JPH10249902A - Injection compression molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve transfer properties by holding a mold to an injection mold opening position of predetermined mold opening quantity during an injection process. SOLUTION: In this molding process, an injection compression molding machine is used and a molten resin is injected into a mold closed at an injection mold opening position of predetermined mold opening quantity (a) to close the mold and compressed by closing the mold up to a final mold clamping position. In this case, on the basis of the correlation between the extension quantity of a tie bar and the opening quantity of the mold during an injection process, the extension quantity of the tie bar by injection pressure is detected during the period from the start of injection to the completion of injection and mold opening quantity is calculated on the basis of the detected extension quantity of the tie bar and the movable plate of the injection compression molding machine is allowed to advance by the distance setting off the mold opening quantity to close the mold to stop the injection mold opening position of the mold opening quantity (a) as shown by a straight line A.

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 performed by using an injection compression molding machine.

[0002]

2. Description of the Related Art In a conventional injection compression molding method performed by using an injection compression molding machine, a fixed mold and a movable mold (hereinafter, referred to as "mold") are moved to a final mold clamping position at the time of completion of a compression step. An injection step of closing a mold at an injection mold open position opened to a predetermined mold opening amount, and injecting and filling a molten resin into a cavity of the mold closed at the injection mold open position,
Following the injection step, a compression step is performed in which the mold is closed and compressed to the final mold clamping position.

[0003]

However, according to the above prior art, when the molten resin is injected and filled into the cavity of the mold closed at the injection mold opening position, the injection compression provided with the toggle type mold clamping device. In the case of a molding machine, the tie bar expands due to the injection pressure of the molten resin, and the link and the like shrink, and the mold opening amount of the mold is reduced by a distance corresponding to the sum of the elongation amount of the tie bar and the shrinkage amount of the link and the like. It will be larger than the injection mold open position. In the case of an injection compression molding machine equipped with a direct pressure type mold clamping device, the tie bar extends and the mold clamping ram shrinks, and the distance corresponding to the sum of the amount of extension of the tie bar and the amount of contraction of the mold clamping ram etc. Only the amount of mold opening increases. When the opening amount of the mold increases during the injection process, a small relative slip occurs between the skin layer and the mold, which is formed by cooling the injection-filled molten resin by the mold, which is an advantage of the injection compression molding method. However, there is a problem that the transferability is impaired. In particular, when molding a molded product such as a Fresnel lens or a light guide plate having a fine gradation on the surface, a decrease in transferability is not preferable.

[0004] The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to realize an injection compression molding method having good transferability.

[0005]

In order to achieve the above object, an injection compression molding method according to the present invention uses an injection compression molding machine to move a mold to a predetermined position with respect to a final mold clamping position at the time of completion of the compression step. An injection step of closing the mold at an injection mold open position in a state where the mold is opened at a mold opening amount, and injecting and filling a molten resin into a cavity of the mold closed at the injection mold open position;
A compression step of closing the mold to the final mold clamping position and compressing the mold following the injection step, wherein during the injection step from the start of injection to the end of injection during the injection step, The amount of elongation of the tie bar due to the injection pressure is detected, the mold opening is calculated based on the detected elongation of the tie bar, and the movable platen of the injection compression molding machine is advanced by a distance to offset the mold opening. By closing, the mold is stopped at the injection mold open position.

[0006]

When the injection compression molding is performed using an injection compression molding machine, the injection mold opening position in which the mold is opened by a predetermined amount with respect to the final mold clamping position at the time of completion of the compression step. As described above, when the mold is closed and the molten resin is injected and filled into the mold cavity, the injection pressure increases the mold opening amount as the molten resin fills the cavity.

In the case of an injection compression molding machine equipped with a toggle type mold clamping device, the tie bar expands and the link shrinks due to the injection pressure during the injection process, and the amount of extension of the tie bar and the amount of shrinkage of the link etc. And the opening amount of the mold increases by a distance corresponding to the sum of Also, in the case of an injection compression molding machine equipped with a direct pressure type mold clamping device, the injection pressure during the injection process causes the tie bar to expand and the mold clamping ram to shrink, and the amount of extension of the tie bar and shrinkage of the mold clamping ram. The opening amount of the mold increases by a distance corresponding to the sum of the amounts.

