JPH02192865A - Method and apparatus for injection-molding - Google Patents

Abstract

PURPOSE:To make uniform the temp. by opening only one or two gate parts at the time of beginning flowing of molten material into cavity, shutting the other gate parts, shutting the opened gate parts when the molten material reaches to both adjacent gate parts and opening both adjacent gate parts. CONSTITUTION:In filling stage, all of the gate parts are opened until the molten material invades into the cavity 4 from an injection sleeve 5 through runner part 6 and gate parts 7. When the molten material begins to invade into the cavity, only one or the adjacent two gate parts are opened as they are and the other gate parts are shut. When the molten material increases the volume and reaches to both gate parts in adjacent to the opened gate parts, the opened gate parts are shut and both adjacent gate parts are opened to introduce the molten material. By repeating the above procedure, the molten material is filled up into the cavity and the filling-up stage is completed and the next feeding-head stage is started and the molten material is held at high pressure state. By this method, smoothening of processing of the molten material is achieved and a casting product having high quality can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an injection molding method and an injection molding apparatus in an injection molding apparatus such as a die casting machine or an injection molding machine for plastics.

[Prior Art] In injection molding equipment such as die casting machines and plastic injection molding machines, molten metal or molten resin is injected into the cavity of a clamped mold, and as the molten material solidifies, the molding process is completed. Goods can be obtained.

In such an injection operation, normally during the filling process, the melt passes through a launch section and a narrow passage called a gate section before reaching the cavity provided in the mold from the injection sleeve. However, in order to avoid as much as possible the cooling and solidification of the molten material during filling, it is necessary to send the molten material to the cavity at high speed, so the gate section in the middle is narrowed to perform high-speed filling.

[Problems to be solved by the invention] In the conventional molding method, the shapes of the runner part and the gate part are fixed, so that the molten material (
The flow behavior of the molten metal is fixed, and the tip of the flow is always exposed to the inner surface of the cavity, which is lower temperature than the molten metal, and to the low-temperature air and other gases filling the cavity. As it moves, the temperature gradually decreases, and the farther it gets from the gate, the more it solidifies and solidifies, making it difficult to flow without losing its fluidity. Therefore, when the cavity is almost filled with molten metal, that is, at the final stage of the filling process, the molten metal at the tip further solidifies and solidifies, and the molten metal does not advance any further and air or gas It is left in its original hollow state,
Filling was sometimes completed while a so-called porosity state was formed. Therefore, even if the pressure is maintained at a high pressure in the subsequent feeding process, the molten metal does not fill the cavities, so that defective parts may be formed there.

[Means for Solving the Problems] In order to solve the above problems, in the present invention, as an injection molding method, the area through which the molten material passes is expanded or contracted in the launch portion communicating with the cavity in the mold, or the molten material is In an injection molding device having a plurality of gate parts that can block the passage of the melt, during the filling process of filling the cavity provided in the mold with the melt,
All gates are opened until the melt enters the cavity, and when the melt begins to enter the cavity, only one gate or two adjacent gates are left open and the other gates are closed. When the melt that has entered the cavity from the opened gate reaches the gates on both sides adjacent to the opened gate, the opened gate is closed and the gates on both sides are closed. We decided to fill the cavity with molten material by opening the cavity.

Further, in the second invention, the injection molding apparatus is provided with a plurality of gate parts in the launch part communicating with the cavity in the mold of the injection molding apparatus, and a plurality of gate parts are provided in the mold in opposition to each gate part. A gate opening/closing cylinder is provided which can move forward and backward in directions that can expand and contract the melt passage area of the gate portion or block the passage of the melt.

[Effect] In the injection molding method of the present invention, in the filling step.

First, all the multiple gates are opened until the molten material enters the cavity from the injection sleeve through the launch section and the gate section, and when the molten material begins to enter the cavity, the number of gates is changed to an odd number. If the number of gates is an even number, one gate portion is left open, and if the number of gates is an even number, only two adjacent gates are left open and the other gate portions are closed to continue the injection and filling operation of the molten material. Then, the molten material from one or two opened gate parts gradually increases in volume within the cavity and reaches the gate parts on both sides adjacent to the opened gate part. At this point, it is time to close the gate that has been open so far, and at the same time open the adjacent gates on both sides to allow the molten material to enter the cavity from there. The path through which the molten material enters the cavity changes repeatedly, and when the molten material enters from all gates, all the cavities are filled with the molten material, and the filling process is completed. After this, the melt enters the feeder step and the melt inside the cavity is maintained at high pressure.

