JP3208756B2 - Injection molding method for thin products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method for a thin product such as an IC card, and more particularly to an injection molding method called high-pressure injection molding (in-mold measurement compression molding).

[0002]

2. Description of the Related Art In injection molding of a molding material such as a thermoplastic resin, for example, a molten resin is filled into a cavity formed between a fixed mold and a movable mold which are closed molds. This resin flows into the cavity from the gate and spreads, but at the edge of the cavity, a dead end occurs and the fluidity of the resin deteriorates. This tendency is
In the case of a thin product such as a C card, it becomes particularly remarkable. In addition, since the hardening due to cooling progresses rapidly at the leading end of the flow of the resin, the product characteristics are likely to be degraded due to residual stress strain or the like, even if the filling is not completed. For example, a defect may occur such that the thickness of the peripheral part of the product is slightly thicker than the thickness of other parts. Further, in the injection molding, the gas (air and resin gas) in the cavity must be released as the cavity is filled with resin. A minute gap is formed as a gas vent. This gas vent causes burrs on the product if the gap size is set too large, and causes a problem of poor filling if the gap size is set too small.

On the other hand, in a compression molding such as a flat-press mold, the resin in the cavity overflows into a flash chamber which is an overflow part, as the mold is closed. However, in the conventional compression molding using the overflow portion, a pair of molds are abutted around the cavity, so burrs are inevitably generated around the product.

In the so-called high-pressure injection molding, which has recently been particularly adopted, first, the cavity is filled with resin in a state where the mold is closed by a weak mold clamping force, and then the mold clamping force is increased to form a fixed mold. The movable mold and the mold are finally closed, and during this final mold closing, the resin is returned from the cavity to the molding material supply device such as a heating cylinder device through the gate, and then the gate is closed and then the cavity is closed. Of resin is compressed. Thereby, the weighing is performed in the mold. As described above, in the high-pressure injection molding, the resin in the cavity must be refluxed for in-mold measurement. However, if the gate is small, there is a problem that the resin in the cavity does not flow smoothly.

In addition, in the conventional high-pressure injection molding, when filling the cavity with the resin, the movable mold is retracted from the fixed mold by the pressure of the resin, and the error in the amount of the resin supplied from the molding material supply device is reduced. I try to absorb it. At this time, as a structure of the mold apparatus, for example, a movable plate that abuts the movable mold is provided on the fixed mold, and the movable plate is urged toward the movable mold by a spring with respect to the fixed mold. Then, in a state in which the mold is closed by a weak mold clamping force, the movable plate abuts against the movable mold, and a gap is formed between the movable plate and the fixed mold. In this state, when the cavity is filled with resin, the movable mold is retracted due to the pressure of the resin and the balance between the mold clamping force and the spring force.

However, when the movable mold is retracted as the cavity is filled with the resin, the spring loses its force and opens between the movable plate and the movable mold to leak the resin. There is a risk. Further, if the movable mold continues to retreat as described above, the entire cavity may not be filled with the resin. These are particularly problematic for thin-walled products such as IC cards.

[0007]

As described above, in the conventional injection molding, since the flowability of the molding material at the edge of the cavity is poor, dimensional characteristics are deteriorated at the peripheral portion of the product. There was a problem. In addition, particularly in high-pressure injection molding, if only a small gate is used to recirculate the molding material from the cavity, the molding material may not be smoothly recirculated, and the in-mold measurement may not be smoothly performed. At the same time, in the conventional high-pressure injection molding, since the mold is opened as the molding material is filled in the cavity, especially in the case of a thin product, there is a problem such as poor filling.

The present invention is intended to solve such a problem, and improves the fluidity of the molding material at the edge of the cavity, thereby improving the dimensional characteristics at the peripheral portion of the product. Another object of the present invention is to make it possible to perform injection molding of a thin-walled product without incomplete filling and the like by reliably performing in-mold measurement.

