JPH03268921A - Injection compression molding method - Google Patents

Abstract

PURPOSE:To enable an improvement in accuracy of an injection compression stroke, by a method wherein a mold is broken by a quantity for a fixed gap after performance of mold register once by limiting a stroke quantity of a mold clamping cylinder, an injection action is performed by blocking the whole port of the mold clamping cylinder and then a mold clamping action of a quantity for a gap is performed. CONSTITUTION:Hydraulic coil is sent to a mold breaking and clamping cylinder 10 through a directional control valve 11 under a state where joining between fitting groove part 13a of a tie bar 13 and a fitting groove part 9a of a half nut 9 is disjoined. A movable die plate 3 is moved forward and a core mold 1 and cavity mold 2 are put together once. Then the half nut 9 is put into the tie bar 13 under this state and the die plates 3, 4 are made into a joined and fixed state once. The core mold 1 and cavity mold 2 are broken by a quantity for a fixed gap (e) necessary for injection and compression by the mold breaking and clamping cylinder 10 from a state kept as it is. At the same time, ports A, B of the mold clamping cylinder 14 of the stationary die plate 4 are blocked. An injection action is performed under this state, after completion of which the hydraulic oil is put into the port A of the mold clamping cylinder 14 through a directional control valve 12. The core mold 1 and cavity mold 2 are cooled by sticking them to each other and compression molding of a molding product is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for injection compression molding a molded article using an injection molding machine.

(Prior Art) FIG. 4 is a sequence diagram of conventional injection compression molding, and FIG. 5 is a side sectional view of a conventional mold clamping device.

In FIG. 5, the mold clamping ram 5 and the movable die plate 3 are moved forward, and the core mold 1 is once fitted into the cavity mold 2 attached to the fixed die plate 4. In this state, the prefill piston 7 is closed. Next, the mold clamping ram 5 is retracted by an amount e necessary for injection compression. In this state, the directional control valve 11 is set to the fully closed position, and all ports of the mold clamping cylinder 6 are blocked. Further, the pressure in the oil chamber A' of the mold clamping cylinder 6 is approximately at atmospheric pressure.

Next, the molten resin is injected from the injection device 8, and the core mold 1 is
When resin is injected between the core mold 1 and the cavity mold 2, the core mold 1 is pushed toward the open side by the fluid pressure at the time of injection. The resin pressure at this time is thought to be approximately 100 kgf/cd, but in order to correspond to this, the pressure in section A' is 20 kgf/co! rise to a certain extent. When the injection operation is completed, the mold clamping ram 5 is moved forward to clamp the mold, and the core mold 1 and the cavity mold 2 are brought into exact alignment and cooling begins.

(Problem B to be Solved by the Invention) In the direct pressure type mold clamping device, the mold clamping cylinder 6 needs a stroke sufficient to open and close the mold.

A prefill valve 7 is also required for supplying and discharging a large amount of oil into the cylinder. On the other hand, even when the mold is injected with the mold open by e, there is still 100 k inside the mold.
A resin pressure greater than g f /ci is generated, and this becomes a large force that tries to open the mold.

This force compresses the oil chamber A' of the large diameter mold clamping cylinder 6, but as mentioned above, the stroke of this cylinder is 1000 mm even in a 300 TON class molding machine, and the stroke of this cylinder is 1000 mm ON class, where injection compression molding is easily applicable. In the case of a molding machine of 2,000 mm, the amount of opening of the mold due to the compression of oil far exceeds that of Inn. Also, prefill valve 7
The sealing force of the valve is not perfect, so when the cylinder internal pressure increases, oil often escapes from the valve sealing surface and the mold opening amount becomes even larger.

Furthermore, the compression stroke in injection compression molding is at most 1 to 2 cm, even when considering the thickness of the molded product.

On the other hand, the mold clamping stroke is 1000un, and A'
The pressure in the area becomes 20±5 kgf/all, and the bulk modulus of oil K = 1.9 x 10'kgf/cff
l, compression amount Δ1tttIIl:Δ! -1X (20±0
．． 5)/1.9 x 10', the opening due to compression is 1.0±0.3 mm, and if the escape of oil from the prefill valve 7 is added to this, it exceeds 20 m+++.

If the thickness cannot be controlled, there will be greater variation in quality, and the advantages of injection compression molding, which require lower injection pressure and therefore less internal distortion, will be diminished. Alternatively, if you want to tightly control the compression stroke, you can use a high-response, large-capacity servo valve and perform feedback control to keep the mold clamping ram in a predetermined position as the mold opens during the filling process. This increases the cost of the device and reduces the economic benefits.

The present invention has been devised in order to reduce the opening amount at low cost.

(Means for Solving the Problems) Therefore, the present invention provides a fixed die plate that holds a fixed mold, a movable die plate that holds a movable mold, and moves the movable die plate forward and backward relative to the fixed die plate. and a tie bar that is coupled and fixed to the fixed die plate to perform mold clamping after the movable die plate approaches the fixed die plate and the fixed die and the movable die are closed, and the tie bar is connected to the movable die plate. Or, the fixed die plate is fixed to the fixed die plate, and the fixed die plate and the moving die plate are connected and fixed by a half nut or a half nut, which is arranged on the opposite mold mounting surface of the moving die plate or the fixed die plate, and opens and closes in a direction approximately perpendicular to the tie bar. In an injection compression molding method in which a molded product is molded using a mold clamping device using a ring and a clamping cylinder disposed on a movable die plate or a fixed die plate, the stroke amount of the clamping cylinder is 100 mm or less, and the mold After fitting (fully opening the mold), the mold is opened by a predetermined gap required for injection compression molding and stopped, all ports of the mold clamping cylinder are bronched, and the injection operation is performed. It is designed to perform a mold clamping operation for mold compression, and this is used as a means to solve the problem.

