JPS62255111A - Injection and compression molding - Google Patents

Abstract

PURPOSE:To obtain proper molding conditions easily through simple and inexpensive structure by a method wherein a parting surface displacement sensor is incorporated into a mold, the mold is opened upon filling for injection while reducing mold clamping force, the mold clamping force is increased in an injection pressure holding zone and the control of a mold opening amount is stopped. CONSTITUTION:A displacement (gap delta), detected by the displacement sensor 21 of a parting surface displacement detecting unit 8, is sent to a controller 30 to control injection and compression. A mold causes compression deformation during mold clamping pressure increasing zone (a), therefore, the displacement of the parting surface is reduced and arrives at the displacement deltaG, corresponding to a mold clamping hydraulic pressure PG. Subsequently, the compression is reduced in a zone (i) for filling for injection and the displacement of the parting surface begins to increase, then, the zone (j), in which the amount of mold opening is controlled, is started at a point C whereat the displacement arrives at a value deltaC. In the zone (j), the hydraulic pressure, applied on an injection cylinder 16, is controlled by a servo valve 38 so as to keep the displacement of the parting surface at a value deltaY. Subsequently, the mold clamping hydraulic pressure is increased to a pressure PE to obtain a high mold clamping force in an injection pressure holding zone (k) and the control of the mold opening amount is stopped to start the control of an injection hydraulic pressure, whereby the mold is closed and resin in a cavity is compressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection compression molding method for forming molded products that require low distortion and high precision, such as plastic lenses and optical discs.

(Prior Art) FIG. 6 shows an outline of a conventional injection compression and molding apparatus and its control circuit diagram. In normal injection molding, when molten resin flows through the molded product cavity of the mold during injection, pressure gradients occur in four directions of flow, which causes residual stress in the molded product. Therefore,
For molded products that require low distortion and high precision, such as plastic lenses and optical discs, injection compression molding is performed to equalize resin pressure by compressing the molded product cavity after molten resin is injected and filled into the molded product cavity. ing. When the resin pressure in the molded product cavity becomes uniform, the residual stress in the molded product is reduced, and a highly accurate molded product with small distortion can be obtained.

Now, in Fig. 6, l is a mold clamping sill, 2 is a mold clamping ram inside the sill, 3 is a tie bar connecting the mold clamping sill 1 and the fixed mold platen 5, and 4 is supported by the tie bar 3 so as to be movable back and forth. It is also a movable mold board connected to the mold clamping ram 2. 106 is a movable side mold attached to the movable die platen 4, 107 is a fixed side die attached to the fixed die platen 5,
2o is a molded product cavity.

In addition, the raw material resin is shown in 1. No cylinders from the hopper ゛1
The fabric of the screw 14 in the figure 3 is supplied to the drawing eye 1 (part 1), is melted and plasticized by heating by a heater (not shown), and rotation of the screw 14 driven by the hydraulic mold 18, and is transferred to the front of the screw 14. The molten resin 12 and j~ are sent and stored.

On the other hand, by sending pressure oil from the hydraulic inflow source 34 through the servo valve 38 to the illustrated side of the injection sill 15, the screw 4 is advanced to the left in the drawing via the injection ram 16 and the bearing box 17. , the molten resin 12 at the tip of the screw 14 is injected into the molded product cavity 2o. In the figure, 130 is a controller, 19 is a position sensor, 31.32 is a hydraulic pressure sensor, 33 is a hydraulic pressure inflow source, and 35 is a proportional electromagnetic IJ IJ-
37 is a 1] 1]-F valve, and 36 is a switching valve.

Molten PA into molded product cavity 20! After the resin 2 is injected and filled, the compression ram 151 is moved in the direction of the molded product cavity 2o by sending pressure oil to the compression cylinder 150 in the movable mold 106 through the switching valve 160, and the resin in the cavity 20 is compress.

However, in this conventional example, a compression cylinder for compressing the resin in the molded product cavity is provided in each mold, resulting in high mold costs and the possibility of sideways movement of the mold. Sometimes it is difficult to incorporate.

Furthermore, it is difficult to set appropriate molding conditions because it is difficult to make fine stroke adjustments of the compression sill that determines the amount of resin compression.

(Problems to be Solved by the Invention 1.) As mentioned above, in the conventional injection compression acid type machine in which a compression sill is installed in the mold, the mold cost for installing the compression sill is high, and the stroke adjustment of the sill is difficult. Since it is not easy, there is a problem that it is difficult to obtain appropriate molding conditions. The present invention aims to solve this problem and provide an injection compression molding apparatus that has a simple structure, is inexpensive, and can easily obtain appropriate molding conditions.

