JPH03247418A - Molding method for resin - Google Patents

Abstract

PURPOSE:To shorten a time necessary for cast of a core and to eliminate ununiformity of the shape of a hollow part by utilizing the hollow core wherein a tubular body is internally chilled in the inside thereof to perform molding of resin and immersing the molded form of resin in a hot bath and passing a heating medium into the tubular body to dissolve the core. CONSTITUTION:A flexible tubular body 2 made of metal is arranged in a mold 1. Melt M of low-m.p. alloy is filled into the space 8 of a product from a nozzle 7 and a hollow core 9 is cast. This core 9 is arranged into a mold 10 and injection molding is performed by injecting resin material P into the space 16 of the product part from a nozzle 15. The formed molded form W of resin is taken out together with the core 9 from the mold 10. The molded form W of resin is immersed together with the core 9 in an oil bath 19 heated by a heater 18 and heated for a prescribed time. When oil 17 is circulated into the tubular body 2 and the core 9 starts melting, the driving source 22 of an exciter 21 is started to impart vibration to the tubular body 2. Fall of molten metal 24 is promoted. The vibrator 21 is rotated in the direction shown in an arrow A, and external force is imparted in the direction for drawing the tubular body 2 from the molded form W. Molten metal 24 falls and the molded form W is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for molding a hollow resin molded product, and more specifically, a method for molding a resin molded product using a soluble core and then removing the molded product from the hollow core. The present invention relates to a resin molding method in which particles are eluted.

2. Description of the Related Art A molding method called a meltable core method has been adopted as a method for molding hollow resin molded products such as intake manifolds of internal combustion engines.

In this molding method, as shown in FIG. 4, injection molding is carried out by a conventional method using a core 51 made of a low melting point alloy such as an aluminum alloy, and the molded resin molded product W is The oil 52 of FIG. 5 is heated to a predetermined temperature by being immersed in the oil bath 53 shown in FIG. A resin molded article W having a shape is obtained. Note that the eluted core 51 is stored as molten metal 54 at the bottom of the oil bath 53.

The core 51 used in this molding method is generally hollow in order to reduce its weight, and as shown in FIG. The molten metal (molten metal) M that is to become the core 51 is filled from the nozzle 56, and the layer on the surface side of the core in contact with the mold surface is solidified, and before the layer inside the core is solidified, the 8th As shown in the figure, by retracting the injection plunger (not shown) in the nozzle 56 or by removing the nozzle 56 from the mold 55 and discharging the unsolidified molten metal M in the mold 55, a hollow I got 51 cores.

Problems to be Solved by the Invention In the conventional molding method, the core 5 from the resin molded product W
Since the resin molded product W is simply left stationary in the oil bath 53 shown in FIG. 5 when the core 51 is eluted, it takes a long time until the core 51 is completely eluted.

In addition, in the process of molding the core 51, which is a prerequisite for the meltable core method, the core 51 is
In addition to taking time to discharge the unsolidified molten metal M inside the core 51, it is difficult to accurately monitor the solidification progress inside the core 51. Even if the molten metal is discharged, the shape of the hollow part of the core 51 is not constant. As a result, molding defects in the resin molded product W occur due to manufacturing variations in the shape of the hollow portion of the core 51.

That is, the hollow core 51 will be eluted from the molded product W by being immersed in the oil bath 53 together with the molded resin molded product W for a predetermined heating time set by a timer, for example. However, as mentioned above, if there is variation in the shape of the hollow part of each core 51, the heating time required for core elution may be too short or too long depending on the degree of variation. Since the core 51 is left behind on the surface, the state of core removal varies, and no improvement in quality can be expected.

The present invention was made in view of the above problems.
The purpose of this is to shorten the time required to elute the core from the resin molded product, as well as reduce the cycle time during core casting by eliminating the need to discharge molten metal during the core casting process. The object of the present invention is to provide a method in which variations in the state of core removal are eliminated by further stabilizing the shape of the hollow portion of the core.

Means for Solving the Problems The present invention uses a flexible tubular body as an insert, and includes a process of casting a hollow core to be cast into the tubular body, and a process of casting the core integral with the tubular body in a mold. The process of molding a hollow resin molded product by setting it in The process includes a step of eluting the molded product.

Effect According to the above method, a hollow shape is obtained by casting a tubular body inside the core, so it is not necessary to discharge molten metal during core casting, and the shape of the hollow part is stabilized. This eliminates the variation. Moreover, by passing a heating medium through the inside of the tubular body during core elution, the core is eluted from the resin molded product.

