JP2009061767A - Injection press molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that air remaining in a cavity does not quickly escape from a tiny vent hole between parting surfaces not to perform good injection charging in injection press molding and that solid mass contained in gas adheres to a gap and the vent hole of a metallic mold to clog or narrow the vent hole or the like. <P>SOLUTION: In an injection press molding method where a molten resin M is injected from an injection device 3 in a state where a movable metallic mold 22 is slightly parted from a fixed metallic mold 40, injection of the molten resin M is started in a state where the cavity 36 is opened outside and is not completely formed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an injection press molding method for injecting molten resin from an injection device in a state where a movable mold is slightly separated from a fixed mold.

The injection press molding method is a molding method in which a molten resin is injected from an injection apparatus in a state where a movable mold is slightly separated from a fixed mold. Therefore, the injection press molding method can inject and fill the molten resin satisfactorily from the gate to the end far from the gate by reducing the flow loss in the cavity even for a thin molded product such as a light guide plate. In addition, the injection press molding method can inject molten resin at a relatively low speed and low pressure compared to the case of injection filling into a cavity having a narrow interval by injection molding, so an injection device having a high speed injection capability is not required. . Furthermore, in normal injection molding, for the type that cuts the gate, the holding pressure cannot be applied from the injection device after the gate is cut. However, in the injection press molding method, the molten resin in the cavity is pressurized after the gate is cut and cooled and solidified. It has the advantage that it can accommodate shrinkage.

However, in the injection press molding method, since the volume in the cavity is enlarged at the time of injection, there is a point that the amount of air that must be excluded from the cavity by injection of the molten resin is larger than in normal injection molding. In the normal injection press molding method, the air in the cavity is discharged to the outside of the mold from a slight gap between the vent hole provided on the parting surface and the mold. However, even if the vent hole is provided, the air discharged from the cavity is not quickly discharged due to the flow resistance at the vent hole portion, so that the advance speed of the molten resin in the cavity is reduced. there were. Further, if the vent hole is enlarged in order to solve this problem, there is a problem that molten resin enters the vent hole, resulting in burrs and poor parallelism. There is also a method of vacuum suction inside the cavity, which increases the cost of the device and increases the cost. In addition, extra time is required for vacuum suction after forming the cavity, so the molding cycle time is extended. There was a problem of being.

Therefore, in the conventional injection press molding method, a thin article is molded as described in Patent Document 1 with a plate thickness of 1.2 mm, Patent Document 2 with a cavity thickness of 4 mm, and Patent Document 3 as not described. Attempting to do so could result in underfilling at the end far from the gate. Also, in the conventional injection press molding method, even if the molten resin is sent to the end of the cavity and molding is completed, the gas sent simultaneously with the molten resin during injection forcibly enters the gap between the vent hole and the mold from the cavity. As a result, there is a problem that solids contained in the gas adhere to the gaps and the vent holes and block the vent holes and the like. For this reason, there has been a problem that the parts of the mold must be disassembled to frequently perform cleaning work.

JP 2000-218654 A (0024, FIG. 1) JP 2000-233428 A (0007, Table 1, Table 2) Japanese Patent Laid-Open No. 2003-145593 (0001, FIG. 1)

In the present invention, in view of the above problems, in the injection press molding method in which the molten resin is injected from the injection apparatus in a state where the movable mold is slightly separated from the fixed mold, the cavity of the fixed mold is formed at the time of injection. If the gap between the surface and the cavity forming surface of the movable mold is narrow, the molten resin will be insufficiently injected and filled to the end of the cavity due to pressure loss, or the air remaining in the cavity will have a slight vent hole between the parting surfaces It is an object of the present invention to provide an injection press molding method that can solve the shortage of injection filling due to the fact that the flow rate of the injected molten resin is weakened in the cavity. In addition, as a result of the gas sent simultaneously with the molten resin entering the gap between the vent hole and the mold from the cavity, the solid matter contained in the gas adheres to the gap and the vent hole and closes the vent hole or the like. It is an object of the present invention to provide an injection press molding method that can eliminate the problem of endangering.

