JP3328140B2 - Injection molding method for partially ultra-thin molded products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for injection-molding a partially ultra-thin molded article, and more particularly to a method for molding a part of the molded article with a thickness of 0.15.
The present invention relates to an injection molding method for a partially ultra-thin molded product having an ultra-thin portion of less than mm.

[0002]

2. Description of the Related Art Molten resin injected and filled into a molding space (cavity) of a mold becomes harder to flow as the cross-sectional area of the flow path of the molten resin becomes smaller, and varies depending on the type of resin. The thickness is 0. When it becomes about several mm,
The molten resin does not completely spread to each of the thin portions.

[0003] Therefore, a part of the molded article is reduced to 0. After injecting and filling the molten resin into the molding space (cavity) of the mold in order to reduce the thickness to about several mm, a predetermined portion of the resin in the molding space is compressed by, for example, a compression core before the resin is solidified. There is known a partial compression molding method in which a thin portion is obtained by compression. However, even with such a partial compression molding method, the thickness of the thin portion that can be achieved is about 0.3 mm.
16 mm was the limit.

Recently, there has been a demand for a partially ultra-thin molded product in which a part of a molded product has an ultra-thin portion of less than 0.15 mm, as electronic devices have become smaller and more sophisticated. An example of such a partially ultra-thin molded product is a card base of a small memory card called a stamp size memory card.

FIG. 8 is a perspective view showing an example of a card base for the small memory card (stamp size memory card). In the figure, reference numeral 50 denotes a thin card base having a size of 45 × 37 mm in length and width and a thickness S.
1 (the thickness S1 of the main portion) is S1 = 0.8 mm. An ultra-thin portion 51 (having a vertical and horizontal dimension of 22 × 14 mm) whose thickness S3 is S3 = 0.13 mm is provided at an intermediate portion of the card base 50 at one side in the longitudinal direction. Around the thin portion 51, the thickness S2 is S
A thin portion 52 of 2 = 0.4 mm is provided.
A flash memory or the like is mounted on the ultra-thin portion 51, and when the memory card is completed as a small memory card, its overall thickness is 0.8 mm.

It is difficult to manufacture the card base 50 having the ultra-thin portion 51 having the thickness S3 = 0.13 mm as described above by ordinary injection molding without partial compression. FIG. 9A shows a mold molding space (cavity) 61A having the same shape as the shape of the card base 50 shown in FIG.
When the molten resin is injected and filled into the mold molding space 61A from the gate 62, as shown in FIG. 9B, the molten resin 63 (shown with dots in the figure) is changed to an ultra-thin portion. It does not reach the formation planned area (space of thickness 0.13 mm) 64 at all. Of course, under extremely high-speed and high-pressure conditions exceeding the injection conditions of normal injection molding, the ultra-thin portion forming scheduled region 64 is formed.
Although it is possible to force the molten resin 63 into the mold, it is difficult to achieve a good product by increasing the internal distortion of the molded product, and the injection mechanism must be extremely large.

Therefore, the thickness S3 =
It is conceivable to manufacture a card base 50 having an ultra-thin portion 51 of 0.13 mm. FIGS. 10 and 11 are views showing a method of forming the card base 50 by a conventional partial compression technique.

That is, as shown in FIG.
Before the injection and filling of the molten resin, the molding space (cavity) 61B is set such that the minimum thickness of the molding space is S2 = 0.4 mm. In this state, the molten resin 63 is injected and filled from the gate 62 into the mold molding space 61B. In this case, as shown in FIG. 10 (b), the molten resin 63 is still completely distributed in the thin space in the mold molding space 61B depending on the size of the thin space. Often not. So in such a case,
Under a condition of a higher speed and a higher pressure than the injection condition of the normal injection molding, the molten resin 63 is forced into all of the inside of the mold molding space 61B slightly.

Next, before the resin 63 in the molding space 61B is solidified, the compression core 65 is driven forward to compress a predetermined portion of the resin 63 as shown in FIG. Attempt to form a part that matches the ultra-thin part. Such a method is a molding method of the card base 50 by a conventional partial compression method.