Embodiment Figures 1 to 3 are diagrams showing an example of the present invention. Figure 1 shows the core elution process, Figure 2 shows the core casting process, and Figure 3 shows the injection molding process. It is shown in

In the core casting process, as shown in FIG.
are arranged, and both ends of this tubular body 2 are connected to joint members 3 and 4.
It is connected to cooling water passages 5 and 6 on the mold 1 side through. While cooling water is made to flow through the tubular body 2, a low melting point alloy (for example, an aluminum alloy ) is filled with molten metal M to cast a hollow core 9.

At this time, cooling of the core 9 to be cast is promoted by flowing cooling water through the tubular body 2, which can contribute to shortening the cycle time during core casting.

In the injection molding process, as shown in FIG. 3, a core 9 into which the tubular body 2 has been cast is first placed in a mold 10, and both ends of the tubular body 2 are fitted with joint members 11. 12 to cooling water passages 13 and 14 on the mold 10 side.

Then, while cooling water is made to flow through the tubular body 2, the nozzle I
5, the resin material P is injected into the product space 16, and injection molding is performed by a conventional method.

At this time, cooling and solidification of the resin molded product W is promoted by flowing cooling water through the tubular body 2.

The molded resin molded product W is taken out from the mold 10 together with the core 9 and transported to a core elution step.

In the core elution process, as shown in FIG. 1, the resin molding is supported by a clamp device (not shown) in an oil bath 19 which is heated by a heater 18 so that the oil 17 inside as a heat bath reaches a predetermined temperature. The product W is immersed in each core 9 and heated at the oil temperature for a predetermined time.

Then, one end of the tubular body 2 is connected in advance to the discharge side of the oil circulation pump 20 and connected to the tip of the arm 23 of the vibrating device 21, and the inside of the tubular body 2 is simultaneously immersed in the oil 17 described above. When the core 9 begins to melt, the drive source 22 of the vibration device 21 is activated to apply vibration to the tubular body 2.

In this way, by flowing the oil 17 inside the tubular body 2, the temperature rise and melting of the core 9 is accelerated, and by applying vibration, the molten metal 24, which is the molten core 9, is prevented from falling under its own weight. promoted.

Furthermore, once the entire core 9 has been melted by heating, the vibrating device 21 is rotated in the direction of arrow A, and the tubular body 2 is substantially melted.
An external force is applied in a direction to pull out the resin molded product W. As a result, the molten metal 24, which is the core 9, falls all at once under its own weight from the resin molded product W with the help of the movement of the tubular body 2, and the resin molded product W shown in FIG. 6 is obtained.

Here, it is assumed that the timing of applying vibration to the tubular body 2 and the timing of rotating the vibration excitation device 21 are set in advance using a timer or the like.

In addition, a high frequency induction coil is placed in the oil bath 19,
Heating by oil temperature and high frequency induction heating may be used together.

Effects of the Invention As described above, according to the present invention, resin molding is performed using a hollow core in which a tubular body is cast, and then the resin molded product is immersed together with the core in a hot water bath and heated. However, since the core is eluted from the resin molded product by passing a heating medium through the tubular body, it has the following effects.

(1) Since the hollow shape of the core can be obtained by casting the tubular body as an insert, there is no need to discharge molten metal during the core casting process to obtain the hollow shape as in the past. In addition to reducing the time required for casting the child, variations in the shape of the hollow part are eliminated and the shape is stabilized.

(2) By stabilizing the shape of the hollow part of the core as described above, there will be no excess or deficiency in the heating time when eluting the core in the core elution process, and as a result, the core removal state This eliminates variations in quality and improves quality.

(3) By passing a heating medium through the tubular body during core elution, the temperature increase and elution of the core are promoted, and the time required for core elution can be significantly shortened.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of the present invention, and is an explanatory diagram of the core elution process, Fig. 2 is an explanatory diagram of the core casting process, Fig. 3 is an explanatory diagram of the injection molding process, and Fig. 4 is an explanatory diagram of the core elution process. is an explanatory diagram of the conventional injection molding process, FIG. 5 is an explanatory diagram of the core elution process,
FIG. 6 is an explanatory diagram showing an example of a resin molded product, and FIGS. 7 and 8 are process explanatory diagrams of a conventional core casting process. ■... Mold for core casting, 2... Tubular body, 9...
Core, 10... Mold for injection molding, 17... Oil as a heat bath, 19... Oil bath, 21... Vibration device, W... Resin molded product. Figure 2 Figure 3 n Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) A hollow resin molded product is molded using a core made of a low melting point alloy, and after the molding is completed, the hollow resin molded product is immersed together with the resin molded product in hot melting and heated. In the method of eluating the particles, a flexible tubular body is used as an insert, and a hollow core is cast to encase the tubular body, and the core integrated with the tubular body is placed in a mold. A process of setting and molding a hollow resin molded product. A resin molded product with a core inside is immersed in hot melt, heated, and a heating medium is passed through the tubular body to mold the core into resin. A resin molding method characterized by comprising: a step of eluting it from a product.