JPH06852A - Multi-stage gas and air venting control method in injection molding machine - Google Patents

Abstract

(57) [Summary] [Purpose] In an injection molding machine, eliminating the influence of gas and air in the cavity on the molded product during the injection process and pressure holding process, and the molded product has the desired shape as a mold. And make sure that there are no burrs on the molded product. [Structure] By a pressure multi-stage control device, the mold clamping force is changed twice during the injection process, that is, the mold clamping forces 1 and 2, and further, during the pressure holding process by changing the mold clamping force 3 through 4 times. The number of times of opening and the amount of opening of the mold are increased, and gas and air in the cavity are exhausted in a total of 6 stages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control method for removing gas and air in an injection process and a pressure holding process of an injection molding machine.

[0002]

2. Description of the Related Art The outline of a conventional injection molding machine will be described below.

1. Main equipment of injection molding machine The injection molding machine is composed of the following devices.

(1) Plasticizing device This is a device that melts a predetermined fixed amount of solid resin so that it can flow.

(2) Injecting device A resin in a fluidized state (plasticized) is filled into a mold at a high speed from a nozzle.

The plasticizing device / injecting device has a structure
Plunger type, pre-plastic type and screw type are available, but a single screw can be used for both plasticization and injection to obtain a uniform molten state, less resin retention area, less pressure loss, etc. The screw-in-line type is most popular due to the characteristics of. The pre-plastic type is plasticized with a dedicated plasticizing screw provided separately,
This is a method in which the plunger is moved forward and injected after it is sent to the front part of the plunger.

(3) Mold clamping device The mold is opened and closed, and the mold is clamped with a strong force so that it will not be opened by the pressure of the resin during injection.

The mold clamping device is classified into a direct pressure type and a toggle type depending on the structure.

(4) Power control unit A hydraulic pressure, a pneumatic mechanical type, or the like is used to generate a force necessary for the operation of each device, and the necessary force is transmitted to each part when needed.

The hydraulic type is composed of an electric motor, a hydraulic pump, various valves, etc., but is equipped with an accumulator mechanism that instantaneously supplies a large amount of high-pressure oil to actuate each actuator at high speed and stability. There is also a molding machine.

(5) Electric control section The operation of each section is sequentially operated according to a preset program.

2. Basic operation of injection molding machine (1) Mold clamping Clamping cylinder closes the mold at low pressure and high speed (first mold clamping), then strengthens the force with a toggle mechanism and clamps at low speed and high pressure to achieve the desired mold. Generate a clamping force (second mold clamping).

FIG. 1 shows an injection molding machine according to an embodiment of the present invention, which is equipped with a multistage pressure control device for evacuating gas and air in the cavity.
A simple pressure control device is provided instead of the multi-stage pressure control device.

(2) Injection Device Advance When the mold clamping is completed, the injection device advances and the nozzle (resin injection port) touches the mold inlet (sprue).

(3) Injection (filling step) When the nozzle touch ends, the screw moves forward while acting as a piston, and the molten resin in the heating cylinder is filled in the mold. At this time, gas and air bleeding is performed only once, and the amount of mold opening is small. If the multistage gas and air bleeding time chart of the embodiment of the present invention shown in FIG. Is.

(4) Holding pressure Since the resin filled in the mold shrinks, pressure is continuously applied until the gate (the resin inlet hole of the molded product) is solidified to replenish the shrinkage resin.

(5) Cooling The resin in the mold is sufficiently cooled and solidified until it can be taken out.

No injection pressure is applied in this step.

(6) Plasticization / Measurement Simultaneously with cooling, the screw is rotated by the hydraulic motor to feed the material toward the nozzle. At this time, it is melted and plasticized by the shear heat insulation by the screw rotation and the band heater wound on the cylinder. When the molten resin accumulates in the nozzle portion, the pressure causes the screw to retract, and the screw continues to retract to the set resin measuring position.

(7) Retracting the injection device The injection device retracts and the nozzle moves away from the mold sprue and returns for the preset timer time.

(8) Mold opening When cooling is completed, the mold is opened by the mold clamping cylinder and the toggle.

(9) When the proximity switch is actuated while the projecting mold is being opened, the projecting mechanism of the mold is operated via the hydraulic cylinder to project and release the molded product.

[0023]

SUMMARY OF THE INVENTION The present invention eliminates the influence of gas and air in a cavity on a molded product during an injection process and a pressure-holding process so that the molded product has a desired shape as a mold. In addition, burrs do not occur in the molded product.

[0024]

According to the present invention, in an injection molding machine, a pressure multistage control device is used to change a mold clamping force a plurality of times during an injection process, and further, at least 1 is performed during a pressure holding process.
The number of mold openings and the amount of mold opening are increased by changing the number of times, and a multistage gas and air bleeding control method for bleeding gas and air in the cavity is adopted to achieve the above object.

The type of resin may be either thermosetting or thermoplastic.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the structure of an injection molding machine according to an embodiment of the present invention will be described with reference to FIG.

