JP2622300B2 - Injection compression molding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an injection compression molding method of a molded article by an injection molding machine.

(Prior Art) FIG. 4 is a sequence diagram of a 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 advanced, and the core mold 1 is once fitted to 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 direction switching valve 11 is set to the fully closed position, and all ports of the mold clamping cylinder 6 are blocked. The pressure in the oil chamber A 'of the mold clamping cylinder 6 is substantially at atmospheric pressure.

Next, when the molten resin is injected from the injection device 8 and the resin is injected between the core die 1 and the cavity die 2, the core die 1 is pushed to the open side by the flow pressure at the time of injection. The resin pressure at this time is considered to be about 100 kgf / cm ^2, but in order to cope with this, the pressure in the portion A ′ rises to about 20 kgf / cm ² . When the injection operation is completed, the mold clamping ram 5 is advanced to perform mold clamping, and the core mold 1 and the cavity mold 2 are brought into close contact to start cooling.

(Problems 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. Also, a prefill valve 7 for supplying and discharging a large amount of oil into and from the cylinder is required. On the other hand, even when the mold is opened while only the mold e is opened, a resin pressure of 100 kgf / cm ² or more is generated in the mold, which is a large force for opening the mold.

By this force, the oil chamber A 'of the large-diameter mold clamping cylinder 6
Is compressed, but as mentioned above, the stroke of this cylinder is 1000 mm even with a 300 ^TON class molding machine and 2000 mm with a 1000 ^TON class molding machine where injection compression molding is easy to apply. The opening amount of 1mm is well over 1mm. Further, since the sealing force of the prefill valve 7 is not always perfect, when the internal pressure of the cylinder rises, oil escapes from the sealing surface of the valve, and the opening amount of the mold often further increases.

Further, the compression stroke in the injection compression molding is at most 1 to 2 mm even when the thickness of the molded product is about the same. On the other hand, the mold clamping stroke 1 is 1000mm, and the pressure of the A 'part is 20 ± 5kgf / c.
At m ² , the bulk modulus K of the oil is K = 1.9 kgf / cm ² , so the compression amount Δl mm: Δl = l × (20 ± 5) /1.9×10 ⁴ , and the opening by compression is 1.0 + 0.3 mm. If the escape of the oil from the prefill valve 7 is added to this, it exceeds 2.0. If the thickness can no longer be controlled, the variation in quality will increase, the injection pressure will need to be low, and therefore the advantage of injection compression molding that the internal strain will be low will be diminished. If you want to control the compression stroke strictly, use a high response, large capacity servo valve,
There is also a method of performing feedback control so as to keep the mold clamping ram at a predetermined position in accordance with the opening of the mold in the filling step, but this increases the cost of the apparatus and reduces the economical advantage.

The present invention has been proposed to reduce the opening amount at low cost and to keep the opening amount small.

(Means for Solving the Problems) For this reason, the present invention provides a fixed die plate for holding a fixed die, a movable die plate for holding a movable die, and the moving die plate moving forward and backward with respect to the fixed die plate. Means and a tie bar, wherein the movable die plate approaches the fixed die plate, and the fixed die and the movable die are closed and fixed to the fixed die plate to perform mold clamping. Or fixed to the fixed die plate, the fixed fixation of the fixed die plate and the movable die plate is disposed on the opposite die mounting surface of the movable die plate or the fixed die plate, and a half nut which opens and closes in a direction substantially perpendicular to the tie bar or A molded product is formed by a mold clamping device performed by half ring and a mold clamping cylinder disposed on a movable die plate or a fixed die plate. In the injection compression molding method for forming, the stroke amount of the mold clamping cylinder is 100 mm or less, and after the mold matching (mold fully closed) is performed once, the mold is opened and stopped for a predetermined gap required for injection compression molding, An injection operation is performed after blocking all ports of the mold clamping cylinder, and then a mold clamping operation for mold compression for the gap is performed. This is a means for solving the problem. Things.

(Operation) After the mold has been matched, the mold is opened and stopped for a predetermined gap required for injection compression molding, and all ports of the mold clamping cylinder are blocked before performing an injection operation. A mold clamping operation for compression is performed. In addition, by suppressing the stroke of the mold clamping cylinder to 100 mm or less, even if the force to open the mold generated during injection is applied to the mold clamping ram,
Only the conventional 100/1000 opening occurs.

