JP2009113221A - Mold for injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for injection molding, which molds a product while significantly suppressing the occurrence of sinks and voids with a simple structure. <P>SOLUTION: In a movable template 22 corresponding to a fixed mold 12, a molding hole 23 in which a slide core 64 is held is opened in an end surface, and a cavity C is formed between the slide core of the molding hole and the fixed template. A spacer 40 having a slope is set between a block 30 fixing the movable template and a movable mounting plate 20. After a molten resin is injected/packed in the cavity, since the movable template is displaced in the movable mounting plate direction by extracting the spacer during cooling, the slide core placed on the movable template is slid/pushed relatively in the fixed template direction via a slide base 60, the resin in the cavity is compressed, and the occurrence of the sink and the void is suppressed. No complex compression mechanism is needed in a parting part located between the fixed template and the movable template. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a structure of an injection mold for molding a resin product by injection molding.

At present, many resin products are manufactured by injection molding. This is a process in which a resin melted by an injection device is injected and filled into a mold, cooled and solidified in the mold, and then taken out.
By the way, the resin product manufactured in this way shrinks at the stage of cooling and solidification due to the characteristics of the resin physical properties, and in the case of a complicated shape, it is pulled by the thick part and the so-called sink occurs on the surface, Or even if it is a simple lump shape, voids are generated inside, so that the product may be defective.
Therefore, various injection molding apparatuses and injection molding methods for preventing the occurrence of sink marks and voids have been proposed.

For example, in Japanese Patent Laid-Open No. 9-248844, as a method of manufacturing a Fresnel lens sheet, after supplying molten resin into a mold, or while supplying, the mold clamping force to the mold is increased to compress the resin. Is disclosed.
The mold apparatus used here has a resin leakage prevention piece housed in the digging of the fixed side mold plate and urged by a spring to protrude from the surface facing the movable side mold plate toward the movable side mold plate. I have. When the molten resin from the injection device connected to the fixed-side mold plate passes through the spool and is supplied to the cavity between the fixed-side mold plate and the movable-side mold plate, the resin leakage prevention piece seals around the cavity. .
By increasing the mold clamping force, the mold closes as much as the resin shrinks at the stage of cooling and solidification, and the aim is to prevent the occurrence of sink marks and voids.
JP-A-9-248844 JP-A-10-58502

  However, since the mold apparatus disclosed in Japanese Patent Laid-Open No. 9-248844 increases the clamping force by pressing and moving the movable side mold plate relatively toward the fixed side mold plate, the fixed side mold plate Therefore, a resin leakage prevention piece is indispensable for sealing the cavity, and the complexity of the structure greatly increases the manufacturing cost of the mold. It becomes a problem.

Similarly, since a resin leakage prevention piece is essential, it is limited to molding a flat product having a simple shape such as a lens, and cannot be applied to a product having a complicated shape in the thickness direction or a shape having a hole.
Also, in the shape of extending the branch part from the bulky body or having a flange in the thickness direction from the periphery, the branch part solidifies first due to the difference in cooling and solidification speed, so that the parting part is appropriately It becomes impossible to close at the timing.

On the other hand, as an injection molding in which the mold surface is displaced without opening the parting part, there is one disclosed in JP-A-10-58502.
The mold apparatus disclosed in Japanese Patent Application Laid-Open No. 10-58502 includes a core on a movable core plate with respect to a cavity plate as a fixed side mold plate. The movable side includes a back plate that can be displaced with respect to the core plate, and a spring is provided between the core and the back plate.

When resin is injected into the cavity between the cavity plate and the core plate with a gap between the core plate and the back plate, the core is retracted to the back plate side under the pressure of the molten resin, and the pressure balance is maintained. Prevents dripping of molten resin.
Simultaneously with the completion of the resin filling, the back plate is pressed against the core plate without any gaps, so that the core also becomes a set position with respect to the cavity plate.

