JP5565828B2 - Injection molding method - Google Patents

Description

  The present invention relates to an injection molding method 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.

In this type of injection molding method, as disclosed in, for example, Patent Document 1, a surface-side cavity forming surface for molding the surface side of a molded product is heated before injecting a molten synthetic resin, so that transferability is improved. Techniques for improvement have been proposed.
JP-A-6-254924

  However, if the synthetic resin molded product has a vertical wall that is substantially parallel to the mold opening direction, the design surface (surface) of the vertical wall is likely to be damaged by the fixed mold, and particularly the vertical wall is subjected to a textured process. When applied, the textured surface is damaged, and when the molded product is coated, there is a problem that it is difficult to perform in-mold coating on the vertical wall surface.

Therefore, in view of the above points, the present invention is configured to open the mold when the fixed mold and the movable mold are opened, even if the injection molded product has a wall substantially parallel to the mold opening direction. It is an object of the present invention to make it easy and prevent the surface of the vertical wall of the molded product from being damaged, and to facilitate in-mold coating of the molded product.

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.
In anticipation of thermal expansion of the movable mold , the gap formed in advance between the fixed mold and the movable mold is thermally expanded by heating the movable mold to eliminate the gap,
A synthetic resin melted in a state where the gap is eliminated is formed by the fixed mold and the movable mold and extends in the horizontal direction and communicates with the first space and is orthogonal to the first space. Injecting and filling into the cavity composed of a second space extending in the direction and substantially parallel to the mold opening direction ;
After that, the movable mold is cooled and thermally contracted, and the synthetic resin is also thermally contracted, and the surface of the wall substantially parallel to the mold opening direction formed by the second space of the synthetic resin molded product and the fixed mold The mold is opened while being separated from the mold .

According to a second aspect of the present invention, there is provided an injection molding method in which a molten synthetic resin is injected and filled in a cavity with a fixed mold and a movable mold closed.
In anticipation of thermal expansion of the movable mold, the gap formed in advance between the fixed mold and the movable mold is thermally expanded by heating the movable mold to eliminate the gap.
Fill and fill the cavity with synthetic resin that has been melted with this gap removed,
Thereafter, the movable mold is cooled and thermally contracted, and the synthetic resin is also thermally contracted to form a space between the outer surface of the synthetic resin molded product and the fixed mold,
It is characterized by injecting paint into this space.

According to the present invention, when the fixed mold and the movable mold are opened , a space is formed between the surface of the wall substantially parallel to the mold opening direction of the injection molded product in the cavity and the fixed mold. Therefore, not only mold opening becomes easy, but also the design surface of the wall substantially parallel to the mold opening direction of the injection molded product is not damaged by the fixed mold. Therefore, when a textured surface is applied to the design surface of the wall substantially parallel to the mold opening direction of the injection molded product, the textured surface can be finished finely. Further, in-mold coating can be easily performed on an injection molded product using the space.

It is a vertical front view of an injection molding device. 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. It is principal part sectional drawing for demonstrating the 3rd step in the case of giving a texturing to an injection molded product. It is principal part sectional drawing for demonstrating the 4th step in the case of giving a texturing to an injection molded product.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS. First, based on FIG. 1, the whole structure of the injection molding apparatus 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 portion 6 having a U-shaped longitudinal section fixed by the locating ring, and a locating ring that is provided near the fixed platen of the fixed first base plate 2 and positions the fixed first base plate 2 with respect to the fixed platen 7 and a sprue bushing 8 disposed adjacent to the locating ring 7.

  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 portion 26 and the lower surface of the concave portion formed on the lower surface of the fixed mold portion 6, and a molten synthetic resin is injected into the cavity S to produce a molded product. The cavity S has a U-shaped longitudinal section, and is composed of a space extending in the horizontal direction and a cylindrical space extending in the vertical direction communicating with the space, and the molded product is substantially parallel to the mold opening direction. It consists of two vertical walls and one horizontal wall, and has a box shape with one side open.

  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. According to the temperature suitable for the synthetic resin injected into the cavity S, the fixed side third base plate 4, the fixed mold part 6, the movable side fourth base plate 24, and the movable mold part A heat medium is constantly supplied so that 26 is maintained at a predetermined temperature.

  Reference numeral 31 denotes a heat medium passage formed along the cavity S in a portion close to the cavity S of the fixed mold portion 6, and hot steam or heated water which is a heating medium in the heat medium passage 31, or for cooling. Cold air or cooling water as a medium is flowed to heat or cool the cavity forming surface side of the fixed mold part 6.

