JPH034021B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applicable to injection molding methods and injection molding methods.
This invention relates to a molding method that prevents parting line marks and burrs from forming on molded objects.

[Conventional technology]

Conventionally, when molding, for example, a pipe-shaped molded product by injection molding or injection molding, a mold and an insert member as shown in the side sectional view of FIG. 4a and the front sectional view of FIG. 4b are used. The molding was done using. That is, the insert member 3 is set in the lower mold 2 with the upper mold 1 open, and then the upper mold 1 is opened.
was closed, the upper mold 1 was brought into close contact with the lower mold 2, and the raw material was injected through the sprue 5 to form a molded article 4.

[Problem that the invention seeks to solve]

However, in the conventional mold structure as described above, since the upper mold 1 and the lower mold 2 are molded together and molded, a parting line 6 is inevitably generated in the part of the molded product corresponding to the mold mating surface. In addition, raw material often leaked into the gap between the mold mating surfaces and burrs were generated.
Therefore, polishing was required as secondary processing, which increased the number of steps and required time and effort to manufacture the molded product. In addition, due to the polishing process, parts of the molded body other than the parting line 6 and burrs are also polished and the surface of the molded body becomes rough, and the desired surface precision of the molded body obtained depending on the surface roughness of the mold is lost. There was a drawback that it was difficult to use. Of course, such drawbacks occur not only in pipe-shaped molded products but also when molded products of any shape are molded using conventional molds.

The present invention has been made in order to solve the above problems, and its purpose is to enable molding without forming parting line marks or burrs on the molded product, and to eliminate the need for secondary processing. The object of the present invention is to provide a molding method.

[Means for solving problems]

The present invention is a molding method for supporting an insert member within a mold member and obtaining a molded body without a parting line on the outer periphery of the insert member, the method comprising: inserting a hollow cylindrical body on the outside of the insert member; The insert member and the outer side of the insert member are inserted through a presser member that fits into the insert member and the hollow cylindrical body.
The hollow cylindrical body is held in the mold member by opening the opening, and by pressing the presser member against the insert member and the hollow cylinder body, the presser member, the insert member, and the hollow cylinder body are brought into close contact, and the hollow cylinder body can be divided in the axial direction. The mold member having heating means is closed, and the space between the outer peripheral surface of the insert member and the inner peripheral surface of the hollow cylindrical body is used as a molding cavity, and a raw material for the molded body is injected into this molding cavity. Molded,
This is a molding method in which a molded body is obtained by subsequently opening the mold member and taking out the molded body from the hollow cylindrical body.

[Preferred mode for carrying out the invention]

Hereinafter, the molding method of the present invention will be explained in detail with reference to the drawings, taking as an example the case of molding a cylindrical molded body. FIGS. 1 and 2 are schematic sectional views showing the manufacturing process of the above example. In this example, the mold member can be divided into an upper mold 7 and a lower mold 8, as shown in FIG. First, the cylindrical body 9 and the insert member 10 that is inserted into the cylindrical body 9 and sets the cavity 13 in the gap between the inner wall of the cylindrical body 9 are held by the insert member holder 1.
1, integrate, and preheat using a desired heating means.

Next, as shown in FIG.
and close the upper mold 7.

The upper mold 7 and lower mold 8 in this example serve to fix the above-mentioned integrated product and to heat and cool it as necessary, so any mold may be used as long as it has similar functions.

Next, as shown in FIG. 2, the hydraulic cylinder 12 attached to the side surface of the lower die 8 is moved forward to press the insert member presser 11, thereby removing the insert member 1.
0 and the member holder 11 are brought into close contact with each other sufficiently so that no gap is created.