(Means and effects for solving the problem) For this reason, the present invention sets the mold clamping reference point at the value of mold clamping oil pressure or mold clamping force, and sets the mold clamping reference point at the value of mold clamping oil pressure or mold clamping force, and 1. Detect displacement of the mold parting surface when the detected value reaches the set value.
(7) In the injection filling section, the mold clamping force is set low. The mold parting surface displacement value that has changed in the mold opening direction by the opening amount set value is controlled by the injection hydraulic circuit as a target, and the mold clamping force is increased in the subsequent injection holding pressure section.
This is designed to stop the displacement of the ξ-ting surface of the mold when the mold is opened, and this is used as a means and function to solve the problem.

(Example) The present invention will be described below with reference to the drawings. Figures 1 to 3 show examples of the present invention, Figure 1 shows an outline of an injection molding machine and its control circuit, and Figure 2 shows an outline of an injection molding machine and its control circuit. 3 is an enlarged sectional view of a part in which a parting surface displacement detection device, which is the main part of the present invention, is incorporated, and FIG. 3 shows the main circuit of the controller of the present invention.

Now, in FIG. 1, the parts other than the mold 7, the notting surface displacement detecting device 8, which will be described later, the slide N21a, which will also be described later, and the controller 30 are the same as those shown in FIG. 6 and the conventional device. Therefore, the description and details of these same parts will be omitted, except that the compression cylinder 150 and its switching valve 160 shown in FIG. 6 are used in this embodiment.

Next, in Fig. 1, which is the main part of the present invention, the part indicated by A will be explained in detail.The details of the part indicated by A are shown in Fig. 2. , 7P are 21 displacement sensors on the .xi.-ting surface of the identification side mold, which are fitted into the sleeve 22. For installation, the sleeve 22 has shoulders 2 on its outer periphery at the large diameter part and the small diameter part.
A rubber pad 23 is attached to prevent the mold from falling through the mold 2a, and the dimensions are such that the rubber pad 23 is slightly compressed before the mold is closed, as shown in the figure.

Dimension 24 is a set screw that prevents the displacement sensor 21 from coming out from the mounting sleeve 22. 21
11-1.a of the displacement sensor 21; The line leads to the outside of the mold and connects to the controller 30 shown at 11121 I7. For installation, the sleeve 22i17t, for example, is press-fitted into the stationary mold 7, and the shoulder 22a of the sleeve 22 is firmly attached to the mold 7. If the adhesion of the rubber pad 22a loosens, it will cause errors in gap measurement and glitches, so to prevent this, always attach the rubber pad 22a before the mold is closed.
3, it is pressed toward the shoulder portion 22a.

In Fig. 3, 3I is the same oil pressure sensor as shown in Fig. 1, and 21 is the same displacement sensor as shown in Fig. 2. This is a setting device for the clamping oil pressure PC, and a setting device for the mold clamping oil pressure PS that crosses the 51 mold clamping reference point. 40 and 41 are amplifiers. 70 is a signal line, and when the mold clamping pressure P≧PC, the comparator 55
A signal is output (ON) from the signal line 65, and 60 is a memory device that stores the human force δ for g-ting from the signal line 65 when the signal from the signal line 70 is switched from OFF to ON.
The value δC at that time is output to the signal line 75. The value of this δC is cleared to 0 when the 1) set signal is input from the signal line 80.Similarly, the mold clamping pressure P≧PS is determined by the signal line 71.
At this time, a signal is output (ON) from the comparator 56, and at that time, the memory 61 stores the human force δ for the displacement of the ξ-ting surface from the signal line 66 (1 to 1), and outputs the value δ5 to the signal line 76. The value of δS is held until a reset signal is input from 81. Furthermore, reset signals to the signal lines 80 and 81 are input at the start of every injection molding cycle (when the mold is closed or opened). Further, the parting surface displacement δ is constantly outputted from the signal line 42. On the other hand, 52 is a mold opening ty setting device, and an adder 57 adds the input y from 52 and the ξ-ting surface displacement reference value δS from the signal line 77, and the total value sy is added to the signal line 7.
8 is output.

