JPH06285936A - Injection compression molding method and toggle type mold clamping device - Google Patents

Abstract

PURPOSE:To accurately stop a mold at a desired position by moving the mold in a closing direction through the crosshead of a toggle mechanism and allowing the crosshead to advance to a predetermined stroke position and moving the same to a prescribed retreat position behind a final stroke position. CONSTITUTION:The position (first stage compression position, second stage compression position, n-th stage compression position and a strain removing process position) of the crosshead part 12a corresponding to the position of a movable plate 30 is calculated. A mold 38 is moved in a closing direction through the crosshead 12a of a toggle mechanism 12 and a prescribed amt. of a molten resin is injected in a mold cavity during or after mold clamping. Next, the crosshead 12a is advanced to a predetermined stroke position to compress the molten resin to mold a molded product. The crosshead 12a is moved to a prescribed retreat position behind a final stroke position to remove the strain on the molded product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection compression molding method and a toggle type mold clamping device.

[0002]

2. Description of the Related Art As a conventional injection compression molding apparatus, there is one disclosed in Japanese Patent Laid-Open No. 61-253520. The injection compression molding apparatus shown therein is of a so-called direct-acting type, and a movable plate is directly attached to a piston rod of a mold clamping cylinder. That is, the movable plate can be moved at the same speed (the same amount of movement) as the piston rod.

[0003]

However, the conventional direct-acting injection compression molding apparatus as described above has a problem that it is troublesome to control the position of the movable plate. That is, in injection compression molding, it is necessary to apply compressive force stepwise by advancing the movable plate stepwise in the compression step of reducing the cavity volume with respect to the molten resin supplied to the mold cavity. In some cases, in order to remove the distortion of the molded product due to compression molding, a step of slightly increasing the cavity volume during the molding (strain removal step) may be necessary. In order to control the position of the movable platen, a high-precision sensor that accurately detects the position of the movable platen and a high-precision flow rate control device that stops the movable platen at a predetermined position are required. It becomes troublesome. The present invention aims to solve such problems.

[0004]

According to the present invention, the position of the toggle mechanism on the crosshead side is measured, and the stroke reducing action of the toggle mechanism is used to control the movable platen position according to the position of the crosshead. The above problems are solved. That is, the injection compression molding method of the present invention includes a mold closing step of moving the mold in the closing direction via the crosshead of the toggle mechanism, and a predetermined amount of molten resin is injected into the mold cavity during or after the mold is closed. The injection process, the compression process of pressing the molten resin with the crosshead at the predetermined stroke position for a predetermined time, and the movement of the crosshead to the predetermined retracted position behind the stroke position It has a strain removing step of moving the mold in the mold opening direction by a corresponding predetermined amount to remove the strain of the molded product, and a molded product removing step of opening the mold and taking out the molded product. The compression process may be performed at a plurality of stroke positions from the first stage compression to the nth stage compression. Also, the toggle type mold clamping device of the present invention is provided with a hydraulic source (1
4) through the main pipe (21), the flow control valve (16), the main switching valve (18) and the first pipe (23) to the mold clamping side oil chamber (10b) of the mold clamping cylinder (10). Is supplied and the oil is returned from the mold opening side oil chamber (10c) through the second pipe (25) and the main switching valve (18) to the tank (29) to open the oil, and thereby via the toggle mechanism (12). The first is provided in a first pipe (23) that communicates the main switching valve (18) with the mold clamping side oil chamber (10b) of the mold clamping cylinder (10). The pilot check valve (17), the first pipe (23), the first pilot pipe (31) for communicating the first pilot check valve (17) with the pilot port (17a), and the first pilot pipe (31). The first switching valve (13) provided, the main switching valve (18) and the mold clamping Mold opening-side oil chamber of the cylinder (10) (10
Second provided in the second pipe (25) communicating with c)
A second pilot pipe (33) that connects the pilot check valve (19) and the second pipe (25) to the pilot port (19a) of the second pilot check valve (19).
And the main switching valve (18) rather than the position where the second switching valve (15) provided in the second pilot pipe (33) and the first pilot check valve (17) of the first pilot pipe (31) are provided. ) Side, a branch pipe (27), a variable throttle valve (22) and a third switching valve (11) sequentially provided in the branch pipe (27) toward the downstream side, and a toggle mechanism (12). Has a position sensor (24) capable of detecting the position on the crosshead (12a) side of the device and a controller (26), and the controller (26) includes a predetermined crosshead (12a). The set strain-removing position is stored and the signal of the measurement position from the position sensor (24) is input, and the controller (26) operates the toggle mechanism (1).
After the crosshead (12a) of 2) reaches a predetermined forward limit position, the first branch pipe (27) is connected to the third switching valve (11).
Is output to a position communicating with the tank (29), the comparison between the measurement position and the set position is started, and when both positions match, the first switching valve (1
In 3), a command signal is output to switch to the pilot port communication position. The reference numerals in parentheses indicate the corresponding members of the embodiment.

