JP2011136515A - Injection molding method and injection molding metallic die - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding metallic die by which a synthetic resin in a cavity can be compressed in a mold and a synthetic resin molding with good appearance quality can be produced without producing a burr, while suppressing the production cost of the metallic die as no metallic die with high production difficulty is not required and also improving durability of the metallic die. <P>SOLUTION: A heating medium is supplied into a heating medium passage 31 of an insert piece 6A of a fixed metallic die part 6 and a heating medium passage 34 of an insert piece 26A of a mobile metallic die part 26 to cause heating. When temperature rises to or above a softening point of the synthetic resin, molten synthetic resin is charged by pouring into a cavity S and pressure is held. Before or after pressure holding ends, the heating medium is supplied into a heating medium passage 32 of an insert piece attaching body 6B of the fixed metallic die part 6 and a heating medium passage 35 of an insert piece attaching body 26B of the mobile metallic die part 26 to cause heating and thermal expansion. After thermal expansion begins, a cooling medium is supplied into the heating medium passage 31 of the insert piece 6A and the heating medium passage 34 of the insert piece 26A to cause cooling. The synthetic resin is hardened while being compressed with pressure equal to or above injection pressure of the synthetic resin. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an injection molding method and an injection mold in which a synthetic resin melted in a cavity is injected and filled in a state where a fixed mold and a movable mold are closed, and the synthetic resin is compressed in the mold. Regarding type.

  As disclosed in, for example, Patent Document 1, the synthetic resin injection molding method heats the surface-side cavity forming surface that molds the surface side of the molded product before injecting the molten synthetic resin, so Techniques for improvement have been proposed.

JP-A-6-254924

  However, in the injection molding method with a press function in which the synthetic resin is compressed in the injection mold, the synthetic resin filled with the mating surfaces forming the cavities of the fixed mold and the movable mold is pressed. Since the molten plastic is poured, the mating surfaces of both molds are closed, the mold is closed, and the synthetic resin is pressed, resulting in burrs in the synthetic resin molded product. There was a problem that the amount of compression (press amount) could not be increased in order to be easy to suppress burrs.

  For this reason, thin-walled products can be used, but for thick-walled products with a large amount of compression, the mating surfaces of both molds need to be opened wide. Burrs will occur.

  Of course, in order to solve this problem, it is necessary to have a mold structure that does not generate burrs. In this case, the difficulty of mold fabrication increases, resulting in higher costs and lower mold durability. There was something to do. In addition, since the press is performed at a temperature lower than the softening point of the synthetic resin, there is a difference in the resin temperature between the synthetic resin injection part and the part far from the injection part, and there is a difference in the compression density of the synthetic resin when pressed. This causes a problem that a difference in appearance quality of the synthetic resin molded product occurs.

  Therefore, in view of the above points, the present invention makes it possible to produce a synthetic resin molded product with good appearance quality by allowing the synthetic resin in the cavity to be compressed in the mold and preventing burrs from being produced. The purpose is to reduce the cost, and to improve the durability of the mold, even if the degree of difficulty is not high.

For this reason, the first invention is an injection molding method in which the fixed mold and the movable mold are closed, and the molten synthetic resin is injected and filled in the cavity.
A nesting piece of at least one of the fixed mold and the movable mold having a nesting piece forming the cavity and a nesting attachment body made of a metal having a high thermal expansion coefficient provided outside the nesting piece. Heat the
After heating the nesting piece of at least one of the fixed mold or the movable mold to raise the temperature above the softening point of the synthetic resin, the molten synthetic resin is injected and filled into the cavity to hold the pressure,
Before and after the end of the pressure holding, the nesting attachment body of the at least one mold is heated and thermally expanded and the nesting piece of the at least one mold is cooled to exceed the injection pressure of the synthetic resin. The synthetic resin is hardened while being compressed at a pressure of 5.

The second invention is an injection molding apparatus for injecting and molding molten synthetic resin into a cavity with the fixed mold and the movable mold closed.
A nesting piece for forming at least one of the fixed die and the movable die and the nesting piece for forming the cavity, and a nesting attachment body made of a metal having a high thermal expansion coefficient provided on the outside of the nesting piece via a heat insulating material. And consisting of
A heating means and a cooling means are provided in the nesting piece and the nesting attachment body of the at least one mold,
When the nesting piece of at least one of the fixed mold and the movable mold is heated by the heating means to raise the temperature above the softening point of the synthetic resin, the molten synthetic resin is injected and filled into the cavity. Before and after the pressure holding, the nesting attachment body of the at least one mold is heated by the heating means to be thermally expanded, and the nesting piece of the at least one mold is cooled by the cooling means. The synthetic resin is cured while being compressed at a pressure equal to or higher than the injection pressure of the synthetic resin.

