JPH0929780A - Molding method for article of complex shape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To be able to give the structural rigidity to a core by molding it from a partly molded rigid material covered with a final molding article. SOLUTION: When molding is conducted, the resultantly obtained partly molded core member 34 is removed from the first mold cavity, and mounted in the second mold cavity 58 for forming it. The partly molded core assembly 34 is covered with a molding. In the covering molding step, plastic material is injected to the periphery of the partly molded assembly 34. The same molding step is completed to obtain a final product by incorporating a complementary inner surface shape 54 to the outer surface of the final product in the second mold cavity 58.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a method for manufacturing an article using a molding method, and more particularly, to overmolding a core (referred to as an overmold) before molding the article by the core loss method. The present invention relates to a method for manufacturing an article.

[0002]

2. Description of the Related Art There are many methods used for producing molded products such as intake manifolds and exhaust manifolds for automobiles, and the best known method is the blow molding method. According to this method, a die (molding die) is made and a molding material is disposed around the die to make a product. But,
This blow molding method has a drawback when molding a product having a complicated inner surface shape or outer surface shape. Its biggest drawback is that it can only produce products whose die structure is not very complex.

In recent years, attempts have been made to manufacture hollow parts with complex geometric shapes. US Patent No. 5,20
No. 7,964 discloses a method of making hollow plastic articles using water soluble resins. This method involves the steps of making two half-shells of a core with a water-soluble resin and joining both shells by solvent welding or other type of welding method into a single piece core. ing. This core is then overmolded with a waterproof resin. Then, the core is covered and hot water is sprayed on the molded product to elute it from the product.

Another method of making hollow parts is US Pat.
590,026 (Goto), which is a process of disposing a stiffening layer on the inside surface of a complex cavity. This process forms a reinforcing layer or film on the inner surface of a complex shape of a molded plastic body. First, a meltable or meltable inert core member is prepared.
Next, a ceramic or metallic reinforcing layer is applied to the outer surface of the core member excluding the outer end of the member. The core member thus covered with the reinforcing material is then placed in the mold cavity. The plastic molded body is integrally molded around the reinforcing layer or film arranged on the core member. Finally, the core member is eluted from the inside of the plastic molded body while leaving the reinforcing layer or film in the molded body.

Despite the molding techniques described above, it is still almost impossible to mold complex core contours. The shift of the core during the molding process is of particular concern when the molded product has a thin wall structure. A representative of this type of molded article requires a high degree of mold tolerance during the molding process.

[0006]

SUMMARY OF THE INVENTION The first object of the present invention is to mold a novel article having a complicated shape, in which the core is covered and molded before the article is covered and molded by the core loss method. To provide a method. A second object of the invention is to implement the above method so that complex geometric contours, which are considered impossible with current molding techniques, can be molded. A third object of the present invention is to eliminate the problem of core displacement in the cover molding process. An object of the present invention is to mold separately cast cores and to assemble them to form a complicated core outline, thereby imparting structural rigidity to the core in the initial covering molding process. An object of the present invention is to provide the above method that is made possible.

[0007]

According to the present invention, a method of covering and molding a core is performed before the covering and molding step of an article using a core loss method, including the following steps. To do. A core member including a rigid main body and a flexible portion which is separated and connected so as to form a space with respect to the main body is formed of a predetermined material, preferably a low melting point alloy. The core member is supported in the mold cavity such that the flexible portion remains rigid during the primary molding process.
In the primary molding process, the plastic material is injected into the first mold cavity, whereby the core member is
A space (void) between the flexible portion and the rigid body is filled with an injection material to form a partially molded article. Upon completion of this primary molding process, the mold cavity is opened and the partially molded article is removed from the cavity. That is, a rigid, partially molded article of core member and injected plastic material is then placed in a second mold cavity and overmolded by injecting the plastic material into the second mold cavity. The overmolded product is taken out of the second mold cavity as a final molded article containing the core member therein. After that, by removing the core member from the final product, a hollow molded product is completed.

[0008]

1 illustrates a hollow molding method 11 of the present invention for producing an article having a complex inner surface shape, outer surface shape or double-sided shape. This method 1
1 is performed according to the following steps. First, in this method (11), a core member is formed (step 12). Next, this core member is inserted into the first mold cavity and supported therein (step 13). Next, the raw material is injected into the first mold cavity (step 14). Then
Withdraw the partially molded article from the first mold cavity (step 15). Next, the partially molded product is inserted as an insert into the second mold cavity and fixed therein (step 16). Another material is injected into the second mold cavity (step 17). The final article is then removed from the second mold cavity (step 18). Finally, the insert core material is removed from the final article (step 19). The resulting finished product, a molded product, is a hollow, intricate, desired inner surface profile that can be applied to any application.