Due to the filling operation in the filling process as described above,
The molten material entering the cavity is supplied into the cavity from different locations one after another, rather than from one fixed location, so compared to a method in which the molten material entering the cavity is filled from only one fixed location, the molten material entering the cavity is The progress of solidification and solidification due to cooling is slow, so the molten material penetrates well into every corner of the cavity.

Therefore, there is very little possibility that casting defects such as bubbles will occur in the molten material within the cavity.

[Example] FIGS. 1 to 4 are diagrams shown to explain an injection molding method and an injection molding apparatus according to an example of the present invention, and FIG. 1 is a schematic configuration diagram of a die-casting machine, and FIG. 3 and 3 show the arrangement of a plurality of gate portions arranged around the cavity, FIG. 2 is a cross-sectional plan view, and FIG. 3 is a longitudinal cross-sectional view. FIG. 4 is an explanatory diagram showing the state of the melt near the cavity and the opening/closing state of the gate at each step in the filling process.

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. It is equipped with.

Cavities 4 are formed on both sides of the dividing surface 3 of the clamped molds 1 a and 2 a. An injection sleeve 5 having a pouring port 5a is inserted into the sleeve hole of the fixed m1, and the inner hole and the cavity 4 are connected to the molds 1a and 2a.
The sleeve 5b is connected to the runner 6 through the runner 6 and the gate 7 above the runner 6.

A gate opening/closing cylinder 20 having a plunger 20a is disposed in the movable mold 2a facing the gate 7 so as to expand or contract the area through which the molten material passes through the gate portion or to block the passage of the molten material. , the plunger 20a can be moved forward and backward.

On the other hand, reference numeral 8 denotes an injection cylinder arranged concentrically with the injection sleeve 5, and a piston rod 8 that moves forward and backward with its hydraulic pressure.
An injection plunger 9 is connected to the injection plunger 9 via a coupling 10, and a plunger tip 11, which is the head of the injection plunger 9, is fitted into an inner hole of the injection sleeve 5 so as to be able to move forward and backward. With this configuration, when the molten metal 12 is supplied from the pouring port 5a into the injection sleeve 5 and the piston rod 8a is advanced by the hydraulic pressure of the injection cylinder 8, the plunger tip 11 moves into the injection sleeve 5 and into the sleeve 5b. The molten metal 12 is pushed out and injected into the cavity 4 through the runner 6 and the gate 7 (filling process). Once the molten metal 12 has been filled into the cavity 4, the injection cylinder 8 continues to be pushed. The molten metal in the cavity 4 is further pushed by the pressing force caused by the action and subjected to the feeding action, and the molten metal in the cavity 4 becomes more dense and filling is completed (boiling process).Then, the molten metal solidifies,
After waiting for cooling, the mold is opened and the solidified cast product is taken out from the cavity 4 (product removal step).

The functions and effects of the present invention in the series of injection operations described above will be explained.

2 and 3 show one embodiment of the present invention,
Five gates 7A connect to the cavity 4 from the runner 6 arranged around the cavity 4.

The 7th, 7C, 70, and 7th are arranged in this order. And, as shown in FIG. 1, a gate opening/closing cylinder 20A is provided opposite each gate.

208.20C, 200, 206 are arranged, and the plunger 20 is connected to the piston and piston rod.
By advancing and retracting movement of a, game) 7A to 7th can be opened and closed separately at any time.

In the injection molding method of the present invention, the step of filling the cavity 4 with the molten metal in the injection sleeve 5 is performed, for example, in the fourth step.
As described in the explanatory diagram of the molten metal state and gate opening/closing state in the cavity filling process shown in the figure, the process is divided into four periods from the 1st step to the 4th step, and each gate opening/closing cylinder is activated by a hydraulic signal at each step. The opening/closing state of each game (7A to 7E) is controlled by operation. Each of these steps is changed depending on the state of the molten metal entering the cavity, but as explained below, (1) the first
In step, all five gates 7A to 7ε are opened, and the injection plunger is operated to start the injection filling operation.

(2) In the second step, when the molten metal passes through the gate 7C located in the center of the five gates and enters the cavity 4, the other gates 7A, 7, 70 are held open while the gate 7C is held open. .7ε is a closed state. Then, the injection operation continues.

