JP5988788B2 - Injection mold - Google Patents

Description

  The present invention relates generally to an injection mold, and more particularly to an injection mold having a sprue bush.

  Conventionally, in injection molding of a thermoplastic resin, an injection mold having a sprue bush formed separately from a mold body may be used. In the injection molding of thermoplastic resin, a molten resin is introduced into a sprue bush from a nozzle heated to a high temperature, and the resin maintained in a molten state is injected from the sprue bush into a molding die (cavity). Since the cavity is kept at a relatively low temperature, the sprue bush attached to the cavity tends to be at a low temperature. Therefore, at the time of molding, the molten resin may be cured in the sprue bushing or in the nozzle heated by the sprue bushing.

  When the molten resin is cured in the sprue bush or the nozzle, the cured resin may remain in the nozzle when the molded body is removed from the mold. When the molten resin is injected from the nozzle next time, the resin remaining in the nozzle may enter the molded body together with the newly injected molten resin, and may deteriorate the appearance of the molded body.

  Therefore, in the mold for injection molding, it is possible to prevent the molten resin from hardening in the sprue bush or nozzle by configuring the sprue bush to have a precise structure or adjusting the temperature. Has been proposed. It has also been proposed to thermally isolate the sprue bush from the nozzle or mold body for introducing the resin into the sprue bush without complicating the configuration of the sprue bush itself.

  For example, Japanese Patent Laid-Open No. 11-99537 (Patent Document 1) describes a heat insulating nozzle of an injection molding machine in which a heat insulating material is provided between a sprue bush and a tip member of the nozzle.

  Japanese Patent Laid-Open No. 2000-317993 (Patent Document 2) discloses that a plurality of irregularities are provided on the outer periphery of the sprue bush between the outer side of the sprue bush and the die, and between the outer side of the sprue bush and the die. An injection mold that efficiently distributes the cooling medium to the gap by providing a gap in the gap and providing a heat insulating portion in the uneven portion or gap on the material inflow side to reduce the flow path of the cooling medium. Is described.

JP-A-11-99537 JP 2000-317993 A

  However, in the heat insulating nozzle described in Patent Document 1, in order to provide a heat insulating material to thermally isolate the sprue bush and the nozzle body, not only the heat insulating material but also the heat insulating material is interposed between the sprue bush and the nozzle main body. In order to fix it, the structure of the nozzle presser is devised, or a member such as a bolt is required.

  On the other hand, in the injection mold described in Patent Document 2, since the gap is for efficiently circulating the refrigerant, the gap is formed over the entire range from the nozzle side to the gate side of the sprue bushing. Has been. However, if the entire outer peripheral surface of the sprue bushing is thermally insulated, the resin is maintained in a molten state even on the gate side of the sprue bushing, and a good gate cut cannot be made at the end of molding.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an injection mold having a sprue bushing with a simple configuration, capable of suppressing a temperature drop at a nozzle tip portion and suppressing a temperature rise at a gate cut portion. That is.

  An injection mold according to the present invention includes a mold body and a sprue bush. The sprue bush has a nozzle side opening and a gate side opening, and is disposed inside the mold body. The mold body includes a holding mold part for holding the sprue bush on the nozzle side opening side of the sprue bushing, and a cavity mold part disposed on the gate side opening side of the holding mold part. A gap is provided between the holding mold part and the outer peripheral surface of the sprue bush, while the cavity mold part and the outer peripheral surface of the sprue bush are in contact with each other.

  In the injection mold according to the present invention, the gap is preferably provided in a region that occupies less than 50% of the total surface area of the outer peripheral surface of the sprue bushing.

  In the injection mold according to the present invention, the gap is preferably provided in a region occupying 10% or more of the total surface area of the outer peripheral surface of the sprue bushing.

  In the injection mold according to the present invention, the gap is preferably provided in a region that occupies 20% or more of the total surface area of the outer peripheral surface of the sprue bushing.

  As described above, according to the present invention, an injection mold having a sprue bushing that can suppress a temperature drop at the nozzle tip portion and can suppress a temperature rise at the gate cut portion with a simple configuration. Can be provided.