[0009]

Means for Solving the Problems The present invention, in order to achieve the above object, the cavity formed between the stationary mold and the movable mold to open and close to each other, through the gate into the material passage and cavity from the molding material supply device A filling step of filling the molding material, and finally after the completion of the filling step, the fixed mold
And a final mold closing step of closing the movable mold with each other. During the final mold closing step, after returning the molding material from the cavity to the material passage side through the gate, the gate is closed, and then the molding in the cavity is performed. In the injection molding method of a thin-walled product for compressing a material ,
A moving body is supported so as to be movable within a predetermined range in the mold opening and closing direction.
The moving body is urged toward the movable type, and
Between the moving body and the movable movable mold plate closed in
A material passage leading to the sprue is formed, and
And a movable die formed to communicate with the edge of the cavity.
-The bar flow section is formed by nesting fixed to a fixed mold
With a mold device for injection molding, the mold clamping force during the filling step is set to a size that does not open the mold due to the pressure of the molding material,
During the filling process, before Kio Bafuro portion molding material is flown from the cavity, it is to cut off each other and the cavity and the overflow portion during the final clamping step.

In the filling step, when the molding material is filled in the cavity for molding the thin-walled product, the gas and the molding material flow out from the edge of the cavity to the overflow portion, so that the edge of the cavity is formed. The fluidity of the molding material in the portion is improved, and the molding material is smoothly and satisfactorily filled up to the edge of the cavity. Also, in the filling step, the mold is not opened by the pressure of the molding material because the mold clamping force is set to be large to some extent, and therefore, the mold is opened by the pressure of the molding material,
It does not mean that the entire cavity is not filled with the molding material. In the subsequent final mold clamping step, the molding material in the cavity returns to the material passage side through the gate, or further flows out to the overflow portion, and the in-mold measurement is performed. After the gate is closed and the overflow portion and the cavity are shut off from each other, the molding material in the cavity is compressed.

[0011]

Hereinafter, an embodiment of the present invention will be described.
This will be described with reference to the drawings. First, the configuration of the injection molding die apparatus will be described. The product P formed by the die apparatus is a main body of an IC card which is a thin product (sheet-like member) as shown in FIG. This IC card is in the form of a flat plate having a thickness of about 1.2 mm, and has a flat surface on one side and a recessed IC on the other side.
A chip mounting portion P1 is formed. A recess P2 is further formed at the center of the IC chip mounting portion P1.

1 to 4, reference numeral 1 denotes a fixed mold as a first mold, and 2 denotes a movable mold as a second mold. The fixed mold 1 and the movable mold 2 move vertically in the drawing. To open and close each other to form a product-shaped cavity 3 therebetween when the mold is closed. Note that the thickness direction of the product P is matched with the mold opening and closing directions of the fixed mold 1 and the movable mold 2.

The fixed die 1 has a fixed mounting plate 6 mounted on a fixed platen (not shown) of an injection molding machine, and a fixed fixed to a surface of the fixed mounting plate 6 on the movable mold 2 side. And a side receiving plate 7. A locate ring 8 and a sprue bush 9 are fixed to the fixed-side mounting plate 6. This sprue bush 9
Is connected to a nozzle 10 of a heating cylinder device which is a material supply device provided in the injection molding machine. The inside is a sprue 11 which is a material passage.
And protrudes toward the movable mold 2 side.

On the movable mold 2 side of the fixed-side receiving plate 7,
A moving plate 16 as a moving body is supported so as to be movable in a predetermined range in the mold opening and closing direction. A sleeve 20 fixed by bolts 19 together with a stopper 18 on the movable mold 2 side of the fixed-side receiving plate 7 slidably penetrates the movable plate 16. The stopper 18 comes into contact with the movable plate 16 from the movable die 2 side, so that the movable plate 16 and the fixed-side receiving plate 7 of the fixed die 1 are fixed.
And the maximum gap between them, that is, the maximum opening amount. Further, a spring 21 which is a biasing means sandwiched between the fixed side mounting plate 6 and the moving plate 16 in a compressed state,
The moving plate 16 is biased toward the movable mold 2 with respect to the fixed-side mounting plate 6. The tip of the sprue bush 9 is slidably fitted in a through hole 22 formed in the movable plate 16.

The fixed mold 1 has a cylindrical first insert 26 fixed between the fixed-side mounting plate 6 and the fixed-side receiving plate 7. The second insert 27 is fixed between the fixed insert 26 and the fixed-side mounting plate 6. The first insert 26 protrudes toward the movable mold 2 through the fixed receiving plate 7 and slidably penetrates a through hole 28 formed in the movable plate 16. The distal end of the first insert 26 protruding from the movable plate 16 toward the movable mold 2 forms a first convex portion 29. In addition, the second nest 27
Penetrates through the inside of the first nest 26,
2nd convex part which protruded further to the movable mold 2 side than the convex part 29 of
Has made 30.