  However, Japanese Patent Application Laid-Open No. 10-58502 has a purpose of preventing the dripping phenomenon of the molten resin due to pressure balance, and prevents the occurrence of sink marks and voids due to shrinkage during cooling and solidification of the resin. Does not have a configuration for.

  Therefore, in view of the above-mentioned conventional problems, the present invention has an object to provide an injection mold that can be molded with a simple structure that can be realized at low cost and that can significantly reduce the occurrence of sink marks and voids. And

  For this reason, the injection mold according to the present invention has a mounting plate that supports the first template so as to be able to stroke with respect to the second template, and extends in the stroke direction on the first template. And a mold hole that opens to an end surface facing the second template and forms a cavity into which the molten resin is injected and filled when the end surface is brought into contact with the second template. The slide core is accommodated, and the slide core is slid to have a pushing means capable of compressing the volume of the cavity.

According to the present invention, by sliding the slide core and compressing the resin in the cavity, it is possible to mold a product that significantly suppresses the occurrence of sink marks and voids.
And since the resin in a cavity is compressed without opening and closing the parting part of a 1st template and a 2nd template, it is not necessary to make the structure of a parting part complicated, and it can implement | achieve at low cost.

Embodiments of the present invention will be described below.
FIG. 1 is a partial external cross-sectional view showing the structure of the embodiment.
On the fixed side of the mold, a fixed side mold plate 12 is attached to the fixed side mounting plate 10, and a nozzle 14 is provided through the fixed side mounting plate 10 and the fixed side mold plate 12. An injection device (not shown) that supplies molten resin is connected to the nozzle 14.
The fixed-side template 12 is provided with a cooling passage 16 through which a coolant flows along a surface corresponding to a movable-side molding hole 23 described later.

The movable side includes a movable side mounting plate 20, a movable side mold plate 22 whose front end face faces the fixed side template 12, and a block 30 that fixedly supports the movable side template 22. The block 30 includes a cover plate 32 that covers the back surface of the movable side template 22, and a leg 34 that extends from the cover plate toward the movable side mounting plate 20. A spacer is provided between the leg 34 and the movable side mounting plate 20. 40 is provided.
The movable side mounting plate 20 is connected to a first hydraulic cylinder (not shown) and can be moved back and forth (stroke) toward the fixed side.
The movable side plate 22 and the cover plate 32 of the block 30 are provided with a molding hole 23 corresponding to the cross-sectional shape of the product main body to be molded, and a slide core 64 is inserted into the molding hole 23. Yes.

A branch recess 24 corresponding to a thin branch extending from the product main body and a runner recess 25 for guiding a molten resin are formed on the front end surface of the movable mold plate 22 connected to the molding hole 23.
Further, the movable side mold plate 22 is provided with a rod hole 26 extending from the runner recess 25 toward the back surface, and a spring accommodating portion 27 whose axial center coincides with the rod hole 26 from the movable side mold plate 22 to the cover plate 32. Is provided. The spring accommodating portion 27 has a bottom wall 36 on the back side of the cover plate 32, and a through-hole 38 whose axial center coincides with the rod hole 26 of the movable side template 22 is provided on the bottom wall.
The movable side template 22 is also provided with a cooling passage 28 surrounding the molding hole 23, and a cooling passage is also provided in the slide core 64 as necessary.

  The leg portion 34 of the block 30 extends from the side edge portion of the cover plate 32 toward the movable mounting plate 20 while avoiding the openings of the molding hole 23 and the through hole 38. A spacer 40 is sandwiched between the tip of the leg 34 and the movable side mounting plate 20.

  The cover plate 32 protrudes laterally from the movable side mold plate 22, and the mold holding wall 50 extends from the movable side mounting plate 20 to the front of the cover plate 32. At the front end of the mold holding wall 50, a spring receiving portion 52 having a recessed spring support hole 53 is provided so as to face the front surface of the cover plate 32. A spring 54 held in the spring support hole 53 is provided between the spring receiving portion 52 and the cover plate 32 to urge the movable side mold plate 22 and the block 30 which are connected and fixed to each other toward the movable side mounting plate 20. ing.

