JPH03174965A - Method and apparatus for injection forming - Google Patents

Abstract

PURPOSE:To prevent the development of casting defect and misrun by heating a die near the thin forming part in a fixed die till coming to the almost uniform temp. as the other die through an induction heating device, injecting and filling up molten material. CONSTITUTION:The induction heating device 20 is connected with the fitting die 1b corresponding to the thin part 4b in cavity 4, and after opening the dies, coating of parting agent with spray and removal of moisture with air blow are executed, and then, the heating to the fitting die 1b is executed for the necessary time with electromagnetic induction action. Then, the other part in the die, e.g. the thin part 4b having cooling velocity faster than the thick part 4a, is concentratedly heated to almost uniformize the temp. in the whole die. After executing preparing in such way, die clamping is executed and the injection and filling-up are executed. By this method, the development of casting defect can be prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an injection molding method and an injection molding apparatus such as a die-casting machine or an injection molding machine, and particularly relates to a cast product having a thin wall portion or a molding product that is susceptible to poor water circulation. The present invention relates to a method and device for controlling the temperature of a mold for casting products.

[Prior Art] Conventionally, the method of controlling the mold temperature of a die-casting machine or injection molding machine is to send a heat medium or cooling water into the mold through a pipe, and adjust the amount of the heat medium according to the temperature displayed by a temperature sensor. Or it controlled the amount of cooling water.

[Problems to be Solved by the Invention] This method has disadvantages in that it is subject to geometrical constraints when arranging the pipes and that the thermal response is slow. In addition, this method makes it difficult to control the temperature locally, so it is difficult to control the mold parts that are prone to casting defects, such as mold parts corresponding to thin-walled parts of the product, and parts that are prone to poor circulation, such as cavities for molten metal and molten resin. Temperature control, such as selective heating to areas that are quickly cooled and solidified after filling, is very difficult, and therefore is insufficient as a measure against local defects. For products with large wall thickness changes, the thinner parts cool and solidify before the thicker parts, resulting in poor water flow in the thinner parts, and the thinner parts solidify in the thicker parts. As a result, even if the die is heated after filling is completed, the feeder has no effect, and it has not been possible to completely eliminate casting defects called sink cavities due to residual air bubbles (pinholes).

Additionally, if the casting weight, that is, the heat capacity of the molten metal or molten resin, is small compared to the size of the mold, the mold temperature during steady operation may not be able to rise to the optimum temperature, and the overall melt flow may be affected. The occurrence of defects such as defects and hot spots could not be avoided.

[Means for Solving the Problems] In the injection molding method of the present invention, in an injection molding apparatus for manufacturing a die-cast product or an injection molded product having locally thin-walled parts, the mold is opened and a release agent is applied by spraying. After removing moisture by air blowing, the mold near the thin-wall forming part in the fixed mold is heated via an induction heating device until the temperature is almost equal to that of other molds, and then, The injection molding method involved mold clamping and injection filling.

Furthermore, the injection molding apparatus of the present invention includes a fixed mold and a movable mold that moves forward and backward relative to the fixed mold to be able to open and close the mold, and fills a cavity in the mold with molten metal or resin and cools the mold. In an injection molding device for manufacturing a cast product, a fitting alloy mold is provided which is fitted to the fixed mold and faces the mold part corresponding to the thin-walled part of the molding amount or the defective part around 7gj, and the fitting alloy mold is fitted with the mold. An induction heating device was provided to connect and heat the fitting alloy mold.

[Function] In the present invention, the induction heating device, which is fitted into a fixed mold and moves forward and backward, is inserted into the mold portion corresponding to the thin-walled part of the molded product or into the location where the drying defect occurs when the mold is opened, and the Because this part is heated and raised in temperature by electromagnetic induction, the temperature becomes almost the same as other parts that cool down slowly.
During cooling and solidification after mold clamping and injection filling in the next process, the same cooling and solidification state as in other parts occurs, and the feeder effect permeates through, making it possible to eliminate casting defects such as blowholes.

