JP2005205807A - Mold for injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for injection molding which enables simultaneous filling from a plurality of gates and also facilitates takeout even in the case of multiple-impression molding, in regard to the injection molding of a shape having a hollow part demanding high precision, such as a precision component gear. <P>SOLUTION: When a first movable plate 13 and a second movable plate 15 are lowered, from a state of closure, to be separated from each other, regulation by locking blocks 45, 45 is canceled and slide blocks 43, 43 slide gradually in the directions of arrows so that they separate from each other. When mold opening is completed, the slide blocks 43 are in a state of being moved to the opposite sides. By this separation of the slide blocks 43, 43, a second sprue part 85 is opened. As a result, a second sprue 75 and a second runner 77 being undercut are exposed and thus takeout is enabled. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an injection mold, and more particularly to an injection mold suitable for molding a precision part having a hollow portion such as a high-precision gear.

  At the time of injection molding of a gear having a hollow portion, a method of injecting a molten material from a single gate into a substantially annular product portion gap has been employed (for example, Patent Document 1). However, when the molded product has a shape having a hollow portion, injection from one place fills the entire annular product portion void so as to bypass the hollow portion, so a short shot (filling Deficiency) and uneven filling are likely to occur, and there is a problem that it is difficult to obtain a molded product with high accuracy.

  Therefore, in order to increase the accuracy of the molded product, rather than injecting the molten material from one gate into the annular product space, the gate is provided at multiple locations, and the molten material is injected simultaneously from each gate to solidify. It is advantageous to allow for more uniform filling. When the molten material is injected from a plurality of gates as described above, a plurality of sprues necessarily connected to each gate are necessary.

  In addition, regarding a multi-cavity molding of a high-precision cylindrical injection molded product, in a mold configuration including a stripper plate and a first mold plate supporting a core block as two movable molds in a fixed mold, The first horizontal runner portion is provided at the boundary between the first template and the stripper plate formed with the first horizontal runner portion, and the second horizontal runner portion is provided at the boundary between the core block and the cavity block. A vertical runner that communicates with the horizontal runner part is provided, the first horizontal runner part branches the sprue tip into a path that matches the number of formations, and the same position as the branch point is aligned with the axis of the mold cavity part The route is branched into a plurality of lines, communicated with the second horizontal runner portion via the vertical runner arranged concentrically with the shaft center, and the same by the second horizontal runner portion The inner end of each branch path of the path is arranged on the axis center of the mold cavity and the object of the axis, and the multi-end gate facing the axis is provided at the inner end of each branch path so as to face each other. A mold for manufacturing a cylindrical injection molded product has been proposed (for example, Patent Document 2).

  Specifically, the method of Patent Document 2 branches from the tip of the sprue in two directions by a runner orthogonal to the sprue, and further branches in two directions at each end of the runner to correspond to four product part gaps. A cylindrical injection molded product is distributed to each position, connected to each product space by two sprues, and further filled from four gates via a semicircular arc outer periphery runner. High precision outer dimensions and inner diameter coaxiality are obtained. In this system, a semicircular arc-shaped outer peripheral runner is provided immediately before the gate to ensure the gate balance by aligning the flow length of the molten material, but this configuration is suitable for cylindrical injection molded products. It cannot be applied as it is to other molded products. In addition, since the structure near the gate is complicated, there is a problem that it is difficult to manufacture the mold.

JP-A-8-276469 (FIG. 1 etc.) JP 2002-321257 A (FIGS. 8, 10, etc.)

  In general, when precision parts are injection molded, in order to increase the precision of the parts, one piece is basic, and many pieces are often avoided to process a plurality of molded products at the same time. When using a single die, the runner is extended radially around the first sprue, and a plurality of second sprues are formed from there to a plurality of gates provided in one product space. As a result, the molten material can be filled evenly, and the problem of gate balance hardly occurs.