  According to the present invention, the synthetic resin in the cavity can be compressed in the mold, and no burr is produced, so that a synthetic resin molded product having a good appearance quality can be manufactured, and the difficulty in manufacturing the mold is not high. At the same time, the cost can be reduced and the durability of the mold can be improved.

It is a vertical front view of an injection mold. It is principal part sectional drawing for demonstrating the 1st step of the injection molding method. It is a principal part sectional view for explaining the 2nd stage similarly. It is a principal part sectional view for explaining the 3rd step similarly. It is a principal part sectional view for explaining the 4th stage similarly.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. First, based on FIG. 1, the whole structure of the injection mold of the 1st Embodiment of this invention is demonstrated. Reference numeral 1 denotes a fixed-side assembly attached to a fixed platen (not shown) with bolts. The fixed-side assembly 1 includes a fixed-side first base plate 2 and a fixed-side first base plate 2 fixed to the fixed-side first base plate 2 with bolts. 2 base plate 3, fixed side third base plate 4 fixed to the fixed side second base plate 3 by bolts, and bolts attached to the fixed side third base plate 4 by being disposed in the recesses of the fixed side third base plate 4. A fixed mold part 6 fixed by the above, a locate ring 7 provided near the fixed platen of the fixed first base plate 2 and positioning the fixed first base plate 2 with respect to the fixed platen; It consists of a sprue bush 8 or the like disposed adjacently.

  A first sprue 9 is formed at the center of the sprue bushing 8 for passing molten synthetic resin injected from an injection nozzle (not shown), and a first runner 10 is formed at the lower end thereof. A second sprue 11 as an outlet of the second runner 12 is formed, and a second runner 12 is formed at a lower end portion of the second sprue 11, and a gate (side gate) 13 as an outlet of the second runner 12 is formed. The gate 13 communicates from the side with an opening formed at the end of the cavity S at the end of the cavity S of the fixed mold portion 6.

  On the other hand, 20 is a movable side assembly attached to a movable platen (not shown) with a bolt. The movable side assembly 20 is a movable side first base plate 21 and a movable side fixed to the movable side first base plate 21 with bolts. A side second base plate 22 (ejector plate), a movable side third base plate 23 fixed to the movable side first base plate 21 by bolts so as to surround the movable side second base plate 22, and the movable side third base plate 23 The movable-side fourth base plate 24 is fixed to the movable-side fourth base plate 24 by a bolt, and the movable mold part 26 is fitted into the concave portion of the movable-side fourth base plate 24 and fixed to the fourth plate 24.

  Then, a guide bar (not shown) erected on the movable side third base plate 23 is inserted into a guide hole provided in the fixed side third base plate 4, and the guide bar is guided into the guide hole. Thus, the movable side assembly 20 can be moved up and down.

  A cavity S is formed by the upper surface of the movable mold part 26 and the lower surface of the fixed mold part 6, and a synthetic resin melted is injected into the cavity S to produce a synthetic resin molded product.

  The fixed mold part 6 includes a nesting piece 6A and a nesting piece mounting body 6B disposed on the outer side (upper side) of the nesting piece 6A via a heat insulating material 27. The movable mold part 26 includes a nesting piece 26A and a nesting piece 26A. The insert piece attachment body 26 </ b> B is disposed on the outer side (lower side) via the heat insulating material 28. The nesting pieces 6A and 26A are made of a special steel suitable for a synthetic resin molding die (for example, CENA1 of Hitachi Metals, Ltd.). Further, the insert piece mounting bodies 6B and 26B are made of, for example, an aluminum alloy having a high thermal expansion coefficient, and are covered with heat insulating materials 27 and 28, respectively. That is, the nesting piece mounting body 6B is thermally insulated from the fixed side third base plate 4 and the nesting piece 6A by the heat insulating material 27. Further, the insert piece mounting body 26B is thermally insulated from the movable side fourth base plate 24 by the heat insulating material 28 and from the insert piece 26A.

  The fixed third base plate 4 and the movable fourth base plate 24 are provided with temperature adjusting means, and are always maintained at a predetermined temperature. That is, 29 is a heat medium passage formed in the fixed third base plate 4 near the fixed mold portion 6, and 30 is a heat medium passage formed in the movable fourth base plate 24 near the movable mold portion 26. A suitable heat medium is supplied to these heat medium passages 29 and 30 according to the temperature suitable for the synthetic resin injected into the cavity S, and the fixed side third base plate 4, the fixed mold part 6, the movable The side fourth base plate 24 and the movable mold part 26 are always maintained at a predetermined temperature.