[Example] Hereinafter, the method and apparatus of the present invention will be described in detail based on the drawings.

1 to 5 show embodiments according to the present invention.

FIG. 1 is a schematic vertical cross-sectional view of a die-casting machine, FIG. 2 is a schematic vertical cross-sectional view showing another embodiment, and FIG. 3 is a surface temperature distribution diagram of the mold of the embodiment shown in FIG. Figure (a) shows the temperature distribution according to the conventional method, Figure 3 (b) shows the temperature distribution according to the heating method of the present invention, and Figure 4 is a schematic vertical cross-sectional view showing another embodiment. Fig. 5 is a surface temperature distribution diagram of the mold of the embodiment shown in Fig. 4, Fig. 5(a) shows the conventional temperature distribution, and Fig. 5(b) shows the temperature distribution according to the heating method of the present invention. shows.

In the figure, l is a fixed plate, 2 is a movable plate, la is a fixed mold, and lb is a fitting alloy mold fitted to the fixed mold 1a, which corresponds to the thin wall part 4b of the product in FIG. 2a is a movable mold,
3 is a dividing surface (parting line), and 4 is a cavity, which is formed by thick parts 4a and 4c and a thin part 4b. 5 is an injection sleeve, 6 is a gate, 7 is an injection cylinder, 8 is a piston row, 9 is an injection plunger, IO is a coupling, 11 is a plunger tip, and 12 is a molten metal.

20 is an induction heating device, in which the penetrating member 20a is a fitting alloy type 1b.
It is fitted and connected to the protruding part of and is detachable. 20b is an insulating material.

In the figure, the die casting machine includes a fixed mold 1a mounted on a fixed platen 1, and a movable mold 2a mounted on a movable plate 2, which is clamped and opened by moving forward and backward with respect to the fixed mold 1a. Both molds 1a and 2 are clamped.
Cavities 4 are formed on both sides of the dividing surface 3 of a. An injection sleeve 5 having a pouring port 5a is inserted into the sleeve hole of the stationary platen 1, and the inner hole and the cavity 4 communicate with each other through a sleeve 6a and a gate 6 provided in the molds 1a and 2a. has been done. 7 is injection sleeve 5
An injection plunger 9 is connected to a piston rod 8, which is moved back and forth by hydraulic pressure, through a coupling lO, and a plunger tip, which is the head of the injection plunger 9, is an injection cylinder arranged concentrically with the cylinder. 11 is fitted into the inner hole of the injection sleeve 5 so that it can move forward and backward.

With this configuration, in the state shown in FIG.
2 is supplied to the piston rod 8 by the hydraulic pressure of the injection cylinder 7.
When the plunger tip 11 is advanced, the plunger tip 11 is advanced within the injection sleeve 5 and the sleeve 6a, and the molten metal 12 is pushed out and injected into the cavity 4 through the gate 6. Once the molten metal 12 has been filled into the cavity 4, the molten metal in the cavity 4 is further pushed by the pressing force caused by the action of the injection cylinder 7, which continues to push, and is subjected to a feeder action, so that the molten metal in the cavity 4 becomes more dense. Filling is completed.

After that, wait for the molten metal to solidify and cool, then open the mold and take out the solidified cast product from the cavity 4.A die casting machine configured and operated in this way has the following steps:
An induction heating device, generally designated 20, is provided.

As shown in FIG. 1, this induction heating device 20 is connected to a fitting alloy mold 1b corresponding to the thin wall portion 4b of the cavity 4, and after opening the mold, it applies a mold release agent by spraying and removes moisture by air blowing. After this, the fitting alloy mold ib is heated for the necessary time by electromagnetic induction, and the other mold parts,
For example, the thin wall portion 4b, which cools down faster than the thick inner wall 4a, is heated intensively to make the temperature of the entire mold substantially uniform. After completing these preparations, the mold is again clamped and the next shot is injected and filled.