However, taking a large number of pieces is overwhelmingly advantageous in terms of manufacturing efficiency. In the case of adopting a multi-point gate method in order to increase the molding accuracy with a large number of pieces, the scrap shape (the shape of the sprue and runner) is inevitably complicated, resulting in an undercut problem.
That is, a plurality of first runners are formed by branching from the first sprues in the substantially orthogonal direction by the same number as the number of the product portion gaps, and the second sprues are extended from the first runners, and the ends thereof are centered. If the second runner is extended radially in a direction substantially orthogonal to each other and a third sprue is formed up to each gate (corresponding to the second sprue in the case of the single piece), an undercut is sure to occur. End up. In order not to cause an undercut, the second sprue is not provided, and the first runner is branched to form a sprue that directly leads from each tip portion to each product portion gap. However, in such a case, since the flow length from the branch point of the first runner to each sprue is not the same, there arises a problem that a subtle difference occurs in the filling timing from each gate and uniform filling cannot be performed.

  Accordingly, the object of the present invention is to enable simultaneous filling from a plurality of gates in injection molding of a shape having a hollow portion that requires high precision, such as precision component gears, and easy to take out even when multiple pieces are taken. It is to provide a mold for injection molding.

  In order to solve the above-described problem, a first aspect of the present invention includes at least a fixed plate, a first movable plate, and a second movable plate, and the first plate has a first sprue portion. An injection mold having a second sprue portion formed on the first movable plate and a third sprue portion formed on the second movable plate, wherein the second sprue portion A mold for injection molding, characterized in that a slide part is provided on the first movable plate that constitutes a split mold.

  According to the invention of the injection molding die, when the first movable plate constituting the second sprue portion is provided with the slide portion to make the split mold, when filling from a plurality of gates or multiple pieces are taken Even if an undercut occurs, scrap can be easily taken out.

Further, according to a second aspect of the present invention, in the first aspect, a plurality of first runner portions branch from the first sprue portion formed at the center of the mold, and each of the first runner portions is connected to the second sprue portion. It is an injection mold characterized by the above.
According to this feature, a plurality of first runner portions are branched from the first sprue portion, so that a large number of pieces can be obtained while maintaining uniform filling of the molten material.

Further, according to a third aspect of the present invention, in the first aspect or the second aspect, a plurality of second runner portions branch from one second sprue portion, and are respectively connected to the third sprue portion. In addition, an injection mold is characterized in that a plurality of gates connected to the plurality of third sprue portions are provided for one product portion gap.
According to this feature, since a molten material can be filled into one product part gap via a plurality of gates, uneven filling of the molten material is suppressed as much as possible, and a highly accurate molded product can be obtained.

The fourth aspect of the present invention is characterized in that, in any one of the first to third aspects, the product part gap has a shape corresponding to an annular molded product having a hollow part. This is an injection mold.
According to this feature, an annular molded product having a hollow portion such as a precision gear can be manufactured with high accuracy by injection molding.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, an inclined pin protrudes from the fixed plate, and the inclined pin is formed on the slide portion. It is an injection mold characterized by being configured to be inserted into and removed from the formed hole.
According to this feature, the split mold can be reliably configured with a simple configuration of inserting the inclined pin into the hole of the slide portion.

Further, a sixth aspect of the present invention is the method according to any one of the first to fifth aspects, further comprising at least one lower plate, the core plate being supported on the lower plate, An injection mold, wherein a product part gap is formed by a core block and a cavity block supported by the second movable plate.
According to this feature, since the boundary between the core block supported by the lower plate and the second movable plate is a parting line, the molded product can be easily taken out.

Further, the seventh aspect of the present invention includes at least a fixed plate, a first movable plate, and a second movable plate, and the first is sequentially from the upstream side to the downstream side in the molten material injection direction. A sprue portion, a second sprue portion, and a third sprue portion are formed, a first runner portion is formed between the first sprue portion and the second sprue portion, and the second sprue portion is A plurality of second runner portions are branched and formed at the center, and a plurality of the third sprue portions are connected via the second runner portions, and the plurality of third sprue portions correspond to a plurality of corresponding gates, respectively. An injection mold that communicates with the product part gap through the first movable plate that forms the second sprue part by providing a slide part to make a split mold, This is an injection mold.
According to the invention of the injection mold, the same effect as the first aspect can be obtained.