The injection press molding method according to claim 1 of the present invention is the injection press molding method in which the molten resin is injected from the injection device in a state where the movable mold is slightly separated from the fixed mold. The injection of the molten resin is started in a state in which the resin is not completely formed. According to a second aspect of the present invention, in the first aspect, the position of the movable mold is detected and the mold opening / closing / clamping mechanism is controlled so that the cavity is opened to the outside and not completely formed. To start injection of the molten resin. Further, a third aspect of the present invention is characterized in that, in the second aspect, after the injection of the molten resin is started, the movable mold is moved toward the fixed mold by a predetermined trigger. Further, according to a fourth aspect of the present invention, in any one of the first to third aspects, the movable frame portion is disposed around the core block having the cavity forming surface so that the movable frame portion can be moved back and forth. A movable mold in which a parting surface that comes into contact with the parting surface of the mold is formed is used.

The injection press molding method of the present invention is an injection press molding method in which injection is performed from an injection device in a state in which a movable mold is slightly separated from a fixed mold, and the cavity is opened to the outside and is completely formed. Since injection is started in the absence of air, the air in the cavity can be easily removed, and even a thin molded product such as a light guide plate can be injected and filled well to the end of the cavity. Furthermore, when the resin used is a type that generates gas, the problem that solids contained in the gas adhere to gaps or vent holes in the mold and block the vent holes or the like can be solved.

The injection press molding method of the present invention will be described with reference to FIGS. FIG. 1 is a front view of an injection press molding machine used in the injection press molding method of the present embodiment. FIG. 2 is a horizontal cross-sectional view of the light guide plate injection press mold according to the present embodiment, and shows a state where the movable mold is stopped at the injection start position. FIG. 3 is a horizontal sectional view of the injection press mold for the light guide plate of the present embodiment, and shows a state when the movable mold starts to close the mold again after the start of injection. FIG. 4 is a horizontal cross-sectional view of the injection press mold for the light guide plate of the present embodiment, and is a view showing a state when pressurization is completed. FIG. 5 is a front view of the movable mold of the injection press mold for the light guide plate. FIG. 6 is a top view of an injection press mold for a light guide plate, showing a mold open state. FIG. 7 is a side view of the injection press mold for the light guide plate, and shows a state where the movable mold is stopped at the injection start position. FIG. 8 is a chart of the injection press molding method of this embodiment.

As shown in FIG. 1, an injection press molding machine 1 used in the injection press molding method of the present embodiment has a heating cylinder 2 a with a built-in screw and an injection device 3 provided with a nozzle 2 b arranged on a bed 4. It is installed. The injection device 3 is controlled by a metering servo motor of a metering mechanism (not shown) and an injection servo motor of the injection mechanism, and the screw rotation speed and screw position are detected by a rotary encoder of the metering servo motor and injection servo motor. The In the mold clamping device 5, four tie bars 8 are arranged between a fixed plate 6 fixed to the bed 4 and a pressure receiving plate 7 arranged on the bed 4, and a movable plate 9 moves to the tie bar 8. It is inserted as possible. The pressure receiving plate 7 is provided with a mold clamping cylinder 10 which is a mold opening / closing / clamping mechanism for performing mold opening / closing and clamping, and a ram 10 a of the mold clamping cylinder 10 is fixed to the back surface of the movable plate 9. The mold closing cylinder 10 that is a mold opening / closing / clamping mechanism controls the speed and mold clamping force when the mold is closed. In this embodiment, the mold opening / closing / clamping mechanism is an example of a mold clamping cylinder 10 controlled by a servo valve, but a toggle mechanism operated by a servo motor and a ball screw mechanism or the like may be used. Further, in the present embodiment, the injection press in which the mold is opened and closed in the horizontal direction has been described. However, the mold may be opened and closed in the vertical direction.

