JPH081298A - Casting method and core extraction device used in the method - Google Patents

Abstract

(57) [Summary] [Purpose] By removing the core in the product trimming process, a special process for extracting the core is unnecessary. In the casting method according to the present invention, the time from when the molten metal is pressed into the cavity until the portion in contact with the core is solidified is T1, and a time longer than T1 by a predetermined time is T1.
2, when the molten metal is in contact with the molten metal for T1 hour, the strength of the molten metal is maintained against the high pressure so that the deformation amount is equal to or less than the shape accuracy required for the product, and
During 1 hour or more and T2 hours or less, the strength of the molten metal deteriorates due to the heat of the molten metal, and plastic deformation is possible only through the undercut portion of the product. At the same time, the other end can be pulled out. A step of producing a core from a resin having a binding force, and after the molten metal is pressed in, at a timing of T1 time or more and T2 hours or less, and when the product is taken out of the mold and trimmed, the core is And withdrawing process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method for casting a product by press-fitting a molten metal into a cavity into which a core is inserted, and a core pulling apparatus used in the casting method.

[0002]

2. Description of the Related Art The conventional technique related to this casting method is
It is described in JP-A-61-293646. In this casting method, a core having a flexible material such as rubber is used to cast a product having an undercut portion. Since a flexible core is used in this technique, the core as a whole can be extracted from the product by passing through the undercut portion while deforming the core after casting. As a result, unlike the conventional sand core, a part of the sand remains in the undercut portion of the product when the core is removed, and the post-treatment is not required.

[0003]

According to the above-mentioned conventional casting method, since the core is made of a flexible material such as rubber, the molten metal is pressed into the cavity, so that the molten metal is melted. There is a problem in that the parts colliding with each other are deformed. Therefore, when using a core such as rubber, it is necessary to reduce the casting pressure to a pressure at which the core is not deformed. However, if the casting pressure is lowered,
There is a problem that a defective product shape is likely to occur. The technical problem of the present invention is that the molten metal has a large strength so that it is not deformed by the high pressure of the molten metal until it solidifies, and after the molten metal solidifies, it is plasticized by the heat of the molten metal. By manufacturing a core and casting using the core, it is possible to perform high-precision high-pressure casting, solve problems such as product shape defects, and easily pull out the core. It is a thing.

[0004]

[Means, actions, and effects for solving the problems]

[Means according to Claim 1 for Solving the Problem] The above-mentioned problem is solved by a casting method having the following features. That is, the casting method according to claim 1 is a casting method for casting a product by press-fitting a molten metal into a cavity into which a core is inserted, and a portion which is in contact with the core after the molten metal is pressed into the cavity. When the time until the solidification is T1 and the time longer than the T1 by a predetermined time is T2, the amount of deformation is against the high pressure of the molten metal while it is in contact with the molten metal for T1 hours. The strength that satisfies the required shape accuracy is maintained, and during the above T1 time and below T2 time, the strength decreases due to the heat of the molten metal and plastic deformation is possible, and at the same time the other end is pulled out. The step of selecting a resin having a mutual bonding force that can also be pulled out, the step of manufacturing a core for molding a hollow portion in the product with the resin selected in the step, and the T1 time after press-fitting the molten metal. Since T2 hours with the following timing,
And removing the core from the product when removing the product from the mold and trimming the product. [Operation of the invention described in claim 1] According to the present invention,
The core maintains a predetermined strength from the time when the molten metal is pressed into the cavity until the portion in contact with the core is solidified, that is, for T1 time, and the core is pressed into the core. Even when the high pressure of the molten metal is applied, the core does not deform below the shape accuracy required for the product. In addition, after the molten metal in the portion in contact with the core is solidified (after T1 time elapses),
Until the time T2 elapses, the core loses its average strength due to the heat of the molten metal, and it becomes plastically deformable enough to pass through the undercut portion of the product. The ends also have mutual coupling forces that allow them to be pulled out. Therefore, if the pulling force for pulling the core is applied at an appropriate timing from the lapse of T1 time to the passage of T2 time, the core can be satisfactorily pulled out from the product. Further, if the proper timing is after the mold opening timing, the core can be pulled out in the trimming step of the product, so that it is not necessary to provide a special step for pulling out the core. [Effect of the invention described in claim 1] According to the present invention,
The core has sufficient strength to withstand the high pressure of the molten metal until the molten metal in contact with the core solidifies, so there is no need to lower the casting pressure as in the past.
It is less likely that product defects will occur. Further, since the core can be pulled out in the trimming process of the product even after the mold opening, it is not necessary to provide a special step for pulling out the core, and the cost can be reduced,
The time required to complete the product is shortened.