  FIG. 1 is a perspective view showing an outline of an injection mold 100 according to an embodiment of the present invention, and FIG. 2 is a sectional view thereof. The injection molding die 100 is used for injection molding of a high-precision gear, and includes a fixed plate 11, a first movable plate 13 as a “first movable plate”, and a “second movable plate”. The upper mold 10a mainly composed of the three plates of the second movable plate 15 and the lower mold mainly composed of the lower first plate 17, the lower second plate 19, the spacer block 21 and the mounting plate 23. 10b. A parting line PL is formed on the boundary surface between the upper mold 10a and the lower mold 10b. The cavity block 51 supported by the second movable plate 15 and the core block 49 supported by the lower first plate 17 form a product part gap 53 (see FIG. 4).

  Magnets 37a and 37b are provided on both sides of the injection mold 100 near the boundary between the upper mold 10a and the lower mold 10b, respectively. The magnets 37a and 37b act so as to enhance the adhesion in a closed state where the upper mold 10a and the lower mold 10b are joined.

  The fixed mold 11, the first movable plate 13, and the second movable plate 15 of the upper mold are configured to be slidable up and down by four support pins 35, and a mold closed state in which these three plates are stacked without gaps, The mold open state can be taken apart from each other. The fixed plate 11 and the first movable plate 13 are provided by four links 33 provided on the front surface and the back surface, and the first movable plate 13 and the second movable plate 15 are provided by four links 39 provided on both side surfaces. The amount of movement during mold opening is limited. The fixed plate 11 is connected to an injection molding machine (not shown) at the locate ring 31.

  FIG. 3 shows the shape of the scrap 70 obtained by filling the injection mold 100 with a molten material such as resin (that is, the shape of the sprue and runner). In the scrap 70, the first sprue 71 is formed in the moving direction of the movable plate (here, the same vertical direction as the vertical sliding direction). From the vicinity of the end of the first sprue 71, first runners 73, 73 are formed to extend in two directions substantially orthogonally. That is, here, the shape of the scrap 70 in the two-piece forming is shown. Since the first runners 73 and 73 are symmetrical, only one side will be described unless otherwise noted.

  A second sprue 75 is formed from the vicinity of the end portion of the first runner 73 toward the moving direction of the movable plate. Further, a plurality (six in this case) of second runners 77 are radially formed in a direction perpendicular to the second sprue 75 as a center. From these six second runners, six third sprues 79 are formed in the respective orthogonal directions toward the corresponding six gates 91 (see FIG. 4). The tip of each third sprue 79 corresponds to each gate 91.

  The shape of the scrap 70 corresponds to the shape of the sprue part and the runner part in the injection mold 100. That is, the first sprue 71 is the first sprue portion 81 (shown by a broken line), the first runner 73 is the first runner portion 83, the second sprue 75 is the second sprue portion 85, and the second runner 77 is the second. The runner 87 and the third sprue 79 correspond to the third sprue 89, respectively.

  The first sprue portion 81 is formed in the vertical direction on the fixed plate 11. The first runner portion 83 is defined by a groove formed on the lower surface of the first plate 11 and the upper surface of the first movable plate 13, and is formed in a direction (and a horizontal direction) orthogonal to the paper surface of FIG. Yes. The first runner portion 83 communicates with the second sprue portion 85 in the vicinity of both ends. Each second sprue portion 85 is formed in the vertical direction by a groove formed facing the boundary surface of the slide blocks 43, 43 supported by the first movable plate 13. The six second runner portions 87 are defined by the grooves formed in the runner plate 47 supported by the second movable plate 15 and the lower surfaces of the slide blocks 43 and 43 supported by the first movable plate 13. The sprue part 85 is formed radially. The six third sprue portions 89 are formed in the vertical direction so as to penetrate the runner plate 47 and the second movable plate 15. The six third sprue portions 89 communicate with the corresponding gates 91 (see FIG. 4), respectively, so that a molten material such as a thermoplastic resin flows into the one product portion gap 53 from the six gates 91. It is configured.