  The nesting piece 6A close to the cavity S of the fixed mold part 6 is provided with heating means and cooling means. That is, 31 is a heat medium passage formed along the cavity S in the insert piece 6A close to the cavity S of the fixed mold portion 6, and the heat medium inlet 31A from each supply source is provided in the heat medium passage 31. The heating medium inlet flows through steam, various oils or heated water, or cooling water or cold air that is a cooling medium, to heat or cool the cavity forming surface side of the fixed mold part 6, The heating medium or cooling medium flowing from 31A into the heat medium passage 31 flows out from the heat medium outlet 31B.

  Reference numeral 32 denotes a heat medium passage composed of a passage extending in the horizontal direction formed in the entire insert piece mounting body 6B of the fixed mold portion 6 and a passage extending in the vertical direction communicating with the passage. Steam or various oils or heating water that is a heating medium flowing into the medium passage 32 from the heat medium inlet 32A, or cold air or cooling water that is a cooling medium is flowed to heat or cool the entire nesting piece attachment body 6B. The heating medium or the cooling medium flowing into the heat medium passage 32 from the heat medium inlet 32A flows out from the heat medium outlet 32B. A partition plate 33 forming a flow path is provided in the heat medium passage 32 extending in the vertical direction.

  Reference numeral 34 denotes a heat medium passage formed along the cavity S in the insert piece 26A close to the cavity S of the movable mold portion 6. The heating medium passage 34 flows into the heat medium passage 34 from the heat medium inlet 34A. Steam, various oils or heated water as a medium, or cooling water or cold air as a cooling medium is flowed to heat or cool the cavity forming surface side of the movable mold part 6, and from the heat medium inlet 34 </ b> A to the heat medium passage 34. The heating medium or the cooling medium that has flowed into the air flows out from the heat medium outlet 34B.

  Reference numeral 35 denotes a heat medium passage composed of a horizontally extending passage formed in the entire insert piece mounting body 26B of the movable mold portion 26 and a vertically extending passage communicating with the passage. Steam or various oils or heating water that is a heating medium flowing into the medium passage 35 from the heat medium inlet 35A, or cold air or cooling water that is a cooling medium is flowed to heat or cool the entire nesting piece mounting body 26B. The heating medium or cooling medium flowing into the heat medium passage 35 from the heat medium inlet 35A flows out from the heat medium outlet 35B. A partition plate 36 that forms a flow path is provided in the heat medium passage 35 extending in the vertical direction.

  The heating means and the cooling means provided in the nesting piece 6A, the nesting piece mounting body 6B, the nesting piece 26A and the nesting piece mounting body 26B are not limited to the heat medium passage, the heating medium, and the cooling medium, but other means. Alternatively, the heating means may be an electric heater, for example.

  Next, the molding operation will be described with particular reference to FIGS. First, the heat medium is supplied to the heat medium passages 29 and 30 described above, and the fixed mold part 6 and the movable mold part 26 are always maintained at a predetermined temperature. In a state where the fixed mold part 6 and the movable mold part 26 are closed, as shown in FIG. 2, the lower surface of the nesting piece 6A of the fixed mold part 6 and the upper surface of the nesting piece 26A of the movable mold part 26 A cavity S filled with synthetic resin is formed between the two.

  In this state, in order to improve transferability, a heating medium is passed through the heat medium passages 31 and 34 of the nesting pieces 6A and 26A to heat the nesting pieces 6A and 26A, and the synthetic resin injected into the cavity S The temperature is raised to a temperature above the softening point.

  Thereafter, the injection nozzle is passed through the sprue bush 8, and the molten synthetic resin is passed through the first sprue 9, the first runner 10, the second sprue 11, the second runner 12 and the gate 13, and the movable mold part 26 and the fixed mold. Injection and injection is performed in the cavity S between the mold part 6 and the injection pressure is maintained and maintained in order to increase the compression density of the synthetic resin filled in the cavity S.

  Further, as shown in FIG. 3, before and after the end of the pressure holding of the synthetic resin (may be at the same time as the end of the pressure holding, or slightly before or after the end of the pressure holding), The heating medium is caused to flow through the heat medium passages 32 and 35 of 26B, and the insert frame attachment bodies 6B and 26B are rapidly heated to raise the temperature and thermally expand. Further, when the thermal expansion of the nesting piece attachment bodies 6B and 26B starts, the heating medium in the heat medium passages 31 and 34 of the nesting pieces 6A and 26A is discharged, and then the cooling medium is flowed to remove the nesting pieces 6A and 26A. Cooling. In this case, when the insert piece mounting bodies 6B and 26B are thermally expanded to increase the compression density of the synthetic resin to a certain density, cooling of the insert pieces 6A and 26A is started.

  As a result, as shown in FIG. 4, in the fixed mold portion 6, the insert piece mounting body 6 </ b> B is thermally expanded to push down the insert piece 6 </ b> A, and in the movable mold portion 26, the insert piece mounting body 26 </ b> B is thermally expanded to insert the insert piece. 26A is pushed up, the cavity S is narrowed, and the insert pieces 6A and 26A forming the cavity S are cooled, so that the synthetic resin filled in the cavity S is cured while being compressed (pressed) at a pressure higher than the injection pressure, It becomes a synthetic resin molded product J.