FIG. 2 illustrates the intake manifold of an internal combustion engine, which includes the flanges required to connect intake manifold 21 to engine block 24 and the fuel distribution system. FIG. 3 shows the manifold arm 31 of the intake manifold 21. As shown, the manifold arm has a plurality of runners 2 separated by a separating inner wall 36.
Including 0, 22 and so on. Inner wall 36 is normally molded during the primary molding process (14), thereby allowing core member 34, and in particular flexible portion 50 (FIG. 4) to bend.
(See) Prevent warpage (deflection) and bending. The inner wall 36 is connected to the outer wall 33 of the manifold arm 31 during the secondary molding step (17).

In the conventional molding method, the complicated internal shape of the hollow product is not correctly molded due to the viscosity and pressure of the molding material used for molding the complicated internal shape. The present invention overcomes the problems of molding complex internal shapes by dividing the molding method into separate steps. According to the preferred example of this method, a complicated surface shape of the intake manifold 21 for an internal combustion engine, which is a hollow product, can be molded. The intake manifold 21 in this example includes first and second dual runners (two runners) 20, 22 and the like, so that when the second runner is used simultaneously with the first runner, additional fuel can be supplied. There is. In the conventional molding method, the wall 36 between the dual runners 20 and 22 is
Is formed in an uneven pattern, that is, one part is thicker than the other part, or one part has a hole. Such uneven molding is the result of high molding pressure which distorts the shape of the core. That is, by compressing the two parts of the core 34, the groove 32 used to form the inner wall 36 disappears, or the groove 32 is expanded to produce an inner wall with increased wall thickness. is there. These problems are due to the inability to properly support the core 34 during the molding process. The discontinuity in the molding operation results in an uneven flow of fuel along the runner. To overcome these problems, the present invention seeks to mold articles of complex surface profile to obtain evenly sized runners 20,22, thereby eliminating unequal fuel flow. It can be said to be a thing.

FIG. 4 shows a core member 34 which is overmolded to form a hollow end product. The core member 34 is generally formed of a metallic material such as a tin / bismuth alloy or other alloy having a melting point lower than that of the material used in the final product. The outer surface of the core member has a complementary relationship with the inner surface shape of the final product (finished molding product). The slot or groove 32 in the core member 34 is used to form a wall 36 that distinguishes the final runner 20 from the runner 22.
The core member 34 is the runner 2 in the final manifold.
It includes a flexible member or portion 50 and a rigid member or portion (body portion) 52 corresponding to 0, 22. In the case of the usual single-step overmolding method, both members 50, 52 are flexible,
Therefore, it lacks rigidity. It is the primary molding process (1
This is due to the fact that the separation wall 36 is distorted due to the fact that it is not firmly supported by the mold (4). According to the present invention, the flexible portion 5 of the core member 34 during the primary molding step (14).
0 and the rigid portion 52 are held firmly so that the gap or groove 32 maintains a uniform spacing during injection of the plastic material. Therefore, it is necessary for the slot 32 to support both parts 50, 52 evenly along the entire length of the core member 34.

In order to achieve uniformity over the entire length of the runner 20, the first step of the molding method of the present invention is the initial covering molding step (see FIGS. 6 and 7). In this step, moldable plastic or other material is injected into the groove 32 between the flexible portion 50 and the rigid portion 52. Both parts 50 and 52 are supported inside the first mold cavity 56 by a support material 60. Core 3
4 is shown to have one flexible portion 50 and one rigid portion 52, the core 34 being two flexible portions each supported during the primary molding process. It can also have individual flexible parts.

The gap or slot 3 in the core member 34
When the material 36 is injected (injected) into the parts 2, the parts 50, 52
And the material 36 in the gap 32 constitutes an integral member. In this method, a core structure (hereinafter referred to as a core assembly) is wholly hardened to be a rigid body, and distortion of the core assembly is reduced in a final molding process. The plastic material injected into the gap of the core member 34 hardens the core and yet most of the complex geometric regions are completely filled with this material. The plastic material that fills the gap 32 and the open area is the core member 3
4 around the outer surface 49, in particular around the connection between the groove 32 and the core member 34, in a random manner. This improves contact and bonding in the secondary molding process, and also helps the secondary molding part adhere to the molding material injected outside the core member during the primary molding process.