[0005]

The molten resin is injected into the mold cavity, and the crosshead of the toggle mechanism is advanced to a predetermined position to position the movable plate at the corresponding position and compress the molten resin in the mold cavity. The maximum compression force acts on the molten resin when the toggle mechanism is fully extended, and compression molding is performed. When the strain relief process is required after compression molding, the movable head is retracted by a predetermined amount by retracting the crosshead to a predetermined position. The moving amount of the movable platen is calculated by multiplying the moving amount of the crosshead by a force ratio (usually 50 to 6).
A small amount of movement is obtained by multiplying the reciprocal of 0). Therefore, even if neither a high-precision position sensor nor a high-precision flow rate control device is used, the position of the crosshead can be controlled using a normal-precision position sensor to accurately position the die at a desired position. You can

[0006]

EXAMPLE FIG. 1 shows an example of the present invention. A mold clamping housing 34 is arranged at a position facing the fixed platen 32.
The movable platen 30 is provided between the fixed platen 32 and the mold clamping housing 34.
Are arranged. The mold clamping housing 34 and the movable platen 30 are connected by the toggle mechanism 12. That is, one end side of each of the plurality of links of the toggle mechanism 12 is connected to the mold clamping housing 34, and the other end side thereof is connected to the movable platen 30. Fixed platen 32
The mold clamping housing 34 are connected to each other by four tie bars 36 (only two of which are visible in the drawing). The tie bars 36 penetrate the movable plate 30, respectively. That is, the movable platen 30 is guided to move in the axial direction by the tie bar 36. A movable mold 38 is fixed to the movable plate 30, and a fixed mold 40 is fixed to the fixed plate 32. In the mold clamping housing 34,
A mold clamping cylinder 10 is attached. The piston rod 10 a of the mold clamping cylinder 10 penetrates the center of the mold clamping housing 34 and is connected to the crosshead portion 12 a of the toggle mechanism 12. The position sensor 24 is provided in the mold clamping housing 34. Position sensor 24
Can detect the position of the crosshead portion 12a. Controller 2 for inputting a measurement position signal from the position sensor 24
6 is provided. The controller 26 is a switching valve 1 described later.
The switching positions of 1, 13, 15 and 18 can be controlled. A flow rate adjusting valve 16 and a main switching valve 18 are sequentially connected to a pipe 21 of the hydraulic pressure source 14 toward the downstream side.
A branch pipe 35 is provided at a position upstream of the position where the flow rate adjusting valve 16 of the pipe 21 is provided, and a relief valve 20 is provided at the branch pipe 35. The return side of the relief valve 20 is communicated with the tank 29. The relief valve 20 can set the upper limit pressure of the hydraulic power source 14. The main switching valve 18 is a three-position switching valve, and one port of this is a pipe 23
Is connected to the mold clamping side oil chamber 10b of the mold clamping cylinder 10. The pipe 23 is provided with a pilot check valve 17. One end of a pilot pipe 31 is connected to the pilot port of the pilot check valve 17. The other end of the pilot pipe 31 is connected to the pipe 23. The pilot pipe 31 is provided with a switching valve 13. That is, in the pilot check valve 17, the hydraulic pressure from the pilot pipe 31 is not introduced into the pilot port of the pilot check valve 17 when the switching valve 13 is located at the symbol position (solenoid excitation position) opposite to the illustrated symbol position. Although the flow from the high pressure side to the low pressure side is allowed, when the switching valve 13 is positioned at the symbol position (solenoid de-energized position) shown in the figure, the hydraulic pressure from the pilot pipe 31 is introduced to the pilot port thereof. The flow from the mold clamping cylinder 10 side is blocked. The other port of the main switching valve 18 is connected to the mold opening side oil chamber 10c of the mold clamping cylinder 10 via a pipe 25. Pipe 23 as well as pipe 25
A valve having the same structure as the above is provided. That is,
A pilot check valve 19 is provided in the pipe 25, and one end of a pilot pipe 33 is connected to a pilot port of the pilot check valve 19. The other end of the pilot pipe 33 is
It is connected to the pipe 25. A switching valve 15 is provided in the pilot pipe 33. As a result, the pilot check valve 19 is connected to the pilot port 3 of the pilot check valve 19 when the switching valve 15 is located at the symbol position (solenoid excitation position) opposite to the illustrated symbol position.
Although the hydraulic pressure from 3 is not introduced and the flow from the high pressure side to the low pressure side is allowed, when the switching valve 15 is located at the symbol position (solenoid de-energized position) shown in the figure, the pilot port is located at this position. The hydraulic pressure from the pilot pipe 33 is introduced to block the flow from the mold clamping cylinder 10 side.
A branch pipe 27 is provided on the upstream side of the position where the pilot check valve 17 of the pipe 23 is provided, and a throttle valve 22 and a switching valve 11 that are sequentially variable from the upstream side are provided on the branch pipe 27.
Is provided. The return side of the switching valve 11 is communicated with the tank 29. When the switching valve 11 is located at the symbol position opposite to the symbol position shown in the drawing, the pipe 23
However, when the switching valve 11 is positioned at the symbol position shown in the figure, the pressure in the pipe 23 can be reduced according to the valve opening of the throttle valve 22. Thereby, the retreat speed of the crosshead 12a of the toggle mechanism 12 can be controlled.