  When the synthetic resin in the cavity S is compressed and cured in this way and the synthetic resin molded product J is formed, the heating medium in the heat medium passages 32 and 35 of the insert piece mounting bodies 6B and 26B is discharged, and instead When the cooling medium is caused to flow in the heat medium passages 32 and 35, the insert piece attachment bodies 6B and 26B are thermally contracted to release the holding pressure. Therefore, as shown in FIG. 5, in the cavity S, slight gaps G1 and G2 are formed above and below the synthetic resin molded product J. Thereafter, the fixed mold part 6 and the movable mold part 26 are opened, and the synthetic resin molded product J is taken out.

  According to the above-described embodiment, the synthetic resin in the cavity S can be reasonably compressed and cured without difficulty by using the thermal expansion of the insert piece mounting bodies 6B and 26B in a state where the mold is closed. In this case, gaps G1 and G2 are formed between the surface of the synthetic resin molded product J and the insert pieces 6A and 26A, so that the mold can be opened smoothly.

  Therefore, in order to produce a molded product by press-compressing and curing a synthetic resin in an injection mold, a mold structure that does not generate burrs is conventionally required. The difficulty of manufacturing increases, the cost increases, and the durability of the mold may be reduced. Also, since the press is performed at a temperature below the softening point of the synthetic resin, the synthetic resin injection part and the part far from the injection part With this, there is a difference in the resin temperature, and there is a difference in the compression density of the synthetic resin when pressed, resulting in a difference in the appearance quality of the synthetic resin molded product, but this problem has been resolved can do.

  That is, it is possible to prevent the occurrence of burrs in the synthetic resin molded product and to prevent the appearance from being impaired as a whole, and it is possible to configure the mold at a low cost and increase the durability of the mold.

  Note that, as described above, in this embodiment, in order to compress the synthetic resin filled in the cavity S in the mold and to make the spaces G1 and G2, the insert piece attachment body of both mold parts 6 and 26 is used. 6B and 26B are heated and the insert pieces 6A and 26A are cooled, and the insert piece mounting bodies 6B and 26B are thermally expanded to be cured while compressing the synthetic resin at a pressure higher than the injection pressure of the synthetic resin. . However, the present invention is not limited to this, and at least one of the nesting piece attachment body 6B of the fixed mold portion 6 and the nesting piece attachment body 26B of the movable die portion 26 is heated, and at least one of the nesting pieces 6A and 26A. Only one side may be cooled.

  As described above, the embodiments of the present invention have been described. However, various alternatives, modifications, and variations can be made by those skilled in the art based on the above description. Including alternatives, modifications or variations.

6 Fixed mold part 6A Nesting piece 6B Nesting piece mounting body 26 Movable mold part 26A Nesting piece 26B Nesting piece mounting body 31 Heat medium passage 32 Heat medium passage 34 Heat medium passage 35 Heat medium passages G1, G2 Gap J Injection molded product S cavity

Claims (2)

In an injection molding method in which a fixed mold and a movable mold are closed, and a synthetic resin melted in a cavity is injected and filled,
A nesting piece of at least one of the fixed mold and the movable mold having a nesting piece forming the cavity and a nesting attachment body made of a metal having a high thermal expansion coefficient provided outside the nesting piece. Heat the
After heating the nesting piece of at least one of the fixed mold or the movable mold to raise the temperature above the softening point of the synthetic resin, the molten synthetic resin is injected and filled into the cavity to hold the pressure,
Before and after the end of the pressure holding, the nesting attachment body of the at least one mold is heated and thermally expanded and the nesting piece of the at least one mold is cooled to exceed the injection pressure of the synthetic resin. An injection molding method characterized in that the synthetic resin is cured while being compressed under the pressure of In an injection molding apparatus that molds by injection-filling molten synthetic resin in a cavity with the fixed mold and the movable mold closed.
A nesting piece for forming at least one of the fixed die and the movable die and the nesting piece for forming the cavity, and a nesting attachment body made of a metal having a high thermal expansion coefficient provided on the outside of the nesting piece via a heat insulating material. And consisting of
A heating means and a cooling means are provided in the nesting piece and the nesting attachment body of the at least one mold,
When the nesting piece of at least one of the fixed mold and the movable mold is heated by the heating means to raise the temperature above the softening point of the synthetic resin, the molten synthetic resin is injected and filled into the cavity. Before and after the pressure holding, the nesting attachment body of the at least one mold is heated by the heating means to be thermally expanded, and the nesting piece of the at least one mold is cooled by the cooling means. Then, the synthetic resin is cured while being compressed at a pressure equal to or higher than the injection pressure of the synthetic resin.

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