Next, the raw material for the molded body is injected into the cavity 13 from the sprue 14. An enlarged view of the vicinity of this sprue 14 is shown in FIG. The raw material for the molded body injected from the sprue 14 passes through the runner 15 and the ring-shaped gate 16 formed around the circumference of the insert member presser 11 into the cavity 1.
3 is filled. With the ring-shaped gate 16,
Since raw materials are simultaneously filled over the entire circumference of the cylindrical cavity 13, defects in the molded product due to voids and welds are extremely unlikely to occur compared to conventional gates provided at one location around the circumference.
Further, since the outer shape of the molded body is formed by the cylindrical body 9, traces of parting lines of the mold or burrs will never occur on this body portion. Furthermore, as mentioned above, the hydraulic cylinder 1
2, the insert member 10 and the member retainer 1
Since the joint surface with 1 is in close contact with the joint surface, leakage of the raw material into the gap between the joint surfaces and generation of burrs on the end surface of the cylindrical molded body is prevented. Even if burrs occur, it is easy to remove only the burrs because they are on the end faces, and even if the burrs are not removed, there is often no problem in using the molded product.

Next, after the raw material filled in the cavity 13 has hardened, the hydraulic cylinder 12 is retreated, and the upper mold 7 and the lower mold 8 are opened again to integrate the pipe 9, the insert member 10, and the member holder. 11
are taken out, these are released from the mold, and the molded product is taken out.

By the method described above, it is possible to mold a molded product without traces of parting lines of the mold or burrs.

In the embodiments described above, the case where a cylindrical molded body is molded has been described, but molded bodies of other shapes can also be molded by the method of the present invention. That is, if a cylindrical member corresponding to the cylindrical body 9 of the above embodiment is used whose cross-sectional shape is polygonal, elliptical, etc., a molded article corresponding to the shape can be molded. Moreover, as the insert member 10,
By using materials having various cross-sectional shapes, the inner surface of the molded body can be made to correspond to the member 10.

The material of the cylindrical body can be metal, rubber, resin, etc., but it is also possible to make a mirror-like product by coating the inner surface of the cylindrical body with resin. Furthermore, by adjusting the surface roughness of the inner surface of the pipe, the surface condition of the molded product can be freely controlled. Moreover, a tube-shaped body whose wall thickness is thinner than that of a pipe can also be used.

〔Effect of the invention〕

According to the present invention, it has become possible to easily mold a molded article without traces of parting lines or burrs on the mold. Furthermore, the parting line and burr polishing steps as secondary processing can be omitted, and the molding time can be shortened. Furthermore, since polishing is not necessary, the surface of the molded product does not become rough. Therefore, the roughness of the surface of the molded body to which the surface roughness of the inner surface of the cylindrical body is transferred becomes its final surface precision. The surface can also be made mirror-like.

With the method of the present invention, a hollow molded body with a clean surface can be molded more easily than with any other molding method.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic sectional views showing the implementation steps of the method of the present invention, Figure 3 is an enlarged view of the vicinity of the sprue, and Figures 4a and 4b are side sectional views showing an example of a conventional mold structure. Figure 1 is a front sectional view. 1, 7: upper mold, 2, 8: lower mold, 3, 10: insert member, 4: molded body, 5, 14: sprue,
6: Parting line, 9: Cylindrical body, 11: Insert member holder, 12: Hydraulic cylinder, 1
3: Cavity, 15: Runner, 16: Ring-shaped gate.

Claims (1)

[Scope of Claims] 1. A molding method for supporting an insert member within a mold member and obtaining a molded product without a parting line on the outer periphery of the insert member, wherein a hollow cylindrical body is provided outside the insert member. Hold the hollow cylindrical body within the mold member with a space between the insert member and the outside thereof through a presser member that fits into the insert member and the hollow cylindrical body, and press the presser member between the insert member and the hollow cylindrical body. The pressing member, the insert member, and the hollow cylindrical body are brought into close contact with each other by pressing the holding member, the mold member that is separable in the axial direction of the hollow cylindrical body and has heating means is closed, and the outer circumferential surface of the insert member and the hollow cylindrical body are closed. The space between the inner circumferential surface of
A mold forming method in which a molded object is obtained by subsequently opening the mold member and taking out the molded object from the hollow cylindrical body.