JP2736752B2 - Injection compression molding method - 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 compression molding method suitable for molding with a mold cavity having a fine shape or the like.

[0002]

2. Description of the Related Art In general, when molding a molded product having a thin and fine irregular surface such as a compact disk, a high degree of shape transferability is required, and
It is necessary to sufficiently eliminate internal stress.

For this reason, conventionally, the resin is injected and filled into a mold in which the movable mold is retracted by a short distance from the mold clamping position, and then the mold is re-clamped, and a pulsating pressure is applied to the filled resin. There is also known an injection compression molding method which is applied (for example, see JP-A-1-267016).

[0004]

However, the above-mentioned conventional injection compression molding method has a problem that the following problems occur.

[0005] First, in the case of a thin molded product such as a compact disk or the like, the flow resistance of the resin flowing on the wall surface of the mold cavity becomes large. Since pulsating pressure is applied to the resin, the flow resistance increases during filling of the resin, and as a result,
The internal stress cannot be sufficiently eliminated, and there is a possibility that warpage or the like may occur, and there is a limit in improving the shape transferability.

Second, since the flow resistance increases, it is necessary to increase the filling pressure. As a result, the capacity of the injection device cannot be reduced, so that the size and cost of the injection device can be reduced. Absent.

The present invention has been made to solve the problems existing in the prior art, and sufficiently eliminates internal stress of a molded article, can reliably prevent warpage and the like, and has a high degree of shape transferability. It is an object of the present invention to provide an injection compression molding method which can secure the injection molding and can contribute to downsizing and cost reduction of the injection device.

[0008]

In the injection compression molding method according to the present invention, the movable platen 11 is moved by the mold clamping device 10 and the movable die 3 attached to the movable platen 11 is slightly set from the mold clamping position Xo. The position of the movable mold 3 is moved backward by a distance Ls, and a repetition signal having a set frequency and amplitude, for example, a sinusoidal AC signal Sx, is applied to the position control signal Sc for controlling the position of the movable mold 3, so that the movable mold 3 is moved backward. While the movable platen 11 is vibrated, the mold 2 in a state where the movable platen 11 is vibrated is injected and filled with a resin, and further, the vibration of the movable platen 11 is stopped during or after the filling of the resin, and thereafter, The movable mold 3 is advanced to the mold clamping position Xo to perform re-clamping.

[0009]

According to the injection compression molding method of the present invention, first, at the time of mold clamping, the movable mold 3 is retracted from the mold clamping position Xo by a small set distance Ls. Thereby, the mold 2 is slightly opened. Then, the movable platen 11 is vibrated in this state. At this time, a position control signal S for controlling the position of the movable mold 3 is provided.
c, a repetitive signal in which the frequency and the amplitude are set, for example,
When the sinusoidal AC signal Sx is applied, the movable board 11 (movable mold 3) repeatedly moves in the front-rear direction with the control position based on the position control signal Sc as a base point, and is vibrated in position.

On the other hand, the mold 2 with the movable mold 3 vibrated
Is filled with resin. At this time, since the movable mold 3 is vibrating, vibration is applied to the resin being filled, and the flow resistance of the resin flowing on the wall surface of the mold cavity is reduced. Therefore, since the resin is smoothly filled, the occurrence of internal stress in the molded product is suppressed, and a high degree of shape transferability is secured. In addition, the injection pressure (capacity) on the injection device side can be reduced.

On the other hand, during or after filling of the resin,
The vibration of the movable platen 11 is stopped, and the movable mold 3 is advanced to the mold clamping position Xo to perform mold clamping again. This allows
The resin filled in the mold 2 is compressed.

[0012]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, the configuration of an injection molding machine 1 that can carry out the injection compression molding method according to the present invention will be described with reference to FIG.