When the primary molding is performed, the resulting partially molded core member 34 is obtained.
Is taken out from the first mold cavity 56 and is inserted into the second mold cavity 58 for secondary molding (see FIGS. 11 and 12).

In the secondary molding operation, the partially molded core assembly 34 is inserted into the second core mold cavity 58, and the partially molded core assembly 34 is covered and molded. Molded. In this overmolding process, a plastic material is injected around the partial molding core assembly 34. In order to obtain the final product by completing the molding process, the second mold core cavity 58 has an inner surface shape 54 that is complementary to the outer surface shape of the final product.

In the preferred embodiment, a resin type material is used as the overmolding plastic material, although other molding materials having a higher melting point than the core material can be used. The secondary molding operation may use the same plastic (plastic) material as in the case of the primary molding, or may inject different types of molding material around the partial molding core assembly 34, It is also possible to make the outer part of the final product by. The secondary molding interacts and bonds with the primary molding, thereby forming a hermetic seal in the molding. Since the partial molding core assembly 34 is fixed in the second mold 58, the assembly 34 does not shift or shift during the secondary molding process. When the secondary molding operation is completed, the entire resulting molded product is taken out of the second mold cavity 58.

It goes without saying that the plastic material used in the primary molding may be different from the material used in the secondary molding. The primary molding material may be a recycled raw material such as a crushed raw material or a plastic material lower than the secondary molding material.

The resulting final product 30 encloses the core member or core assembly (see FIG. 9) and has a plastic material surrounding it. The final product 30 is placed in an oven or other suitable device where the material of the core member 34 is removed or lost due to its liquefaction. This step removes the core, resulting in a hollow article with a complex internal shape. Other methods may be used to remove the core member from the final product, and as other methods, for example, the core material may be incinerated, evaporated, or other known methods may be adopted.

Applying a secondary molding operation eliminates the concern of core shift. According to the single lost core molding process, the core shifts in the molding machine and the plastic material spreads unevenly each time, resulting in the molding of inaccurate or defective products. It will be. The primary molding process eliminates the concern that the internal shape may not be accurately molded. In addition, complex shapes, and even core shapes that were previously considered impossible, can be molded using the conventional core-loss molding method in conjunction with the secondary molding process. became.

As shown in FIG. 8, a plurality of core members 34 are first partially molded and then placed in a single second mold cavity 58 where the entire core assembly manifold system is molded. Can be done. In the molding process using the insert of the core assembly, the concern that the mold (mold) and the core are displaced is eliminated. Therefore, several core assemblies 3
4 can be overmolded in the second molding step.

[0021]

As can be understood based on the description of the above embodiment, according to the molding method of the present invention, since the two-step injection molding is performed, it is possible to improve the complicated hollow shape object having high structural rigidity. It becomes possible to mold accurately. In addition, the injection molding can be performed without concern that the core will shift. Further, in the first (primary) injection molding, it is possible to use pulverized raw materials (recycled products) and low-grade raw materials, which brings about a cost reduction effect. Further, the internal shape of the hollow molded article can be variously desired.

[Brief description of drawings]

FIG. 1 is a process drawing showing a molding method of the present invention.

FIG. 2 is a perspective view showing a hollow manifold formed by the method of the present invention.

FIG. 3 is a sectional view taken along line 3-3 in FIG. 2;

FIG. 4 is a perspective explanatory view showing a core member used in the method of the present invention.

5 is a cross-sectional view taken along line 5-5 of FIG.

FIG. 6 is an explanatory perspective view showing the core member after the initial (primary) molding operation according to the present invention.

FIG. 7 is a sectional view taken along lines 7-7 of FIG. 6;

FIG. 8 is a perspective explanatory view showing a plurality of core members arranged to mold the core assembly used in the method of the present invention.

FIG. 9 is a perspective explanatory view showing a molded product after the secondary molding step according to the present invention.

FIG. 10 is an explanatory view showing another embodiment of the core member used in the method of the present invention.

FIG. 11 is an explanatory view showing a first mold cavity used in the primary molding operation according to the method of the present invention.

FIG. 12 is an explanatory view showing a second mold cavity used in a secondary molding operation according to the method of the present invention.

