JP4695456B2 - Injection mold apparatus and injection molding method - Google Patents

Description

  The present invention relates to a so-called multi-cavity injection molding technique, and more particularly, to an injection mold apparatus and an injection molding method suitable for a balanced runner arrangement.

  2. Description of the Related Art Conventionally, in a so-called single-piece injection molding technique, a welding position and a filling balance are arbitrarily adjusted by changing a flow passage cross-sectional area of a runner communicated with a cavity (described below). Patent Document 1).

  In addition, even in the multi-cavity injection molding technology, by changing the flow passage cross-sectional area of the runner, the flow of molten resin into the cavities and the pressurization state are changed to suppress variations between the cavities. Is known (see Patent Document 2 below).

  Furthermore, in the multi-cavity product, it is also known that the surface shape of a molded product is improved by cutting the resin after the molten resin is filled into each cavity and before the resin is cured (described below). (See Patent Document 3).

Japanese Patent Laid-Open No. 4-251652 JP-A-5-433 Japanese Patent Laid-Open No. 9-327846

  By the way, a plastic lens widely used in a small camera or an optical pickup device mounted on a mobile phone or a vehicle can be easily reduced in size, weight and cost, and has a diffraction surface on the lens surface. In recent years, there has been a great increase in demand due to the ease of processing such as forming an annular zone and making the lens surface an aspherical surface.

  Manufacturing such a plastic lens by using a multi-cavity injection molding technique has been conventionally performed, and a mold apparatus capable of molding 16 or even 32 plastic lenses at a time is also known. It has been.

  However, the conventional mold apparatus for molding a plastic lens has a problem that the yield is greatly reduced when the number of multi-chips is increased. The cause is the influence of molding shrinkage of the molten resin. That is, since the molten resin filled from the sprue through each runner to each cavity is pulled in the direction of the sprue due to molding shrinkage at the time of curing, a specific internal stress acts on the plastic lens at the time of curing. It is conceivable that the lens shape changes after the lens is opened or a refractive index distribution is generated inside, so that the desired optical performance cannot be obtained.

  Such pull during molding shrinkage can be suppressed to some extent by setting the distance from the sprue to each cavity, that is, the length of each runner. However, when adopting a balanced runner arrangement that is widely used for reasons such as easy filling balance adjustment, as the number of cavities increases, it is necessary to place each cavity away from the sprue due to space constraints, It is difficult to shorten the runner length.

  On the other hand, as shown in Patent Document 3 above, after the molten resin is filled into each cavity, before the resin is cured, for example, the resin is cut at the intermediate portion or gate portion of the runner, and at the time of molding shrinkage. It may be possible to prevent pulling. However, in the case of performing such cutting, it is necessary to take a measure such as individually holding each separated molded product by suction using a suction device when taking it out of the mold, which complicates the operation. Also, in the case of a plastic lens, if it is taken out from the mold in a state where it is not sufficiently cured and sucked and held, there is a risk that the lens surface will be distorted, so it takes time to take out each molded product from the mold. There is also a problem that it is necessary to extend the length, which greatly reduces productivity.

  In recent years, in order to realize further mass production of plastic lenses, it has been required to injection-mold more plastic lenses at once with a single mold device. To meet this demand, the number of cavities is increased. The above-described influence during molding shrinkage and the problem of the method of taking out from the mold and workability become more prominent.

  The present invention has been made in view of such circumstances, and more injection molding is performed once on a molded product such as a lens or a diffraction grating while ensuring the desired performance by reducing the influence of molding shrinkage. An object of the present invention is to provide an injection mold apparatus and an injection molding method that can be performed and that a molded product can be easily taken out from the mold.

  An injection mold apparatus according to the present invention, in an injection mold apparatus having a plurality of cavities filled with molten resin, faces a sprue to which the molten resin is supplied and an outlet of the sprue. And a plurality of runners extending from the resin distribution start end to the plurality of cavities, and the molten resin is filled in the plurality of cavities, and then the resin distribution start end. The resin flow paths at the inlet portions of the plurality of runners are narrowed so that the molten resin in the plurality of cavities and the plurality of runners is drawn in the direction of the sprue due to molding shrinkage during curing. The resin flow path narrowing means that suppresses the resin and the resin cured in the sprue, the plurality of runners, and the plurality of cavities are connected to each other after the mold is opened. A projecting means which projects in state, is characterized in that it comprises a.

