JPH07148562A - Method and device for preventing shrinkage cavity - Google Patents

Abstract

PURPOSE:To produce a formed product having dense structure without shrinkage hole by using a shrinkage cavity preventing device and pressurizing a material by projecting end parts of plural pressurizing pins, at the time of solidifying the material filled up into a cavity of a metallic mold. CONSTITUTION:The molten metal is injected into the cavity 4 in the metallic molds 2, 3 by the action of an injection plunger 6 and after filling up the cavity 4, the cast product starts solidification. At this time, working oil is fed to the head side of a cylinder 11 and a pressurizing pin fitted plate 9 is pushed out. Then the tip part of each of pressurizing pins 7, 8 is advanced into the molten metal in the cavity 4. At this time, each pressurizing pin 7 is advanced through a spring 10 inserted in the pressurizing pin fitted plate 9. The molten metal stored in a storing part of the molten metal at the thick walled part has different solidifying speeds according to conditions such as the size of the molten metal storing part. At the unsolidified position, the pressurizing pin 7 is advanced till being exerted with a prescribed spring force and the development of the shrinkage cavity is prevented and the cast product having dense structure is produced by the pressurizing force of the spring.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding apparatus such as a tie casting machine and an injection molding machine, in which a metal mold is filled with molten metal or a plastic of resin to form a molded product.
The present invention relates to a method and an apparatus for preventing shrinkage cavities that prevent shrinkage cavities in molded articles.

[0002]

2. Description of the Related Art Conventionally, for example, when casting a large cast product with a die casting machine at a high pressure, even if pressure is applied with an injection plunger to prevent shrinkage cavities, a thick wall portion is formed at a position away from the sprue. In some cases, since the molten metal in the narrow passage in the middle cools and solidifies faster, pressure is not transmitted to the thick part and shrinkage cavities occur, so generally this part is pressurized to prevent shrinkage cavities. It has been considered to provide a pressure pin for the feeder.

[0003]

However, when the area is large and the shape is complicated, a large number of thick portions are scattered and the sizes thereof are different. Therefore, many pressure pins having different sizes are arranged. There is a need to. Then, it is necessary to install a hydraulic cylinder that applies a necessary pressing force to each of the pressurizing pins, but this is practically impossible in terms of structure.

In order to solve this problem, a pressure pin mounting plate is provided on the back surface of the mold, a plurality of pressure pins are arranged on the plate, and the pressure pin hydraulic cylinder is operated to apply pressure. ， Can be pressurized at the same time.

However, many thick-walled parts in a cast product have different shapes, sizes, mold temperatures, distances from the sprue, etc., so that the amount and timing of solidification are different, and one cylinder simultaneously applies them. Even if the pressure is applied, the pressure pin stops moving at the first solidified portion, and then does not press the other portions, and most of the cylinder output is applied to the first pressure pin and the addition The pressure pin may be damaged.

[0006]

According to the present invention, in order to solve such a problem, a plurality of tips of a compression pin for preventing shrinkage cavities are made parallel to each other so that they can be projected into a cavity of a mold. Do not directly fix the other end of the pressure pin to the movable pressure pin mounting plate, for example, make a cylindrical hole at the pressure pin mounting position of the pressure pin mounting plate and A shrinkage cavity prevention device attached via a spring according to the force required for pressurization was used.

[0007]

When the material filled in the cavity of the mold is solidified, the tips of the plurality of pressure pins are projected and pressed to produce a molded product having a compact structure without shrinkage cavities.

[0008]

FIG. 1 shows an apparatus for carrying out the method according to the invention.
1 shows an embodiment, 1 is a fixed plate, 2 is a fixed mold, 3 is a movable mold, 4 is a mold cavity, 5 is a casting sleeve,
6 is a casting plunger. When the molten metal is cast into the cavity 4, for example, at places where shrinkage cavities are likely to occur, such as thick-walled parts, a plurality of pressure pins 7 and 8 for preventing shrinkage cavities or feeders are provided in parallel with each other. The pressure pins 7 and 8 are provided so as to project into the cavity 4.

A pressure pin mounting plate 9 is provided reciprocally in the axial direction inside the fixed mold 2 or in the rear space thereof, and the rear ends of the pressure pins 7 and 8 are mounted on the pressure pin. Board 9
It was attached via a spring 10 or directly fixed thereto. 11 is a hydraulic cylinder attached to the fixed platen 1, 12
Is a piston rod, and the tip of the piston rod 12 is fixed to the rear surface of the pressure pin mounting plate 9.