1 is a cross-sectional view schematically showing an entire injection molding system using an injection mold according to an embodiment of the present invention. It is sectional drawing which shows roughly the whole sprue bush used for the injection die of Example 1 of this invention. It is sectional drawing which shows roughly the whole sprue bush used for the injection die of Example 2 of this invention. It is sectional drawing which shows roughly the whole sprue bush used for the injection die of a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an injection molding system using an injection mold 1 according to an embodiment of the present invention mainly includes an injection mold 1 and a molten state in the injection mold 1. And a nozzle 2 for introducing the resin.

  The injection mold 1 includes a mold body 10, a sprue bush 20, a refrigerant pipe (not shown), and the like. The mold body 10 includes a mounting plate 111, a holder 112, and a cavity mold 12 that are separately formed. The mounting plate 111 and the holder 112 are an example of the holding mold part 11.

  The sprue bush 20 is formed separately from the mold body 10. A sprue 21 is formed inside the sprue bush 20, and the sprue 21 communicates with the outside through a nozzle side opening 22 and a gate side opening 23. On the outer peripheral surface of the sprue bushing 20, a convex portion 41, a convex portion 42, and a groove are formed. The convex portions 41 and 42 are for preventing positioning and rattling of the sprue bushing 20. In this embodiment, a first groove 31, a second groove 32, and a third groove 33 are formed as the grooves. These grooves are formed, for example, by cutting the outer peripheral surface of the sprue bush 20 around the entire axis. The first groove 31 is formed on the outer peripheral surface of the sprue bush 20 at a portion disposed in the mounting plate 111, and is formed on the side closest to the nozzle side opening 22 among the three grooves. The second groove 32 and the third groove 33 are formed in a portion provided in the holder 112 on the outer peripheral surface of the sprue bush 20. A groove is not formed in a portion of the outer peripheral surface of the sprue bushing 20 disposed inside the cavity mold part 12.

  In the position where the first groove 31, the second groove 32, and the third groove 33 are formed, a gap is formed between the outer peripheral surface of the sprue bush 20 and the mounting plate 111 or the holder 112. . That is, in the first groove 31, the second groove 32, and the third groove 33, the outer peripheral surface of the sprue bush 20 and the mold main body 10 are not in contact with each other. The outer peripheral surface of the sprue bush 20 is in contact with the outer peripheral surface of the sprue bush 20 and the mold body 10 at the portion disposed inside the cavity mold portion 12.

  The nozzle 2 is positioned via the locate ring 4 so that the center of the nozzle 2 is aligned with the axis of the sprue bushing 20. A heater 3 is attached to the nozzle 2. No heater is disposed at the nozzle tip 2 a that contacts the sprue bushing 20.

  In the injection molding system configured as described above, the molten resin passes through the nozzle 2 and is introduced into the sprue bush 20 from the nozzle tip 2a, and the cavity mold portion 12 is inserted into the sprue bush 20 from the gate side opening 23. It is injected into the cavity and molded. At the time of molding, the molten resin remains in the nozzle tip 2a and in the sprue 21 of the sprue bushing 20.

  When molding is completed, the mold is opened, and a take-out machine takes out the molded body and moves it. This take-out machine is provided with a cutter, and separates the molded body after movement from the sprue 21.

  At the time of molding, the heat of the molten resin in the sprue 21 is conducted to the mounting plate 111, the holder 112, and the cavity mold part 12 through the sprue bush 20. In the mounting plate 111, the first groove 31 is formed in the sprue bushing 20, and there is a gap between the sprue bushing 20 and the mounting plate 111. In the holder 112, the second groove 32 and the third groove 33 are formed in the sprue bush 20, and there is a gap between the sprue bush 20 and the holder 112. In the gap portion, heat is not easily conducted from the sprue bushing 20 to the low temperature mounting plate 111 or the holder 112, and there is a heat insulating effect. By doing in this way, compared with the case where the space | gap part is not provided between the sprue bush 20 and the metal mold | die main-body part 10, in the sprue bush 20, the attachment plate 111 or holder It is possible to suppress a temperature drop in a portion disposed in 112. Moreover, since the temperature drop of the sprue bushing 20 on the side close to the nozzle 2 can be suppressed, the temperature drop of the nozzle tip 2a that contacts the sprue bushing 20 can also be suppressed.

