JPH0749146B2 - Die casting method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die casting method, and more particularly to a die casting method using a plunger tip having a double structure.

(Prior Art) Conventionally, in the die casting method, generally, as shown in FIGS. 3 and 4, the molten metal is poured from the hot water inlet 20 into the sleeve 21, and the single plunger tip 22 is moved forward. The molten metal was pumped into the mold cavity 23.

(Problems to be Solved by the Invention) However, in the conventional method, when the molten metal is poured into the sleeve 21, the filling rate of the molten metal in the molten metal reservoir 28 in the sleeve 21 (the volume of the molten metal with respect to the inner volume of the sleeve 21 and the sprue bush 24 is Ratio is low (generally 20% to 50% level), so even if the plunger tip 22 is moved forward at a low speed, most of the molten metal is pushed up to the front surface of the plunger tip 22 and rises, and the wave front 25 A so-called trapping phenomenon occurs in which an air pocket 27 is formed between the general molten metal surface 26 and the molten metal surface 26, and the molten metal containing residual air is filled into the mold cavity 23 by the subsequent high-speed injection, and the “gas hole” is directly formed in the product. Remained as a cause of product defects such as pressure leakage, rough material cracks, and wrinkles. Further, since the wave front portion 25 generated by this trapping phenomenon is cooled by the wall surface of the sleeve 21 and solidifies early, not only is it difficult to fill the molten metal into the mold cavity 23, but also solidified metal is mixed in the product. It also caused the abnormal chill layer.

The present invention has been made in view of the above conventional problems,
By using the basic principle of the Accurad method using a double-structured plunger tip, it is intended to reduce the volume of the pool in the sleeve and to provide a die casting method that does not cause a trapping phenomenon.

The Accurad casting method is to perform low-speed injection at the same time with the inner and outer rods, and then to further extrude the inner tip at a predetermined timing, pressure-feed the molten metal in the center of the sleeve, trap air, and This is a casting method that prevents shrinkage due to solidification shrinkage.

(Means for Solving the Problems) As a means for solving the above problems, the present invention is a die casting method in which the molten metal injected into the sleeve is pressure-fed into the mold cavity by advancing the double structure plunger tip. In the method, the inner plunger tip is projected into the pool inside the sleeve before pouring, and after pouring, the outer plunger tip is advanced, and then both plunger tips are moved forward integrally, and the molten metal is poured into the mold cavity. It is characterized by being pumped.

(Function) With such a method, when the molten metal is injected, the inner plunger tip projects into the sleeve, so the volume inside the sleeve is reduced by the protruding volume, and conversely the molten metal is filled into the sleeve. The rate is increased. In this state, if the outer plunger tip is advanced to press the molten metal, the filling rate of the molten metal is further increased, and air is not entrained in the molten metal. After that, both plunger tips are integrally advanced, and the molten metal is pressure-fed to the mold cavity at high speed.

(Example) FIG. 1 shows an example of an apparatus for carrying out the method of the present invention. In the figure, 1 is a sleeve, 2 is a sprue bush, and 3 is a runner portion, which communicates with a mold cavity of a molding die (not shown). Two plunger tips, an outer plunger tip 4 and an inner plunger tip 5, are inserted into the sleeve 1. The two plunger tips 4 and 5 are fitted together as follows. That is, the inner plunger tip 5 has a flange 9 formed in the middle of the rod portion 7, and the inner plunger tip 5 is inserted into the outer plunger tip 4.

8a and 8b are stepped portions provided on the outer plunger tip 4, and within the range S until the flange 9 provided on the inner plunger tip 5 contacts the stepped portions 8a and 8b, the inner plunger tip 5 is the outer plunger tip. The outer plunger tip 4 and the inner plunger tip 5 move together in the sleeve 1 when the flange 9 and the step portions 8a and 8b are in contact with each other freely in and out of the sleeve 1. The outer plunger tip 4 and the inner plunger tip 5 are driven by different driving sources so that the two plunger tips 4 and 5 are positioned relative to each other.

A cooling hole 10 is formed in the inner plunger tip 5, and a hole 12 is provided along the axial center of the rod portion 7 so as to communicate with the hole 10. Then, insert the cooling pipe 11 into the hole 12
The cooling medium that has flowed inside flows out into the cooling hole 10, and the flowing-out cooling medium is discharged through the gap between the hole 12 and the cooling pipe 11.