[0010]

However, in the molding method using the partial compression technique according to the prior art described above,
It is difficult to achieve the above-mentioned S3 = 0.13 mm as the thickness of the ultra-thin portion by the compression / indentation by the compression core 65, and a value exceeding S3 = 0.13mm (for example, 0.16mm) is inevitable. Value). This is because the compression is performed by the compression core 65 after completely injecting and filling the resin 63 into the mold molding space 61B. In other words, the skin layer immediately formed on the outer peripheral side of the filled resin is formed. This is because the compression is performed by the compression core 65 when the outer solidified film, referred to as “the outer solidified film” grows considerably, becomes difficult to compress to the target thickness due to the resistance of the skin layer.

The molten resin 63 injected into the molding space 61B has a portion having a small flow resistance (the S1).
= 0.8 mm space) (the space where the flow resistance is large) (the space of the S2 = 0.4 mm) is filled last, so as shown in FIG. A weld line 66 is inevitably generated in the ultra-thin portion 51 'compressed by the core 65. However, if the weld line 66 is present in the ultra-thin portion 51 'which is extremely thin and has the smallest mechanical strength, a fatal problem that a crack is easily generated from the weld line 66 due to impact or the like also occurs. .

[0012] Therefore, a technical problem to be solved by the present invention is to solve the above-mentioned problems of the prior art.
mm (for example, a thickness of 0.13 m
m ultra-thin part) to make a part ultra-thin molded product easy
It is to make molding possible. Another object of the present invention is to make it possible to mold a partially ultra-thin molded product without generating weld lines in the ultra-thin portion.

[0013]

In order to achieve the above-mentioned object, the present invention relates to a molded article having a main part having a thickness of S1.
Part is an ultra-thin part having a thickness S3 of less than S3 = 0.15 mm.
The thickness S2 of the periphery of the ultra-thin portion is S2 = 0.2 mm.
Partial ultra-thin molding with a thin portion where S2 <S1
In the injection molding method for products, the overall thickness is uniform at S1
Inject and fill the molten resin into the mold molding space
Before the filling of the molten resin in the mold molding space is completed
Then, the first partial compression mechanism is driven to move the inside of the mold forming space.
The skin layer compresses a predetermined part of the ungrown molten resin.
Thus, the ultra-thin portion is formed, and then the mold
After the filling of the molding resin with the molten resin is completed, the second partial pressure
Drive the compression mechanism to remove the unsolidified resin around the ultra-thin wall.
Compression, thereby forming said thin section, and so on.
It is.

[0014]

[0015]

Embodiments of the present invention will be described below in detail with reference to the drawings. 1 to 3 show one embodiment of the present invention.
It is a schematic operation explanatory view of the injection molding method of the partially ultra-thin molded article according to the embodiment, (a) of each figure shows a cross section of a main part of a mold mechanism, and (b) of each figure shows each figure. 3A shows a resin plane in a mold molding space corresponding to FIG.

This embodiment is an application example for molding a card base 50 for a small memory card (stamp size memory card) shown in FIG. 8 and described above. I omit it.

1 to 3, reference numeral 1 denotes a fixed mold, 2
Is a movable mold, PL is a mold release surface, 3 is a mold molding space (cavity) formed by both molds 1 and 2 in a mold clamped state,
4 is a gate, 5 is a first compression core having a rectangular cross section provided on the movable mold 2, 6 is a second compression core having a rectangular cross section provided on the movable mold 2, 7 is It is a molten resin (resin). Note that the first compression core 5 and the second compression core 6 are 2
It has a heavy structure.

Before injection after mold clamping, the mold mechanism is in the state shown in FIG. 1A, and the first and second compression cores 5 and 6 are in the retracted position, and The entire molding space 3 is set to the uniform thickness S1 = 0.8 mm.

Then, when the injection start timing is reached, the molten resin 7 is injected from the gate 4 into the mold molding space 3,
The molten resin 7 starts to be filled in the molding space 3. At this time, since the molding space 3 is set as a relatively thick space having a uniform thickness, the flow path resistance is small, and the molten resin 7 is smoothly and quickly filled into the molding space 3. By providing a single gate 4 at an appropriate position with respect to the molding space 3, the junction of the molten resin 7 does not occur in the molding space 3 (that is, a weld line does not occur). Considered.