As described above, in the method and apparatus of the present invention, the temperature of the thin wall part is raised in the same way as other parts, so when the molten metal is cooled and solidified, the thin wall part cools down quickly, which causes bubbles to form due to insufficient feeder effect. The occurrence of casting defects such as residual particles is reduced.

FIG. 2 shows another embodiment, and even when the cavity 4 is complicated and has severe bending, the temperature distribution at three points A, B, and C in the mold after opening the mold shown in FIG. For example, the distribution was in the state shown in Figure 3(a), but the induction heating method of the present invention has a good heat transfer effect, is efficient in a short period of time, and can selectively target areas that are significantly cooled. Since the temperature could be increased, the temperature distribution was almost uniform as shown in FIG. 3(b).

Furthermore, as shown in Figure 4, when the mold weight is large compared to the product weight, the mold temperature after opening is conventionally as low as about 150 degrees, as shown in Figure 5 (a). Even if the feeder is incomplete after the shot is finished and P manufacturing defects are likely to occur, induction heating can uniformly raise the temperature of the entire surface of the mold in a short time, improving product quality and increasing work efficiency.

The principle of induction heating is that when an alternating current voltage is applied to a coil to generate an alternating magnetic field, an eddy current is generated in the heated object that is in the path of the magnetic flux, and the Joule heat generated by this eddy current is used to heat the metal. It is used to heat.

[Effects of the Invention] As explained above, according to the method and apparatus of the present invention, after the mold is opened, the parts of the mold corresponding to the thin-walled parts of the product, the parts of the mold where poor circulation is likely to occur, or the entire mold can be removed. Since the entire mold, which is extremely cooled, is heated almost uniformly and then injected and filled, it is possible to prevent casting defects and poor circulation, and the quality of the cast product is significantly improved. In addition, since the induction heating method is adopted as the heating method, the heating temperature can be increased quickly, the working time can be shortened, the working efficiency can be improved, and the productivity can be improved.

[Brief explanation of drawings]

1 to 5 show an embodiment according to the present invention, FIG. 1 is a schematic longitudinal sectional view of a die casting machine, FIG. 2 is a schematic longitudinal sectional view showing another embodiment, and FIG. 3 is a schematic longitudinal sectional view of a die casting machine. 3(a) shows the temperature distribution according to the conventional method, and FIG. 3(b) shows the temperature distribution according to the heating method of the present invention. Figure 4 is a schematic vertical cross-sectional view showing another embodiment, Figure 5 is a surface temperature distribution diagram of the mold of the embodiment shown in Figure 4, and Figure 5 (a) shows the conventional temperature distribution. 5(b) shows the temperature distribution according to the heating method of the present invention. 1... Fixed plate, 2... Movable plate, la... Fixed mold, 1b... Fitting alloy mold. 2a...Movable mold, 3...Dividing surface, 4
...Cavity, 4a...Thick walled part. 4b...Thin wall part, 4C...Thick wall part, 5...
...Injection sleeve, 6...Gate, 7
...Injection cylinder, 8...Piston rod, 9...Injection plunger, 20...
...Induction heating device, 20 a --0fj entry,
20 b-, QIi material.

Claims (2)

[Claims] (1) In an injection molding device that manufactures die-cast products or injection molded products that have locally thin walled parts, after opening the mold and applying a mold release agent by spraying and removing moisture by air blowing, the inside of the fixed mold is An injection molding method, in which the temperature of the mold near the thin-walled portion is heated via an induction heating device until the temperature becomes almost uniform with that of other molds, and then the mold is clamped and injection-filled. (2) Injection molding that includes a fixed mold and a movable mold that moves forward and backward to open and close the fixed mold, and manufactures a cast product by filling a cavity in the mold with molten metal or resin and cooling it. In the device, a fitting alloy mold is provided which is fitted into the stationary mold and faces the mold part corresponding to the thin-walled part of the molded product or the location where there is poor metal circulation, and connected to the fitting alloy mold. An injection molding device characterized by being equipped with an induction heating device for heating.