  In the mold apparatus for injection molding according to the present invention, the resin flow path constricting means has a constricting rod whose tip is disposed opposite to the sprue outlet and extends in the axial direction of the sprue and is movable in the axial direction. In addition, the resin flow path can be narrowed by projecting the tip of the constriction rod into the resin distribution flow start end.

  Further, the stenosis rod may be a cylindrical stenosis rod formed in a cylindrical shape, and the protruding means may have a protruding pin that is movable in the axial direction of the sprue inside the cylindrical stenosis rod.

  Further, when constricting the resin flow path, due to the protrusion of the tip portion of the cylindrical stenosis rod, the tip portion of the protruding pin is depressed relative to the tip portion of the cylindrical stenosis rod. When taking out the cured resin so that the molten resin accumulates in the part, and the pin protrudes so as to reduce the volume of the depressed part, the pin moves relative to the constricted rod and is depressed. You may comprise so that resin hardened | cured in the part may be protruded.

  The injection molding method according to the present invention is an injection molding method using a mold having a plurality of cavities filled with molten resin, and is arranged so as to face the sprue of the mold and the outlet of the sprue. And a plurality of molten resin injection procedures for filling the plurality of cavities with the melted resin through a plurality of runners extending from the resin distribution start end to the plurality of cavities; After the molten resin is filled in the cavity, the resin flow paths at the inlet portions of the plurality of runners at the resin distribution start end portion are narrowed to melt in the plurality of cavities and the plurality of runners. Resin flow path constriction procedure for suppressing the resin from being drawn in the direction of the sprue due to molding shrinkage during curing, a mold opening procedure for opening the mold, and the sprue Among them, in the plurality of runners, and the resin was cured in the plurality of cavities, and performing the projecting extraction procedure taken protrude from the mold in a state that connected to each other, in this order.

  The “sprue exit” means a sprue opening that is usually provided along the dividing surface (PL surface) of the mold.

  In the injection mold apparatus and the injection molding method of the present invention, after the molten resin is filled into the plurality of cavities, the resin flow paths at the inlet portions of the plurality of runners at the resin distribution start end are narrowed to By preventing the molten resin in each cavity and multiple runners from being pulled in the direction of the sprue due to molding shrinkage during curing, it is possible to prevent changes in the shape of the molded product after mold opening Therefore, the performance of the molded product can be ensured.

  In addition, the resin cured in the sprue, in the plurality of runners, and in the plurality of cavities is ejected in a state of being connected to each other after the mold is opened. Therefore, it is easy to take out the molded product from the mold and the workability is good. Furthermore, since it is not necessary to suck and hold individual molded products, it is possible to shorten the time for taking out from the mold, thereby improving productivity.

  As described above, according to the injection mold apparatus and the injection molding method of the present invention, the influence at the time of molding shrinkage can be reduced and the molded product can be easily taken out. It is possible to increase the number of cavities, and, for example, it becomes possible to efficiently and in large quantities injection-mold plastic optical elements such as lenses and diffraction gratings that require high optical performance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an overall configuration of an injection mold apparatus according to an embodiment of the present invention.

  An injection mold apparatus 1 shown in FIG. 1 is for taking a large number of plastic optical elements (hereinafter referred to as “plastic optical elements”) such as lenses and diffraction gratings. The mold parts 10 and 20, and the channel narrowing means 30 and the protruding means 40 supported by the support plate 50 are provided.

  The first mold part 10 includes a fixed mold 11, a fixed back plate 12, a sprue bush 13, and a nested mold 14, and a conical sprue to which molten resin is supplied inside the sprue bush 13. 2 is formed. Note that a locate ring, a fixed-side mounting plate, and the like are appropriately installed in the first mold part 10, but these are not shown.

  On the other hand, the second mold part 20 includes a movable mold 21 and a movable back plate 22, and a plurality of melted resins are filled between the movable mold 21 and the fixed mold 11. , And a plurality of runners 4 extending from the resin split flow start end 3 to the cavities 6 (see FIG. 1 only one), a resin split flow start end 3 arranged to face the outlet 2a of the sprue 2. Only one is shown) and a gate 5 serving as an inlet of molten resin from the runner 4 to the cavity 6 is formed. The number of cavities 6 and runners 4 can be set as appropriate. For example, 16 runners 4 are provided radially in a direction orthogonal to the axis X of the sprue 2, and 2 for each runner 4. A total of 32 cavities 6 can be provided. In this embodiment, a balanced runner layout is employed. That is, the plurality of cavities 6 are arranged at substantially equal distances from the axis X, and the lengths and cross-sectional areas of the runners 4 are set to be substantially equal to each other.