Injection of molten resin 7 into mold space 3
As the filling progresses, the molten resin 7 completely spreads over the ultra-thin portion forming region for forming the above-mentioned ultra-thin portion 51,
Further, at a predetermined timing before the injection and filling of the molten resin 7 into the mold molding space 3 are completed, FIG.
As shown in (1), the first compression core 5 is driven forward by a predetermined amount. Thereby, the molten resin 7 in which the skin layer in the region where the ultra-thin portion is to be formed is not grown is compressed by the first compression core 5, and the ultra-thin portion 51 having the thickness S3 = 0.13 mm is formed. It is formed. Thus, the thickness S3 = 0.
The reason why partial compression is possible to an ultra-thin wall thickness of 13 mm is because the skin layer compresses the ungrown molten resin 7 as described above, so that resistance from the resin is relatively small.
Thereby, the thickness S3 = 0.1 which could not be achieved in the past.
Partial compression up to 3 mm is possible, and good thickness dimensional accuracy of the ultra-thin portion 51 can be ensured. Furthermore, since no weld line is generated in the ultra-thin portion 51,
There is no danger that the ultra-thin portion 51 will crack.

Along with the partial compression by the first compression core 5 described above, the final step of injection and filling proceeds, and the molten resin 7 completely spreads to every corner in the mold molding space 3, whereby the injection is completed.・ Filling is completed. Immediately after this, the second compression core 6 is driven forward by a predetermined amount, whereby the unsolidified resin 7 around the previously formed ultra-thin portion 51 is compressed by the second compression core 6. And the thickness S2 = 0.4 described above.
The thin portion 52 of mm is formed. The partial compression by the second compression core 6 can be easily and easily achieved even after the injection and filling are completed because the compression is only performed to the thickness S2 = 0.4 mm, which was easily attainable even in the past. Is done. In the present embodiment, S2 is set to 0.4 mm. However, it is of course possible to set S2 to a value of about 0.2 mm which can be reliably achieved by conventional partial compression.

Next, a mold mechanism used in the injection molding method of the partially ultra-thin molded article of the present embodiment will be described with reference to FIGS. 4 to 6 are views showing the configuration of a mold mechanism of an injection molding machine for molding a partially ultra-thin molded product. FIG. 4 shows the state of FIG. 1 and FIG. 5 shows the state of FIG. FIG. 6 corresponds to the state shown in FIG.

4 to 6, reference numeral 11 denotes a fixed die plate, 12 denotes a fixed die (corresponding to the fixed die 1) attached to the fixed die plate 11, 13 denotes a movable die plate, and 14 denotes a movable die plate. A movable mold (corresponding to the movable mold 2) attached to the die plate 13 and a first compression core 15 capable of moving forward and backward by a predetermined amount with respect to the movable mold 14 (the first compression core). 16 corresponds to the movable mold 1
A second compression core (corresponding to the second compression core 6) that can move forward and backward by a predetermined amount with respect to the fourth compression core 4.

The movable die plate 13 is configured to be able to move forward and backward with respect to the fixed die plate 11 by a mold opening / closing drive source and a mold opening / closing drive mechanism (not shown). A compression servomotor (electric servomotor for compression) 17 is mounted on the movable die plate 13.
The rotation of the motor 17 is transmitted to a pulley 18 via a timing belt (not shown). Reference numeral 19 denotes a rotation holder which is rotatably held on the movable die plate 13 via a bearing. The pulley 18 and the nut body 20 are integrally connected to the rotation holder 19. Reference numeral 21 denotes a ball screw shaft screwed to the nut body 20, which is driven forward and backward by the nut body 20.

Reference numeral 22 denotes a toggle link mechanism mounted on the movable die plate 13. One end 22a of the link is pivotally supported on the movable die plate 13, and the other end 22b of the link.
Are supported by a compression plate 23. One end of a ball screw shaft 21 is integrally connected to the crosshead 22 c of the toggle link mechanism 22.
The toggle link mechanism 22 is driven by the forward / backward movement, and thereby the compression plate 23 is driven forward / backward.