  Reference numeral 32 denotes a heat medium passage formed by a horizontally extending passage formed in the entire movable mold portion 26 and a vertically extending passage communicating with the passage. Steam or heated water that is a heating medium flowing in from the heat medium inlet 33 or cold air or cooling water that is a cooling medium is flowed to heat or cool the entire movable mold part 26. A partition plate 34 forming a flow path is provided in the heat medium passage 32 extending in the vertical direction, and the heat medium flowing into the heat medium passage 32 from the heat medium inlet 33 flows out from the heat medium outlet 35.

  Reference numeral 27 denotes a heat insulator provided between the movable mold part 26 and the movable fourth base plate 24, and insulates the movable mold part 26 and the movable fourth base plate 24 from each other.

  Next, in particular, referring to FIGS. 2 to 5, as shown in FIG. 2, a gap 36 allowing thermal expansion of the fixed mold part 6 and the movable mold part 26 is formed between the fixed mold part 6 and the movable mold part. A gap 37 is formed between the fourth plate 24 and the movable mold part 26 in the same manner, and is formed in advance between the mold part 26 and allowing thermal expansion of the movable mold part 26. That is, the gaps 36 and 37 are formed in advance in consideration of the thermal expansion of the movable mold part 26. The gap 37 is formed on the outer periphery of the vertical surface according to the shape of the movable mold part 26, and is not limited to the position shown in the drawing.

  First, in the state of FIG. 2 in which the fixed mold part 6 and the movable mold part 26, which are constantly supplied with the heat medium in the heat medium paths 29 and 30 and are maintained at a predetermined temperature, are closed. When a heating medium having a temperature equal to or higher than the softening point of the synthetic resin is allowed to flow through 31 and a heating medium having a temperature equal to or higher than the softening point of the synthetic resin is caused to flow through the heat medium passage 32, both mold parts 6 and 26 are heated. For example, a stationary mold portion 6 made of age hardened steel (for example, an expansion coefficient of 0.0000125) and a movable mold portion 26 made of an aluminum alloy having a large expansion coefficient (for example, an expansion coefficient of 0.0000236). , And expands within an upper 180 ° range (upward and lateral directions) with the heat insulator 27 as a boundary, and the gaps 36 and 37 employed are eliminated due to the difference in expansion coefficient. In this case, by raising the temperature of both mold parts 6 and 26, the transferability of the synthetic resin can be improved, and the design surface of the injection molded product J can be finished finely.

  That is, the bottom surface of the cavity S is formed on the upper surface of the stepped portion 26A of the movable mold portion 26, abuts against the outer surface of the stepped portion 26A and the lower end portion of the cavity forming surface of the fixed mold portion 6 and this stepped portion 26A. The outer upper surface 26B communicating with the lower end part contacts the lower surface of the fixed mold part 6, and the peripheral side surface of the movable mold part 26 contacts the movable side fourth base plate 24, so that the fixed mold part 6 and the movable mold part 6 are movable. Only the cavity S remains between the mold parts 26 as shown in FIG.

  Note that the heating medium may start to flow through the heat medium passages 31 and 32 before the mold closing, and then the mold closing may be started.

  In the state of FIG. 3, the injection nozzle is passed through the sprue bush 8, and the molten synthetic resin is moved through the first sprue 9, the first runner 10, the second sprue 11, the second runner 12 and the gate 13. Injecting injection into the cavity S between 26 and the fixed mold part 6, and maintaining the injection pressure to increase the compression density of the synthetic resin, the pressure is maintained.

  After this pressure holding, the synthetic resin begins to shrink and harden. Thereafter, the heating medium in the heat medium passages 31 and 32 is discharged, and a cooling medium having a temperature lower than the softening point of the synthetic resin is supplied to the heat medium passages 31 and 32, respectively. The part 26 is rapidly cooled. Then, the synthetic resin is cured while shrinking in the same direction as the direction in which the movable mold part 26 is thermally contracted, and an injection molded product J of the synthetic resin is obtained. In this case, the time required for shrinkage of the synthetic resin by rapid cooling is shorter than the time required for shrinkage of the synthetic resin during normal resin molding.

  That is, the movable mold part 26 is thermally contracted while being held in the injection molded product J, and the synthetic resin pressed against the cavity S forming surface of the fixed mold part 6 is peeled off from the surface of the fixed mold part 6. As shown in FIG. 5, a space (gap) G is generated between the fixed mold part 6 (the surface of the fixed mold part 6 where the cavity S is formed) and the surface of the injection-molded product J. Clearances 36 and 37 are formed between the portion 6 and the movable mold portion 26 and between the fourth plate 24 and the movable mold portion 26.