[Means according to Claim 2 for Solving the Problems] The above-mentioned problems can be solved by a core extracting device having the following features. That is, the core extracting device according to claim 2 is a core extracting device for extracting a core used in the casting method according to claim 1 from a product, and a press for trimming a product formed by casting. A pulling mechanism attached to the mold and a movable part of the pulling mechanism, the core of the core protruding from the product in a state where the product is set at a predetermined position of the press mold. It has a hook part that fits with a part. [Operation of the invention described in claim 2] According to the present invention,
With the cast product set in a predetermined position of the press die, a part of the core protruding outside the product can be fitted with the hook portion of the core pulling device. Here, since the part of the core projecting to the outside of the product is not directly heated by the molten metal, the strength hardly decreases. Therefore, even if the pulling mechanism is operated, the fitting between the core and the hook does not come off,
The core can be reliably pulled out of the product during the product trimming process. [Effect of the invention described in claim 2] According to the present invention,
Since the core can be pulled out in the trimming step of the product, it is not necessary to provide a special step for pulling out the core, which can reduce the cost and shorten the time required to complete the product.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A casting method according to an embodiment of the present invention and a core extracting device used in the method will be described below with reference to FIGS. In this embodiment, the product x having an undercut portion is cast by a die casting machine (not shown), and the core n used in the casting has a high glass transition point such as polycarbonate ( (160 ℃), and a synthetic resin core with high impact strength and ductility is used. FIG. 3 shows a general temperature change of the molten metal (aluminum alloy molten metal, solidification temperature 550 ° C.) during casting (hereinafter referred to as molten metal characteristic A),
A general state of temperature change of the core n formed of polycarbonate (hereinafter referred to as core property G1),
The vertical axis represents temperature and the horizontal axis represents time. The molten metal characteristics A and the core characteristics G1 vary in inclination depending on the shape of the product, the arrangement and size of the core n, and the like.

On the time axis of FIG. 3, t0 represents the timing of starting the molten metal injection, and ta represents the timing when the filling of the molten metal into the cavity 14 is completed. In addition,
Between t0 and ta, the temperature of the molten metal does not almost drop and is about 7
It is held at 00 ° C. The molten metal filled in the cavity 14 is cooled by the mold and the core n and its temperature is lowered,
Time tb from the time (ta) when the molten metal filling is completed
(T1 time has elapsed from t0), the portion in contact with the core n reaches the solidification temperature of 550 ° C, and the molten metal in that portion solidifies.
The molten metal is further cooled in the mold, the whole is solidified and the product x is molded, and then the mold is opened and taken out from the mold.

On the other hand, the core n receives heat from the molten metal and its temperature rises. Since polycarbonate, which is the material of the core n, has a low thermal conductivity, the internal temperature gradually rises from the side close to the surface even if the temperature of the surface in contact with the molten metal becomes almost equal to the temperature of the molten metal. To do. And the temperature is
Plasticize in order from the part where the temperature reaches 215 ° C to 225 ° C.
The temperature of the core n shown in FIG. 2 represents the average temperature. When the temperature of the core n is from room temperature to 160 ° C. (high rigidity region), the polycarbonate is hardly plasticized and the core n maintains high strength. Therefore, even when the casting pressure used in a normal die casting machine is applied to the core n, the deformation amount of the core n is kept below the shape accuracy required for the product, and the core n is used as a die casting core. Demonstrate its original function. Generally, the thickness of the product, the size of the core n, etc. are set so that the molten metal in the cavity 14 solidifies while the core n is in the high rigidity region. Here, tc in FIG. 2 represents the time during which the core n is still in the high rigidity region even after the molten metal in the cavity 14 is solidified.

