JPS6378720A - Molding die - Google Patents

Abstract

PURPOSE:To make it possible to shorten the required time of the heating and cooling cycle of a molding part and consequently improve the productivity by a structure wherein metallic molding parts consisting of a cavity are provided in such a manner that a non-metallic heat insulating part, on the molding part of which a cooling passage is provided and on the rear part of which an induction heating coil is arranged, is formed on the rear part of the molding parts. CONSTITUTION:A cavity is formed by closing a fixed mold and a movable mold. In addition, molding surfaces 3 are heated by flowing oil through cooling passage 7. At this time, the heat transfer between the coil and a heating plate 2 is done speedily. In addition, no heat dissipates beyond a ceramic heat insulating mamber 4 to its rear part. After the stopping of the circulation of the oil, high frequency current is passed through a copper pipe 10 so as to generate induction current in a ring core 1 and the heating plate 2 in order to heat the respective molding surfaces 3 up to 200 deg.C. No induction current generates in the heat insulating member 4 and in the oil in the cooling passage 7 and neither the member nor the oil are heated. By injecting resin in the cavity under the condition that the molding surfaces 3 are held at 200 deg.C, the resin keeps its high fluidity and closely contacts with the molding surfaces 3. Finally, the high frequency current is stopped and oil is circulated through the cooling passage 7 so as to cool the respective molding surfaces 3 in order to solidify the resin.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention is directed to the manufacture of precision molded products such as substrates for magnetic disks.
7. Used for construction. Between the Toragata Kinkyo.

(Prior Art) Generally, extremely high precision surface smoothness is required for substrates for magnetic disks and optical disks. Therefore, when manufacturing these substrates by injection molding, when injecting the resin into the cavity, the fixed mold and the movable mold are heated to heat the molding surface to a temperature higher than the resin solidification temperature to prevent the resin from entering the cavity. After the resin is sufficiently spread, each mold is cooled to solidify the resin and then released from the mold.

One of the above-mentioned heating methods uses induction heating as disclosed in Japanese Unexamined Patent Publication No. 57-4748. The above publication discloses two types of methods. That is, in the first method, before injecting the resin, a metal body (hereinafter referred to as an inductor) having a coil connected to a high-frequency oscillator is sandwiched between a movable mold and a fixed mold, and a high-frequency current is applied to the coil. 1) After heating the molded part by high-frequency induction heating, the mold is opened, the inductor is removed, the mold is closed again, and the resin is injected into the cavity.The second method is to use a movable mold. In this method, the inductors are embedded in the backs of molding parts of fixed molds, and each molding surface is heated by high-frequency induction heating when the molds are closed, and resin is injected into the cavities.

(Problems to be Solved by the Invention) However, each of the above induction heating methods has the following problems.

In the first method, the work of attaching and removing the inductor is necessary before injecting the resin, which is complicated, and the heated molding part is The disadvantage was that it was cooled.

In the second method, since the inductor is in direct contact with the molding part, induction heating is applied not only to the molding part of each mold but also to the inductor, which increases the heat capacity.
Heating and cooling took a long time, resulting in poor productivity.

(Means for Solving the Problems) This invention has been made to solve the above problems, and its main feature is that it has a molded part made of metal that forms a cavity, and has a molded part on the back of the molded part. The molding die is characterized in that a metal heat insulating part is formed, a cooling passage is provided on the molding part side of the heat insulating part, and an induction heating coil is arranged at the back of the heat insulating part.

(Function) When a high frequency current is passed through the induction heating coil, an induced current is generated in the molded part, and the molded part is heated by induction. Since the heat insulating part interposed between the coil and the molded part is made of non-metallic material, no induced current is generated and no heating occurs. This heat insulating section blocks the transmission of heat to the back rather than the heat insulating section. Therefore, only the molded part is efficiently heated in a short time.

Further, after the resin is injected into the cavity in the heated state, the induction heating is stopped, and the molded part is cooled by circulating a refrigerant in the cooling passage, thereby cooling the resin in the cavity. At this time, since the refrigerant almost directly contacts the molded part, the molded part and the resin are quickly cooled.

Therefore, the time required for heating and cooling cycles of the molding section can be shortened, and productivity is improved.

(Embodiment) Hereinafter, an embodiment of the present invention will be described based on the drawings from FIG. 1 to FIG. 3.

In FIG. 1, reference numeral 20 denotes a molding unit of a molding die, and the molding unit 20 has a cylindrical ring core 1 made of metal. A step portion 1a is formed at the outer peripheral end of the ring core 1, and a protrusion portion 1b protruding toward the center is formed on the same side as the step portion 1a.