However, in either the toggle-type clamping device or the direct-pressure-type clamping device, there is a correlation between the amount of extension of the tie bar and the amount of contraction of the link or the clamping ram in the injection process. The amount of contraction of the link or the mold clamping ram can be calculated from the amount of expansion of the mold by a predetermined arithmetic expression, and the amount of mold opening caused by the above-described injection pressure can be calculated.

Therefore, the present invention detects the amount of extension of the tie bar due to the injection pressure during the injection process from the start of injection to the end of injection, and calculates the mold opening amount based on the detected amount of extension of the tie bar. The mold is stopped at the injection mold open position by moving the movable plate of the injection compression molding machine forward by a distance to cancel the mold opening amount and closing the mold. As a result, there is no minute relative slip between the skin layer and the mold caused by cooling the injection-filled molten resin by the mold, and the transferability is significantly improved.

[0010]

Embodiments of the present invention will be described with reference to the drawings.

When performing injection compression molding using an injection compression molding machine, the mold is closed at an injection mold open position, and molten resin is injected and filled into a cavity of the mold at the injection mold open position. As the molten resin becomes full, the injection pressure causes the die opening amount of the die to become larger than the injection die opening position as shown by the die opening amount fluctuation characteristic B in FIG.

As described above, there is a correlation between the amount of elongation of the tie bar during the injection process and the amount of mold opening of the mold caused by the injection pressure. Can be calculated.

The present invention is based on the above findings,
Using an injection compression molding machine, the mold is closed at an injection mold open position in a state where the mold is opened with a predetermined mold opening amount with respect to the final mold clamping position at the time of completion of the compression step, and the injection mold is opened. Injection compression comprising an injection step of injecting and filling a molten resin into a cavity of the closed mold, and a compression step of closing and compressing the mold to the final mold clamping position following the injection step. In the molding method, the amount of elongation of the tie bar due to the injection pressure is detected from the injection start time to the end of injection in the injection step, and the mold opening amount is calculated based on the detected elongation of the tie bar. By moving the movable platen of the injection compression molding machine forward by a distance to offset the opening amount and closing the mold, as shown by a straight line A in FIG. Stop at the open position.

FIG. 2 is an explanatory view showing an example of an injection compression molding machine provided with a toggle type mold clamping device used for carrying out the injection compression molding method according to the present invention. And a plurality of tie bars 4 for connecting the fixed plate 1 and the mold clamping housing 3 to each other, and an axial direction between the fixed plate 1 of the tie bar 4 and the mold clamping housing 3. The movable platen 2 is movably guided, and includes an extendable toggle link mechanism 8 that connects the mold clamping housing 3 and the movable platen 2, and the toggle link mechanism 8 is a tip of a rod 6 a of a piston 6 of a mold clamping cylinder 5. It is connected to a crosshead 7 fixed to the section.

The mold clamping cylinder 5 has one end of a first conduit 11 communicating with the mold closing chamber 5a and one end of a second conduit 12 communicating with the mold opening chamber 5b. The other end of each of the pipe 11 and the second pipe 12 is connected to a discharge pipe 13 of a hydraulic pump 15 via a servo valve 14 and a drain pipe 16 whose other end is opened to a tank 17. It is constituted so that it may be communicated in a way.

A control unit 20 for controlling the servo valve 14
Comprises a servo valve controller 22 connected to the servo valve 14 via a servo amplifier 21, and a first calculation unit 23 and a second calculation unit 24 connected in parallel with the servo valve controller 22. Between the unit 23 and the servo valve controller 22
The switch 25a is interposed and the second operation unit 2
The second switch 25b is interposed between the servo switch 4 and the servo valve controller 22.

A crosshead position detector 10a for detecting the position of the crosshead and a tie bar extension detector 10c for detecting the amount of extension of the tie bar are additionally provided. A mold opening detector 10b for detecting the mold opening amount in the mold and displaying it on the mold opening indicator 26 is provided.

The steps of the injection compression molding method of the present invention will be described with reference to an example in which an injection compression molding machine equipped with a toggle mold clamping device shown in FIG. 2 is used.

