JPH01190421A - Core separation - Google Patents

Abstract

PURPOSE:To separate a product and a core without leaving any chucking marks on the surface of the product, by injection-molding a core whose retaining sections are formed of a material having a melting point higher than a material with a low melting point, forming a core main body, and then melting and removing the core main body while the core retaining section is retained. CONSTITUTION:A core 1 is set in an automatic injection molding die, and injection molding is carried out by a conventional procedure to mold a molded product 6. Resin is coat molded integrally in a core main body 4 of the core 1 of the molded product 6, and said resin portion forms a product 5. Then, the product 6 is chucked with retaining sections 2, 2 of the core 1, hung by means of jigs 21 and retained in the state of being impregnated in heat oil 23 in a heating oil tank 22, while the core main body 4 heated with the heating oil 23 up to its melting point and the core main body 4 constituted of a material of low melting point of the core 1 is melted. The molded product 5 can be manufactured without any chucking marks by said process.

Description

[Detailed description of the invention] [Purpose of the invention]

(Industrial Application Field) The present invention is used to mold plastic parts having a hollow part by injection molding, and is particularly used to separate a core used to form the hollow part from a product part. The present invention relates to a method for separating cores. (Prior art) Plastic injection molding is a method in which the molding material is plasticized in a heated cylinder, press-fitted into the mold cavity under high pressure, cooled and solidified, and then taken out as a molded product. Even complex shapes can be obtained in a single molding process, so it is used for molding various automotive parts such as instrument panels, instrument housings, console boxes, front grills, instrument gears, and connectors. has been done. In addition, a core made of a low melting point alloy that has a melting point lower than the heat resistance temperature of the plastic molded product is inserted into a mold and then injection molded, and after cooling, the molded product integrated with the core is taken out. After that, it is also possible to mold parts with even more complex shapes with hollow parts by heating the low melting point alloy that forms the core to the melting point and melting and separating only the core and removing it. There is. Conventionally, injection molding of such hollow parts has been carried out using the method shown in Fig. 3 (a).
) is used, as shown in FIG. By injection molding on top of that, WS3 (b)
) A molded product 16 is obtained in which the core 11 and the product 15 are integrally molded. Subsequently, the molded product 16 obtained by injection molding is placed in a jig 2 as shown in FIG. 4(a).
1, the part corresponding to the product 15 is chucked and suspended, and is immersed and held in heated oil 23 filled in a heated oil tank 22. When the temperature of the heating oil 23 reaches the melting point of the low melting point alloy forming the core 11, only the core 11 made of the low melting point alloy is melted and separated, as shown in FIG. 4(b). A product 15 having a hollow portion was obtained through the process of (Problems to be Solved by the Invention) However, in the process of separating the product 15 and the core 11, the molded product 16 is heavy because it is integrated with the core 11, as shown in FIG. 4(a). As described above, since the product 15 is chucked, surface flaws on the product 15 due to this chucking are unavoidable, which poses a major problem in terms of product quality and yield. The present invention was made by focusing on the above-mentioned problems in the method of separating the product and the core in the conventional injection molding method, and its purpose is to manufacture hollow parts using a low melting point alloy core. To provide a core separation method capable of separating a product and a core without leaving chucking defects on the surface of the product in injection molding.

[Structure of the invention]