A heating plate 2 is fitted onto the center side of the projection 1b of the ring core 1. The heating plate 2 is made of metal, has a disc shape, is thicker than the projection 1b, and has a hole 2a in the center.
is formed.

The ring core 1 and the heating plate 2 have their right surfaces flush with each other in FIG. 1, and each right surface has a mirror finish.
It has extremely precise smoothness.

The ring core 1 and the heating plate 2 constitute a molding section, and the right surfaces of the ring core 1 and the heating plate 2 form the molding surface 3.
becomes.

Also, inside the ring core 1, the back of the heating plate 2 (the first
In the figure, the left side of the heating plate 2) is made of ceramics (SiC).
A heat insulating member 4 (heat insulating part) is arranged and fixed to the heating plate 2 with four equally distributed bolts 5.

Ceramics (SiC), which is the material of the heat insulating member 4, has excellent mechanical strength, impact resistance, and thermal shock resistance, low high frequency absorption, and furthermore, has low heat conductivity, high insulation properties, and free machinability. .

The heat insulating member 4 has a disc shape, and the heating plate 2 is located in the center.
A hole 4a having the same diameter as the hole 2a is formed.

In the heat insulating member 4, an inner groove 6a and an outer groove 6b having a U-shaped cross section are formed concentrically on the side in contact with the heating plate 2.

As shown in FIG. 2, the outer groove 6b is separated into left and right parts at the upper and lower parts of the figure, and the inner groove 6a is separated into left and right parts at the lower part of the figure. The outer groove 6b and the inner groove 6a are connected to each other at the left and right lower portions.

The inner groove 6a and the outer groove 6b are made into a closed cross section by the heating plate 2, and a cooling passage 7 is formed inside the inner groove 6a and the outer groove 6b.

Further, as shown in FIG. 2, the ring core 1 and the heat insulating member 4 have a refrigerant inlet passage 8 extending from the upper outer circumferential surface of the ring core 1 toward the center and reaching the left and right upper ends of the outer groove 6b.
a and a refrigerant outlet passage 8b are formed. The refrigerant inlet passage 8a and the refrigerant outlet passage 8b are connected to a refrigerant supply device (not shown), and the refrigerant flowing through the cooling passage 7 is controlled to a desired temperature by a temperature control device (not shown).

O-ring grooves 4 b and 4 c are formed in the heat insulating member 4 at a portion facing the inner end of the heating plate 2 and at a portion facing the outer end, and each O-ring groove 4 b and 4 c is provided with an O-ring groove. 9
a, 9b are attached to seal the refrigerant flowing through the cooling passage 7.

Furthermore, inside the ring core 1, on the back of the heat insulating member 4 (on the left side of the heat insulating member 4 in FIG. 1), a copper pipe 10 as an induction heating coil is arranged in a spiral shape. The outermost end 10a and the innermost end 10b of the pipe 10 are connected to a high frequency oscillator (not shown).

Back of copper pipe 10 (left side of copper pipe 10 in Figure 1)
An insulating member 11 is fixed to the upper and lower portions, and a hole 11a having the same diameter as the hole 2a of the heating plate 2 is formed in the center of the insulating member 11.

A pair of molding unit units 20 are prepared and fixed to fixed and movable bases (both not shown) with their molding surfaces 3 facing each other.

Note that the holes 2 at 4 a in the heating plate 2, the heat insulating member 4, and the insulating member 11 of the fixed molding unit 20 are the same.

A sprue bush (not shown) is inserted and fixed in 11a, and the heating plate 2 of the movable molding unit 20, the heat insulating member 4, and the six holes 2 at 4 a of the insulating member 11.

A center core (not shown) is inserted and fixed in 11a.

Then, in a state where the fixed mold and the movable mold are closed, a cavity (not shown) is formed between the molding surface 3 of the image forming unit 20.

A case will be described in which a magnetic disk substrate is molded in the above configuration.

A fixed mold and a movable mold are closed to form a cavity, and oil as a refrigerant is circulated in the cooling passage 7, and each molding part unit) 2
Heat the molding surface 3 of No. 0 to 130°C. At this time, since the oil is in direct contact with the heating plate 2, heat transfer between the refrigerant and the heating plate 2 occurs extremely quickly. Heat is also transferred to the ring core 1 via the contact surface between the heating plate 2 and the ring core 1. On the other hand, since the heat insulating member 4 is made of ceramics having a low heat transfer coefficient, heat does not diffuse further to the back than the heat insulating member 4 does.