The mold holding wall 50 and the spring 54 are provided at a plurality of locations around the cover plate 32, for example, on each side when the planar shape of the cover plate is a quadrangle.
As a result, the movable side mold plate 22, the block 30 and the spacer 40 are unitized and can be displaced together with the movable side mounting plate 20 with respect to the fixed side. The block 30 can be displaced with respect to the movable mounting plate 20 along the mold holding wall 50.

The contact surface 41 of the spacer 40 with the leg portion 34 of the block 30 is inclined, and the spacer 40 has a rust shape in which the inner side is thinner than the outer side.
The spacer 40 includes a screw hole 42 that meshes with a screw shaft 45 extending from the motor 44, and can slide on the movable side mounting plate 20 by driving the motor 44. The motor 44, the screw shaft 45, and the screw hole 42 of the spacer 40 constitute a spacer driving mechanism.

A slide base 60 is disposed in a space between the spacer 40 and the leg portion 34 of the block 30.
The slide base 60 includes a first plate 61 and a second plate 62. A slide core 64 to be inserted into the mold hole 23 of the movable side mold plate 22 and the cover plate 32 is attached to the first plate 61 by a bolt 65, and a pusher 66 corresponding to the through hole 38 of the cover plate 32 is attached. It has been. The second plate 62 covers the bolt hole that appears on the back surface of the first plate 61 and holds the head of the pusher 66.

The slide core 64 has a function of pushing in the resin in the molding process of the resin in the molding hole 23 and extruding the resin as a product from the molding hole 23 after cooling.
Although not particularly shown, a return spring may be provided between the slide base 60 and the cover plate 32 so as to bias the slide base 60 toward the movable mounting plate 20.

In a state where the motor 44 is driven and the spacer 40 is pushed into the predetermined position, the distance between the cover plate 32 and the movable side mounting plate 20 becomes the first distance. When the movable side template 22 is brought into contact with the fixed side template 12, the space between the slide core 64 and the fixed side template 12 in the molding hole 23 becomes a cavity C filled with resin.
The axial length of the cavity C, that is, the distance between the fixed side template 12 facing the molding hole and the front end surface of the slide core 64 is set to be longer than the axial length of the product main body by a predetermined amount. Yes.

The movable side mounting plate 20 is provided with a rod hole 21 through which a protruding rod 70 extending from a second hydraulic cylinder (not shown) is passed, and the slide core 64 can be slid by pushing the slide base 60 with the protruding rod 70. It is like that.
A runner protrusion rod 73 having a head 74 on the cover plate 32 side is inserted into the rod hole 26 of the movable side template 22, and the head 74 is directed toward the bottom wall 36 of the spring accommodating portion 27 by a spring 76 disposed in the spring accommodating portion 27. Is being energized.

In a state where the head 74 of the runner protrusion rod 73 is in contact with the bottom wall 36 of the spring accommodating portion 27, a predetermined gap S is provided between the head 74 and the tip of the pusher 66.
When the slide core 64 compresses the resin in the cavity C during the molding process, if the pusher 66 that is displaced together with the slide core 64 via the slide base 60 simultaneously presses the runner ejection rod 73, the resin in the runner recess 25 having a small capacity is obtained. As a result, the slide core 64 cannot sufficiently compress the product portion in the cavity C as a result of the high compression ratio or the solidification of the runner portion due to the small capacity. Further, by compressing the runner portion having a small capacity, a burden is imposed on the gate of the nozzle 14.
For this reason, it is preferable to set the predetermined gap S so that the pusher 68 contacts the runner protrusion rod 73 for the first time after the compression of the product main body by the slide core 64 stops.