The injection press molding machine 1 is provided with a position sensor 11 for detecting the position of the movable plate 9 (equal to the position of the movable mold) with respect to the pressure receiving plate 7, and the position sensor 11 is connected to the controller 12. The controller 12 is connected to a hydraulic circuit that controls the mold clamping cylinder 10 of the mold opening / closing and clamping mechanism such as a servo valve and a pressure sensor. Therefore, in the injection press molding machine 1, the position of the movable mold 22 is detected, and the mold clamping cylinder 10 can be feedback controlled. Further, as described above, the controller 12 is connected to the injection servomotor and the rotary encoder of the metering motor, the servo amplifier, the temperature sensor of the heating cylinder, and the like. Therefore, in the injection press molding machine 1, the screw position of the injection device 3, the screw forward speed, the screw rotation speed, the heating cylinder temperature, and the like can be feedback controlled, and the injection speed, the pressure holding switching position, and the pressure during pressure holding can be controlled. The injection amount is controlled. The position sensor 11 may be attached between the fixed plate 6 and the movable plate 9 or between the fixed die 40 and the movable die 22 and may be either a contact type or a non-contact type.

An injection press mold 21 for a light guide plate according to this embodiment shown in FIGS. 2 to 7 simultaneously forms two light guide plates for a mobile phone having a diagonal size of 3 inches and a plate thickness of 0.3 mm by an injection press molding method. It is a mold. First, the movable mold 22 will be described. A heat insulating plate 39 is attached to the movable platen 9 side of the mold body 23 of the movable mold 22. Further, core blocks 24 and 24 having a cavity forming surface 24a formed on the front surface are fixed to the mold body 23. The cavity forming surface 24a is a pattern forming surface for forming a transfer pattern on the light guide plate P1. The core block 24 is fixed to the mold body 23 together with the runner block 25 having a runner forming surface 25a, and gate cutter members 26 and 26 are attached between the core block 24 so as to be able to move forward and backward. An ejector pin 27 is attached to the center of the runner block 25 so as to be able to move forward and backward. A cooling medium flow path 37 is formed inside the core block 24, and a cooling medium flow path 38 is formed inside the runner block 25 so as to surround the ejector pin 27. As shown particularly in FIGS. 5 and 6, a first movable frame portion 30 and a second movable frame portion 31 are attached to the mold main body portion 23 by springs 28 and 29, respectively. The first movable frame portion 30 and the second movable frame portion 31 are provided to be relatively movable.

As shown in FIG. 5, the first movable frame portion 30 of the present embodiment is provided on the side farthest from the gate and forms the light incident surface of the light guide plate P1. Therefore, the first movable frame portion 30 is provided on both sides of the movable mold 22 in the injection press mold for the light guide plate of the present embodiment in which two light guide plates P1 are taken simultaneously. However, when one light guide plate is simultaneously formed in the mold, it is formed only on one side. The second movable frame portion 31 forms the upper and lower side surfaces of the cavity 36 where the light guide plate P1 is formed and the upper and lower side surfaces of the runner P2. Therefore, in FIG. 5, it is provided on both the left and right sides. As shown in FIG. 6, the stroke of the spring 28 of the first movable frame portion 30 substantially coincides with the stroke of the movable mold 22 that moves forward after the start of injection. In this embodiment, the effective stroke by which the spring 28 of the first movable frame 30 can contract is 0.3 mm. The effective stroke by which the spring 29 of the second movable frame portion 31 can contract is 1.3 mm, which is longer than the effective stroke of the spring 28 of the first movable frame portion 30. Therefore, as apparent from FIG. 6, when the mold is opened, the parting surface 31 a of the second movable frame portion 31 protrudes toward the fixed mold 40 rather than the parting surface 30 a of the first movable frame portion 30. In the injection press mold 21 for the light guide plate, the elastic force when the spring 28 and the spring 29 are contracted by the effective stroke is set to be substantially equal, so that the parting surfaces 30a and 46a and the parting surface 31a. 46a is desirable to prevent resin leakage.