When starting the molding, the first switch 25a is opened and the second switch 25b is closed by a command from the molding cycle control unit 27 for controlling all the steps of the injection compression molding, and the servo valve controller is controlled. 22
And the second operation unit 24 are connected. The second arithmetic unit 24 converts the mold opening amount a sent from the molding cycle control unit 27 into a corresponding crosshead position, and
Send to The servo valve controller 22 determines the position of the crosshead detected by the crosshead position detector 10a as a second position.
A servo valve control signal for matching the position of the crosshead sent from the arithmetic unit 24 is output to the servo valve 14 via the servo amplifier 21. As a result, the servo valve 14 is switched to the mold closing port, pressure oil is introduced into the mold closing chamber 5a, the crosshead 7 advances together with the piston 6 and the rod 6a, and the mold is opened at the mold opening position a. The mold is closed.

After the above, the molding cycle control unit 2
7, the second switch 25b is opened, and the first switch 25a is closed.
3 and the servo valve controller 22 are connected, and the injection of the molten resin into the cavity of the mold 9 is started.

After the above, as the molten resin fills the cavity, the injection pressure causes the tie bar 4 to expand and the links and the like to shrink, and the amount of expansion of the tie bar 4 is detected by the tie bar expansion detector 10c and the first arithmetic unit 23 And the detected tie bar elongation is converted to a crosshead position for canceling the mold opening caused by the injection pressure. The servo valve controller 22 outputs a servo valve control signal for matching the position of the crosshead detected by the crosshead position detector 10 a with the crosshead position sent from the first arithmetic unit 23 to the servo amplifier 21.
Is output to the servo valve 14 via. As a result, the servo valve 14 is switched to the mold closing port, pressure oil is introduced into the mold closing chamber 5a, and the crosshead 7 is advanced by a distance that cancels the mold opening caused by the above-described injection pressure. 2 is advanced by a distance to offset the mold opening calculated based on the detected tie bar elongation. as a result,
The mold is kept stopped at the injection mold open position.

After the above, the molding cycle control unit 2
7, the injection of the molten resin is stopped, the first switch 25a is opened, the second switch 25b is closed, and the servo valve controller 22 and the second arithmetic unit 24 are connected. . As a result, the crosshead 7 is moved forward based on the compression process control signal sent from the molding cycle control unit 27 to perform compression by closing the mold to the final mold clamping position.

In the case of an injection compression molding machine having a direct pressure type mold clamping device, the above-described crosshead position detector 10 is used.
Alternatively, by providing a mold clamping ram position detector, a movable platen position detector, or the like, injection compression molding can be performed according to the above-described steps.

[0024]

Since the present invention is configured as described above, the following effects can be obtained.

During the injection process, from the start of injection to the end of injection, the cavity is injected with molten resin while the mold is stopped at the preset injection mold open position. As a result, the relative slip between the skin layer and the mold, which is caused by the above, is eliminated, and the transferability of the surface shape processed on the cavity surface of the mold is improved.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a mold opening amount and time in an injection compression molding method according to the present invention and a conventional injection compression molding method.

FIG. 2 is an explanatory view showing an example of an injection compression molding machine provided with a toggle-type mold clamping device used for carrying out the injection compression molding method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixed board 2 Movable board 3 Mold clamping housing 4 Tie bar 5 Mold clamping cylinder 5a Mold closing chamber 5b Mold opening chamber 6 Piston 6a Rod 7 Crosshead 8 Toggle link mechanism 9 Mold 9a Fixed mold 9b Movable mold 10a Cross Head position detector 10b Type opening amount detector 10c Tie bar extension detector 11 First line 12 Second line 13 Discharge line 14 Servo valve 14a Pilot line 15 Hydraulic pump 16 Drain line 17 Tank 20 Control unit 21 Servo Amplifier 22 Servo valve controller 23 First operation unit 24 Second operation unit 25a First switch 25b Second switch 26 Die opening indicator 27 Molding cycle control unit

Claims (1)

[Claims] 1. An injection compression molding machine, wherein a mold is closed to an injection mold open position in which the mold is opened by a predetermined mold opening amount with respect to a final mold clamping position at the time of completion of the compression step. An injection step of injecting and filling a molten resin into a cavity of the mold closed at an injection mold opening position; and a compression step of closing and compressing the mold to the final mold clamping position following the injection step. In the injection compression molding method consisting of, during the injection process from the start of injection to the end of injection, the elongation of the tie bar due to injection pressure is detected,
The mold opening amount is calculated based on the detected elongation amount of the tie bar, and the movable platen of the injection compression molding machine is advanced by a distance to cancel the mold opening amount to close the mold, thereby closing the mold. An injection compression molding method characterized by stopping at an injection mold open position.