The resin pellets stored in the hopper 1 are
It is supplied to the heating cylinder 6. Since the heating cylinder 6 is heated by the heater 7 for heating, the resin pellets are melted. The heating cylinder 6 and the injection cylinder 2 are connected,
The screw 3 is fitted over both cylinders, and the injection cylinder 2 accommodates one end portion of the screw 3, one end shaft portion of the rotation / moving device 4 of the screw 3, and the shaft coupling 5.
8 is a water cooling cylinder, 9 is a torpedo, 10 is a nozzle, 1
Reference numeral 1 is a fixed platen.

Reference numeral 12 is a mold clamping cylinder, 13 is a piston which reciprocates in the mold clamping cylinder 12, 14 is an intermediate mechanism for transmitting the motion of the piston 13 to the movable platen 15, 16 is a hydraulic ejector, 17 is a fixed platen 11 and a mold. A tie bar that connects with the flange of the tightening cylinder 12 and serves as a guide when the movable platen 15 moves, 18 is a mold, 19 is a molded product, 20 is a sprue runner, and 21 is a multistage pressure control device. However, to be exact, the mold clamping cylinders 12 on both sides of the piston 13 are provided with hydraulic pressure supply devices and hydraulic discharge devices, but they are not shown for convenience. The same applies to the injection cylinder 2.

After the movable platen 15 is stopped at a predetermined position by the pressure multi-stage control device 21 and the mold clamping is completed, when the rotation / moving device 4 of the screw 3 is rotated, the screw 3 is rotated and the molten resin is discharged into the nozzle. Fill the mold 18 from 10. Since the resin filled in the mold 18 shrinks,
Continue to apply pressure until the gate solidifies to replenish the shrinkage resin.

Thereafter, the operation of the injection molding machine until the molded product is projected and released is the same as that of the above-mentioned conventional technique.

Next, a multistage gas and air bleeding control method in an injection molding machine, which is a feature of the present invention, will be described with reference to a time chart of one embodiment shown in FIG.

The horizontal axis represents elapsed time, the upper half of the vertical axis represents the mold clamping degree, and the lower half of the vertical axis represents the injection process or pressure switching.

In the injection process (or pressure switching) S0 to S4, when the mold clamping force 1 is not set to the maximum pressure at the position S2 (when gas and air are being released), the time mold clamping force 1 at T1 is set.
The mold clamping force is controlled to the pressure set in. As a result, the mold is slightly opened, and gas and air escape.

After the time T1 has expired, the mold is re-clamped to the maximum pressure and the injection is restarted. Further, at the position S3, gas and air are released for T2 time by the mold clamping force in the same manner as described above, and the mold clamping and injection are restarted after the time is up. Also in this case, when the mold clamping force 2 is set to the maximum pressure, the gas and air bleeding control is not performed.

Then, at the S4 position, each holding time T3 to T
By controlling the mold clamping force to the pressure set by the mold clamping forces 3 to 6 corresponding to No. 6, gas and air bleeding is performed while preventing the occurrence of burrs.

In this pressure holding step, the mold clamping force is controlled simultaneously with the pressure holding without interruption.

As described above, in this embodiment, gas and air bleeding control can be performed in six stages, and various resin types and temperature and pressure molding conditions can be dealt with.

[0038]

EFFECTS OF THE INVENTION According to the present invention, the gas and air in the cavity are discharged in multiple stages during the injection process and the pressure-holding process, so that the molded product has a desired shape as a mold, and There are no vacant spaces caused by gas or air in the molded product, and further, burrs are less likely to occur in the molded product.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an injection molding machine according to an embodiment of the present invention.

FIG. 2 is a time chart of multistage gas and air release in the injection molding machine according to the embodiment of the present invention.

[Explanation of symbols]

 1 Hopper 2 Injection Cylinder 3 Screw 4 Screw Rotating and Moving Device 5 Shaft Coupling 6 Heating Cylinder 7 Heating Heater 8 Water Cooling Cylinder 9 Torpedo 10 Nozzle 11 Fixed Platen 12 Clamping Cylinder 13 Piston 14 Intermediate Mechanism 15 Movable Platen 16 Hydraulic Ejector 17 Tie bar 18 Mold 19 Molded product 20 Spruler 21 Pressure multi-stage control device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuo Shinohara 1111 Kawaharashiro-cho, Ryugasaki-shi, Ibaraki Ibaraki Plant, Nisshin Kogyo Seisakusho (72) Nobuhiko Tokushige 731, Naganuma-cho, Inage-ku, Chiba, Chiba Prefecture 1 Sumitomo Heavy Industries, Ltd. Chiba Works

Claims (1)

[Claims] 1. Injection molding for increasing the number of mold openings and the amount of mold opening by changing the mold clamping force a plurality of times during the injection process and at least once during the pressure holding process to remove gas and air from the cavity. Gas and air bleeding control method for machine.