Next, to explain the operation of the above embodiment, in FIG. 1, the switching valve 36 directs the pressure oil from the hydraulic inflow source 33 to the mold closing side (left side in the figure) or the mold opening side (left side in the figure) of the mold clamping sill 1. (right side) and supply it. That is, when the solenoid a is energized, the pressure oil from the hydraulic inflow source 33 flows to the left side of the mold clamping ram 1, causing the mold clamping ram 2, and therefore the movable mold platen 4 and the movable mold 6 connected thereto, to the right side. move towards
Perform the mold closing action. Conversely, when solenoid b is energized, the pressure oil from the hydraulic inflow source 33 flows to the right side of the mold clamping sill 1, moves the mold clamping ram 2, movable mold platen 4, and movable mold 6 to the left, and opens the mold. At the neutral position, where neither solenoid a nor b is energized, the mold closing side,
When the mold is opened, both oils are released to the tank.

When the solenoid Va is energized and the mold closing operation is performed as described above, after the mold is closed, the mold clamping pressure rises to the set pressure of the solenoid valve 35 and is maintained. Ru. The set pressure of this 11-leaf valve 35 is changed by an electric signal from the controller 30. In addition, during the injection operation, the mold clamping pressure increases sufficiently.1. It will be done after that.

Next, the injection operation will be described. Pressure oil is sent from the hydraulic inflow source 34 through the servo valve 38 to the side of the injection sill 15 shown in the drawing, and then passes through the injection ram 16 and the bearing box 17 to the 1. The screw 14 is advanced to the left in the figure, and the molten resin 12 at the tip of the screw 14 is injected into the molded product cavity 20.

When the oil pressure of the relief valve 37 rises too much,
1- It is a safety valve that closes.

Further, a parting surface displacement detecting device 8 is used to detect the gap δ in FIG. That is, in Figure 2,
The displacement sensor 21 transmits an output (voltage or current) proportional to the gap δ through the lead wire 21a! , and generate it. Now, the first
In the figure, the displacement (gap δ in Figure 2) detected by the parting surface displacement detection device 8 is sent to the controller 3o, and the controller 30 uses the path (b) in Figure 3 to transmit the displacement as shown in Figure 4. Performs injection compression control.

In Fig. 4, the time axis is common in the diagram of mold clamping oil pressure and parting surface displacement, and the points with 1 and 2 attached to the same alphanumeric symbol in the drawing diagram indicate the same point in time. represent. In the figure, δ1) is the parting surface displacement immediately after each of the molds 6 and 7 is closed, with no clamping force acting i. In addition, in the mold clamping pressure increase section a, due to the compressive deformation of the mold due to the increase in parting surface receiving pressure, the displacement of the chiming surface represented by the gap δ in Fig. 2 decreases, and the parting surface corresponding to the mold clamping hydraulic pressure PG decreases. The contact surface displacement reaches δG.

Subsequently, in the injection filling section i, the molded product cavity 20
Since the resin pressure acts in the direction of opening the mold, the compressive deformation decreases L2, and therefore the ξ-ting surface displacement begins to increase and the displacement δ. Section J in which the mold opening amount is controlled at point C, which reaches
Enter. In section j, the mold is opened by the resin pressure in the molded product cavity, and the hydraulic pressure acting on the injection cylinder 16 is controlled by the servo valve 38 in FIG. 1 so that the parting surface displacement remains at a constant value δ. In the injection filling section 1, the injection speed is controlled in the same manner as before until entering the section J in which the mold opening amount is controlled.

The length of section J that controls the amount of mold opening is set by a timer,
When the “section” ends, the mold clamping oil pressure is raised to PE, and
The mold opening amount control 1 is stopped and switched to the injection holding pressure section K in which the injection oil pressure is controlled. The length of the pressure holding section is also set by a timer.

As described above, in the injection filling section 1, the mold clamping oil pressure PG
The mold is opened by low mold clamping force (7) and the resin pressure in the molded product cavity, and the amount of mold opening is controlled so that the displacement of the gating surface is δ.

In the next injection holding pressure section K, the mold clamping oil pressure P1. ), and by stopping the mold opening amount control 1 and changing the injection hydraulic pressure M [, the mold clamping force becomes larger than the mold opening force caused by the resin pressure in the molded product cavity, and the mold opening force increases. The mold is closed and the resin within the molded cavity is subjected to partial pressure.

