JPH06126797A - Device for injection molding of thermoplatic rein - Google Patents

Abstract

PURPOSE:To provide a device for injection molding of thermoplastic resin which is favorable to decrease dimensional failure in the rising time of a molding stage. CONSTITUTION:A round rod-shaped heating part 70 of an electric heater system is inserted into an insertion hole 10 formed on a stationary die plate 1 holding a stationary die 5. A round rod-shaped heating part 71 of the electric heater system is inserted into an insertion hole 3O formed on a movable die plate 3 holding a movable die 6. Escape of heat in the stationary die 5 and the movable die 6 is restrained in the rising time of a molding stage because the stationary die plate 1 and the movable die plate 3 are heated by the heating parts 70, 71 and the temperature is regulated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin injection molding apparatus. This device is suitable for injection molding precision parts made of thermoplastics.

[0002]

2. Description of the Related Art Conventionally, as a thermoplastic resin injection molding apparatus, a fixed die plate for holding a fixed die, a movable die plate for holding a movable die, and an injection machine for injecting a thermoplastic resin have been used. Things are known. In this apparatus, a thermoplastic resin is injected from an injection machine into a cavity formed by a fixed mold and a movable mold that are closed, and after the resin is solidified, the fixed mold and the movable mold are opened to take out a molded product.

By the way, at the time of starting the molding process, the temperature of the molding die is unstable, and it takes a considerable time (generally 60 to 90) to reach a constant temperature.
(About a minute), and dimensional defective products such as dimensional variations easily occur during this period. Dimensionally defective products are not preferable especially for precision parts. Dimensionally defective products are particularly likely to occur at the start of molding after holidays. Therefore, an injection molding apparatus has been developed in which the molding die is equipped with a heating unit for heating the molding die with hot water or an electric heater to adjust the temperature of the molding die.

[0004]

However, even in the above apparatus, since the die plate holding the die is cold, the heat of the die is taken by the die plate, which is not necessarily a measure for reducing defective products. Not enough. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an injection molding device of a thermoplastic resin, which is advantageous for reducing defective products at the start of the molding process.

[0005]

A thermoplastic resin injection molding apparatus according to the present invention enables a fixed die plate holding a fixed die and a solid die plate to be faced to and moved away from the fixed die plate. A movable die plate that is disposed and holds a movable die that is closed to a fixed die by proximity,
It is composed of an injection machine that injects a thermoplastic resin into a cavity formed by a fixed mold and a movable mold that are closed, and the fixed die plate and the movable die plate have a heating unit that heats the die plate. To do.

The heating unit is an electric heater type, hot water heating type,
A steam heating method or the like can be adopted. The heating unit may be built in the die plate or may be held on the outer surface of the die plate. The heating unit has a predetermined time (for example, 1 to
It can have a timer function so that it stops after 2 hours. This is because heating of the die plate is most necessary within a predetermined time from the start of the molding process.

[0007]

The thermoplastic resin is injected from the injection machine into the cavity formed by the fixed mold and the movable mold which are closed, and after the solidification, the fixed mold and the movable mold are opened and the molded product is taken out. In the molding step, the heating unit heats the fixed die plate and the movable die plate to adjust the temperature. Therefore, heat escape from the fixed die and the movable die to the die plate is suppressed.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the device of the present invention will be described below with reference to the drawings. This injection molding apparatus is arranged on the rear side of the fixed die plate 1, a fixed die plate 1 made of metal in the shape of a square plate, a movable die plate 3 made of metal in the shape of a square plate facing the fixed die plate 1. It is composed of an injection machine 4. The movable die plate 3 is arranged so as to be movable along the guide rod 2.

In this apparatus, a fixed die 5 and a movable die 6 as molding dies are used, and the fixed die 5 is held on the mounting surface 1a of the fixed die plate 1 and the movable die 6 is mounted on the mounting surface 3a of the movable die plate 3. Held in. A tube 90 is connected to the fixed die 5 and the movable die 6, and the temperature of the fixed die 5 and the movable die 6 is adjusted by a heat medium supplied from the tube 90.

In this embodiment, the movable die plate 3 moves closer to or farther from the fixed die plate 1 by driving the hydraulic mechanism. Fixed type 5 and movable type 6 due to proximity
Is clamped, and the fixed mold 5 and the movable mold 6 are opened by separation. The injection machine 4 has a cylinder and a plunger inserted in the cylinder. By driving the plunger, the thermoplastic resin is injected into the cavities of the fixed die 5 and the movable die 6.