(Means for Solving the Problems) The core separation method according to the present invention uses a part of the core made of a low melting point material as a high melting point material, and is used for transporting the molded product or immersing it in heated oil. By performing the chucking with the part made of the high melting point material, it is possible to avoid the occurrence of scratches on the product surface, and the structure is made by injection molding using a core made of a low melting point material. , a method of obtaining an injection molded product by melting and separating and removing the core after molding, in which a part of the core is made of a material having a higher melting point than a low melting point material forming the core body as a core holding portion. The present invention is characterized in that after injection molding is performed using a core formed with a core, the core is separated by holding the core holding portion and melting and removing the core body portion. (Example) FIGS. 1 and 2 are diagrams for explaining the structure of a core used in an example of the present invention and the process of a core separation method according to the present invention. The core 1 used in the method of the present invention shown in FIG. It is composed of a single-shaped core material 3 which is connected by screwing, and a core body 4 made of a low melting point material cast around the core material 3. The core 1 having the above structure was set in a normal injection mold and injection molded according to a conventional method to obtain a molded product 6 shown in FIG. 1(b). In the molded product 6, the core body 4 of the core 1 is integrally coated with the resin, and this resin portion becomes the product 5. Next, the molded product 6 is chucked by the holding portion 2°2 of the core 1, suspended by a jig 21 as shown in FIG. 2(a), and immersed in heated oil 23 in a heated oil tank 22. As shown in FIG. 2(b), the core body 4 made of the low melting point material of the core 1 is heated by heating the core body 4 to its melting point with the heating oil 23. By melting only the portion, it is possible to obtain the product 5 without causing chucking flaws. As described above, since the molded product 6 is chaffed by the core holding part 2 made of a high melting point material, the product 5 is not chaffed, and the product 5 is chaffed by the core holding part 2 made of a low melting point material. Even after the main body 4 is melted out, it is held by the core material 3 of the core 1 and will not separate from the jig 21 and fall into the heated oil tank 22. In addition, in the above embodiment, an example was shown in which the holding portion 2 of the core 1 made of a high melting point material and the core material 3 are joined by screws, but the method of the present invention is not necessarily limited to this. Rather, it is sufficient that the structure can hold the product 5 even after the core body 4 made of a low melting point material is eluted, and can be easily extracted from the product 5 afterwards.
Various aspects can be considered in the mold design. Further, the core holding portion 2 made of a high melting point material and forming a part of the core 1 is not limited to an alloy, but as long as the above function can be achieved at the melting temperature of the core body 4 made of a low melting point material. , it can also be applied to pure metals, resins, etc. Furthermore, the type of low melting point alloy forming the core body 4 is not limited to the Pb-3n-based alloy, but must be selected depending on the characteristics of the resin to be molded.

【Effect of the invention】

As explained above, the core separation method according to the present invention involves injection molding using a core made of a low melting point material, and then melting and removing the core after molding to obtain an injection molded product. A part of the core, which was conventionally made only from a low melting point alloy, is now made of a high melting point material, and the core holding part made of the high melting point material performs chucking for transporting the molded product or immersing it in heated oil. This makes it possible to prevent chucking defects from occurring on the product surface, and greatly contributes to improving the quality of injection molded products and improving product yield.

[Brief explanation of the drawing]

7n1 Figures (a) (b) and Figure 2 (a) (b)
) is a diagram illustrating an embodiment of the present invention. FIG. 1(a) is a front view illustrating the structure of the injection molding core used in the present invention, and FIG. 1(b) illustrates a molded product injection molded using the core of FIG. 1(a). Front view, Figure 2 (
a) and (b) are explanatory diagrams sequentially illustrating the steps of separating the product and the core, and FIGS. 3(a), (b) and 4(a) and (b) are diagrams illustrating the conventional method, FIG. 3(a) is a front view illustrating a conventional injection molding core, FIG. 3(b) is a front view illustrating a molded product injection molded using the core of FIG. 3(a), FIGS. 4(a) and 4(b) are explanatory diagrams sequentially illustrating a conventional process of separating a product and a core. 1... Core, 2... Core holding part (high melting point material), 3... Core material (
(high melting point material), 4... core body (low melting point material), 5... product. Patent Applicant Nissan Motor Co., Ltd. Patent Attorney Yutaka Oshio 7 Figure 1 (0) Figure 1 (b) Figure 2 (.) Figure 2 (b) Figure 3 (CI) 1 Figure II4 (0 ) 2 and @3 Figure (b) Figure 4 (b)

Claims (1)

[Claims] (1) In a method of obtaining an injection molded product by injection molding using a core made of a low melting point material and then melting and separating the core after molding and removing it, a part of the core is used to form a core body. After injection molding is performed using a core in which a core holding portion is made of a material having a higher melting point than a material with a higher melting point than a material with a lower melting point, the core holding portion is held and the core main body portion is melted and removed. A core separation method characterized by separating.