The pressure pin 8 at the final solidifying portion is fixed to the pressure pin mounting plate 9, but the other pressure pins 7 are necessary for pressing the pressure pin mounting plate 9 and each pressure pin 7. It was attached via the spring 10 according to various forces. At the pressure pin 7 mounting portion of the pressure pin mounting plate 9, a cylindrical hole 13 is provided in the pressure pin mounting plate 9 in the axial direction, and a spring 10 composed of a compression spring is arranged in the hole 13. , Spring retaining plates 14 and 15 are arranged on both sides of the spring 10, and both spring retaining plates 14 and 15 are arranged.
By connecting the bolt nets 16 with an appropriate force and adjusting the bolt nets 16, the force of each spring 10 can be appropriately set to the force required for pressurization.

The rear end portion of the pressure pin 7 is a flange portion 7a, and the rear surface of the flange portion 7a is in contact with the front surface of the front spring pressing plate 14. Reference numeral 9a is a cover plate for holding the flange portion 7a attached to the front surface of the pressure pin attachment plate 9. In addition,
The flange portion 7a and the spring retainer plate 14 may be
It can also be attached integrally with bolts and the like.

Next, the operating state will be described. By the action of the injection plunger 6, the molten metal is injected into the cavities 4 of the molds 2 and 3, and when the filling is completed, the cast product begins to solidify, but at this time, the working oil is sent to the head side of the cylinder 11 to apply it. The pressure pin mounting plate 9 is pushed out. Then, the tips of the pressurizing pins 7 and 8 enter the molten metal in the cavity 4. At this time, each pressure pin 7 advances through the spring 10 inserted in the pressure pin mounting plate 9.

The molten metal accumulated in the thick-walled basin has a different solidification rate depending on the size, shape, mold temperature and other conditions of the basin. The pressurizing pin 7 pressurizes forward according to the reaction force of the spring 10, but when it is rapidly solidified, the pressurizing pin 7 stops while applying the spring force. On the other hand, the unsolidified portion advances until it reaches a predetermined spring force to prevent the occurrence of shrinkage cavities, and the applied pressure produces a cast product having a dense structure.

Before the pressure pin 7 and the pressure pin mounting plate 9 are advanced, the spring 10 is in a fully extended state as shown in FIG. 2A, but as shown in FIG. When the pressure pin mounting plate 9 moves forward by A, the pressure pin 7 moves forward according to the magnitude of the resistance of the molten metal located at a position corresponding to the pressure pin 7. At that time, if the advance distance B of the pressure pin 7 is smaller than the advance distance A of the pressure pin mounting plate 9, the flange portion 7a retreats considerably with respect to the cover plate 9a, and the spring 10 contracts by the distance C and is added. A force corresponding to the spring force at that time is applied to the pressure pin 7 and the molten metal corresponding to the pressing pin 7, and the feeder action is performed accordingly.

The pressurizing force of the pressurizing pin 8 against the thick portion where solidification is finally completed corresponds to the force obtained by subtracting the spring force of the other pressurizing pin 7 from the output of the cylinder 11, and the force exerts a predetermined force. It is taken out or pressed to a certain position to prevent shrinkage cavities and produce a good quality cast product with a dense structure. In this way, it is possible to easily and easily obtain a good quality cast product with no shrinkage cavities in the entire cast product. It is not necessary to use the spring 10 for the pressurizing pin 8 for the thick portion that is finally solidified. INDUSTRIAL APPLICABILITY The present invention can be used not only in die casting for casting molten metal, but also in injection molding for resins and the like.

[0016]

According to the present invention, a plurality of tips of pressurizing pins for preventing shrinkage cavities are provided in parallel with each other so as to project into the cavity of the mold, and the other end of the pressing pins is movable. By using a shrinkage cavity prevention device attached to the pressure pin attachment plate via a spring, when the material filled in the cavity of the mold is solidified, the tips of the plurality of pressure pins are projected to apply pressure. Therefore, it is possible to easily and easily manufacture a molded product having a close-packed structure with no shrinkage cavities.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing one embodiment of an apparatus for carrying out the method of the present invention.

FIG. 2 is an explanatory diagram showing an operating state of a rear portion of a pressure pin according to the present invention.

[Explanation of symbols]

 1 Fixed Plate 2 Fixed Mold 3 Movable Mold 4 Cavity 5 Casting Sleep 6 Casting Plunger 7,8 Pressure Pin 9 Pressure Pin Mounting Plate 10 Spring 11 Cylinder

Claims (2)

[Claims] 1. A pressurizing pin attachment plate for preventing shrinkage cavities, wherein a plurality of tips of the pressurizing pin are provided in parallel with each other so as to project into a cavity of a mold, and the other end of the pressurizing pin is movable. Using a shrinkage cavity prevention device attached via a spring, when the material filled in the cavity of the mold is solidified, the tips of the plurality of pressure pins are projected to apply pressure to prevent the shrinkage cavity. Method. 2. A pressurizing pin attachment plate for preventing shrinkage cavities is provided in parallel with each other so as to project into the cavity of a mold so that the other end of the pressurizing pin can move. A shrinkage cavity prevention device attached via a spring.