  The channel narrowing means 30 is fixed to the plate 31, two plates 31 and 32 that are spaced apart in the vertical direction in the figure, a guide pin 33 that connects the two plates 31 and 32 to each other, and the plate 31. The cylindrical constriction rod 34 and the rod bush 35, and a guide pin 36 that engages with the guide hole 51 of the support plate 50 are provided. The cylindrical constricting rod 34 extends through the second mold part 20 in the direction of the axis X of the sprue 2, and a tip part 34 a thereof is disposed opposite to the outlet 2 a of the sprue 2. The cylindrical constricting rod 34 is movable in the direction of the axis X of the sprue 2 with respect to the second mold part 20, and the tip part 34 a protrudes into the resin distribution start end part 3. Thus, the resin flow path of the inlet portion 4a of each runner 4 at the resin distribution start end 3 is narrowed.

  The protruding means 40 includes two plates 41 and 42 joined to each other, a first protruding pin 43 fixed to the plate 41, and a second protruding pin 44 (hereinafter referred to as an optical surface transfer surface). (Referred to simply as “second protruding pin 44”), a pin bush 45, and a guide pin 46 that engages with the guide hole 52 of the support plate 50. The first protruding pin 43 extends in the direction of the axis X inside the cylindrical stenosis rod 34 and is movable in the direction of the axis X with respect to the cylindrical stenosis rod 34. The portion 43a is disposed to face the outlet 2a of the sprue 2. On the other hand, the second protruding pin 44 passes through the second mold part 20 and extends substantially in parallel with the first protruding pin 43, and the tip 44a thereof serves as an optical surface transfer surface of the cavity 6. It is composed. Although only one first protruding pin 43 is provided, the same number of second protruding pins 44 as the set number of cavities 6 is provided corresponding to each cavity 6, for example.

  Next, the operation of the injection mold apparatus 1 will be described. 2 to 4 are views showing the operation of the injection molding die apparatus 1. FIG. 2 shows the state when the resin flow path is narrowed, FIG. 3 shows the state when the mold is opened, and FIG. 4 shows the state when the resin protrudes. . 5 is an enlarged view of a portion A in FIG. 2, and FIG. 6 is a view in the direction of arrow B in FIG.

  In the state shown in FIG. 1, molten resin is injected from an injection molding machine (not shown) and supplied to the sprue 2. The molten resin supplied to the sprue 2 is diverted from the resin diversion start end 3 to the runners 4 and filled into a plurality of cavities 6.

  After filling with the molten resin, as shown in FIG. 2, the flow path narrowing means 30 moves so that the tip end portion 34 a of the cylindrical constriction rod 34 protrudes into the resin distribution start end 3, and at the resin distribution flow start end 3. The resin flow paths at the inlet portions 4a of the plurality of runners 4 are narrowed (see FIGS. 5 and 6), and the molten resin in the plurality of cavities 6 and the plurality of runners 4 is sprue 2 due to molding shrinkage during curing. Suppresses being pulled in the direction of. It should be noted that the degree of narrowing of the resin flow path varies depending on the cross-sectional shape and length of the runner 4, the type of the resin material, and the like, and thus is difficult to refer to. As an example, the cross-section of the runner 4 is circular as in this embodiment, and the cross-sectional shape of the connecting portion between the resin in the sprue 2 and the resin in the runner 4 (hatched in FIG. 6) is an arc and string. In the case of forming a shape surrounded by, the distance d between the thickest portions is set in the range of 0.2 mm to 1.2 mm, more preferably in the range of 0.3 mm to 0.7 mm. .

  When the flow path constricting means 30 moves, the protruding means 40 does not move. For this reason, the tip part 43a of the first protruding pin 43 (see FIG. 1), which has been slightly depressed from the tip part 34a of the cylindrical constricting rod 34, is further depressed by the movement of the flow path constricting means 30 (see FIG. 1). 2), the melted resin is accumulated in the depressed portion (hereinafter referred to as “depressed portion”). This depressed portion functions as a so-called sprue lock portion. That is, the molten resin accumulates in the depressed portion and is cured, so that the resin cured in the sprue 2 stays on the second mold portion 20 side when the mold is opened, and comes off from the first mold portion 10. It has become easier.