Next, the operation of this embodiment will be described. First, as a preparatory work, the position of the crosshead portion 12a corresponding to the position of the movable platen 30 (first stage compression position, second stage compression position, n
The stage compression position and the strain relief process position) are obtained by calculation, and these and the holding time of each stage are input to the controller 26 as setting data. Further, the valve opening of the flow rate adjusting valve 16 and the throttle valve 22 and the injection start timing are input to the controller 26. The relief valve 20 is set to a predetermined set relief pressure. This completes the preparation for injection compression molding. The relationship between the position of the crosshead portion 12a of the toggle mechanism 12 and the pressing force generated at this time is made into a mathematical expression based on the pressure receiving area of the mold clamping cylinder 10, the supply pressure, the dimensional specifications of the toggle mechanism 12, and the like. It is possible to set. Further, the moving distance of the movable platen 30 with respect to the moving distance of the crosshead portion 12a is a small moving distance corresponding to the reciprocal of the force magnification ratio of the toggle mechanism 12. Next, in response to a command from the controller 26, the first switching valve 13 and the second switching valve 13
The main switching valve 18 is switched to the symbol position on the right side in the drawing while the switching valves 15 are all in the excitation position (the symbol position on the side opposite to the symbol position shown in FIG. 1), and the hydraulic power source 14
The oil whose flow rate is adjusted by the flow rate adjusting valve 16 from the main pipe 21, the main switching valve 18, the first pipe 23, and the first pilot check valve 17 to the mold clamping side oil chamber 10b of the mold clamping cylinder 10. The piston rod 10a and the crosshead 12a integral therewith are moved forward. That is, the mold closing operation is started. During mold closing, molten resin is injected into the mold cavity from an injection device (not shown) at a predetermined timing, and the compression process is started.

Next, the injection compression molding process will be described with reference to FIG. The position of the crosshead 12a is determined by the position sensor 2
4 has been detected, and the controller 26 is set as the measurement position.
Has been entered in. The controller 26 compares the measurement position with the set position, and the measurement position (crosshead 12a position)
When the stored pressure matches the stored one-stage compression position, a command signal is output to switch the first switching valve 13 and the second switching valve 15 to the illustrated pilot port communication position, respectively.
As a result, both pilot check valves 17 and 19 block the first pipe 23 and the second pipe 25, respectively.
The entire movable part is stopped at the one-stage compression position. The force in the forward direction due to the hydraulic pressure P confined in the mold clamping side oil chamber of the mold clamping cylinder 10 in the compression process is balanced with the restoring force f of the tie bar 36, which makes it possible to stop at a substantially constant position. is there. Such an operation is sequentially repeated to perform 2-stage compression to n-stage compression. Upon completion of the n-stage compression, the comparison operation between the measurement position by the position sensor 24 and the stored set strain relief process position is started. The main switching valve 18 is switched to the symbol position on the left side in the drawing, the first switching valve 13 and the second switching valve 15 are switched to the excitation position (the symbol position opposite to the symbol position shown in FIG. 1), and The 3 switching valve 11 switches to the non-excitation position (symbol position shown in FIG. 1). As a result, hydraulic pressure is introduced into the mold opening side oil chamber 10c of the mold clamping cylinder 10, and the oil in the mold clamping side oil chamber 10b is transferred to the first pipe 23, the pilot check valve 17, the first branch pipe 27,
It is opened to the tank 29 through the throttle valve 22 and the third switching valve 11, and the piston rod 10a starts to retreat at a low speed. If the measurement position matches the set position, the first
The switching valve 13 is switched to the non-excitation position shown in FIG. 1, whereby the pilot check valve 17 is blocked and the movable part is stopped at the strain relief process position. That is, the strain relief process of the molded product is performed. After molding, the mold is opened and the molded product is taken out from the molds 38 and 40.

