JPS6096427A - Injection molding method - Google Patents

Abstract

PURPOSE:To make the surface of a molded object highly accurate and smooth, by a method wherein after a cooland liquid remaining within a medium passage has been removed from the passage through compressed air at the time of starting of induction heating, the induction heating is made until the time before completion of filling of resin from after mold break and the cooland liquid is supplied to the medium passage until the time before the mold break from after completion of the filling. CONSTITUTION:Simultaneously with mold break, a main flow pipes 10a, 10b and flow pipes 13a, 13b are communicated with each other respectively by changing over solenoid valves 15, 16. Then cooling water remaining within a medium passage 8 is removed outside by compressed air from a compressed air supply device 14. At the same time a high-frequency electric current is sent to an induction heating coil 17 and induction heating of a molding component 23 is made up to the middle of resin filling. With this construction, transcription in a molding surface 24 becomes favorable and the surface 52a of a molded object 50 is made highly accurate and smooth. When the filling of molten resin to a part wherein a flange 52 is molded within a cavity 40 is completed, the main flow pipes 10a, 10b and a flow pipe 11 are made to communicate with each other through actions of the solenoid valves 15, 16. Then cooling water is supplied to the medium passage 8 from a water chiller 12 until directly before mold break. With this construction, a sink can be prevented and stabilization in product measurements is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a method of injection molding resin by controlling mold temperature.

(Prior Art) In the conventional injection molding method, a refrigerant liquid is passed through the mold to constantly cool the mold. However, with this method, during injection filling, the molten resin in contact with the molding surface of the mold is cooled and its fluidity is reduced, so the transferability of the mold is reduced.
The surface of the molded product will no longer be smooth. Furthermore, when the flow of molten resin splits into two directions within the cavity and merges again, the fluidity of the resin is reduced due to the above-mentioned reasons, resulting in incomplete merging, resulting in scratches (welds) at the merging area of the molded product. ) is created. Therefore, it is difficult to obtain a molded article with high precision and a smooth surface using the above method.

For this reason, in the case of products requiring highly accurate surfaces, lathe cutting had to be performed after molding.

(Object of the Invention) The present invention has been made based on the above, and its object is to provide an injection molding method that can control the mold temperature and make the surface of the molded product smooth with high precision. .

(Structure of the Invention) The gist of the present invention is to provide a mold with a medium passage and an induction heating coil, perform induction heating at least after the mold is opened and before the completion of resin filling, and at least after the resin filling is completed. An injection molding method characterized in that a refrigerant liquid is supplied to a medium passage before mold opening, and when switching from refrigerant liquid supply to induction heating, compressed air is supplied to the medium passage to remove the refrigerant liquid. be.

Hereinafter, an example of an apparatus for carrying out the method of the present invention will be described with reference to FIGS. 1 to 6. As schematically shown in FIG. It has a mobile type 3. The fixed mold 2 is fixed to the plate 4, and the movable mold 3
is connected to a moving cylinder 6 via a plate 5. By the operation of this moving shilling-6, the moving type 3
moves to close and open the mold.

In the figure, 7 is an injection cylinder, and this injection cylinder 7
Molten resin is then injected and filled into the mold 1.

Fixed type 2. Each of the mobile molds 3 is provided with a medium channel 8.9. Main flow pipes 10a and 10b are connected to the outlet and outlet of the medium passage 8, respectively.

A water cooler 12 is connected to the medium passage 8 via the main flow pipes 10a, 10b and the flow pipe 11.

Further, the inlet of the medium passage 8 is connected to a compressed air supply device 14 via a main flow pipe 10a and a flow pipe 13a. The outlet of the medium passage 8 is communicated with the outside via the main flow pipe 10b and the flow pipe 13b. Main flow pipe 10a
and flow pipe 11. A solenoid valve 15 is provided at the connection portion between the main flow pipe 10b and the flow pipes 11 and 13b, and a solenoid valve 16 is provided at the connection portion between the main flow pipe 10b and the flow pipes 11 and 13b. These solenoid valves 15 and 16 are operated simultaneously by a timer. The fixed mold 2 further includes an induction heating coil 17 built therein. A high frequency oscillator 19 is electrically connected to the induction heating coil 17 via a transformer 18 .

The injection mold 1 of this embodiment has a molded product 50 shown in FIG.
It is designed to be molded. This molded product 50 has a cylindrical portion 51 and a flange 52 formed at one end of the cylindrical portion 51. In particular, the surface 52a of the flange 52 is required to be highly precise and smooth.