  In the above-described aspect, the tip portion 43a of the first protruding pin 43 is slightly depressed from the tip portion 34a of the cylindrical constriction rod 34 before the flow path constricting means 30 moves. The part that is slightly depressed is designed to function as a sprue lock. On the other hand, in the state before the flow path constricting means 30 moves, the tip end portion 34a of the cylindrical constriction rod 34 and the tip end portion 43a of the first protruding pin 43 are located at substantially the same height, It is also possible to form a depressed portion that functions as a sprue lock portion for the first time when the means 30 moves.

  After a predetermined cooling time, the mold is opened by moving the first mold part 10 away from the second mold part 20 as shown in FIG. At this time, the cured resin in the sprue 2, the runners 4, the gates 5, and the cavities 6 remains on the second mold part 20 while being connected to each other.

  After the mold is opened, as shown in FIG. 4, the protruding means 40 moves until its own plate 41 and the plate 31 of the flow path constricting means 30 come into contact with each other. At this time, the tip portion 43a of the first protruding pin 43 moves relative to the constriction rod 34 so as to reduce the volume of the depressed portion, and protrudes the resin cured at the depressed portion. At the same time, the tip 44a of the second protruding pin 44 is configured to protrude the resin (molded product) cured in the cavity 6. Thereby, the resin hardened in the sprue 2, the runners 4, and the cavities 6 is protruded from the second mold part 20 in a state of being connected to each other.

  After this protrusion, the protrusion means 40 and the flow path narrowing means 30 cooperate to move until the tip of the guide pin 33 of the flow path narrowing means 30 comes into contact with the movable back plate 22, and the cured resin is removed. It has come to protrude further. At this time, the resin cured in the sprue 2, the runners 4, and the cavities 6 by the suction device, the robot hand, or the operator holding the resin portion cured in the sprue 2 by hand, etc. , And taken out from the second mold part 20 while being connected to each other.

  As described above, in the injection mold apparatus 1 of the present embodiment, after the molten resin is filled into the plurality of cavities 6, the resin flow paths of the inlet portions 4 a of the plurality of runners 4 at the resin distribution start end 3 are provided. The narrowed resin prevents the molten resin in the plurality of cavities 6 and the plurality of runners 4 from being drawn in the direction of the sprue due to molding shrinkage during curing. For this reason, it is possible to prevent the plastic optical element from being deformed after the mold is opened and impairing the intended optical performance.

  In addition, since the resin cured in the sprue 2, the plurality of runners 4 and the plurality of cavities 6 is taken out in a state of being connected to each other after the mold is opened, each plastic optical element is taken out in a state of being separated from each other. Compared with, workability of taking out from the mold is better. Furthermore, since it is not necessary to suck and hold individual plastic optical elements, it is possible to shorten the time taken out from the mold, thereby improving productivity.

  Therefore, according to the mold apparatus 1 for injection molding, since the number of cavities can be increased while adopting a balanced runner arrangement, plastic optical elements requiring high optical performance are efficiently injection-molded in large quantities. It is possible.

  Next, an embodiment of an injection molding method according to the present invention will be described. FIG. 7 is a flowchart showing the procedure of an injection molding method according to an embodiment of the present invention.

  The injection molding method of the present embodiment is performed by the following procedure using the above-described injection molding die apparatus 1.

  (1) Close the first mold part 10 and the second mold part 20 shown in FIG. 1 according to a predetermined mold clamping procedure (see step S1 in FIG. 7).

  (2) The molten resin is injected from the injection molding machine, and the molten resin is filled into the cavities 6 through the sprue 2, the runners 4, and the gates 5 shown in FIG. Step S2).

  (3) As shown in FIG. 2, the resin flow path of the inlet portions 4a of the plurality of runners 4 at the resin distribution start end 3 is narrowed so that the molten resin in the plurality of cavities 6 and the plurality of runners 4 Further, it is suppressed from being pulled in the direction of the sprue 2 due to molding shrinkage at the time of curing (refer to step S3 in FIG. 7).

  (4) The molded product (or filled resin or the like) is cooled according to a predetermined cooling procedure (see step S4 in FIG. 7).

  (5) As shown in FIG. 3, the 1st metal mold | die part 10 is isolate | separated from the 2nd metal mold | die part 20 (a mold opening procedure, refer FIG.7 S5).

  (6) As shown in FIG. 4, the resin hardened in the sprue 2, the plurality of runners 4 and the plurality of cavities 6 is projected from the second mold part 20 in a state of being connected to each other. Is taken out from the second mold part 20 (projecting and taking out procedure, see step S6 in FIG. 7), and a series of procedures of the injection molding method is completed.

  The taken out resin is sent to the next step such as gate cutting.