Reference numeral 24 denotes a first compression bar whose one end is integrally connected to the compression plate 23.
The other end of 4 is inserted so as to be able to move forward and backward in the movable mold 14 so that the first compression core 15 can be driven forward. Reference numeral 25 denotes a second compression bar having one end integrally connected to the crosshead 22c.
The other end of the compression bar 25 is inserted in the movable mold 14 so as to be able to move forward and backward, so that the second compression core 16 can be driven forward. That is, the first compression bar 24 is connected to the output side of the toggle link mechanism 22 and applies a force corresponding to the enlargement ratio of the toggle mechanism to the first compression core 1.
5, the second compression bar 25 is connected to the toggle link mechanism 2
2 and is applied to the second compression core 16 with the same force as the input side of the toggle link mechanism 22.

Next, the operation of the above-described mold mechanism will be described. Before the injection after the mold clamping, the mold mechanism is in the state shown in FIG. 4, and the mold molding space (cavity) at this time is set so that the entire thickness is equal to the thickness S1 = 0.8.
mm, and the first and second compression cores 15, 16 are in the retracted position. Although not shown, the first and second compression cores 15 and 16 are provided with a biasing behavior in the right-hand direction in the drawing by spring force, and the distal ends of the first and second compression cores 15 and 16 are provided. The surface is flush with the release surface PL.

In the above state, when the injection start timing in the molding cycle is reached, the injection and filling of the molten resin into the mold is started by an injection mechanism (not shown) using an electric servomotor as an injection drive source. As a result, the molten resin starts to be filled into the molding space from the gate (not shown). The electric servomotor as the above-mentioned injection drive source is controlled by feedback control so that the actually measured speed value of the injection / filling process follows the set speed value. , Injection resin speed) is precisely controlled.

The injection / filling process based on the above-mentioned speed feedback control proceeds, and the molten resin completely spreads over the region where the ultra-thin portion 51 is to be formed for forming the ultra-thin portion 51. Measured stroke information (actual rotation amount information) from the injection control system is reached at a predetermined timing before the injection and filling of the molten resin into the space is completed.
When the compression control system recognizes the compression control system, the compression control system rotates the compression servomotor 17 by, for example, speed feedback control, and advances the crosshead 22c through the pulley 18, the nut body 20, and the ball screw shaft 21, and As a result, the toggle link mechanism 22 is driven in the direction in which it is stretched. In addition, the drive of the toggle link mechanism 22 by the compression servomotor 17 can have a good response. However, when the mechanical delay is in an unacceptable range, the timing for starting the compression servomotor 17 is determined. It is only necessary to advance the mechanical delay time.

As shown in FIG. 5, the compression servomotor 1
7, when the toggle link mechanism 22 is driven in the direction in which the first compression bar 2 extends, the first compression bar 2
4 is driven forward, and the first compression core 15 is driven forward, whereby the molten resin in which the skin layer in the region where the ultra-thin portion is to be formed is not grown is compressed by the first compression core 15. The ultra-thin portion 51 having the thickness S3 = 0.13 mm is formed. In the present embodiment, the pushing operation of the first compression core 15 by the first compression bar 24 is completed at a point where the toggle link mechanism 22 is completely extended (that is, a dead point). To obtain a greater compression force. That is, compared to the forward stroke of the crosshead 22c, the first compression bar 24
Although the forward stroke is extremely small, the partial compression by the first compression core 15 is performed at a timing at which the greatest force is obtained by the expansion rate of the toggle link force.

By doing so, it is possible to compress the molten resin in which the skin layer is not grown, and to realize the toggle link mechanism 2.
2, the thickness S3 = 0.13, which could not be achieved in the past,
The ultra-thin portion 51 mm can be reliably and easily formed, and it is not necessary to use a large and expensive drive source having power as a drive source for the compression mechanism.

