken out from the molding die 10 in this way. In the molded product of FIG. 4, the portions 12e 'and 12f' are resin molded bodies filled in the passages of the sprue 12f from the gate 12e. The portion 12h 'is a resin molded body filled in a predetermined proportion of the volume in the overflow portion 12h. The portion 12i 'is a resin molded body filled in the small communication passage 12i.

  Since these molded bodies 12e ', 12f', 12h ', 12i' are unnecessary parts as product shapes, they are cut out from the resin block body 14.

  By the way, according to the present embodiment, when the molten resin is injected into the molding die 10, the overflow portion 12 h communicating with the resin final filling portion of the cavities 11 b and 12 b is in an underfilled state (short shot), and the overflow portion Since the space portion always remains in 12h, even when the resin filling into the cavities 11b and 12b is completed, the internal pressure of the molding die 10 can be kept extremely low.

  Thereby, it can avoid that the insert component 13 is damaged by the excessive mold internal pressure. In addition, it is possible to avoid the adverse effect of the molding die 10 itself due to excessive mold internal pressure.

  Since the overflow portion 12h communicates with the resin final filling portion of the cavities 11b and 12b, the molten resin does not overflow to the overflow portion 12h before the resin filling into the cavities 11b and 12b is completed. .

  In addition, since the overflow portion 12h communicates with the resin final filling portion of the cavities 11b and 12b by the small communication passage 12i, the small communication passage 12i flows through the molten resin when the molten resin overflows to the overflow portion 12h side. Distribution resistance. Thereby, resin filling into the cavities 11b and 12b can be performed more reliably.

  Therefore, even if the overflow part 12h is added to the molding die 10, the molding of the resin block body 14 is not hindered.

(Other embodiments)
The present invention is not limited to the above-described embodiment and can be variously modified. For example, in the above-described embodiment, the overflow part 12h is formed on the fixed mold 12 side, but the overflow part 12h may be formed on the movable mold 11 side. Further, the overflow part 12 h may be formed over both the movable mold 11 and the fixed mold 12.

  In the above-described embodiment, the example in which the insert part 13 is set on the movable mold 11 side has been described. However, the insert part 13 may be set on the fixed mold 12 side.

  In the above-described embodiment, the insert part 13 is insert-molded integrally with the resin block body 14, but the insert part 13 is not insert-molded integrally with the resin block body 14, and is only used for injection molding of the resin member. The invention may be applied.

It is sectional drawing which shows the shaping die by one Embodiment of this invention. It is a top view of the movable type of FIG. It is a top view of the fixed type | mold of FIG. It is a perspective view which shows the molded article immediately after taking out from the inside of a shaping die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Molding die, 11 ... Movable type | mold, 12 ... Fixed type | mold, 11b, 12b ... Cavity,
12e ... Gate, 12h ... Overflow part, 13 ... Insert part.

Claims (4)

The mold (10) communicates with the cavity (11b, 12b), the gate (12e) for injecting molten resin into the cavity (11b, 12b), and the final resin filling portion of the cavity (11b, 12b). An overflow part (12h),
In the injection step of injecting molten resin from the gate (12e) into the cavity (11b, 12b), after the filling of the molten resin into the cavity (11b, 12b) is completed, the overflow portion (12h) An injection molding method characterized in that the injection step is terminated when the molten resin overflows by a predetermined volume relative to the volume. An injection amount necessary for the molten resin to overflow into a predetermined volume of the overflow portion (12h) is set in advance,
The injection molding method according to claim 1, wherein the injection process is terminated when an injection amount in the injection process reaches the set injection amount. The overflow part (12h) communicates with the resin final filling part of the cavity (11b, 12b) by a small communication path (12i) having a cross-sectional area smaller than the cross-sectional area of the overflow part (12h). The injection molding method according to claim 1 or 2. The injection molding according to any one of claims 1 to 3, wherein an insert part (13) is set in advance in the cavity (11b, 12b), and then the injection step is executed. Method.

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