The specific structure of the mold 1 will be explained with reference to FIGS. 3 to 6. The mold 1 has one shot and produces a molded product 50 as shown in Fig. 2.
Two pieces are molded. As shown in FIG. 5, a gate 21 is formed in the center of the stationary mold 2, and the injection cylinder 7 described above is connected to this gate 21. Recesses 22 for runner construction are formed on both sides of the gate 21. Further, two molding members 23 are inserted and fixed into the fixed mold 2. The molded member 23 has a highly precisely finished circular molding surface 24 and a circular convex portion 25 at its center. Figure 3.

As shown in FIG. 4, the fixed mold 2 includes the molding member 23.
A closing member 26 is inserted and fixed behind the. The aforementioned medium passage 8 is formed in an annular shape at the opening between the molding member 23 and the closing member 26 . The medium passage 8 is partially closed by a closing member (not shown), has a C-shaped cross section, and both ends thereof communicate with a medium flow port (not shown) formed in the fixed mold 2. . Molding member 23
The above-mentioned induction heating coil and coil 1 are mounted on the surface of the medium passage 8 side.
7 are arranged in a ring.

As shown in FIGS. 3, 4, and 6, two molding recesses 31 are formed in the movable mold 3 at positions facing the molding member 23 of the fixed mold 2. As shown in FIGS. A molding surface 32 is formed inside the molding recess. A runner concave portion 33 is formed between the two molding concave portions 31 . Molding recess 31
A core 34 is installed in the center of the. A cylindrical protruding member 35 is installed on the outer periphery of the core 34.
The tip of this ejecting member 35 is located at the bottom of the molding recess 31 and is adapted to eject the molded product from the movable mold 3.

In the above configuration, in the mold clamping state shown in FIG. 3, the runner concave part 22 of the fixed mold 2 and the runner concave part 33 of the movable mold 3 match, and the runner through which the molten resin passes is shaped like I& At the same time, the molded product 24 of the fixed mold 2 and the molding surface 3 of the movable mold 3
A cavity 40 is formed between the two. Further, the convex portion 25 of the fixed mold 2 and the core 34 of the movable mold 3 are in contact with each other. When molten resin is injected from the injection cylinder 7 in this mold-clamped state, the molten resin passes through the gate 21 of the fixed mold 2 and further flows into the two cavities 40 via the runners.

The molten resin that has flowed into the cavity 40 is divided into two flows by the convex portion 25 and the core 34 as shown by the arrows in FIG. 6, and finally merges at the part farthest from the runner. After the molten resin is filled into the cavity 40 as described above, it is cooled and solidified to form a molded product 50 shown in FIG. After cooling and solidifying, the mold is opened as shown in Fig. 4 to form a molded product 50.
Take out.

Next, temperature control of the mold 1, which is a feature of the present invention, will be explained in detail with reference to FIG. The movable mold 3 is cooled by constantly flowing normal cooling water of about 25° C. through the medium passage 9, as in the conventional method. In the fixed mold 2, heating and cooling are performed alternately.

First, at the same time as the mold is opened, the solenoid valves Is and 16 are switched to connect the main flow pipes 10a and 10b with the flow pipes 13a and 13b, respectively, thereby allowing the medium passage 8 of the fixed mold 2 to be connected to the compressed air supply device 14. This compressed air immediately removes cooling water (described later) remaining in the medium passage 8 from the previous molding cycle to the outside from the medium passage 8.

At the same time as the compressed air is supplied, a high frequency current is passed through the induction heating coil 17 to induction heat the molded member 23. On this occasion,
Since a space consisting of the medium passage 8 is formed behind the induction heating coil 17, the induction heating effect is not directed toward the closing member 26 but is directed mainly toward the molding member 23. Therefore, the temperature of the molding surface 24 of the molding member 23 can be efficiently raised. Induction heating is performed until the middle of resin filling. By induction heating, the temperature of the molding surface 24 of the fixed mold 2 is raised to about the softening temperature of the resin (for example, 100 to 120''C in the case of vinyl chloride resin).

As a result, even if the injected molten resin comes into contact with the molding surface 24, the fluidity is not lost, the transferability on the molding surface 24 is improved, and the surface 52a of the molded product 50 can be made smooth with high precision. . Furthermore, the flow of resin within the cavity 40 is divided into two parts and finally merges, as described above.
As described above, since the fluidity is high, the merging is smooth, and welding on the surface 52a of the molded product 50 can be prevented.