[Explanation of reference numerals] 11 ... Mold forming method 12 ... Core member forming step 13 ... First mold cavity mounting step 14 ... Primary mold injection molding step 15 ... Partial molded product removing step 16 ... Second mold cavity mounting step 17 ... Second mold cavity injection molding process 18 ... Finished product removing process 19 ... Core member removing process 20, 22 ... Runner 21 ... Suction manifold 24 ... Engine block 30 ... Final molded product 32 ... Slot, groove, gap or void 33 ... Plastic Material 34 ... Core member, core assembly 36 ... Separation wall (plastic material) 49 ... Core member outer surface 50 ... Flexible section (flexible portion) 52 ... Rigid section (rigid body) 56 ... First mold cavity 58 ... 2nd mold cavity 60 ... Support material

Claims (15)

[Claims] 1. A molded article having an internal shape complementary to the shape of a core member, the core member comprising a rigid body and a flexible portion connected to the rigid body to form a void. Forming a core member made of a predetermined material, the core member having the flexible portion in the first mold cavity so that the flexible portion maintains rigidity during injection of the plastic material. Supporting; filling the plastic material into the void between the flexible portion and the rigid body by injecting the plastic material into the first mold cavity such that the core member becomes a rigid body. Partially molding; opening the first mold cavity and removing the partially molded rigid body obtained therefrom;
Placed in a second mold cavity having a surface shape that is complementary to the external shape of the molded article; supporting the partially molded article in the second mold cavity, and in this state into the second mold cavity. Overmolding a final molded article from the partially molded rigid body by injecting a plastic material;
A method of molding a complex shaped article comprising the steps of removing the final article from the second mold cavity and removing the core member from the final article. 2. The method according to claim 1, wherein in the core member removing step, the core member is removed from the final article by liquefying it. 3. In the core member removing step, the core member is removed from the final article by evaporation.
The method of claim 1. 4. The method according to claim 1, wherein in the core member removing step, the core member is removed from the final article by incineration. 5. The step of placing the partially molded rigid body in the second mold cavity comprises placing a plurality of the partially molded rigid bodies in the second mold cavity. The method described in. 6. The molded article has an internal shape complementary to the shape of the core member, and the core member includes a rigid body and a flexible portion connected to the rigid body to form a gap. Forming a core member of a predetermined material; supporting the core member in the first mold cavity such that its flexible portion remains rigid during injection of the first molding material; The plastic material is filled into the space between the flexible portion and the rigid body by injecting the first molding material into the first mold cavity, whereby the core member is a rigid body. Partially opening the first mold cavity and taking out the partially molded rigid body obtained from the first molded cavity; Installed in a cavity; the partially molded rigid body is supported in the second mold cavity, and in this state, a second mold is placed in the second mold cavity.
Overmolding a final molded article over the plurality of partially molded rigid bodies by injecting a plurality of partially molded rigid bodies; and removing the final molded article from within the second mold cavity, and A method of molding an article having a complex shape comprising the steps of removing the core member from the final article. 7. The method of claim 6, wherein the first molding material is plastic. 8. The method of claim 6, wherein the second molding material is plastic. 9. The method of claim 6, wherein the predetermined material of the core member is an alloy of tin and bismuth. 10. The method according to claim 6, wherein in the core member removing step, the core member is removed from the final article by liquefying it. 11. The method according to claim 6, wherein in the core member removing step, the core member is removed from the final article by evaporation. 12. The method according to claim 6, wherein in the core member removing step, the core member is removed from the final article by incineration. 13. The method according to claim 7, wherein the second molding material is a plastic grinding material. 14. The second mold cavity has a surface profile that is complementary to the external profile of the molded article.
The method of claim 6. 15. The molded article has an internal shape complementary to the shape of the core member, the core member including a body and a flexible portion connected to the body to form a void. Molding a core member of such construction from a predetermined material; supporting said core member in a first mold cavity such that its flexible portion maintains rigidity during injection of the plastic material; Plastic material said first
The plastic material is filled into the void between the flexible portion and the body by injection into a mold cavity, thereby partially molding the core member into a rigid body; Open the mold cavity and remove the partially molded rigid body obtained from it;
Placing the partially molded rigid body in a second mold cavity having a surface profile that is complementary to the external shape of the molded article;
A final molded article is overmolded from the partially molded rigid body by supporting it in a mold cavity and injecting the plastic material into the second mold cavity in this state; A method of molding an article having a complex shape, comprising the steps of removing from the second mold cavity and removing the core member from the final article.