Next, the molding procedure using the injection molding die configured as described above will be described with reference to the flowchart of FIG.
The molding process starts from a state in which the movable side mold plate 22 and the fixed side mold plate 12 are separated from each other with the movable side mounting plate 20 being moved to the retracted position by the first hydraulic cylinder.
First, in step 100, the spacer 40 and the protruding rod 70 extending from the second hydraulic cylinder are set to the initial positions.
That is, the spacer 40 is pushed inward by the spacer drive mechanism, and the distance between the cover plate 32 and the movable side mounting plate 20 is the first distance.
Further, the protruding rod 70 is retracted from the front surface of the movable side mounting plate 20.

In step 101, the first hydraulic cylinder is operated to move the movable side mold plate 22 integrally with the movable side mounting plate 20 to the fixed side, and is brought into contact with the fixed side mold plate 12 and clamped at a constant pressure. . In this state, as described above, the cavity C corresponding to the product main body portion in which the molding hole 23 is closed between the movable side mold plate 22 and the fixed side mold plate 12 by the fixed side mold plate 12 and the slide core 64. Is formed.
In the state where the distance between the cover plate 32 and the movable side mounting plate 20 is the first distance, the length of the cavity C, that is, the distance between the front end surface of the slide core 64 and the fixed side template 12 is the axis of the product main body. It is set longer than the design value of the direction length by a pushing amount described later.

In the next step 102, the molten resin is supplied from the injection device connected to the nozzle 14 on the fixed side. The molten resin is filled into the cavity C from the nozzle 14 through the runner recess 25. The previous FIG. 1 shows this state.
Even when there is no return spring between the slide base 60 and the cover plate 32, the slide core 64 is pushed by the filled molten resin until the slide base 60 to which the slide core 64 is attached is seated on the movable mounting plate 20. fall back.
Thereafter, in step 103, it is checked whether or not a predetermined time has elapsed after filling the molten resin. During this time, the resin filled in the cavity C is cooled.

When a predetermined time set in advance elapses, the routine proceeds to step 104 where the mold clamping pressure is released.
In step 105, the motor 44 of the spacer driving mechanism is driven to extract the spacer 40 by a predetermined amount and the mold clamping pressure is applied again in step 106.
As a result, as shown in FIG. 3, when the spacer 40 is extracted, the block 30 is relatively displaced toward the movable side mounting plate 20 along the inclination between the spacer 40 and the leg portion 34 of the block 30, and the cover plate 32. And the distance between the movable side mounting plates 20 is shortened to become the second distance.

As a result, the front end surface of the slide core 64 in the molding hole 23 moves relatively toward the fixed-side template 12 by the difference between the first distance and the second distance, and the resin in the middle of cooling in the cavity C Push in.
The extraction amount of the spacer 40 is set so that the distance between the front end face of the slide core 64 moved thereby and the fixed-side template 12 becomes the design value of the axial length of the product main body.

  In step 107, it is checked whether or not a predetermined time for ensuring the completion of cooling has passed. When the predetermined time has passed, the routine proceeds to step 108, and the movable side mounting plate is moved by the first hydraulic cylinder as shown in FIG. 20 is returned to the retracted position and the mold is opened. At the retracted position of the movable-side mounting plate 20, the fixed-side template 12 and the movable-side template 22 are spaced apart from each other more than the axial length of the product main body.

Thereafter, in step 109, as shown in FIG. 5, the slide base 60 is pushed out by the second hydraulic cylinder. A slide core 64 attached to the slide base 60 slides in the molding hole 23 to push out the cooled and molded product main body from the molding hole 23. At the same time, the pusher 66 also pushes the runner portion connected to the product main body portion from the movable side template 12 via the runner protrusion rod 73.
As a result, the product P is released and one molding is completed.

Next, the result of measuring the amount of sink for each resin material for an example in which a cube having a side of 70 mm as a product body was molded using the mold of the embodiment will be shown. Here, ABS, POM (polyacetal), PC (polycarbonate), PMMA (acrylic), PBT (polybutylene terephthalate), and PP (polypropylene) were used as the resin material.
The mold clamping force before and after releasing in step 104 is 150 t (tons).
The actual pushing amount set for each resin material is shown in FIG. Here, the pushing amount is an amount by which the slide core 64 is slid in the direction of the fixed side template 12 by extracting the spacer 40 outward in step 105. For reference, the theoretical shrinkage calculated from the catalog value corresponding to the above indentation amount when assuming that products of the same cube (each side 70 mm) were made is also shown. The indentation amount is the actual molding temperature and indentation timing. The optimal amount is set in advance by experiments in combination with the above.