In this embodiment, a plurality of insertion holes 10 are formed in the side surface of the fixed die plate 1, and a round bar-shaped electric heater type heating unit 70 is inserted into each insertion hole 10. The insertion hole 30 is also formed on the side surface of the movable die plate 3.
The electric heater type heating unit 71 having a round bar shape is also inserted into each of the insertion holes 30. The total number of heating parts 70 inserted into the fixed die plate 1 is four, and the total number of heating parts 71 inserted into the movable die plate 3 is four. The heating units 70 and 71 have a diameter of 12 mm and a length of 1
The one having a power of 20 W and a power of 300 W was used. Heating unit 70,
A power feed line 74 is connected to 71.

The movable die plate 3 is equipped with a first temperature sensor 93 for detecting its temperature, and the fixed die plate 1 is equipped with a second temperature sensor 94 for detecting its temperature. The signals of the first temperature sensor 93 and the second temperature sensor 94 are transmitted to the control panel 8 via signal lines 93a and 94a.
Entered in. Now, in the molding step, the movable die plate 3 approaches the fixed die plate 1, and the fixed die 5 and the movable die 6 are clamped. In the cavity formed by the fixed mold 5 and the movable mold 6 in the mold clamped state, 270 to 280
A thermoplastic resin (11 nylon) of about ° C is injected from the injection machine 4. The conditions for injection molding by the injection machine 4 are a cylinder temperature of 260 to 270 ° C. and an injection molding pressure of 80 to 90 kg / cm ² . Further, in the molding process (when forming a non-defective product), the mold temperature of the fixed mold 5 is 42 to 45 ° C.
In addition, the mold temperature of the movable mold 6 is set to 38 to 42 ° C.

After the resin is solidified, the movable die plate 3 is separated from the fixed die plate 1 so that the fixed die 5 and the movable die 6 are separated.
The mold is opened and the molded product (gear) is taken out. At the start of the molding process as described above, the heating units 70, 71
Is being fed with heat to generate heat, whereby the fixed die plate 1 and the movable die plate 3 are respectively heated and temperature-controlled. At this time, the temperature of the movable die plate 3 is detected by the first temperature sensor 93, and the fixed die plate 1
Is detected by the second temperature sensor 94, and
The fixed die plate 1 is controlled to about 45 ° C by the control panel 8,
The temperature of the movable die plate 3 is adjusted to about 40 ° C.

As described above, in this embodiment, since the fixed die plate 1 and the movable die plate 3 are heated by the heating units 70 and 71 and the temperature is adjusted at the start of the molding process, the mold heat of the fixed die 5 is changed. Escape to the fixed die plate 1 and escape of die heat of the movable die 6 to the movable die plate 3 are suppressed. Therefore, the fixed mold 5 and the movable mold 6 are maintained in an appropriate temperature range, and dimensional defects such as dimensional variation at the time of rising can be suppressed.

In this embodiment, the control panel 8 has a timer function, and a predetermined time (for example, 1 to 2) immediately after the start of the molding process.
After the elapse of time, the fixed die plate 1 and the movable die plate 3 are heated to an appropriate temperature range. To be done. (Other Examples) In addition, the device of the present invention is not limited to the above-described embodiments shown in the drawings. For example, the shapes of the heating units 70 and 71 are not limited to the round bar shape, and may be changed as necessary. Can be carried out.

[0016]

According to the apparatus of the present invention, the escape of mold heat of the fixed mold and the movable mold is suppressed, which is advantageous for reducing defective products at the start of the molding process.

[Brief description of drawings]

FIG. 1 is a perspective view showing a main part of an apparatus.

[Explanation of symbols]

In the figure, 1 is a fixed die plate, 3 is a movable die plate,
4 is an injection machine, 5 is a fixed type, 6 is a movable type, 70 and 71 are heating units, and 8 is a control panel.

Front page continued (72) Inventor Katsuya Kato 1 Ochiai, Nagachi, Kasuga-cho, Nishikasugai-gun, Aichi Toyoda Gosei Co., Ltd. In the company

Claims (1)

[Claims] 1. A fixed die plate for holding a fixed die, a solid die plate facing the solid die plate, arranged so as to be close to and away from the fixed die plate, and close to the fixed die to close the die. A movable die plate that holds a movable die, and an injection machine that injects a thermoplastic resin into a cavity formed by the fixed die and the movable die that are closed, and the fixed die plate and the movable die plate are And a thermoplastic resin injection molding apparatus having a heating unit for heating the die plate.