  As mentioned above, although embodiment of this invention was described, this invention is not restricted to embodiment mentioned above, A various aspect can be changed.

  For example, in the above-described embodiment, a balanced runner arrangement is adopted, but the present invention can also be applied to a non-balanced runner arrangement.

  In the above-described embodiment, a mode of so-called vertical clamping injection has been described as an example, but other mold clamping modes such as lateral clamping horizontal injection and mold mounting modes can also be adopted.

  Moreover, although the said embodiment demonstrated taking the injection molding of the plastic optical element as an example, this invention is applicable to the injection molding of various molded articles.

Overall view of injection mold equipment The figure which shows the state at the time of the resin flow path constriction of the mold apparatus for injection molding The figure which shows the state at the time of mold opening of the mold apparatus for injection molding The figure which shows the state at the time of resin protrusion of the mold apparatus for injection molding Part A enlarged view of FIG. B direction arrow view of FIG. Flow chart showing the procedure of injection molding method

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection mold apparatus 2 Sprue 2a (Sprue) outlet 3 Resin distribution start end part 4 Runner 4a (Runner) inlet part 5 Gate 6 Cavity 10 First mold part 11 Fixed mold 12 Fixed back plate 13 Sprue bush 14 Nesting type 20 Second mold part 21 Movable type 22 Movable back plate 30 Channel narrowing means 31, 32 Plate 33 (of channel narrowing means) Guide pins 34 (of channel narrowing means) 34 Stenosis rod 34a ( Tip portion 35 of rod constriction 40 Rod bushing 40 Projection means 41, 42 Plate 43 (of projection means) First projection pin 43a Tip portion of first projection pin 44 Second projection having optical surface transfer surface Pin 44a (second projecting pin) tip 45 pin bush 46 guide pin (for projecting means) 50 support plate 51, 52 Axis d-spacing of wellbore X sprue

Claims (5)

In an injection mold apparatus having a plurality of cavities filled with molten resin,
A sprue to which the molten resin is supplied;
A resin distribution flow start end arranged to face the outlet of the sprue;
A plurality of runners extending from the resin distribution start end to the plurality of cavities;
After the melted resin is filled in the plurality of cavities, the resin flow path at the inlet portion of the plurality of runners at the resin distribution start end is narrowed, and the inside of the plurality of cavities and the plurality of runners A resin flow path constricting means for suppressing the molten resin from being pulled in the direction of the sprue due to molding shrinkage during curing;
Protruding means for projecting the resin cured in the sprue, the plurality of runners, and the plurality of cavities in a state of being connected to each other after the mold is opened,
A mold apparatus for injection molding, comprising: The resin flow path narrowing means is
A distal end portion disposed opposite to the sprue outlet, extending in the axial direction of the sprue and having a constriction rod movable in the axial direction;
2. The injection mold according to claim 1, wherein the resin flow path is narrowed by projecting the tip of the constricting rod into the resin distribution start end. apparatus. The stenosis rod is a cylindrical stenosis rod formed in a cylindrical shape,
3. The mold apparatus for injection molding according to claim 2, wherein the protruding means has a protruding pin that is movable in the axial direction of the sprue inside the cylindrical constricting rod. When constricting the resin flow path, due to the protrusion of the tip of the cylindrical stenosis rod, the tip of the protruding pin is recessed relative to the tip of the cylindrical stenosis rod. So that the molten resin accumulates in the part,
And when taking out the hardened resin, the protruding pin moves relative to the constricted rod so as to reduce the volume of the depressed portion, and the cured resin in the depressed portion is removed. 4. The mold apparatus for injection molding according to claim 3, wherein the mold apparatus is configured to project. In an injection molding method using a mold having a plurality of cavities filled with molten resin,
The plurality of cavities are connected to the mold through a sprue of the mold, a resin distribution start end arranged to face the sprue outlet, and a plurality of runners extending from the resin distribution start end to the plurality of cavities. A molten resin injection procedure for filling the molten resin;
After the melted resin is filled in the plurality of cavities, the resin flow paths at the inlet portions of the plurality of runners at the resin distribution start end are narrowed, and the inside of the plurality of cavities and the plurality of runners A resin flow path constriction procedure for preventing the molten resin from being pulled in the direction of the sprue due to molding shrinkage during curing;
Mold opening procedure for opening the mold;
A projecting and taking out procedure in which the resin cured in the sprue, in the plurality of runners, and in the plurality of cavities is ejected from the mold in a state of being connected to each other;
Are performed in this order.

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