Further, the first movable frame portion 30 is fitted with a light incident surface forming block 34 inside, and a light incident surface of the light guide plate P1 is formed by the light incident surface forming portion 34a of the light incident surface forming block 34. The light entrance surface forming block 34 and the surface of the first movable frame portion 30 on the fixed mold side form a parting surface 30a that comes into contact with the fixed mold 40 described later. The inner surface of the second movable frame 31 on the core block side forms a side surface forming surface 31b of the light guide plate P1 and the side surface forming surface 31c of the runner, and the front surface on the fixed mold side forms a parting surface 31a. . And between the core block 24 and the 1st movable frame part 30 and the 2nd movable frame part 31, the air path 35 for ejecting air at the time of mold release is formed.

Next, the fixed mold 40 will be described. As shown in FIGS. 2 to 4, a fixed mold 40 attached to the fixed plate 6 of the injection press molding machine 1 includes a mold main body 41, a cavity forming block 42, an insert block 43, a sprue bush 44, a gate. The cutter member 45 and the contact block 46 are formed. A heat insulating plate 47 is attached to the fixed plate side of the mold main body 41, and a hole into which a nozzle of an injection device (not shown) is inserted is formed, and a locating ring is attached around the hole. A cavity forming block 42 is attached to the movable mold side of the mold main body 41, and a cavity forming surface 42a facing the movable mold 22 of the cavity forming block 42 is a pattern forming surface. A cooling medium flow path 49 is formed inside the cavity forming block 42. An air passage 48 is formed so as to surround the cavity forming block 42. In this embodiment, the cavity forming block 42 and the contact block 46 are formed on substantially the same surface, and the surface of the contact block 46 facing the movable mold 22 is a parting surface 46a.

Further, an insert block 43 is disposed in the mold main body 41 together with the cavity forming block 42. The insert block 43 is provided with a sprue bush 44 provided with a hole whose diameter is increased toward the movable platen at the center thereof. Around the sprue bush 44, a cooling medium flow path 50 for cooling the runner P2 and the sprue P3 is formed. A runner forming surface 43 a is formed on the surface of the insert block 43 facing the movable mold 22 from the tip of the sprue bush 44 toward the cavity forming surface.

Next, the molding method of the present invention will be described with reference to the chart of FIG. In this embodiment, the light guide plate P1 having a diagonal size of 3 inches and a plate thickness of 0.3 mm is molded in a molding cycle time of 4.4 seconds. The breakdown is: mold opening / closing time (including removal time) 1.4 seconds, injection delay time 0.1 seconds, injection time 0.05 seconds, pressure holding time 0.45 seconds, cooling time 2.4 seconds (substantially Cooling starts from the start of injection). Before molding is started, the origin position of the position sensor 11 is set. The origin position A5 of the position sensor 11 moves the movable mold 22 forward relative to the fixed mold 40, and after all the parting surfaces 30a, 31a, 46a are in contact with each other, the springs 28, 29 contract further. Then, the first movable frame portion 30 and the second movable frame portion 31 are retracted, and the position where the core block 24 is most advanced is set as the origin. At the time of molding, first, the mold clamping cylinder 10 which is a mold opening / closing / clamping mechanism is operated, and the movable platen 9 and the movable mold 22 are started to move from the mold opening completion position A1 to perform mold closing. At this time, the positions of the movable platen 9 and the movable mold 22 detected by the position sensor 11 are sent to the controller 12, and feedback control of the mold clamping cylinder 10 is performed by a servo valve (not shown). After the transition from the high speed mold closing to the low speed mold closing by the control of the mold clamping cylinder 10, the parting surface 31a of the second movable frame portion 31 of the movable mold 22 shown in FIG. 46 abuts against the parting surface 46a. At that time, the parting surface 30a of the first movable frame portion 30 is positioned so as to recede toward the movable plate with respect to the parting surface 31a of the second movable frame portion 31 and is not simultaneously contacted.