When the temperature of the core n is between 160 ° C. and about 200 ° C. (medium rigidity region), the surface side of the core n is plasticized, but the core has a portion having high rigidity. Existing. Therefore, the average strength of the core n is lowered and the core n can be pulled out from the product x, but it is not extended or broken more than necessary even if a tensile force is applied. Therefore, if the pulling-out force from the core pulling-out mechanism 18 to be described later is applied to the skirting board portion nh of the core n at an appropriate timing in the middle rigidity region, the core n is efficiently pulled out from the product x. be able to. Further, in the region where the temperature of the core n exceeds 210 ° C. (low rigidity region), the core n plasticizes to a portion close to the core, so that the average strength of the core n sharply decreases. For this reason, when the pulling-out force is applied to the core n that has reached the low rigidity region, the core n cannot withstand the force and is torn or overextended, making it difficult to pull out.

In this embodiment, the core n is pulled out during the trimming process when the core x is in the medium rigidity region and the product x is taken out of the mold. Therefore, as shown in FIG. 1, the trimming press die 10 is provided with a core pulling device 18. The trimming press die 10 is composed of an upper die 12 connected to an elevating device (not shown) and a lower die 14 for horizontally supporting the product x at a predetermined position. The casting plan portion xb and the like can be cut from the product x in a state in which it is lowered to the matching position. Further, the core extracting device 18 is horizontally attached to the lower surface of the upper mold 12 by a device stand 16.

The core withdrawing device 18 is a device for horizontally withdrawing the core n from the product x, and includes a hydraulic cylinder 18y and the piston rod 1 of the hydraulic cylinder 18y.
The hook portion 18e is fixed to the tip of the 8p. Here, as shown in FIG. 2, the hook portion 18e is a hook-shaped member formed in a substantially C-shaped plane, and on the other hand, the hook portion 18e is formed on the skirting board portion nh of the core n cast around the product x. Is a ring-shaped groove h that fits with the hook portion 18e from above and below.
m is formed. And, as shown in FIG.
When the piston rod 18p extends from the hydraulic cylinder 18y by a predetermined dimension, the hook portion 18e is formed on the product x
It comes to be located right above the skirting board portion nh of the core n protruding from the outside. Therefore, when the upper die 12 is lowered to a predetermined position while the hook portion 18e is held right above the skirting board portion nh of the core n by the hydraulic cylinder 18y,
Simultaneously with the cutting of the casting plan portion xb and the like from the product x, the hook portion 18e of the core withdrawing device 18 is fitted to the skirting board portion nh of the core n. The stroke of the hydraulic cylinder 18y is set to such a length that the core 16 can be horizontally withdrawn to the outside of the product x with the piston rod 18p housed. That is, the piston rod 18p of the hydraulic cylinder 18y corresponds to the extraction mechanism of the core extraction device of the present invention and its movable portion.

Next, a method of pulling out the core n from the product x will be described with reference to FIGS. 4 (A) to 4 (E). As described above, when the mold n is opened and the product x is taken out from the mold with the core n in the middle rigidity region, the product x is conveyed to the trimming press mold 10 and then the product shown in FIG. As shown in FIG. At this time,
A piston rod 18p extends from the hydraulic cylinder 18y of the core pulling-out device 18 by a predetermined size, and the hook portion 18e is a core box n of the core n that is cast around the product x.
Positioned directly above h. In this state, as shown in FIG. 4 (B), the upper die 12 is lowered to a position where it engages with the lower die 14 to move the product x from the casting plan portion xb.
When the cores n are cut, the hooks 18e are fitted into the grooves hm provided in the skirting board nh of the core n. next,
As shown in FIGS. 4C and 4D, the hydraulic cylinder 18y of the core withdrawing mechanism 18 is actuated in a direction to accommodate the piston rod 18p, and the core n is horizontally withdrawn from the product x. n is detached from the hook portion 18e by its own weight and falls. In this way, when the core n is extracted from the product x, the upper die 12 rises and the product x is taken out from the trimming press die 10, and further, the core extracting device 1
The hook portion 18e of No. 8 is returned to the original state, and the work of pulling out the core n is completed.