After approximately 2/3 of the molten resin filling time has elapsed, in other words, when filling of the molten resin into the part of the molded product 50 where the flange 52 is to be formed in the cavity 40 is completed, the electromagnetic valve 15.
．． 16, the main flow pipe 10a+10b and the flow pipe 1
1, and from the water cooler 12 to the medium passage 8 of the fixed mold 2.
Cooling water (refrigerant liquid) of approximately 5°C is supplied to the As a result, the temperature of the molding surface 24 of the fixed mold 2 is finally about 60°.
It decreases to about C. The molten resin is kept under pressure and cooled by the molding surface 24 of the fixed mold 2 and the molding surface 32 of the movable mold 3 to solidify. As described above, since sufficient cooling is performed, sink marks can be prevented and product dimensions can be stabilized. The cooling water is supplied until just before the mold is opened.

Note that the present invention is not limited to the above embodiments, and various embodiments are possible. For example, induction heating is carried out at least from after the mold is opened until before the filling of the resin is completed. Therefore, it may be applied until halfway through the filling of the resin as in the above embodiment, or until the completion of the filling. This may be continued until a predetermined period of time has elapsed after the completion of filling. Similarly, the refrigerant liquid is
The refrigerant liquid can be supplied at least from the time the filling of the resin is completed until the mold is opened. Alternatively, it may be started after a predetermined period of time has passed after filling is completed. In this way, the induction heating time period and the refrigerant liquid supply time period can be selected according to the type of resin, product shape, etc. without departing from the gist of the present invention.

Furthermore, in the above embodiment, the method of the present invention was applied to temperature control only for fixed types, but the present invention is not limited to this, and can also be applied to temperature control only for mobile types, and can also be applied to temperature control only for fixed types and mobile types. It can also be applied to both temperature control.

(Effects of the Invention) As explained above, in the method of the present invention, induction heating and cooling with a refrigerant liquid are performed alternately, and the temperature of the molding surface of the mold is raised during resin filling. This improves the transferability of the mold, makes the surface of the molded product smooth with high accuracy, and prevents welding.

Therefore, when a high-precision surface is required, it is possible to omit the work of lathe-cutting the molded product to obtain a high-precision surface. In addition, by lowering the temperature of the molding surface and sufficiently cooling the molten resin, it is possible to prevent sink marks and stabilize the product dimensions. Moreover, since the refrigerant liquid remaining in the medium passage can be immediately removed by compressed air at the start of induction heating, switching from cooling to heating of the mold can be performed quickly and efficiently.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing an example of an apparatus for carrying out the method of the present invention, Fig. 2 is a perspective view showing a molded product obtained by the apparatus of Fig. 1, and Fig. 3 is a cross section of the mold showing the mold clamping state. Figure, 4th
The figure is a cross-sectional view of the mold showing the mold open state, Figure 5 is a front view of the fixed mold, Figure 6 is a front view of the movable mold, and Figure 7 explains one example of one molding cycle according to the method of the present invention. It is a diagram. DESCRIPTION OF SYMBOLS 1...Injection mold, 2...Fixed mold, 3...Movable type, 8...Fixed medium path, 9...Movable medium path, 12...Water cooler , 14... Compressed air supply device, 15° 16... Solenoid valve, 19... High frequency oscillator, 4o... Cavity, 50... Molded product applicant Sekisui Chemical Co., Ltd. Representative Fujinuma. Profiteering Figure 1 Figure 2 Figure 4 Figure 4 Procedural Techniques (U-Osho Hayabusa t) 1937, q/lθ, Mr. Commissioner of the Patent Office 2, Name of Invention Injection Molding Process 3, Person Making Amendment Case Relationship (patent applicant) Address: 2-4-4 Nishitenma, Kita-ku, Osaka Name (217)
Sekisui Chemical Co., Ltd. Drawing 5, Contents of correction Figure 1 Figure 1 tA7 is corrected as shown in the attached sheet. Figure 1

Claims (1)

[Claims] A medium passage and an induction heating coil are provided in the mold, and induction heating is performed at least after the mold is opened and before the resin filling is completed, and refrigerant liquid is applied to the medium passage at least after the resin filling is completed and before the mold is opened. An injection molding method characterized by supplying compressed air to a medium passage and displacing the refrigerant liquid when switching from refrigerant liquid supply to induction heating.