  In this way, by adopting a method of injecting a molten material from a plurality of gates 91, even in a product part gap having a shape corresponding to a molded product having a hollow part such as a gear, the molten material can be uniformly filled and the outer dimensions It is possible to obtain a highly accurate molded product having excellent accuracy. Further, since the six second runners 77 spread radially around the second sprue 75, the flow of the molten material into each third sprue portion 89 proceeds substantially simultaneously, and each gate 91 An even filling from (see FIG. 4) can be ensured.

  In the shape of the scrap 70 as shown in FIG. 3, since the second runner 77 is undercut, the injection mold 100 of the present embodiment is provided with a slide mechanism on the first movable plate 13, and the scrap 70 can be taken out.

4 to 6 are cross-sectional views of the main part of the injection mold 100, FIG. 4 shows a state when the mold is closed, FIG. 5 shows a state in the middle of mold opening, and FIG. Each subsequent state is shown.
The first movable plate 13 is provided with a pair of slide blocks 43 and 43 as “slide portions”. The slide blocks 43, 43 are configured to be slidable in directions that come into contact with and separate from each other.

  A pair of angular pins 41, 41 as “inclined pins” are fixed to the fixed plate 11, and the angular pins 41, 41 protrude obliquely downward toward the slide blocks 43, 43. The fixed plate 11 is provided with a pair of locking blocks 45 and 45 so as to be positioned on both sides of the angular pin 41. The locking blocks 45, 45 project as convex portions toward the first movable plate 13, and are configured to restrict the slide blocks 43, 43 from both sides in a mold-closed state (FIG. 4).

  The slide blocks 43, 43 are formed with through holes 42, 42 as "holes" in an oblique direction so as to correspond to the angular pins 41, 41. When the mold is closed, the through holes 42, 42 are angularly formed in the through holes 42, 42. Pins 41 and 41 are inserted, respectively.

  When the first movable plate 13 and the second movable plate 15 are lowered from the mold closed state to separate the plates, the restriction by the locking blocks 45 and 45 is released as shown in FIG. Slides gradually away from each other in the direction indicated by the arrows in the figure. When the mold opening is completed, the slide block 43 is moved to both sides. The second sprue portion 85 is opened by the separation of the slide blocks 43 and 43. As a result, as shown in FIG. 5, the second sprue 75 and the second runner 77 that are undercut are exposed.

  When the fixed plate 11 and the first movable plate 13 are separated by mold opening, the upper end of the first sprue 71 is cut. Further, when the first movable plate 13 and the second movable plate 15 are separated from each other, the tip end portion of the third sprue is cut at the gate 91 portion. As shown in FIG. 6, the scrap 70 cut in this way can be taken out from between the slide blocks 43 and 43 which are separated from each other.

  When the first movable plate 13 and the second movable plate 15 are lifted and joined to the fixed plate 11 from the mold open state, the slide blocks 43 and 43 are close to each other so as to be sandwiched from both sides by the locking blocks 45 and 45. The angular pins 41, 41 are inserted into the through holes 42 of the slide blocks 43, 43. As the slide blocks 43 and 43 abut against each other, a second sprue portion 85 is formed at the boundary portion.

  As described above, the second sprue portion 85 is formed by the slide blocks 43 and 43, and the second sprue 75 is configured to be opened by the slide mechanism, so that the molten material is evenly distributed to the second runner portions 87 and 87. Inflow at the same time as distribution becomes possible.

  The lower mold 10b is a fixed side including a lower first plate 17, a lower second plate 19, a spacer block 21, a second mounting plate 23, a first ejector plate 25, and a second ejector plate 27 as main components. The second mounting plate 23 is attached to an injection molding machine (not shown).