The movable die 2 has a movable mounting plate (not shown) mounted on a movable platen of an injection molding machine, and a movable receiving plate fixed to a surface of the movable mounting plate on the fixed mold 1 side. It has a plate (not shown) and a movable mold plate 36 fixed to a surface of the movable receiving plate on the fixed mold 1 side. The movable mold plate 36 abuts against the movable plate 16 on the fixed mold 1 side and closes. The movable mold plate 36 and the movable plate 16
A guide insert 37 is fixed to 16, and the movable mold plate 36 is formed with a through hole 38 into which the guide insert 37 is slidably fitted.

The fixed mold 1 is attached to the movable mold plate 36.
A first concave portion 41 is formed in which the first convex portion 29 is slidably and slidably fitted. Also, the first concave portion
A second concave portion 42 into which the second convex portion 30 of the fixed mold 1 is removably and slidably fitted is formed at a central portion of 41. The fitting surface between the first convex portion 29 and the first concave portion 41 and the fitting surface between the second convex portion 30 and the second concave portion 42 form a columnar surface parallel to the mold opening / closing direction. ing. First
Although a certain gap is set between the fitting surfaces of the convex portion 29 and the first concave portion 41 for gas venting, the second convex portion 30
There is almost no gap between the fitting surfaces of the first and second concave portions 42 so that burrs do not occur on the product P. The final product-shaped cavity 3 is formed by the second projection 30 and the second recess 42. That is,
The tip surface of the second convex portion 30 forms one surface of the product P, the bottom surface of the second concave portion 42 forms the other surface of the product P, and the inner peripheral surface of the second concave portion 42 Are formed.
An overflow portion 43 communicating with the edge of the cavity 3 is formed between the first convex portion 29 and the first concave portion 41 fitted to each other. The cavity 3 is cut off from the overflow portion 43 when the concave portion 42 is fitted. The overflow portion 43 is formed over the entire circumference of the cavity 3. Further, the volume of the overflow section 43 is larger than the volume of the cavity 3.

Further, a runner 46 is formed between the closed movable plate 16 and the movable mold plate 36 of the movable mold 2 as a material passage leading to the sprue 11. A gate 47 from the runner 46 to the cavity 3 is formed between the periphery of the projection 29 and the periphery of the second recess 42 of the movable mold 2. The gate 47 communicates with the overflow section 43, but the second convex section 30 and the second concave section
42 are closed by fitting each other. That is, the second convex portion 30 and the second concave portion 42 form gate opening / closing means for opening / closing the gate 47. In addition,
The force with which the spring 21 urges the movable plate 16 is set to a force that keeps the movable plate 16 and the movable mold 2 closed against the pressure of the resin R in the runner 46.

Next, an injection molding method using the mold apparatus will be described. The mold clamping device of the injection molding machine first closes the fixed mold 1 and the movable mold 2 with a relatively weak fixed clamping force. At this time, as shown in FIG.
16 and the movable mold 2 abut and close. On the other hand, fixed type 1
The fixed-side receiving plate 7 and the movable plate 16 are opened with a predetermined opening amount A1. That is, the mold clamping force and the force of the spring 21 are balanced. The first projection 29 of the fixed mold 1 is fitted in the first recess 41 of the movable mold 2, but the second projection 30 of the fixed mold 1 is fitted in the second recess 42 of the movable mold 2. The runner 46 and the cavity 3 are in communication with each other by the open gate 47, and the cavity 3 and the overflow portion 43 are in communication with each other. In this state, the molten thermoplastic resin R as a molding material is injected from the nozzle 10 of the heating cylinder device to the sprue 11. This resin R
Is filled into the cavity 3 from the sprue 11 through the runner 46 and the gate 47 or the overflow section 43 (filling step). At the time of this filling step, the air, the gas of the resin R, and the resin R flow from the cavity 3 to the overflow portion 43.
Leaked to The overflow section 43 does not have to be full.