  By suppressing the temperature drop between the molten resin in the sprue 21, the portion of the sprue bush 20 disposed in the mounting plate 111 or the holder 112, and the nozzle tip 2 a where the heater 3 is not disposed, When pulled out from the injection mold 1, the molten resin in the sprue bush 20 and the nozzle 2 is also pulled by the molded body and pulled out from the gate-side opening 23 of the sprue bush 20. Thus, at the start of the next molding (at the time of the next shot), the resin remaining in the nozzle 2 at the time of the previous molding is injected into the cavity together with the resin newly supplied into the sprue bush 20 and cold slag. Can be prevented from occurring.

  On the other hand, no groove is formed in the portion of the sprue bushing 20 disposed in the cavity mold part 12, and the outer peripheral surface of the sprue bushing 20 is in contact with the cavity mold part 12. Therefore, heat is likely to be conducted from the sprue bush 20 to the low-temperature cavity mold part 12 on the side near the gate-side opening 23 in the sprue bush 20.

  By doing in this way, the temperature rise of the gate side opening 23 (gate cut part) can be suppressed, the resin of the gate side opening 23 can be hardened at the time of gate cut, and it becomes easy to perform gate cut.

  In this embodiment, the gap is formed by cutting the outer peripheral surface of the sprue bush to form a groove, but the gap is formed by cutting the inner surface of the mold main body. Alternatively, a spacer may be provided between the mold body and the sprue bush.

  As described above, the convex portions 41 and 42 are for preventing positioning and rattling of the sprue bushing 20. In order to prevent the sprue bush 20 from rattling, for example, it is not preferable to cut the entire convex portion 41 to provide the groove 32.

  As described above, the injection mold 1 includes the mold body 10 and the sprue bush 20. The sprue bush 20 has a nozzle side opening 22 and a gate side opening 23, and is disposed inside the mold body 10. The mold body 10 includes a holding mold part 11 for holding the sprue bushing 20 on the nozzle side opening 22 side of the sprue bushing 20 and a cavity mold disposed on the gate side opening 23 side of the holding mold part 11. And a mold part 12. A gap is provided between the holding mold part 11 and the outer peripheral surface of the sprue bushing 20, while the cavity mold part 12 and the outer peripheral surface of the sprue bushing 20 are in contact with each other.

  The nozzle tip 2a and the nozzle-side opening 22 in the sprue bushing 20 can be formed simply by forming a gap on the side close to the nozzle-side opening 22 of the sprue bush 20 without arranging a separate heat insulating material. The temperature drop with the near side can be suppressed. As a result, it is possible to prevent the resin on the side close to the nozzle side opening 22 in the nozzle 2 and the sprue 21 from being cured.

  The void portion has a simple structure that can be formed by cutting the outer peripheral surface of the sprue bushing 20, for example. Compared with the case where a heat insulating material is added, it is not necessary to make a large modification to the sprue bush 20 or the mold main body 10. Further, it is not necessary to use a device such as a temperature controller in order to warm the sprue bushing 20.

  As described above, according to the present invention, the injection molding gold provided with the sprue bush 20 that can suppress the temperature drop of the nozzle tip 2a and suppress the temperature rise of the gate cut portion with a simple configuration. A mold 1 can be provided.

  By using the injection mold of the present invention for injection molding, it was confirmed by the following experiment that it is possible to suppress the temperature drop at the nozzle tip and the temperature rise at the gate cut part.

  As the injection mold 1, the first groove 31, the second groove 32, and the third groove 33 are formed in the sprue bush 20 like the injection mold 1 shown in FIG. 1. Used (Example 1) and the one having only the first groove 31 (Example 2) were used. Moreover, the thing in which the space | gap part was not formed was used as a comparative example. In any of Example 1, Example 2, and Comparative Example, PSL steel (SUS630 improved product) having a thermal conductivity of 15.8 W / m · K (at 20 ° C.) was used as the material of the sprue bushing 20. . The mounting plate 111 and the holder 112 were made of S50 material (SC material), and the cavity mold part 12 and the core mold part (not shown) were made of SC material or SUS material. As the mounting plate 111, the holder 112, and the cavity mold part 12, those shown in FIG. 1 were used.