Furthermore, the mold clamping cylinder 10 continues to operate, and the movable platen 9 is moved forward by about 1.0 mm while urging the spring 29 between the mold body 23 and the movable frame 31 of the movable mold 22 in a contracting direction. The When the position sensor 11 detects that the movable platen 9 and the movable mold 22 have reached the injection start position A2 shown in FIGS. 2 and 7, the mold clamping cylinder 10 is temporarily stopped. At that time, the mold clamping cylinder 10 is positioned at the injection start position A2 with a mold clamping force slightly applied in the mold closing direction. The injection start position A2 is a position where the cavity forming surface 24a of the movable mold 22 is slightly separated from the cavity forming surface 42a of the fixed mold 40 from the pressurization completion position A4. 3 mm apart. In this state, a gap D of 5 μm is still formed between the parting surface 30a of the first movable frame portion 30 of the movable mold 22 and the parting surface 46a of the contact block 46 of the fixed mold 40. ing. Accordingly, at the injection start position A2, one of the cavities 36 is opened to the outside, and the cavity 36 is not completely formed. (Rather than opening through the vent hole, the parting surfaces 30a, 46a are opened without contacting each other.) The parting surface 30a and the parting surface 46a at the injection start position A2 The gap D may be such that the gas of the molten resin M in the cavity is sufficiently discharged. Therefore, for example, in the small light guide plate P1 corresponding to 2 to 5 inches, it may be 5 to 10 μm. In the range below 5 μm, the outgassing effect cannot be sufficiently expected, and in the range above 10 μm, in the case of the small light guide plate P1, the length of the cavity 36 in the resin flow direction is short, so the gap D is unnecessarily large. Widening is not preferable. For example, in the case of a large light diffusion plate corresponding to 30 to 50 inches, the gap D is desirably set to 10 to 20 μm.

Next, after an injection delay time of 0.1 seconds elapses, the injection device 3 is operated and injection is started. In addition to this embodiment, the injection may be started when the moving movable mold is in a predetermined position where the cavity is not completely formed. In the present embodiment, the injected molten resin M is polycarbonate, and the set temperature of the front portion of the heating cylinder 2a is set to 340 to 380 ° C. Further, the injection speed varies depending on the molded product, and cannot be generally stated, but is preferably 100 to 400 mm / sec. In particular, 300 mm / sec or more is desirable for a light guide plate having a thickness of 0.2 to 0.4 mm. If the injection speed is too high, the molten resin may reach the gap D before the gap D of the cavity 36 is closed. When the screw position of the injection device 3 is advanced by a predetermined amount by a sensor such as a rotary encoder of an injection servo motor and sent to the controller 12, a signal is sent from the controller 12 to the mold clamping cylinder 10. As shown in FIG. 3, remolding by the movable mold 22 is started, and the parting surface 30a and the parting surface 46a are brought into contact with each other. In this case, the timing of re-mold closing by the mold clamping cylinder 10 varies depending on the size and shape of the molded product, the type / temperature of the resin, the injection speed, etc., but it depends on the injection stroke from the injection start position to the holding pressure switching position. A position advanced by 30 to 60% is desirable. In addition to the detection value of the screw position at the time of injection, the trigger for the start of re-mold closing includes the time measured by the timer from the start of injection, the detection value of the resin pressure sensor in the cavity, the mold opening / closing / clamping mechanism, A detection value of a load cell or a strain sensor provided in the tie bar may be used.

In the present invention, the air remaining in the cavity 36 can be released from the gap D wider than the vent hole by performing the control. In the present invention, the molten resin M does not flow out from the open portion of the cavity 36 by starting re-closing at a predetermined timing during injection. In particular, since the internal pressure of the air in the cavity 36 does not increase at the initial stage of injection, the flow rate of the molten resin M flows to the end of the cavity 36 without decreasing. Further, it is possible to solve the problem that the solid matter contained in the gas adheres to the air flow paths 35, 48, etc., and closes the gaps, vent holes, etc. of the air flow paths 35, 48, etc.