Along with the partial compression by the first compression core 15 described above, the final stroke of injection and filling is in progress.
At the timing when the partial compression by the compression core 15 is substantially completed, the molten resin 7 completely spreads to every corner in the mold molding space, and the injection and filling are completed. This state is shown in FIG. 5, and thereafter, the compression head 17 drives the crosshead 22c forward by a predetermined amount.
When the crosshead 22c is driven forward from the state shown in FIG. 5, as shown in FIG. 6, the second compression core 16 is driven forward by a predetermined amount by the second compression bar 25 directly connected to the crosshead 22c. As a result, the unsolidified resin around the previously formed ultra-thin portion 51 is removed from the second compression core 16.
To form the thin portion 52 having the thickness S2 = 0.4 mm.

The above-mentioned partial compression by the second compression core 16 can be achieved easily in the past by the thickness S2 = 0.4.
mm, the pressing force of the second compression core 16 via the second compression bar 25 directly connected to the crosshead 22c, that is, without using the expanded force of the toggle link mechanism 22. Even so, partial compression up to the thickness S2 = 0.4 mm can be reliably and easily achieved. During the partial compression operation by the second compression core 16, the toggle link mechanism 22 is operated by the advance of the crosshead 22 c, and the operation after the dead point causes the first compression bar 24 to retreat very slightly. However, the amount of retreat is set at 0. Several mm
Since the value is several orders of magnitude smaller than the forward stroke, there is no problem.

In the above description, the partial compression operation by the second compression core 16 uses the forward force of the crosshead 22c that causes the toggle link mechanism 22 to operate after the dead point. The partial compression operation by the core 16 may use the forward force of the crosshead 22c that causes the toggle link mechanism 22 to perform an operation before the dead point. In this way, even during the partial compression operation by the second compression core 16, the first compression bar 24 is slightly advanced due to the operation of the toggle link mechanism 22 near the dead point. As described above, in the vicinity of the dead point, the crosshead 22c is set at 0. Since the amount of advance of the first compression bar 24 is smaller by several orders of magnitude than the stroke of advance by several mm, the thickness accuracy of the ultra-thin portion 51 is not impaired, and there is no problem.

FIG. 7 is a simplified explanatory diagram of the injection and compression control system of this embodiment. In the figure, 17 is the compression servomotor, 31 is the compression servomotor 17.
A pulse generator for detecting the number of revolutions of the motor; 32, a motor control circuit for driving the compression servomotor 17 by feedback control; 33, a servomotor for injection (electric servomotor for injection); A pulse generator 35 for detecting the number of revolutions is a motor control circuit for driving the injection servomotor 33 by feedback control.

The motor control circuit 35 has a preset speed setting value for the injection / filling process and the pulse generator 3
4 is input, and the motor control circuit 35 controls the injection servomotor 33 so that the measured speed value obtained by appropriately calculating this measurement information follows the set speed value. Drive by control. Thereby, the advance speed (in other words, the injection resin speed) and the position of the screw (not shown) of the injection mechanism are precisely controlled.

The measurement information from the pulse generator 34 is also input to the motor control circuit 32, whereby the motor control circuit 32 recognizes the advance position of the screw (not shown) of the injection mechanism and advances the screw. It is determined whether or not the position (that is, the degree of filling of the molding resin 17 with the molten resin) has reached a preset compression start timing. When the compression start timing is reached, the drive of the compression servomotor 17 is started. I do. Motor control circuit 32
, A preset speed setting value of the compression stroke and measurement information from the pulse generator 31 are input, and an actual measurement speed value obtained by appropriately calculating the measurement information follows the set speed value. Thus, the motor control circuit 32 drives the compression servomotor 17 by speed feedback control. As a result, the forward speed and position of the crosshead 22c are precisely controlled.

As described above, in the present embodiment, the injection servo motor 33 executes the injection stroke by feedback control, and refers to the injection stroke information in the injection stroke that is precisely controlled, and the compression servo motor 17 Since the partial compression process is started, as described above, the ultra-thin portion 51 is reliably formed without losing the timing at which the skin layer compresses the ungrown molten resin. It becomes possible.