  For this reason, when the fixed mold part 6 and the movable mold part 26 are opened to take out the injection molded product J from the cavity S, the surface of the injection molded product J and the fixed mold part 6 are in close contact with each other. In addition, since the surface of the injection molded product J and the fixed mold part 6 are separated from each other, in particular, the vertical wall of the injection molded product J is separated from the vertical surface of the fixed mold part 6, the mold can be opened smoothly. In addition, the vertical wall surface (design surface) of the injection molded product J can be prevented from being damaged by preventing the vertical wall of the injection molded product J from coming into contact with the vertical surface of the fixed mold portion 6.

  Further, as shown in FIGS. 6 and 7, even when a textured groove 6 </ b> A is formed in the fixed mold portion 6 and the side surface of the vertical wall of the injection molded product J is textured, a synthetic resin is formed in the cavity S. (See FIG. 6), the heating medium in the heat medium passages 31 and 32 is discharged, the cooling medium is supplied to the heat medium passages 31 and 32, and the fixed mold portion 6 and the movable mold portion 26 are moved. Upon rapid cooling and subsequent mold opening, between the surface of the injection molded product J and the fixed mold part 6, particularly between the embossed surface 38 of the injection molded product J and the vertical surface of the fixed mold part 6. Since the space G (gap) is formed, the mold opening can be performed without damaging the embossed surface 38 of the injection molded product J. Accordingly, it is possible to finely finish the texture applied to the design surface of the vertical wall of the injection molded product J.

  As described above, both the mold parts 6 and 26 are heated or cooled in order to eliminate the gaps 36 and 37 and to make the space G. However, the present invention is not limited to this. Only 26 may be heated or cooled.

  Then, in the case where in-mold coating is applied to the surface of the injection molded product J before opening the mold, in the state shown in FIG. 5 or 7, the thermosetting property is formed in the gap G formed on the outer periphery of the injection molded product J. Inject an appropriate amount of paint. In this case, a heating medium is allowed to flow through the heat medium passages 31 and 32, or only through the heat medium passage 32, and the fixed mold portion 6 and the movable mold portion 26 or only the movable mold portion 26 is thermally expanded. Then, the molded product J is pressed (pressed), and the paint is cured, so that the paint is pressed onto the surface of the injection molded product J. In this case, as described above, by raising the temperature of both mold parts 6 and 26, the transferability of the synthetic resin can be improved, and the design surface of the injection molded product J has already been finished finely. Therefore, the quality of the painted surface can be improved even if the coating film is thin.

  Thereafter, the heating medium is discharged from the heat medium passages 31 and 32, or from the heat medium passage 32, and this time, the cooling medium is allowed to flow through both the passages 31 and 32 or only the passage 32. A space (gap) is created between the surface of the molded product J and the fixed mold portion 6, particularly between the vertical wall of the injection molded product J and the vertical surface of the fixed mold portion 6, thereby smoothing the mold opening. It is possible to prevent the vertical wall surface (design surface) of the injection molded product J from being damaged.

  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 26 Movable mold part 31 Heat medium passage 32 Heat medium passages 36, 37 Gap 38 Textured surface G 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,
In anticipation of thermal expansion of the movable mold , the gap formed in advance between the fixed mold and the movable mold is thermally expanded by heating the movable mold to eliminate the gap,
A synthetic resin melted in a state where the gap is eliminated is formed by the fixed mold and the movable mold and extends in the horizontal direction and communicates with the first space and is orthogonal to the first space. Injecting and filling into the cavity composed of a second space extending in the direction and substantially parallel to the mold opening direction ;
After that, the movable mold is cooled and thermally contracted, and the synthetic resin is also thermally contracted, and the surface of the wall substantially parallel to the mold opening direction formed by the second space of the synthetic resin molded product and the fixed mold An injection molding method characterized in that the mold is opened while being separated from the mold. 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,
In anticipation of thermal expansion of the movable mold, the gap formed in advance between the fixed mold and the movable mold is thermally expanded by heating the movable mold to eliminate the gap.
Fill and fill the cavity with synthetic resin that has been melted with this gap removed,
Thereafter, the movable mold is cooled and thermally contracted, and the synthetic resin is also thermally contracted to form a space between the outer surface of the synthetic resin molded product and the fixed mold,
After injecting a thermosetting paint into this space, at least the movable mold is heated and thermally expanded to press and cure the injected paint on the synthetic resin molded product,
An injection molding method comprising cooling at least the movable mold after curing the paint.

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