Also, the mold closing speed when closing the gap D after the start of injection is more advantageous when the molten resin M is pressurized after the cavity 36 is closed. And the amount of air in the cavity 36 can be reduced. However, in the electric toggle mechanism, it is difficult to increase the startup speed of the mold opening / closing / clamping mechanism, and in this embodiment, high-speed mold closing is realized by sending oil accumulated in the accumulator to the mold clamping cylinder 10. In this embodiment, it is possible to close the mold at a high speed by raising the time required to reach the maximum pressure (pressure increase speed) in 0.03 seconds. Note that the value of the pressure increase rate at this time is desirably raised in 0.02 to 0.05 seconds. In this case, the maximum value of the mold closing speed is preferably 5 to 40 mm / sec, although it depends on the molded product and the set value of the interval D. It is desirable that the cavity 36 is completely closed and the resin pressure in the cavity 36 after the pressure increase is 25 to 80 MPa. When it is desired to eliminate the impact caused by the contact between the parting surfaces 30a and 46a, the pressure may be increased rapidly after the parting surfaces 30a and 46a are contacted to form the cavity 36.

As shown in FIG. 8, the movable mold 22 further becomes the fixed mold 40 after passing through the cavity closing position A3 where the parting surface 30a and the parting surface 46a are in contact with each other by the mold clamping cylinder 10. The molten resin M in the cavity 36 is rapidly pressurized and compressed. On the other hand, on the injection device 3 side, when the screw is advanced and the injection is completed, the pressure is switched from the holding pressure switching position to the pressure control, and holding pressure is performed. Thereafter, on the mold side, the gate cutter member 26 is advanced at a predetermined timing, and the light guide plate P1 and the runner P2 are separated. After the gate is cut by the gate cutter member 26, the holding pressure from the injection device 3 does not reach the cavity 36, but the mold clamping cylinder 10 can pressurize the molten resin M in the cavity 36. In molding that performs transfer such as the light guide plate P1, sink marks do not occur even if shrinkage occurs due to cooling, and satisfactory transfer molding can be performed.

Then, by the operation of the mold clamping cylinder 10, the core block 24 of the movable mold 22 moves forward 0.3 mm from the injection start position A2, and the springs 28 and 29 of the first movable frame portion 30 and the second movable frame portion 31 are completely moved. When contracted and reaches the pressurization completion position A4 shown in FIG. 4, a light guide plate P1 having a plate thickness of 0.3 mm is formed. Meanwhile, the molten resin used for the next molding is measured on the injection device 3 side. Although not shown, when a predetermined time elapses, compressed air for mold release is applied from the air passage 48 of the fixed mold 40 to the cavity 36.

Next, the mold clamping cylinder 10 is operated to perform pressure release and mold opening in order. When the pressure is released, the springs 28 and 29 of the first movable frame portion 30 and the second movable frame portion 31 are expanded again on the movable mold 22 side, and the first movable frame portion 30 and the second movable frame portion 31 are moved. Each is advanced relative to the mold body 23, the core block 24, and the runner block 25. The movable mold 22 and the movable platen 9 are returned from the pressurization completion position A4 to the injection start position A2. When the mold is opened next, the light guide plate P1, the runner P2, and the sprue P3 are taken out while being held on the movable mold 22 side, and moved to the mold opening completion position A1. At the same time, the compressed air is ejected through the core block 24 and the air passage 35 between the first movable frame portion 30 and the second movable frame portion 31. At the mold opening completion position A1, the ejector pin 27 of the ejector device is moved forward, and the runner P2 is released from the runner formation surface 25a. Further, at the mold opening completion position A1, the light guide plate P1, the runner P2, and the sprue P3 are taken out by a take-out robot (not shown). Although not shown, the take-out robot used in the present embodiment holds the sprue P3 and the like with a chuck and sucks the light guide plate P1 with a suction cup and takes it out of the movable mold 22. When the light guide plate injection press mold 21 is thermally expanded by the continuous molding of the light guide plate P1, it is desirable to correct the origin position A5 of the position sensor 11 or the cavity closing position A3.