As described above, according to this embodiment, the core n is formed of polycarbonate, and the molten metal in contact with the core n is solidified while the polycarbonate is in the high rigidity region. For this reason, even if a high casting pressure generally used in the die casting method is applied to the core n, the amount of deformation becomes less than the allowable value. Therefore, unlike the conventional case, it is not necessary to lower the casting pressure, and the defective shape of the product x does not occur. Further, the core n is heated by the heat of the molten metal to reach the medium rigidity region, and the core n is pulled out in a state where the strength is lowered. Therefore, in order to pull out the core n in a later step, There is no need to reheat the core n. Therefore, it is possible to prevent blister defects and thermal distortion of the product x due to reheating and to save energy. Further, even if the proper timing for pulling out the core is after the mold opening timing of the mold, the core can be pulled out in the trimming step of the product x, so that it is necessary to separately provide a step for pulling out the core n. The cost can be reduced and the time can be shortened. Here, since the skirting board portion nh of the core n is in contact with the mold and is cooled by the mold, it is not directly heated by the molten metal and is maintained with high strength. Therefore, even if the core pulling-out mechanism 18 is operated, the connection between the core print nh of the core n and the hook portion 18e of the core pulling-out mechanism 18 is not disconnected. In this embodiment,
Although the hydraulic cylinder 18y is used as the core extracting device 18, an air cylinder, an electric motor, or the like may be used.

[Brief description of drawings]

FIG. 1 is a schematic side view of a trimming press die used in a casting method according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the hook portion and the core skirting portion of the pulling device provided in the trimming press die used in the casting method according to the embodiment of the present invention.

FIG. 3 is a graph showing a temperature change characteristic of a molten metal during casting and a temperature change characteristic of a core.

FIG. 4 is a process chart showing a core extracting procedure in the casting method according to the first embodiment of the present invention.

[Explanation of symbols]

 x product n core nh skirting part hm groove 10 trimming press type 18 core extracting device 18y hydraulic cylinder (pulling mechanism) 18p piston rod (moving part of the pulling mechanism) 18e hook part

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuichi Tomitaka 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd. (72) Inventor Takashi Murakami 2-1-1 Asahi-cho, Kariya, Aichi Aisin Seiki Co., Ltd. Within

Claims (2)

[Claims] 1. A casting method for casting a product by press-fitting a molten metal into a cavity into which a core is inserted, the time from when the molten metal is pressed into the cavity until a portion contacting the core is solidified. Is T1 and a time longer than the T1 by a predetermined time is T2, the amount of deformation against the high pressure of the molten metal during the contact with the molten metal for T1 hours is the shape accuracy required for the product. Mutual strength can be maintained while maintaining a satisfactory strength, and plastic deformation is possible due to the decrease in strength due to the heat of the molten metal during the time T1 or more and the time T2 or less, while at the same time pulling out one end A step of selecting a resin having a binding force, a step of manufacturing a core for molding a hollow portion in the product with the resin selected in the step, and a step of T1 time or more and T2 hours or less after press-fitting the molten metal. And a step of pulling out the core when the product is taken out of the mold and trimmed. 2. A core withdrawing device for withdrawing a core used in the casting method according to claim 1 from a product, which is attached to a press die for trimming the product formed by casting. And a hook portion that is connected to the movable portion of the pulling mechanism and that fits with a part of the core projecting to the outside of the product when the product is set at a predetermined position of the press die. And a core extracting device.