Next, the flow of oil is stopped, and a high-frequency current with an output of 15 kW and 400 kHz is passed through the copper vibrator 10 using a high-frequency oscillator to generate an induced current in the ring core 1 and heating plate 2, and each molding surface 3 is heated to 200°C. Induction heating is performed to achieve this. At this time, no induced current is generated in the heat insulating member 4 made of non-metallic ceramics and the oil in the cooling passage 7, and the insulating member 4 and the oil are not heated by induction. That is, since only the limited portions of the ring core 1 and the heating plate 2 are heated by induction, the heating can be performed quickly. Furthermore, the presence of the heat insulating member 4 prevents heat from diffusing toward the back side of the ring core 1 and the heating plate 2.

In this example, the temperature of the molding surface 3 was set to 130°C.
The time required to raise the temperature from 200° C. to 200° C. was 5 seconds.

Then, resin is injected into the cavity while the molding surface 3 is maintained at 200° C. by induction heating. At this time, the molding surface 3 is at an extremely high temperature that is higher than the resin solidification temperature.
The resin maintains high fluidity and flows to every corner within the cavity, coming into close contact with the molding surface 3.

After that, the flow of high-frequency current to the copper pipe 10 is stopped, and oil is circulated in the cooling passage 7, and each molding surface 3
is cooled again to 130°C. This cooling solidifies the resin.

Then, the fixed mold and the movable mold are opened and the solidified product inside the cavity is taken out.

In this example, the time required from the start of induction heating until the product was taken out was about 60 seconds.

The magnetic disk substrate formed in this way had an extremely smooth surface and had extremely little distortion such as warping or deformation.

The graph in FIG. 3 shows the temperature change over time of the molding surface 3 in the above example, and the vertical axis represents the temperature of the molding surface 3, and the horizontal axis represents time.

In the figure, point A is the starting point of induction heating, point B is the starting point of resin injection, and point 0 is the point of product removal.

This invention is not limited to the above-mentioned embodiments, and various embodiments are possible.

For example, the heat insulating part may be made of ceramics such as A1□O=, SiN, C, etc., or it may be made of plastics instead of ceramics, or it may be made of ceramics and plastics. It may also be a layered composite material.

Further, a thin metal film having a thickness of 5 μm to 20 mm is formed on the surface of the heat insulating portion by a method such as vapor deposition, sputtering, or ion blating, and this metal ? ! A thin film may be used as the molded part. In this case, the cooling passage may be provided in the form of a tunnel as close as possible to the metal thin film inside the heat insulating section.

Furthermore, the refrigerant flowing through the cooling passage may be water or steam.

(Effects of the Invention) As explained above, according to the present invention, since the non-metallic heat insulating part is formed between the metal molded part and the induction heating coil, the molded part to be subjected to induction heating is can be made extremely small, and as a result, the heat capacity can be made small. Furthermore, the heat insulating portion can prevent heat from dispersing to the back. Therefore, the molding part can be heated extremely efficiently and in a short time.

Further, since the cooling passage is provided on the molding part side of the heat insulating part and the refrigerant comes into almost direct contact with the molding part, the molding part can be cooled extremely efficiently and in a short time.

As a result, the time required for heating and cooling cycles of the molding section can be shortened, and productivity can be improved.

Further, when injecting the resin into the cavity, the temperature of the molding section can be maintained at or above the resin solidification temperature, so it is possible to mold extremely high quality products.

[Brief explanation of the drawing]

The drawings from FIG. 1 to FIG. 3 show one embodiment of the present invention, and FIG. 1 is a sectional view taken along line 1-1 of FIG. 2, and FIG. FIG. 3 is a graph showing the temperature transition of the molded part. DESCRIPTION OF SYMBOLS 1... Ring core (molding part), 2... Heating plate (molding part), 4... Cross-sectional part, 7...
...Cooling passage, 10...Induction heating filter.

Claims (4)

[Claims] (1) It has a metal molded part that forms the cavity, a non-metallic heat insulating part is formed on the back of the molded part, a cooling passage is provided on the molded part side of the heat insulating part, and it is guided to the back of the heat insulating part. A molding die characterized by having a heating coil arranged therein. (2) The molding die according to claim 1, wherein the heat insulating portion is made of ceramics. (3) The molding die according to claim 1, wherein the heat insulating portion is made of plastic. (4) Claim 1, wherein the heat insulating portion is made of a layered composite material of ceramics and plastics.
Molding mold described in section.