The present invention is not enumerated one by one, but is not limited to that of the above-described embodiment, and it goes without saying that those skilled in the art also apply modifications made in accordance with the spirit of the present invention. is there. For example, the type and application of the molded product are not limited as long as it is a thin plate molded product that is difficult to be molded by a normal injection molding machine. For example, it may be a light guide plate, a light diffusion plate, a lens, a disk substrate, a vehicle window, or the like having a larger size (area). Particularly, among them, a small light guide plate with a thickness of 0.1 to 0.3 mm (corresponding to a diagonal size of 2.5 to 6 inches), a disk substrate, a medium light guide plate with a plate thickness of 0.3 to 0.5 mm, It is effective for molding a molded product that is difficult to be molded by conventional injection press molding such as a diffusion plate (diagonal dimension is equivalent to 6 to 15 inches).

And for example, in the case of molding of a direct gate in which molten resin is injected from the sprue all around, or a disk substrate in which the center hole is opened after the molten resin is injected from the sprue all around It is also possible to perform injection from a state in which the parting surface of the fixed mold and the parting surface of the movable mold are separated from each other so that they do not contact and fit at all and the entire periphery of the cavity is open to the outside. This point will be further described. By controlling the mold opening / closing and clamping mechanism, the parting surface of the movable mold and the parting surface of the fixed mold are brought into contact at any point with a slight separation of 5 to 20 μm. Stop not to stop. The molten resin is compressed after the injection is started, and the parting surfaces are brought into contact with each other before the molten resin is ejected from the gap between the parting surfaces.

Further, in the present embodiment, the entire first movable frame portion 30 is a parting surface 30a, and the gap D with the parting surface 46a of the fixed mold 40 is closed by the operation of the mold clamping cylinder 10, but the injection starts. Even if the width of the parting surface to be contacted later is narrower than about 1 mm, it has a sufficient effect of bleeding. Then, in addition to the mold opening / closing / clamping mechanism, the block may be moved by an actuator such as a hydraulic cylinder provided in the mold to close the gap for venting the air in the cavity.

It is a front view of the injection press molding machine used for the injection press molding method of this embodiment. It is a horizontal sectional view of the injection press mold for light guide plates of this embodiment, and is a figure showing the state where the movable mold stopped at the injection start position. It is a horizontal sectional view of the injection press mold for light guide plates of this embodiment, and is a figure showing the state at the time of re-mold closing start after the start of injection. It is a horizontal sectional view of the injection press die for light guide plates of this embodiment, and is a figure showing the state at the time of pressurization completion. It is a front view of the movable metal mold | die of the injection press metal mold | die for light guide plates of this embodiment. It is a top view of the injection press metal mold | die for light guide plates of this embodiment, Comprising: It is a figure which shows a mold open state. It is a side view of the injection press metal mold | die for light guide plates of this embodiment, Comprising: It is a figure which shows the state which the movable metal mold | die stopped in the injection start position. It is a chart figure of the injection press molding method of this embodiment.

Explanation of symbols

1 Injection press molding machine 10 Clamping cylinder (Clamping mechanism)
DESCRIPTION OF SYMBOLS 11 Position sensor 12 Controller 21 Injection press mold for light guide plates 22 Movable mold 24 Core block 28, 29 Spring 30 1st movable frame part 30a, 31a, 46a Parting surface 31 2nd movable frame part 36 Cavity 40 Fixed mold 46 Contact block D Gap M Molten resin P1 Light guide plate

Claims (4)

In an injection press molding method for injecting molten resin from an injection device in a state where the movable mold is slightly separated from the fixed mold,
An injection press molding method characterized by starting injection of a molten resin in a state where a cavity is opened to the outside and not completely formed. Detecting the position of the movable mold, controlling the mold opening / closing and clamping mechanism, moving the movable mold to a position where the cavity is open to the outside and not completely formed, and injecting molten resin The injection press molding method according to claim 1, wherein 3. The injection press molding method according to claim 2, wherein the mold opening / closing / clamping mechanism is controlled by a predetermined trigger after the start of injection of the molten resin, and the movable mold is moved toward the fixed mold. A movable frame portion is disposed around a core block having a cavity forming surface so that the movable frame portion can move forward and backward, and a movable mold having a parting surface abutting against the parting surface of the fixed mold is formed on the movable frame portion. The injection press molding method according to any one of claims 1 to 3, wherein the injection press molding method is used.

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