In the filling step, since the mold clamping force is large enough to withstand the pressure of the resin R in the mold apparatus, the movable mold 2 does not recede.
The opening A1 between the fixed-side receiving plate 7 and the moving plate 16 is kept constant. If the movable mold 2 is retracted by the pressure of the resin R in the mold apparatus and the opening between the fixed-side receiving plate 7 and the moving plate 16 increases, the force of the spring 21 is lost, and the movable plate 16 moves with the movable plate 16. There is a possibility that the gap between the side mold plate 36 and the resin R leaks. Also, when the movable mold 2 continues to retreat as described above,
There is a possibility that the entire cavity 3 is not filled with the resin R. These are particularly problematic for thin-walled products such as IC cards. However, in the present embodiment, even when the IC card is formed, the opening amount A1 between the fixed receiving plate 7 and the movable plate 16 is kept constant, as described above, and the movable plate 16 and the movable There is no problem such as a gap between the two and there is no problem of poor filling. On the other hand, when the resin R flows out of the cavity 3 to the overflow section 43, an error in the amount of the resin R injected from the injection molding machine is absorbed.

After the completion of the filling step, the mold clamping device increases the clamping force, and the fixed mold 1 and the movable mold 2 are finally closed (final mold clamping step). In the final mold clamping step, the fixed mold 1, the movable plate 16 and the movable mold 2 are closed. Accordingly, the excess resin R in the cavity 3 is removed from the gate which is still open.
Returning from 47 to the runner 46, the resin in the mold apparatus returns to the heating cylinder apparatus. Alternatively, the excess resin R in the cavity 3 further flows out to the overflow section 43.
Then, as shown in FIG. 2, when the second convex portion 30 of the fixed mold 1 starts to be fitted into the second concave portion 42 of the movable mold 2, the gate 47 closes, and the cavity 3 and the overflow portion 43 move together. It is shut off, and at this point, a certain amount of the resin R remains in the cavity 3 (a measuring step).

Thereafter, as shown in FIG. 3, the fixed-side receiving plate 7 and the moving plate 16 are closed until they abut against each other, and accordingly, the resin R in the cavity 3 is pressurized and compressed (compression step). . The compression amount is equal to the opening amount A2 between the fixed receiving plate 7 and the moving plate 16 at the end of the measuring step. This compression step increases the density of the product and compensates for shrinkage due to solidification of the resin R due to cooling. Therefore,
For this compensation, it is not necessary to perform the pressure holding step on the heating cylinder device side.

After the resin R in the cavity 3 is sufficiently cooled and solidified, the fixed mold 1 and the movable mold 2 are opened by the mold clamping device. Accordingly, the resin in the cavity 3, that is, the product P and the resin R solidified in the sprue 11, the runner 46, and the overflow portion 43 first leave the fixed mold 1. Next, a runner ejecting pin (not shown) provided on the movable mold 2 ejects the resin R solidified in the sprue 11, the runner 46 and the overflow section 43 to release the resin R from the movable mold 2, and to the movable mold 2 side. A provided product ejecting pin (not shown) projects the product P and releases the product P from the movable mold 2. Further, the resin R solidified in the sprue 11, the runner 46 and the overflow section 43
After the product P is taken out, the mold is closed again, and the above steps are repeated.

As described above, according to the structure of the above embodiment, the resin R is allowed to flow out of the cavity 3 to the overflow section 43 during the filling step, thereby absorbing the error in the amount of the resin R supplied from the injection molding machine. In addition, since the in-mold measurement is performed in the subsequent measurement process, the amount of the resin filled in the cavity 3 can be accurately controlled, and the resin R in the cavity 3 can be compressed by the subsequent compression process. Together with this, it is possible to form a high-precision product P with stable quality.

Further, the flowability of the resin R at the edge of the cavity 3 is improved by the overflow portion 43.
Even when molding an IC card which is a thin product, the resin R is smoothly and satisfactorily filled up to the edge of the cavity 3. Thereby, it is possible to reduce the residual stress and strain at the peripheral portion of the product P and improve the dimensional characteristics at the peripheral portion of the product P. In addition, since the resin R flows out smoothly from the cavity 3 during the measuring step, the in-mold measurement can be reliably performed. Furthermore, since the gas vent can be performed by using the overflow portion 43 that is finally shut off from the cavity 3, reliable gas vent can be performed.

Moreover, since the overflow portion 43 is formed over the entire circumference of the cavity 3, the flowability of the resin R is enhanced over the entire circumference of the cavity 3, which is more effective. Furthermore, since the volume of the overflow section 43 is larger than the volume of the cavity 3, the flowability of the resin R from the cavity 3 to the overflow section 43 is not impaired by the overflow section 43 being in a full state. 43 effects can be reliably demonstrated.