Further, as shown in FIG. 2, the shape of the water heater 15 is such that molten metal can be poured toward the gap between the sleeve 1 and the inner plunger tip 5. In FIGS. 1 (a), (b), and (c), the reference numeral 14 is a sprue core, and in FIGS. 1 (a), (b), and 2, the reference numeral 16 is used. Shown is a basin.

An embodiment will be described below with reference to FIG. First of all
The outer plunger tip 4 is set at a predetermined position with respect to the sleeve 1 as shown in FIG. (In this embodiment, the tip is aligned so that it does not reach the pouring port 13)
At this time, the flange 9 provided on the inner plunger tip 5 and the stepped portion 8a are in contact with each other, and the tips of the two plunger tips 4 and 5 are flush with each other. Next, as shown in FIG. 1 (b), the outer plunger tip 4 is kept in the same position and only the inner plunger tip 5 is attached to the flange 9 and the step portion.
It is pushed out until it comes into contact with 8b to reduce the volume inside the sleeve 1. After that, if you pour from the pouring port 13,
The filling rate of the molten metal will be increased. Next, with the inner plunger tip 5 in the same position, the outer plunger tip 4 is pushed out until the step portion 8a and the flange 9 come into contact with each other, and the molten metal in the molten metal reservoir portion 16 is pressure-fed to the sprue bush 2. Thereby, the filling rate of the molten metal is further increased. After that, the two plunger tips 4 and 5 are integrally advanced to feed the melt containing no residual air into the mold cavity at high speed. During this pumping, both plunger tips 4,5
It is not necessary for the tip of the to be flush. That is, a step may be formed at the tips of the plunger tips 4 and 5. However, it is necessary to advance both plunger tips 4 and 5 as a unit in order to send the molten metal to the mold cavity at high speed.

In this embodiment, when the outer plunger tip 4 is advanced, the step portion 8a of the outer plunger tip 4 contacts the flange 9 of the inner plunger tip 5,
The tips of both plunger tips 4 and 5 are flush with each other, and they are advanced together. In this way, by integrally advancing both plunger tips 4 and 5, the pressure feeding of the molten metal to the mold cavity is completed.

After that, if only the inner plunger tip 5 is pulled back, the outer plunger tip 4 is also pulled back at the same time.
The state shown in FIG.

In the above process, the injected molten metal fills the space between the sleeve 1 and the inner plunger tip 5 and the narrow space in the sprue bush 2.

(Effects of the Invention) As described in detail above, according to the die casting method of the present invention, the inner plunger tip is projected into the sleeve before pouring, and then pouring is performed. The volume was reduced, the trapping phenomenon was prevented, and defects due to pressure leakage, cracking of rough material, and wrinkling could be reduced. After that, by pushing out the outer plunger tip, the filling rate of the molten metal in the sleeve was further increased, and the entrainment of air was completely eliminated.
Further, by pushing out the inner plunger tip and the outer plunger tip at the same time, there is an excellent effect that the filling into the cavity is surely performed to every corner.

[Brief description of drawings]

1 and 2 show one embodiment of the present invention, FIG. 1 is a view showing a casting process, (a) shows a state before pouring, a vertical sectional view, (b) shows pouring FIG. 2C is a vertical cross-sectional view showing a starting state, FIG. 2C is a vertical cross-sectional view showing a state of pumping into the cavity, and FIG. FIG. 3 and 4 are conventional examples, and FIG. 3 is a vertical cross-sectional view of a die casting apparatus.
FIG. 4 is a vertical sectional view showing the trapping phenomenon. 1 …… Sleeve 4 …… Outer plunger tip 5 …… Inner plunger tip

Claims (1)

[Claims] 1. A die-casting casting method in which the molten metal injected into a sleeve is pressure-fed into a mold cavity by advancing a double-structured plunger tip, in which the inner plunger tip is projected into a molten metal pool inside the sleeve before pouring. A die-casting casting method, characterized in that, after pouring and pouring, the outer plunger tip is advanced, then both plunger tips are integrally advanced, and the molten metal is pressure-fed to the mold cavity.