Example 1
As shown in FIGS. 1 and 2, three grooves of a first groove 31, a second groove 32, and a third groove 33 were formed on the outer peripheral surface of the sprue bush 20 by cutting. The diameter D ₁ of the end portion of the sprue bush 20 on the gate side is 35 mm, the diameter D ₂ of the positioning convex portion 42 on which the third groove 33 is formed is 40 mm, and the first groove 31 and the third groove 33. diameter _{D 3} at the position 37 mm, the diameter _{D 4} of the end of the nozzle 2 side of the sprue bush 20 is 40 mm, the diameter _{D 5} at the position of the second groove 32 47 mm, the second groove 32 is formed diameter _{D 6} of the convex portions 41 for positioning was 50 mm.

The distance L ₁ from the end of the sprue bush 20 on the nozzle 2 side to the first groove 31 is 8 mm, the width L ₂ along the axial direction of the sprue bush 20 of the first groove 31 is 34.3 mm, The distance L ₃ from the first groove 31 to the second groove 32 is 8 mm, the width L ₄ along the axial direction of the sprue bush 20 of the second groove 32 is 6.5 mm, and the distance L ₃ on the gate side of the second groove 32 is from the end, the distance L ₅ to the end of the gate-side of the convex portion 41 in which the second grooves 32 are formed 5.5 mm, on the gate side of the convex portion 41 in which the second grooves 32 are formed The distance L ₆ from the end to the third groove 33 is 10 mm, the width L ₇ of the third groove 33 is 10 mm, and the third groove 33 is formed from the end of the third groove 33 on the gate side. convex distance L ₈ to the end of the gate-side of the convex portion 42 of 20 mm, the third groove 33 is formed to have Distance _{L 9} between the end portion of the gate side to the end portion of the gate of the sprue bush 20 of the 42 was 75.5mm. The total length of the sprue bushing 20 in the axial direction was 177.8 mm.

  The surface area of the outer peripheral surface of the sprue bushing 20 in the first groove 31, the second groove 32, and the third groove 33 was about 30% of the total surface area of the outer peripheral surface of the sprue bushing 20. That is, the gap was provided in a region occupying about 30% of the total surface area of the outer peripheral surface of the sprue bushing 20.

  Resin molding was performed using the injection mold 1 provided with the sprue bush 20 configured as described above. The temperature of the molten resin at the nozzle tip 2a was about 200 ° C. The temperature of the sprue bush 20 in the nozzle side opening 22 was 56.5 ° C., and the temperature of the sprue bush 20 in the gate side opening 23 was 34.0 ° C.

  When 41 molded bodies were manufactured by injection molding, it was confirmed that no cold slag was generated in all the molded bodies. Moreover, in all the molded products, the gate cut was good.

(Example 2)
Only the sprue bush 20 of the injection mold 1 was changed to a sprue bush 20a having the form shown in FIG. As shown in FIG. 3, only the first groove 31 was formed by cutting the outer peripheral surface of the sprue bushing. The distance L _{1 ′} from the end of the sprue bush 20 on the nozzle 2 side to the first groove 31 is 13 mm, and the width L _{2 ′} along the axial direction of the sprue bush 20 of the first groove 31 is 29.3 mm. It was. Further, the width L ₁₀ of the positioning convex portion 41 adjacent to the gate side end of the first groove 31 is 20 mm, and the width L ₁₁ of the convex portion 42 adjacent to the gate side of the convex portion 41 is 40 mm. Met. Other diameters, distances, and widths indicated by the same symbols as in FIGS. 1 and 2 (Example 1) were the same as in Example 1.

  The surface area of the outer peripheral surface of the sprue bushing 20a in the first groove 31 was about 17% of the total surface area of the outer peripheral surface of the sprue bushing 20a. In other words, the gap was provided in a region occupying about 17% of the total surface area of the outer peripheral surface of the sprue bushing 20a.

  Resin molding was performed using the injection mold 1 provided with the sprue bush 20a configured as described above. The temperature of the molten resin at the nozzle tip 2a was about 200 ° C. The temperature of the sprue bush 20a in the nozzle side opening 22 was 37.5 ° C., and the temperature of the sprue bush 20a in the gate side opening 23 was 28.1 ° C.

  When 41 molded bodies were manufactured by injection molding, all the molded bodies had good gate cuts. Moreover, although cold slag was observed in some molded products, there was more of the molded product in which the occurrence of cold slag was not observed.