In the above description of the embodiment, the movable part of the mold clamping device is sequentially stopped at a plurality of predetermined positions during the compression process. However, the invention is not limited to this, and the compression starts and the final compression is performed. It is also possible to continuously move the movable part to the position. Further, in the above description of the embodiment, the mold clamping device is arranged so that the shaft center is horizontal, but the mold clamping device may be arranged so that the shaft center is vertical. In the description of the above embodiment, the position sensor 2 that measures the position of the crosshead 12a is used.
However, instead of this, a sensor for measuring the extension of the tie bar 36 may be provided to calculate the position of the movable part from the extension of the tie bar 36.

[0010]

As described above, according to the present invention, the toggle type mold clamping device stops the mold at a plurality of desired positions to perform the compression process, or slightly retracts the mold to distort the mold. It is possible to perform injection compression molding such as performing a taking step. Therefore, even in the injection compression molding, there is no need to precisely measure the position of the mold or precisely control the flow rate supplied to the mold clamping cylinder.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram illustrating a compression process.

[Explanation of symbols]

 10 mold clamping cylinder 10a piston rod 10b mold clamping side oil chamber 10c mold opening side oil chamber 11 third switching valve 12 toggle mechanism 12a crosshead 13 first switching valve 14 hydraulic power source 15 second switching valve 16 flow control valve 17 first Pilot check valve 18 Main switching valve 19 Second pilot check valve 20 Relief valve 21 Main pipe 22 Throttle valve 23 First pipe 24 Position sensor 25 Second pipe 26 Controller 27 Branch pipe 29 Tank 30 Movable plate 32 Fixed plate 34 Mold clamping Housing 36 Tie bar 38 Movable mold 40 Fixed mold

Claims (3)

[Claims] 1. A mold closing step of moving a mold in a closing direction via a crosshead of a toggle mechanism, an injection step of injecting a predetermined amount of molten resin into a mold cavity during or after mold closing, and a cross. A compression process in which the molten resin is compressed to form a molded product by advancing the head to a predetermined stroke position, and distortion of the molded product is removed by moving the crosshead to a predetermined retracted position behind the final stroke position. An injection compression molding method comprising: a strain removing step of performing the above step; and a molded product removing step of opening the mold to take out a molded product. 2. The injection compression molding method according to claim 1, wherein the compression step is performed at a plurality of stroke positions from the first stage compression to the nth stage compression. 3. A mold clamping cylinder (10) from a hydraulic pressure source (14) through a main pipe (21), a flow rate adjusting valve (16), a main switching valve (18) and a first pipe (23). Hydraulic pressure is supplied to the side oil chamber (10b) and the mold opening side oil chamber (10
A toggle-type mold clamping device for performing mold clamping through a toggle mechanism (12) by releasing oil from c) through the second pipe (25) and the main switching valve (18) to the tank (29). A first pilot check valve (17) provided in a first pipe (23) communicating the main switching valve (18) with the mold clamping side oil chamber (10b) of the mold clamping cylinder (10); Piping (23) and first pilot check valve (17)
First pilot pipe (31) communicating with the pilot port (17a) of No. 1, a first switching valve (13) provided in the first pilot pipe (31), a main switching valve (18) and a mold clamping cylinder ( The second pilot check valve (19) provided in the second pipe (25) communicating with the mold opening side oil chamber (10c) of 10), the second pipe (25) and the second pilot check valve (19). )
Second pilot pipe (33) communicating with the pilot port (19a) of the second pilot valve, the second switching valve (15) provided in the second pilot pipe (33), and the first pilot of the first pilot pipe (31). A branch pipe (27) provided on the main switching valve (18) side of the position where the check valve (17) is provided, and a variable throttle valve (sequentially provided on the branch pipe (27) toward the downstream side ( 22) and a third switching valve (11), a position sensor (24) capable of detecting the position of the toggle mechanism (12) on the crosshead (12a) side, and a controller (26), The controller (26) stores the predetermined set strain relief position of the crosshead (12a) and also receives the signal of the measurement position from the position sensor (24). , Toggle mechanism ( After the crosshead (12a) of 2) reaches a predetermined forward limit position, a command signal is sent to the third switching valve (11) to switch the first branch pipe (27) to a position communicating with the tank (29). A toggle characterized by outputting and outputting a command signal to start comparison between the measurement position and the set position and, when both positions coincide, switch to the pilot port communication position to the first switching valve (13). Type mold clamping device.