Further, an overflow portion 43 is formed by fitting a first convex portion 29 provided on the fixed mold 1 into a first concave portion 41 provided on the movable mold 2, and provided on the first convex portion 29. The second
The convex portion 30 is fitted into the second concave portion 42 provided in the first concave portion 41 to shut off the overflow portion 43 and the cavity 3, so that burrs are generated at the edge of the product P. Can be prevented and no post-processing is required.

Since the overflow portion 43 is formed not by the movable plate 16 but by the insert 26 fixed to the fixed die 1, the pressure of the resin R applied to the overflow portion 43 is fixed to the fixed die 1 (fixed side mounting). Received by board 6),
Accordingly, it is possible to prevent the movable plate 16 and the movable mold 2 from opening due to the pressure of the resin R.

It should be noted that the present invention is not limited to the above embodiment, and various modifications can be made. For example,
In the above embodiment, a runner is provided between the movable mold 2 and the moving plate 16.
Although 46 is formed, for example, if the gate can be of a direct gate type, it is not necessary to form the material passage by a moving body such as a moving plate. In particular, in this case, the moving body can be provided not on the fixed type but on the movable type. Contrary to the above embodiment, a first convex portion forming an overflow portion is provided on a movable mold,
May be provided in a fixed mold. Further, a second convex portion that blocks the overflow portion and the cavity may be provided in the first concave portion, and the second concave portion may be provided in the first convex portion.

The product to be molded is not limited to an IC card, and the present invention can be applied to molding of thin products having various shapes. Further, in the above embodiment, the injection molding of a thermoplastic resin is described as an example. However, the present invention relates to injection molding of ceramics using a thermoplastic resin as a binder, injection molding powder metallurgy, or thermosetting resin. It can be applied to injection molding of various molding materials such as injection molding.

[0031]

According to the present invention, after the filling step of filling the cavity with the molding material, the molding material is returned from the cavity to the material passage side during the final mold clamping step of finally closing the mold. Then, in the injection molding method of closing the gate and then compressing the molding material in the cavity, the mold clamping force during the filling step is set to a size that does not open the mold due to the pressure of the molding material, and during the filling step, the mold The molding material flows out of the cavity into the overflow portion formed between the bodies and leading to the edge of the cavity, and the cavity and the overflow portion are mutually shut off during the final mold clamping process, so that molding at the edge of the cavity is performed. The fluidity of the material is improved, which can improve dimensional characteristics at the periphery of the product,
In-mold measurement can be performed reliably, and thin-walled products can be favorably injection-molded without causing poor filling. Also, over
The flow part is formed by nesting fixed to a fixed mold
The movable body and the movable mold are opened by the pressure of the resin.
Can be suppressed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold apparatus used in an example of the injection molding method of the present invention, showing a filling step.

FIG. 2 is a cross-sectional view when the gate is closed during the final mold clamping step.

FIG. 3 is a cross-sectional view at the end of the final mold clamping step.

FIG. 4 is a plan view showing the vicinity of a cavity of the movable die.

FIG. 5 is a perspective view of an IC card to be molded.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixed type 2 Movable type 3 Cavity 6 Fixed side mounting plate 7 Fixed side receiving plate 11 Sprue (material passage) 16 Moving plate (moving body) 26 Insert 36 Moving side mold plate 43 Overflow part 46 Runner (material passage) 47 Gate R resin (molding material)

Claims (1)

(57) [Claims] 1. A filling step of filling a molding material into a cavity formed between a fixed mold and a movable mold that open and close with each other through a gate from a molding material supply device to a material passage and a cavity, and a final step after completion of the filling step. Fixed type
And a final mold closing step of closing the movable mold with each other. During the final mold closing step, after returning the molding material from the cavity to the material passage side through the gate, the gate is closed, and then the molding in the cavity is performed. In the injection molding method of a thin-walled product for compressing a material ,
A moving body is supported so as to be movable within a predetermined range in the mold opening and closing direction.
The moving body is urged toward the movable type, and
Between the moving body and the movable movable mold plate closed in
A material passage leading to the sprue is formed, and
And a movable die formed to communicate with the edge of the cavity.
-The bar flow section is formed by nesting fixed to a fixed mold
With a mold device for injection molding, the mold clamping force during the filling step is set to a size that does not open the mold due to the pressure of the molding material,
During the filling process, before Kio Bafuro portion molding material is flown from the cavity, the injection molding method of thin-walled products, characterized by blocking each other with said cavity and the overflow portion during the final clamping step.