As shown by the solid line in FIG. 7, the sink marks of the products molded with the indentation amount in FIG. 6 are all within 1 to 1.5% except that PP is about 2%. A broken line is a comparative example in the case where molding is performed without pressing, and the distance between the front end surface of the slide core 64 and the fixed-side template 12 is fixed to 70 mm. It can be seen that 8-14% sink marks are generated in the comparative example, whereas the sink marks are remarkably suppressed in the examples.
FIG. 8 shows the molding result in the case of POM. In the product P ′ of the comparative example, as shown in FIG. As shown to a), it became about 1 mm and significant sink suppression was obtained.

In the present embodiment, the movable side template 22 corresponds to the first template in the invention, the fixed side template 12 corresponds to the second template, and the movable side mounting plate 20 corresponds to the mounting plate.
Further, the slide core seated on the movable side mounting plate 20 via the slide base 60 by moving the spacer 40 in the pulling direction and changing the support position of the movable side template 22 toward the movable side mounting plate 20. The structure which slides 64 interlockingly comprises the pushing means.

The embodiment is configured as described above, and the movable side mounting plate 20 that supports the movable side mold plate 22 is disposed so as to be able to stroke with respect to the fixed side mold plate 12. A molding hole 23 is formed which forms a cavity C which extends and opens at an end surface facing the fixed side mold plate 12 and is injected and filled with molten resin when the end surface is brought into contact with the fixed side mold plate 12. Since the slide core 64 is housed inside and the slide core 64 is slid to compress the volume of the cavity C, the resin in the cavity is compressed to reduce the occurrence of sink marks and voids. Can be molded.
And since the resin in the cavity C is compressed without opening and closing the parting parts of the movable side mold plate 22 and the fixed side mold plate 12, the structure of the parting part does not need to be complicated and can be realized at low cost. .

  In particular, the movable core plate 22 is supported on the movable mounting plate 20 via the spacer 40 that can change the support position from the movable mounting plate 20 as a configuration in which the volume of the cavity C is compressed by sliding the slide core 64. Since the position of the slide core 64 in the molding hole 23 is relatively changed in conjunction with the change in the support position of the movable side template 22, the slide core 64 can be easily operated by operating the spacer 40. Can be slid.

More specifically, the spacer 40 is provided between the block 30 to which the movable side template 22 is fixed and the movable side mounting plate 20 so as to be movable in parallel with the movable side mounting plate 20 and is in contact with the block 30. Since the surface 41 is an inclined surface and the slide core 64 is seated on the movable side mounting plate 20, the block 30 and the movable side can be moved by moving the spacer 40 in parallel with the movable side mounting plate 20. The side mold plate 22 is displaced along the inclined surface in a direction approaching the movable side mounting plate 20, and the slide core 64 seated on the movable side mounting plate 20 slides in the molding hole 23 in the direction of the cavity C.
Since the spacer 40 has an inclined surface, the sliding amount of the slide core 64, that is, the pressing amount can be arbitrarily and continuously changed, and an appropriate pressing amount is obtained by experiment according to the shape of the product to be molded, the resin material, and the like. The work at the time becomes easy.

  Further, a runner ejection rod 73 is supported on the movable side mold plate 22, the slide core 64 is seated on the movable side mounting plate 20 via the slide base 60, and the slide base 60 further corresponds to the runner ejection rod 73. A pusher 66 is attached. When the slide base 60 is pushed out from the seating position on the movable mounting plate 20 by the rod 70, the slide core 64 releases the product from the molding hole 23, and the pusher 66 projects from the runner. Since the rod 73 is pushed to release the runner, the slide core 64 used for resin compression of the cavity becomes a simple structure that also serves as mold release extrusion of the product.