(3) In the third step, the amount of molten metal entering the cavity 4 from the gate 7c gradually increases, and eventually the gates 7 on both sides of the gate 7C,
At the point when the molten metal is filled up to the point 70, the gate 7c
Close gate 7 and leave gate 70 open (gate 7
A and 7E remain closed), and after this, the molten metal will not enter the cavity until the gate is closed.

The progress of the molten metal supplied from 7D and entering the cavity is leveled.

(4) In the fourth step, the amount of molten metal entering the cavity increases further, and when it reaches the gates 7A and 7E at both ends, the gates 7B and 70 are closed and the gates 7A and 7ε are switched to the open state. .

Thereafter, the molten metal in the cavity almost uniformly fills the blank space to complete the filling process, and all gates are kept open to enter the feeding process.

In the filling process consisting of each step described above, the opening/closing timing of the gate at the boundary of each step is determined by a trial shot before actual operation based on the correlation between the intrusion state of the molten metal and the advancing position of the plunger tip 11 of the injection cylinder. The lever 8 moves forward and backward at the same time as the piston rod 8a.
It is defined by a limit switch 13 which emits a signal by a striker 8C attached to b.

In the embodiment described above, the number of gates is an odd number, but when the number of gates is even, the gates that are kept open in the second step may be the two adjacent gates in the middle.

In the above-described embodiment, each gate is opened in each step, but the area through which the molten metal passes through the gate may be reduced instead of being completely closed.

The filling process is divided into steps according to the number of gates, and the opening/closing state of the gates is changed from step 1 to the next step, and the entrance of the molten metal is different for each step. In the conventional method, only the first molten metal that enters the cavity constantly touches the inner wall of the mold that makes up the cavity, which is cooler than the molten metal, and cools and solidifies more significantly than the subsequent molten metal. Unlike the intrusion situation, the temperature of each part of the molten metal entering the cavity is equalized.

Moreover, in the injection molding apparatus which is the second invention, the first invention
In addition to being able to adopt the injection molding method of the invention, it is also possible to select the best injection conditions (for example, the speed at which the molten metal passes through the gate during high-speed injection) to achieve the best island flow depending on the shape of the cavity, that is, the shape of the required product. Not only can it be set arbitrarily by moving the gate opening/closing cylinder forward and backward, but the selection range of combinations of the gate passage area and the injection cylinder advancing speed is expanded, and the possibility of finding the optimum injection conditions is expanded.

[Effects of the Invention] In the injection molding method of the present invention, the progress of the molten metal entering the cavity is leveled, and the temperature of the molten metal in the cavity is promoted to be uniform. is filled with molten metal to obtain high quality cast products.

In addition to making the injection molding method described above possible, the injection molding apparatus of the present invention can arbitrarily set the gate opening amount by moving the gate opening/closing cylinder forward and backward, so that other injection conditions such as injection cylinder speed can be adjusted. This expands the selection range of combinations and expands the possibility of finding the optimal injection conditions to create high-quality cast products.

[Brief explanation of the drawing]

1 to 4 show embodiments of the present invention, FIG. 1 is a schematic diagram of a die-casting machine, and FIGS. 2 and 3 show an arrangement of a plurality of gate parts arranged around a cavity. 2 is a sectional plan view, and FIG. 3 is a vertical sectional view. FIG. 4 is an explanatory diagram showing the state of the melt in the cavity and the opening/closing state of each gate in the filling process. 4... Cavity, 5... Injection sleeve,
6...Runner, 7...Gate 8...
Injection cylinder, 11... Injection plunger tip, 20... Gate opening/closing cylinder. Procedural amendment (formality) May 2, 1999

Claims (2)

[Claims] (1) In an injection molding device, the runner section communicating with the cavity in the mold has a plurality of gate sections that can expand/contract the passage area of the molten material or block the passage of the molten material. During the filling process of filling the cavity with melt, all gates are opened until the melt enters the cavity, and when the melt begins to enter the cavity, one gate or phase is opened. Only two adjacent gate parts are left open while the other gate parts are closed, and when the melt that has entered the cavity from the opened gate part reaches the gate parts on both sides adjacent to the opened gate part. An injection molding method characterized in that the cavity is filled with a molten material by closing the opened gate and then opening the gates on both sides. (2) A plurality of gate parts are provided in the runner part communicating with the cavity in the mold of the injection molding apparatus, and the melt passage area of the gate part is expanded/contracted or An injection molding device characterized by being provided with a gate opening/closing cylinder that can move forward and backward in a direction capable of blocking the passage of molten material.