Here, in this embodiment, the mold/groove surface displacement reference point δ8 is set as the point corresponding to the set hydraulic pressure f')s of the mold clamping reference point because the parting surface displacement corresponding to the mold clamping hydraulic pressure 0 In terms of δD, the contact between both sides of the mold is uneven, and there is a risk that it will not close completely.
This is because it is thought that it is better to use the state where the mold clamping oil pressure is slightly lowered as the reference point.In the detection of the parting surface displacement δ, errors may occur due to temperature and other environments. In this device, in every cycle of the injection acid type, the parting surface displacement δ corresponds to the set mold clamping pressure pc and PS for the mold opening amount control start point and the mold clamping reference point. and δ5 detected 1
, the error is small within one cycle, and the accuracy is good.

Note that the mold opening amount control starting point is /ξ meeting displacement δ as in this embodiment. Of course, it is also possible to determine it by setting the screw position and time without using. Also,
Since the mold clamping oil pressure and the mold clamping force are in a proportional relationship, by incorporating a conversion circuit therefor, the mold clamping force can be easily used in place of the mold clamping oil pressure in this embodiment.

FIG. 5 shows a characteristic diagram of injection control in another embodiment.
This embodiment differs from the embodiment shown in FIG. 4 in that the parting surface displacement δF is controlled to a constant value in the injection holding pressure section K, in which injection hydraulic pressure is controlled in the same section. Note that the above δF is determined by setting the mold clamping pressure Pp as in the above embodiment, and by setting the mold clamping pressure K at the time of mold clamping pressure increase.
PFK is obtained by detecting the displacement of the cutting surface corresponding to the parting surface, or the amount of compression Z is determined from the parting reference displacement δ5.
is set, and let δ5-2 be the value. Therefore, in the embodiment shown in FIG. 5, the compression displacement amount δ, -δF7'l of the resin in the molded product cavity is kept constant, so the variation in compression for each mold cycle is smaller than in the previous embodiment. There is an advantage.

(Effects of the Invention) As explained in detail above, the present invention is constructed by incorporating a groove surface displacement sensor into a mold, opening the mold by lowering the mold clamping force during injection and filling, and opening the mold. The amount is precisely controlled by parting surface displacement #12, the mold clamping force is increased in the injection holding pressure section, and the mold opening amount control is stopped to close the mold and compress the resin in the molded product cavity. , an injection compression molding device with a simple structure and low cost can be realized. Furthermore, since the mold opening amount can be changed simply by changing the set value, appropriate molding conditions can be easily found.

Furthermore, since the above-mentioned mold opening amount is highly accurate, there are many excellent effects such as less molding fluctuation.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of an injection compression molding apparatus showing an embodiment of the present invention and a system diagram including its control circuit, Fig. 2 is an enlarged view of section A in Fig. 1, and Fig. 3 is a diagram of the controller of the present invention. The circuit diagram of the main part, Fig. 4 is a special diagram of the injection compression side of the present invention, Fig. 5
The figure is an injection compression control characteristic diagram in another embodiment of the present invention.
FIG. 6 is a side view of a conventional injection compression molding apparatus and a system diagram including its control circuit. Explanation of main parts of the figure 6.7... Mold 8 - Nominated surface displacement detection device 21... Displacement sensor 21a... Lead wire 22... Sleeve 30 Controller 31 Oil pressure sensor 35 Proportional electromagnetic relief valve 50.51. 52...Setter 55, 56-Comparator 57
...Adder 60.61...Memory Figure 4 Procedural Amendment June 6, 1986 Director General of the Patent Office Michibe Uga 1, Indication of Case Patent Application No. 1988-99114 2, Title of Invention Injection compression molding method 3, relationship with the case of the person making the amendment Patent applicant address: 5-1, Maruno Potter-chome, Chiyoda-ku, Tokyo Name:
(620) Mitsubishi Heavy Industries, Ltd. 46 Agent address: 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. Name (6124) Patent attorney Akatsuki Sakama, 2 others 5
, Sub-agent 7, Full text of the specification to be amended 8, Contents of amendment

Claims (1)

[Claims] Set the mold clamping reference point with the value of mold clamping oil pressure or mold clamping force, and calculate the displacement of the mold parting surface when the detected value of mold clamping oil pressure or mold clamping force when increasing mold clamping pressure reaches the set value. It is detected and stored as the mold parting surface displacement reference point, and the mold clamping force is lowered during the injection filling section, and from the middle of the injection filling section onward, the mold opening amount setting value is set from the mold parting surface displacement reference point. The mold parting surface displacement value that changes in the mold opening direction is controlled by the injection hydraulic circuit as a target, and the mold clamping force is increased in the subsequent injection holding pressure section to stop the mold parting surface displacement control during the mold opening. Characteristic injection compression molding method.