The lower first plate 17 abuts against the second movable plate 15 of the upper mold 10a via the parting line PL in the mold closed state, and as described above, the product block gap is formed by the core block 49 and the cavity block 51. 53 (see FIG. 4) is formed. After the mold opening, the upper mold 10a and the lower mold 10b are separated by the parting line PL, so that the product part gap 53 is opened (see FIG. 1). In this state, the molded product can be taken out by using a plurality of ejector pins 55.
Each ejector pin 55 is configured to pass through the first ejector plate 25 disposed between the spacer blocks 21, and the lower portion abuts against the second ejector plate 27. By moving the first ejector plate 25 and the second ejector plate 27 upward, the ejector pin 55 protrudes toward the product portion gap 53 in conjunction with the first ejector plate 25 and the second ejector plate 27, and pushes out the molded product 60 as shown in FIG. Works. By this operation, the molded product 60 obtained by injection molding can be easily taken out.

<Action>
In an injection molding die, a configuration is known in which a slide core is provided at an undercut portion of a molded product, and after the molten material is injection molded, the slide core is moved to take out the molded product. However, in the injection mold 100 of the present embodiment, a slide mechanism is provided on the first movable plate 13 in which the second sprue 75 is formed, and the scrap 70 that is undercut can be extracted. The reason why the filling flow path that causes the undercut is intentionally formed is that even when a large number of pieces are taken, it is possible to allow the molten material to flow into the product portion gap 53 from the plurality of gates 91 to eliminate filling unevenness, This is to ensure dimensional accuracy.

  That is, the first runner portion 83 branches according to the number of molded products to enable a large number of pieces, and the molten material is poured from each second sprue portion 85 to the center of the plurality of second runner portions 87, Furthermore, the flow timing of the molten material can be aligned by guiding the molten material to one product portion gap 53 via the plurality of third sprue portions 89 and the plurality of gates 91. Therefore, even in the case of taking a large number of pieces, it is possible to ensure uniform filling of the molten material.

Test example 1
Tooth profile accuracy measurement:
A gear was molded using the injection mold 100 of the present invention, and the roundness of the outer periphery of the product was measured with a roundness measuring device. When the runout of the maximum value and the minimum value of the outer periphery from the center of the molded product was measured, the runout was 12 μm, and high dimensional accuracy corresponding to class 0 was obtained according to the Japan Gear Industry Association Standard (JGMA standard).

  On the other hand, for comparison, the end of the first runner 73 diverges radially and is connected to each gate 91 via each second sprue (that is, the second sprue 75 is not formed in the scrap 70 of FIG. 3). The gears were injection-molded in the same manner using a mold having a configuration in which the end portion of the first runner 73 was branched and directly connected to each third sprue 79. As a result, when the shake of the maximum value and the minimum value of the outer periphery was measured, the shake was 20 μm. This was a dimensional accuracy corresponding to the first grade in the Japan Gear Industry Association standard (JGMA standard).

  From the above test results, it was shown that sufficiently accurate gears can be obtained even in multi-cavity molding by using the injection mold of the present invention.

Test example 2
In the process of injection molding of a gear using the injection molding die 100 of the present invention, short shots at each stage (here, filling) when passing through the third sprue portion 89, immediately after passing through the gate 91, and immediately before filling is completed. ) And a molded product when filling was completed, and the inflow / filling state of the molten resin was observed. As a result, it was confirmed that the resin evenly flows into each of the six third sprue portions 89 when passing through the third sprue portion 89. In the short shot immediately after passing through the gate 91, the molded product in the middle of filling, which is in the shape of petals corresponding to the six gates 91, can be obtained, and it can be confirmed that the resin flows evenly from the six gates 91. It was.

  In addition, in the short shot immediately before the completion of filling, the resin from each gate 91 grew uniformly, and no filling unevenness was observed, confirming that simultaneous filling was performed. Furthermore, it was confirmed that a molded product with high accuracy can be obtained by filling the entire resin from the molded product when filling is completed. From this test result, it was found that in the injection mold 100 of the present invention, the molten resin was uniformly introduced and filled, and the gate balance was good.