(Comparative example)
Only the sprue bush 20 of the injection mold 1 was changed to a sprue bush 20b having the form shown in FIG. As shown in FIG. 4, the outer peripheral surface of the sprue bushing was not cut and no groove was formed. That is, the outer peripheral surface of the sprue bush 20b is in contact with the mold body 10 in the entire region.

From the end of the nozzle 2 side of the sprue bush 20b, the distance _{L 12} to the convex portion 41 for positioning the nozzle 2 side was 42.3 mm. Other diameters, distances, and widths indicated by the same symbols as in FIGS. 1 and 2 (Example 1) or FIG. 3 (Example 2) were the same as those in Example 1 or Example 2.

  Resin molding was performed using the injection mold 1 provided with the spray bush 20b configured as described above. The temperature of the molten resin at the nozzle tip 2a was about 200 ° C. The temperature of the sprue bush 20b in the nozzle side opening 22 was 32.4 ° C., and the temperature of the sprue bush 20b in the gate side opening 23 was 24.7 ° C.

  When 41 molded bodies were manufactured by injection molding, in almost all molded bodies, the resin escaped from the sprue 21 was poor at the time of gate cutting, and the resin remained in the sprue 21 and the nozzle 2 and almost all Cold slag was observed in the molded body.

  From the above results, as in Example 1 and Example 2, by forming a gap in the portion disposed in the holding mold part 11 on the outer peripheral surface of the sprue bushings 20 and 20a, the nozzle side It was found that the temperature drop at the opening 22 can be prevented. At the same time, the temperature rise in the gate side opening 23 could be suppressed. In Example 1 and Example 2, compared with the comparative example, although the temperature in the gate side opening 23 was high, favorable gate cut was possible. Further, it can be seen that the temperature difference in the gate side opening 23 between Examples 1 and 2 and the comparative example is smaller than the temperature difference on the nozzle 2 side, and the temperature rise is suppressed.

  As described above, in the injection mold according to the present invention, the gap is preferably provided in a region that occupies less than 50% of the total surface area of the outer peripheral surface of the sprue bushing.

  By doing so, it is possible to prevent the temperature drop in the entire sprue bushing and prevent the resin in the vicinity of the gate side opening from being hardened when the gate is cut.

  In the injection mold according to the present invention, it is preferable that the gap is provided in a region occupying 10% or more of the total surface area of the outer peripheral surface of the sprue bushing.

  By doing in this way, in Example 2, the cutting process of the sprue bushing was minimized and a certain effect could be obtained.

  In the injection mold according to the present invention, it is preferable that the gap is provided in a region that occupies 20% or more of the total surface area of the outer peripheral surface of the sprue bushing.

  By doing in this way, in Example 1, the cold slag could be almost completely eliminated and the gate cut was also good.

  The embodiment disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and includes all modifications within the scope and meaning equivalent to the terms of the claims.

  1: injection mold, 10: mold body, 11: holding mold, 12: cavity mold, 20, 20a: sprue bush, 22: nozzle side opening, 23: gate side opening, 31: First groove, 32: second groove, 33: third groove.

Claims (4)

Mold body,
An injection mold comprising a sprue bush disposed inside the mold body and having a nozzle side opening and a gate side opening,
The mold body includes a holding mold part for holding the sprue bush on the nozzle side opening side of the sprue bush, and a cavity mold part disposed on the gate side opening side with respect to the holding mold part. Including
A gap is provided between the holding mold part and the outer peripheral surface of the sprue bushing,
For the outer peripheral surface of the sprue bush, the entire surface from the boundary surface between the cavity mold part and the holding mold part to the gate side opening end of the sprue bush is in contact with the cavity mold part . Mold.   The injection mold according to claim 1, wherein the gap is provided in a region that occupies less than 50% of the total surface area of the outer peripheral surface of the sprue bushing.   The injection mold according to claim 2, wherein the gap portion is provided in a region that occupies 10% or more of the total surface area of the outer peripheral surface of the sprue bushing.   The injection mold according to claim 2, wherein the gap is provided in a region that occupies 20% or more of the total surface area of the outer peripheral surface of the sprue bushing.

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