The injection molding machine 1 comprises a mold clamping device 10 for supporting the mold 2 and an injection device 5. In the drawing, the injection device 5 shows only a part of the heating cylinder 6 side. On the other hand, the mold clamping device 10 is
1 and a fixed platen 12. The movable platen 11 has a movable mold 3 attached thereto, and the fixed platen 12 has a fixed mold 13 attached thereto.
Further, a mold clamping cylinder 15 for moving the movable platen 11 is provided. The mold clamping cylinder 15 has a built-in ram 16.
The movable platen 11 is attached to the tip of 6. Thus, the inside of the mold clamping cylinder 15 is partitioned by the ram 16 into the front oil chamber 15f and the first rear oil chamber 15r. Further, a second rear oil chamber 15s is provided inside the ram 16. On the other hand, each oil chamber 15f, 1
5r and 15s are configured to be connectable to a hydraulic pressure source 20 and an oil tank 21 via a switching valve 17, a servo valve 18 and a switching valve 19. Therefore, the movable mold 3 is connected to each of the switching valves 17, 1
9 and the servo valve 18 are controlled to advance, retreat or stop.

On the other hand, 30 is a control circuit. Control circuit 3
As 0, a pressure sensor 31, which detects the mold clamping pressure as a pressure detection value Pd, a position sensor 32, which detects the position of the movable mold 3 as a position detection value Xd, and a position detection value Xd from this position sensor 32, as a detection system. A speed converter 33 is provided to obtain a speed detection value Vd by differentiating with time.

The apparatus further includes a pressure control system circuit 34 for performing pressure feedback control, a speed control system circuit 35 for performing speed feedback control, and a position control system circuit 36 for performing position feedback control. The input side of the pressure control system circuit 34 has a pressure detection value Pd
The deviation between the speed detection value Vd and the velocity command value Vc is applied to the input side of the speed control system circuit 35, and the input side of the position control system circuit 36 is applied to the input side of the speed control system circuit 35. A deviation between the position detection value Xd and the position command value Xc is given.

Further, a sine-wave AC signal generation circuit 37 for outputting a sine-wave AC signal Sx (see FIG. 3A) whose frequency and amplitude are set is provided. , Can be selectively given to the regular position command value Xcs. With this, when the sine wave AC signal Sx is output from the sine wave AC signal generation circuit 37,
The normal position command value Xcs can be changed according to the frequency and the amplitude of the sine-wave AC signal Sx. Therefore, the position command value Xc includes a regular position command value Xcs.
Only the case where only the normal position command value Xcs (position control signal Sc) is changed by the sinusoidal alternating signal Sx is included.

On the other hand, the outputs of the pressure control system circuit 34, the speed control system circuit 35 and the position control system circuit 36 are
9 to the servo valve control circuit 40.
The output of the servo valve control circuit 40 is provided to the servo valve 18. Therefore, the pressure control system circuit 34, the speed control system circuit 35, or the position control system circuit 36
Is selectively connected to the input side of the servo valve control circuit 40, it is possible to perform speed feedback control, pressure feedback control, and position feedback control for the movable mold 3.

Next, an injection compression molding method according to the present invention including the operation of the injection molding machine 1 will be described with reference to FIGS.

FIG. 1 shows the operating characteristics of each part. At the time of mold clamping, first, the speed control system circuit 35
Is selected, and the movable platen 11 is advanced from the mold opening position. At this time, as shown in FIG. 1, first, high-speed mold clamping is performed at the set speed Vm, and when approaching the fixed platen 12 side, the mold is slowed down to the low set speed Vn to perform mold clamping. In this case, the set speeds Vm and Vn are the speed command values Vc. The position of the movable mold 3 at this time is indicated by Xm.

Next, the pressure control system circuit 34 is selected by the loop switching section 39, and high-pressure mold clamping is performed with the set pressure Pp. In this case, the pressure command value Pc becomes the set pressure Pp.
Thereby, the so-called origin search is performed, and the movable mold 3 is set to the mold clamping position Xo. The above is a normal mold clamping operation.

On the other hand, according to the present invention, the loop switching unit 39
To select the position control system circuit 36, and move the movable mold 3 backward from the mold clamping position Xo by a small set distance Ls. In this case, the retracted position of the movable mold 3 that defines the set distance Ls becomes the regular position command value Xcs. Thereby, the mold 2 is slightly opened. The set distance Ls (retreat position) is usually 0.1
mm.