(Function) After the molds are matched, the mold is opened by a predetermined gap required for injection compression molding, then stopped, all ports of the mold clamping cylinder are blocked, and the injection operation is performed. Perform mold clamping operation for compression. In addition, by suppressing the stroke of the mold clamping cylinder to 100 seconds or less, even if the mold opening force generated during injection is applied to the mold clamping ram,
Only the conventional 100/1000 difference occurs.

(Example) The present invention will be described below with reference to the embodiments shown in the drawings. Fig. 2 shows a mold clamping device for carrying out the method of the present invention, and shows a fixed mold (
A fixed die plate 4 that holds a cavity mold 2), a movable die plate 3 that holds a movable mold (core mold 1),
The movable die plate 3 is moved forward and backward relative to the fixed die plate 4, and after the movable die plate 3 approaches the fixed die plate 4 and the fixed mold and the movable mold are closed, the movable die plate 3 is connected and fixed to the fixed die plate 4. The tie bar 13 is fixed to the movable die plate 3 or the fixed die plate 4, and the fixed die plate 4 and the movable die plate 3 are connected and fixed by the movable die plate 3 or the fixed die plate. This is done by a half nand 9 or a half ring that is disposed on the die plate 4 opposite to the die mounting surface and opens and closes in a direction substantially perpendicular to the tie bar 13. Further, FIG. 1 shows a sequence when injection compression is performed using the mold clamping device shown in FIG. 2.

Now, as shown in FIG. 3, a half nut 9 is provided with a mold thickness adjusting mechanism in the axial direction of the tie bar 13 by a known means not shown in the retaining groove 13a of the tie bar 13 and the fixed die plate 4.
With the coupling with the engagement groove 9a removed, pressurized oil is sent from a hydraulic power source (not shown) to the mold opening/closing cylinder 10 via the directional control valve 11, the movable die plate 3 is advanced, and the core mold 1 is moved forward.
and the cavity mold 2 attached to the fixed die plate 4 are once aligned. Next, with the molds matched, tie bar 13
Insert the half nand 9 into the retaining groove 13a of the movable die plate 3 and the fixed die plate 4 to once connect and fix them, and from this state, use the mold opening/closing cylinder 10 to open the core mold 1 by a predetermined gap e necessary for injection compression. and open cavity mold 2.

Then, when it is opened as described above, the fixed die plate 4
Boat A of the mold clamping cylinder 14 provided inside the
Block B (state in Figure 2). In this state, the injection operation is completed, and pressurized oil is put into the A port of the sloppy mold clamping cylinder 14 from a hydraulic source (not shown) via the switching valve 12, the core mold 1 and the cavity mold 2 are perfectly aligned, cooled, and molded. Performs injection compression molding of products. In addition, in Figure 2,
The explanation has been given using an example in which the half nut 9 and the mold clamping cylinder 14 are arranged on the fixed die plate 4, but depending on the mold clamping force capacity of the injection molding machine, they may be arranged on the movable die plate 3 side, and the same effect can be obtained. The effect can be obtained.

(Effects of the Invention) Since the present invention is configured as described above, the accuracy of the compression stroke for injection compression can be improved by simply blocking all the boats of the mold clamping cylinder, compared to the conventional direct pressure type mold clamping device. It can be much higher than . In addition, since the prefill valve inside the mold clamping cylinder used in conventional direct pressure mold clamping devices is not required, there is no leakage of oil from the sealing surface of the prefill valve, eliminating problems such as large changes in the amount of mold opening. I can do it.

[Brief explanation of drawings]

FIG. 1 is a sequence diagram of an injection compression molding method according to an embodiment of the present invention, FIG. 2 is a cross-sectional view of a mold clamping device for carrying out the method of the present invention, and FIG. 4 is a sequence diagram showing a conventional injection compression molding method, FIG. 5 is a sectional view of a conventional mold clamping device, and FIG. 6 shows a prefill valve other than the one shown in FIG. 5. FIG. Explanation of main parts of the figure 1.2 - Mold 3 - Moving die plate 4 - Fixed die plate 9 - Half nut 10 - Type opening/closing cylinder 11 - Switching valve 13 - Tie 8' - 13a - Engagement groove 14 - Mold clamping cylinder e-・Predetermined clearance required for injection compression 4 [! 1 Figure 6 JPJJ Figure 2 Figure 3 Procedure Nfu Seisho

Claims (1)

[Claims] a fixed die plate that holds a fixed mold; a movable die plate that holds a movable mold; means for moving the movable die plate forward and backward relative to the fixed die plate; the movable die plate approaches the fixed die plate; After the fixed mold and the movable mold are closed, the tie bar is fixed to the fixed die plate and clamps the mold, and the tie bar is fixed to the movable die plate or the fixed die plate, The connection and fixation with the movable die plate or the fixed die is achieved by a mold clamping device using a half nut or half ring that is installed on the side opposite to the mold mounting surface of the movable die plate or the fixed die plate and opens and closes in a direction approximately perpendicular to the tie bar, and the movable die plate or the fixed die plate. In an injection compression molding method in which a molded product is molded using a mold clamping cylinder arranged on a plate, the stroke amount of the mold clamping cylinder is 100 mm or less, and injection compression molding is performed after mold matching (mold fully closing) is performed. The mold is opened and stopped by a predetermined gap required for the mold, and all ports of the mold clamping cylinder are blocked before the injection operation is performed.
An injection compression molding method characterized in that a mold clamping operation is then performed to compress the mold by the amount of the gap.