Embodiments The present invention will be described below with reference to the embodiments in the drawings.
The figure shows a mold clamping device for carrying out the method of the present invention, wherein a fixed die plate 4 for holding a fixed mold (cavity mold 2),
Moving die plate 3 holding moving mold (core mold 1)
Means for moving the movable die plate 3 forward and backward with respect to the fixed die plate 4, and the fixed die plate 4 after the movable die plate 3 approaches the fixed die plate 4 and the fixed mold and the movable mold are closed. A tie bar 13 that is fixed and fixed to perform mold clamping; the tie bar 13 is fixed to the movable die plate 3 or the fixed die plate 4; Alternatively, the fixing is performed by a half nut 9 or a half ring which is provided on the opposite die mounting surface of the fixed die plate 4 and opens and closes in a direction substantially perpendicular to the tie bar 13. FIG. 1 shows a sequence when injection compression is performed by the mold clamping device of FIG.

Now, as shown in FIG. 3, the engagement groove 13a of the tie bar 13
A tie bar is attached to the fixed die plate 4 by a known means (not shown).
In a state where the half nut 9 having the mold thickness adjusting mechanism in the axial direction of 13 is disengaged from the engagement groove 9a, pressure oil is sent from the hydraulic source (not shown) to the mold opening / closing cylinder 10 via the direction switching valve 11. Then, the movable die plate 3 is moved forward, and the core die 1 and the cavity die 2 attached to the fixed die plate 4 are once aligned. Next, the mating groove of the tie bar 13 is
13a, the half nut 9 is inserted, the movable die plate 3 and the fixed die plate 4 are once joined and fixed, and from this state, the core mold 1 and the cavity mold are separated by a predetermined gap e required for injection compression by the mold opening / closing cylinder 10. Open 2.

Then, when opened as described above, the ports A and B of the mold clamping cylinder 14 provided inside the fixed die plate 4.
Is blocked (the state shown in FIG. 2). In this state, the injection operation is performed. When the injection operation is completed, pressurized oil is supplied to the A port of the mold clamping cylinder 14 from a hydraulic source (not shown) via the switching valve 12, and the core mold 1 is discharged.
And the cavity mold 2 are closely fitted and cooled, and injection molding of the molded product is performed. In FIG. 2, the example in which the half nut 9 and the mold clamping cylinder 14 are arranged on the fixed die plate 4 has been described. However, depending on the mold clamping force of the injection molding machine, the half nut 9 and the mold clamping cylinder 14 may be arranged on the movable die plate 3 side. The same operation and 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 adjusted by a simple means that only blocks all ports of the mold clamping cylinder, and the conventional direct pressure type mold clamping device is used. Can be raised more than in. In addition, since a prefill valve in the mold clamping cylinder used in the conventional direct pressure type mold clamping device is not required, there is no escape of oil from the seal surface of the prefill valve, and problems such as a large change in the mold opening amount are eliminated. Can be.

[Brief description of the 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 performing the method of the present invention, and FIG. FIG. 4 is a cross-sectional view showing a state in which a nut is disconnected, FIG. 4 is a sequence diagram showing a conventional injection compression molding method, FIG. 5 is a cross-sectional view of a conventional mold clamping device, and FIG. 6 is a prefill valve in FIG. It is sectional drawing which shows the other operation state of. Explanation of main parts in the figure 1,2 ... Mold 3 ... Movable die plate 4 ... Fixed die plate 9 ... Half nut 10 ... Die opening / closing cylinder 11 ... Switching valve 13 ... Tie bar 13a ... Engagement Groove 14: Mold clamping cylinder e: Predetermined clearance required for injection compression

Claims (1)

(57) [Claims] 1. A fixed die plate for holding a fixed mold,
A moving die plate for holding the moving die, means for moving the moving die plate forward and backward with respect to the fixed die plate, and the moving die plate approaches the fixed die plate, and the fixed die and the moving die are closed. With a tie bar that is fixed and fixed to the rear fixed die plate and performs mold clamping,
The tie bar is fixed to the movable die plate or the fixed die plate. The fixed die plate and the movable die plate are connected and fixed on the opposite die mounting surface of the movable die plate or the fixed die plate. In the injection compression molding method of molding a molded product by a mold clamping device performed by a half nut or a half ring that opens and closes, and a mold clamping cylinder disposed on a movable die plate or a fixed die plate, the stroke of the mold clamping cylinder The amount should be 100 mm or less, after the mold matching (mold fully closed) is performed, the mold is opened and stopped for a predetermined gap required for injection compression molding, and the injection operation is performed after blocking all the ports of the mold clamping cylinder. And then performing a mold clamping operation for mold compression for the gap.