[0039]

As described above, according to the present invention, a part of the molded product is formed into an ultra-thin portion having a thickness of less than 0.15 mm (for example, an ultra-thin portion having a thickness of about 0.13 mm). It is possible to provide a partially ultra-thin molded product that can easily and surely mold an ultra-thin molded product and that does not generate weld lines in the ultra-thin portion.

[Brief description of the drawings]

FIG. 1 is a schematic operation explanatory view of an injection molding method for a partially ultra-thin molded article according to one embodiment of the present invention.

FIG. 2 is a schematic operation explanatory view of an injection molding method for a partially ultra-thin molded article according to one embodiment of the present invention.

FIG. 3 is a schematic operation explanatory view of an injection molding method for a partially ultra-thin molded article according to one embodiment of the present invention.

FIG. 4 is an explanatory view showing a configuration of a mold mechanism of an injection molding machine used for an injection molding method for a partially ultra-thin molded article according to one embodiment of the present invention.

FIG. 5 is an explanatory view showing a configuration of a mold mechanism of an injection molding machine used for an injection molding method of a partially ultra-thin molded article according to one embodiment of the present invention.

FIG. 6 is an explanatory view showing a configuration of a mold mechanism of an injection molding machine used in an injection molding method for a partially ultra-thin molded article according to one embodiment of the present invention.

FIG. 7 is a simplified explanatory diagram of an injection and compression control system of an injection molding machine used in an injection molding method for a partially ultra-thin molded article according to one embodiment of the present invention.

FIG. 8 is a perspective view showing an example of a card base for a small memory card (stamp size memory card).

FIG. 9 is an explanatory diagram in a case where the card base of FIG. 9 is manufactured by ordinary injection molding.

FIG. 10 is an explanatory diagram of a case where the card base of FIG. 9 is manufactured by injection molding using a conventional partial compression method.

FIG. 11 is an explanatory diagram of a case where the card base of FIG. 9 is manufactured by injection molding using a conventional partial compression method.

FIG. 12 is a plan view of a card base for explaining problems according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 12 Fixed-side mold 2, 14 Movable-side mold 3 Mold forming space (cavity) 4 Gate 5, 15 First compression core 6, 16 Second compression core 7 Molten resin (resin) 11 Fixed Die plate 13 Movable die plate 17 Compression servo motor 18 Pulley 20 Nut body 21 Ball screw shaft 22 Toggle link mechanism 22c Crosshead 23 Compression plate 24 First compression bar 25 Second compression bar 31, 34 Pulse generator 32 Compression servo Motor control circuit for motor 33 Servo motor for injection 35 Motor control circuit for servo motor for injection

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B29C 45/56 B29C 45/66 B29C 45/80

Claims (3)

(57) [Claims] 1. A part of a molded product having a thickness S1 of a main part thereof is an ultra-thin portion having a thickness S3 of less than 0.15 mm, and the periphery of the ultra-thin portion is S2 = S2 = 0.2mm
This is an injection molding method for a partially ultra-thin molded product having a thin portion where S2 <S1. The molten resin is injected and filled into a mold molding space having a uniform overall thickness in S1. At a point in time before the filling of the molten resin into the molding space, the first partial compression mechanism is driven to compress the predetermined portion of the ungrown molten resin by the skin layer in the molding space, Thereby, the ultra-thin portion is formed. Next, after the molten resin is completely filled in the mold molding space, the second partial compression mechanism is driven to drive the unsolidified portion around the ultra-thin portion. A method for injection-molding a partially ultra-thin molded article, comprising compressing a resin to form the thin portion. 2. An injection servo motor according to claim 1, wherein the injection drive source is an electric servomotor, the injection process is executed by feedback control, and the drive source of the first and second partial compression mechanisms is an electric servomotor. A partial compression stroke is started upon recognizing that the forward movement position of the first member has reached a position corresponding to a preset compression start timing, wherein the injection molding method of a partially ultra-thin molded article is performed. 3. The first and second partial compression mechanisms according to claim 1, wherein the first and second partial compression mechanisms include a common electric servomotor and a toggle link mechanism, and at least the super-force is generated by a compression force expanded by the toggle link mechanism. An injection molding method for a partially ultra-thin molded article, characterized in that a thin part is formed.