Then, the movable mold 3 is vibrated in this state. That is, the sine wave AC signal generation circuit 37 outputs the signal from FIG.
Is applied to the addition circuit 38.
As a result, the sine wave AC signal Sx is added to the normal position command value Xcs, and the normal position command value Xcs becomes the position command value Xc that changes according to the frequency and amplitude of the sine wave AC signal Sx. Command value Xc and position detection value Xd
Is applied to the position control system circuit 36. Therefore, the movable mold 3 repeatedly moves in the front-rear direction with the control position based on the regular position command value Xcs as a base point, and is vibrated in position.

On the other hand, in this state, the injection step is started, and the resin is injected and filled into the mold 2 in a state where the movable mold 3 is vibrated.
Note that the injection speed Vi in the injection step is shown in a simplified manner. In the injection step, since the movable mold 3 is vibrating, vibration is applied to the resin being filled, and the flow resistance of the resin flowing on the wall surface of the mold cavity is reduced. Therefore, the resin is smoothly filled.

After the filling of the resin is completed, the output of the sine-wave AC signal Sx from the sine-wave AC signal generation circuit 37 is stopped, and the vibration of the movable mold 3 is stopped. The mold is advanced to the mold clamping position Xo to perform mold clamping again. In this case, the movable mold 3 is advanced by position control.
Thereby, the resin filled in the mold 2 is compressed at a high pressure. The resin pressure at this time is indicated by Pm,
The time required for re-clamping is indicated by Tm. When the weighing process on the injection device 5 side is completed, the mold is opened at the time point to.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment.

For example, the sine-wave AC signal Sx shown in FIG. 3A has been exemplified as the repetitive signal, but the pulse signal Sy shown in FIG. 3B and the triangular wave AC signal Sx shown in FIG.
Any repetitive signal such as z can be used. In addition, although the case where the vibration is stopped after the completion of the filling is illustrated, the vibration can be stopped during the filling and the mold can be re-clamped if necessary. Further, the position control signal Sc is exemplified by the regular position command value Xcs, but may be the position detection value Xd. In addition, it is possible to arbitrarily change the detailed configuration, method, and the like without departing from the gist of the present invention.

[0028]

As described above, according to the injection compression molding method of the present invention, the movable platen is moved by the mold clamping device, and the movable mold attached to the movable platen is retracted by a small set distance from the mold clamping position. In addition, by applying a repetition signal in which a frequency and an amplitude are set to a position control signal for controlling the position of the movable die, the movable plate is vibrated at the retracted position of the movable die, and the movable plate is vibrated. Injecting and filling the resin into the mold, and further stopping the vibration of the movable plate during or after the filling of the resin, and then moving the movable mold forward to the mold clamping position to perform the mold re-clamping. It produces such remarkable effects.

Since vibration is applied to the resin being filled, the flow resistance of the resin is reduced, and the resin is smoothly filled. Therefore, internal stress in the molded product can be eliminated, and the occurrence of warpage and the like can be reliably prevented, and , A high degree of shape transferability can be secured.

Since the flow resistance is reduced, the injection pressure (capacity) on the injection device side can be reduced, which can contribute to downsizing and cost reduction of the injection device.

[Brief description of the drawings]

FIG. 1 is an operation characteristic diagram of each part when molding by an injection compression molding method according to the present invention,

FIG. 2 is a block diagram of an injection molding machine capable of performing the injection compression molding method.

FIG. 3 is a signal waveform diagram of a repetitive signal that can be used in the injection compression molding method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 injection molding machine 2 mold 3 movable mold 10 mold clamping device 11 movable plate Xo mold clamping position Ls set distance Sc position control signal Sx sinusoidal AC signal

Claims (2)

(57) [Claims] The movable platen is moved by a mold clamping device.
A position control for retracting the movable mold attached to the movable platen from the mold clamping position by a small set distance and controlling the position of the movable mold
Add repetitive signal with frequency and amplitude set to control signal
By, movable together to vibrate the movable platen in the retracted position of the movable die, and injecting and filling the resin into a mold in a state in which the movable platen is vibrated, and further, during filling of the resin or after completion of filling
An injection compression molding method, comprising: stopping vibration of a board ; thereafter, moving the movable mold to a mold clamping position to perform mold clamping again. 2. The injection compression molding method according to claim 1, wherein a sinusoidal alternating signal is used as the repetitive signal.