  The present invention has been described above with reference to various embodiments. However, the present invention is not limited to the above embodiments, and can be applied to other embodiments within the scope of the invention described in the claims. It is.

  For example, the injection mold 100 according to the embodiment of FIG. 1 has a two-piece configuration, but the same operational effects can be obtained even with a three-piece configuration or more. Even in the case of a single piece, gate balance is ensured and high-precision injection molding is possible.

  The mold of the present invention can be used for injection molding, and is particularly suitable for injection molding of precision parts having hollow portions such as gears. Accordingly, it can be used for molding a large number of high-precision helical gears and the like, and can also be used for injection molding of various precision parts used in a recording apparatus such as a printer.

The perspective view which shows the outline | summary of the metal mold | die for injection molding. Sectional drawing which shows the internal structure of the metal mold | die for injection molding. Drawing showing the shape of scrap. The principal part sectional drawing which shows the mold closing state of the metal mold | die for injection molding. The principal part sectional drawing which shows the state in the middle of mold opening of an upper metal mold | die. The principal part sectional drawing which shows the state after the mold opening of an upper metal mold | die. The perspective view explaining the product delivery state of a lower mold.

Explanation of symbols

11 fixed plate, 13 first movable plate, 15 second movable plate, 17 lower first plate, 19 lower second plate, 21 spacer block, 23 mounting plate, 25 first ejector plate, 27 second ejector plate, 31 locate Ring, 33 link, 35 Support pin, 37a, 37b Magnet 39 link, 41 Angular pin, 42 Through hole, 43 Slide block, 45 Locking block, 47 Runner plate, 49 Core block, 51 Cavity block, 53 Product part gap, 55 Ejector pin, 60 molded product, 70 scrap, 71 1st sprue, 73 1st runner, 75 2nd sprue, 77 2nd runner, 79 3rd sprue, 81 1st sprue part, 83 1st runner part, 85 2nd sprue part, 87 2nd runner part, 89 3rd sprue part, 91 cavity, 100 injection mold, PL parting line

Claims (7)

At least a fixed plate, a first movable plate, and a second movable plate;
A first sprue portion is formed on the fixed plate, a second sprue portion is formed on the first movable plate, and a third sprue portion is formed on the second movable plate. Type,
An injection mold, wherein the first movable plate constituting the second sprue portion is split by providing a slide portion.   2. The injection mold according to claim 1, wherein a plurality of first runner parts branch from the first sprue part formed at the center of the mold and are respectively connected to the second sprue part. .   3. A plurality of second runner portions branch from one second sprue portion and are connected to the third sprue portions, respectively, and connected to the plurality of third sprue portions. A mold for injection molding, characterized in that a gate is provided for one product part gap.   The injection mold according to any one of claims 1 to 3, wherein the product part gap has a shape corresponding to an annular molded product having a hollow part.   5. The tilting pin according to claim 1, wherein an inclined pin protrudes from the fixing plate, and the inclined pin is configured to be inserted into and removed from a hole formed in the slide portion. A mold for injection molding, characterized in that   6. The method according to claim 1, further comprising at least one lower plate, wherein the lower plate supports the core block, and is supported by the core block and the second movable plate. A mold for injection molding, characterized in that a product part gap is formed by a cavity block to be formed. The first sprue portion, the second sprue portion, and the third sprue portion having at least a fixed plate, a first movable plate, and a second movable plate in order from the upstream side to the downstream side in the injection direction of the molten material. A sprue part is formed,
A first runner portion is formed between the first sprue portion and the second sprue portion,
A plurality of second runner portions are branched and formed around the second sprue portion, and a plurality of the third sprue portions are connected via the second runner portion,
The plurality of third sprue parts are injection molds communicating with the product part gap via a plurality of corresponding gates, respectively.
An injection mold, wherein the first movable plate forming the second sprue portion is split by providing a slide portion.

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