  At this time, in a state where the slide base 60 is seated on the movable side mounting plate 20, the support position of the movable side mold plate 22 changes between the pusher 66 and the runner protrusion rod 73 during the resin pushing in the cavity C. Even so, since a gap of a distance that does not contact is provided, it is possible to prevent the pusher 66 from pushing the runner protrusion rod 73 when the resin is pushed into the cavity C, and as a result, the runner portion having a small capacity is not compressed. The This avoids a situation in which a burden is applied to the gate of the nozzle 14 or a resin pushing amount in the cavity C is insufficient.

In the above-described embodiment, the portion of the fixed-side template 12 that faces the molding hole 23 of the movable-side template 22 is flat, but corresponding molding irregularities are formed according to the shape of the product. be able to. Similarly, the surface of the slide core 64 facing the cavity C can also be formed with an uneven portion in accordance with the required shape of the product.
Of course, in addition to the slide core 64, a loose core for releasing the undercut portion can be additionally provided for molding a product having the undercut portion.
Further, although the cavity and the slide core are provided on the movable side, the present invention is not limited to this, and these may be provided on the fixed side.

It is a partial appearance sectional view showing the structure of an embodiment. It is a flowchart which shows the molding point by the metal mold | die of embodiment. It is a figure which shows the state which pushed in the resin in a cavity with a slide core. It is a figure which shows the retracted position of the movable side. It is a figure which shows the mold release state of a product. It is a figure which shows the pushing amount of an Example. It is a figure which shows the sink ratio of an Example and a comparative example. It is a figure which shows the amount of sink marks of an Example and a comparative example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fixed side mounting plate 12 Fixed side template 14 Nozzle 16, 28 Cooling passage 20 Movable side mounting plate 21 Rod hole 22 Movable side plate 23 Molding hole 24 Branch recessed part 25 Runner recessed part 26 Rod hole 27 Spring accommodating part 30 Block 32 Cover Plate 34 Leg portion 36 Bottom wall 38 Through hole 40 Spacer 41 Contact surface 42 Screw hole 44 Motor 45 Screw shaft 50 Mold holding wall 52 Spring receiving portion 53 Spring support hole 54 Spring 60 Slide base 61 First plate 62 Second plate 64 Slide core 66 Pusher 70 Extrusion rod 73 Runner extrude rod 74 Head 76 Spring C Cavity

Claims (5)

The mounting plate that supports the first template is disposed so as to be able to stroke with respect to the second template,
The first template is formed with a cavity that extends in the stroke direction and opens at an end surface facing the second template, and is filled with an injection of molten resin when the end surface is brought into contact with the second template. With molding holes,
The molding hole accommodates the slide core inside,
An injection mold characterized by having pressing means capable of compressing the volume of the cavity by sliding the slide core.   The pushing means supports the first template on the mounting plate via a spacer capable of changing the support position from the mounting plate, and in combination with the change in the support position of the first template. 2. The injection mold according to claim 1, wherein the position of the slide core in the hole is relatively changed. The spacer is provided between the block to which the first template is fixed and the mounting plate so as to be movable in parallel with the mounting plate, and the contact surface with the block is an inclined surface,
The injection mold according to claim 2, wherein the slide core is disposed while being seated on the mounting plate. The first template supports a runner extrusion rod,
The slide core is attached to a slide base, and is seated on the attachment plate through the slide base;
A pusher corresponding to the runner protruding rod is further attached to the slide base,
By pushing the slide base from the seating position on the mounting plate, the slide core is configured to release the product from the molding hole, and the pusher is configured to release the runner by pressing the runner ejection rod. The mold for injection molding according to claim 3.   In the state where the slide base is seated on the mounting plate, the distance between the pusher and the runner push-out rod does not come into contact with the change of the position of the slide core due to the change in the support position of the movable mold plate by the pushing means. The injection mold according to claim 4, wherein a gap is provided.

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