JPS5950505B2 - Plastic molded products and their molding methods - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a plastic molded product and a method for manufacturing the same.
More specifically, during or after molding the molded product, it buffers the shrinkage of the resin and prevents the convex part that protrudes from the plate-shaped part of the molded product from falling down. This invention relates to a plastic molded product that can be reliably maintained perpendicular to a plate-like part, and a method for manufacturing the same.

In recent years, a considerable amount of plastic has been used for industrial purposes such as mechanical parts and electrical parts, and the plastic molded products used for these purposes must be precision products with little dimensional error and excellent shape accuracy. is required.

However, conventionally, when molding a molded product that integrally has a convex part that projects perpendicularly from a plate-like part, shrinkage of the resin occurs during or after molding, and especially when multiple convex parts are formed. In the case of a molded product having a shape such as the one shown in the figure, there is a disadvantage that the convex portions are slightly inclined due to the contraction of the resin, and the convex portions are not reliably maintained perpendicular to the flat plate portion. In addition, the mutual parallelism of the convex parts was often not maintained.In particular, polyacetal, which is a typical engineering plastic, has a high molding shrinkage rate.
When manufacturing machine parts using this material, maintaining the verticality of the convex portion is a serious problem, and when molding other resins with large mold shrinkage rates such as high-density polyethylene, polypropylene, and polyvinyl chloride. had a similar problem.For this reason, conventionally, when molding a molded product 1 integrally having a convex portion 3 vertically protruding from a plate-like portion 2, a method such as that shown in FIG. A rib a is provided to prevent the convex part 3 from falling down, or a rib a is provided along the circumferential direction in contact with the protruding part of the convex part 3 of the plate part 2, as shown in FIG. The former rib installation method requires extra resin material to install the ribs, and the ribs do not move in the direction of contraction. It is uncertain whether the ribs will act in the supporting direction or in the supporting direction, and it is not possible to reliably prevent the convex portion from collapsing. When assembling, there were drawbacks such as the ribs getting in the way during the assembly process and reducing assembly efficiency.

In addition, the latter method of corner lightening by forming concave grooves tends to cause "burrs" when the molded product is released from the mold, and because the lightening is done in a concave shape, a shrinkage difference occurs in the flat plate part, which causes the flat plate to It has disadvantages such as warpage in many cases and is not desirable from a design point of view. As a result of intensive studies to eliminate the above-mentioned drawbacks, the inventor of the present invention found that when molding a molded product that integrally has a convex part that projects perpendicularly from the plate part, the convex part of the plate part of the molded part When a V-shaped groove is formed along the circumferential direction near the installation location, the contraction of the resin is buffered by this V-shaped groove, and the convex part is reliably prevented from collapsing, and the convex part is prevented from collapsing against the plate-like part. Verticality and mutual parallelism of convex parts are not affected by shrinkage of the resin after molding, and there is no warping or twisting in the plate parts, and the molding shrinkage is among the highest among plastics. It was discovered that the present invention is also effective when molding polyacetal, which is said to belong to It can reliably prevent warpage, twisting, etc. of shaped parts, and it can reliably maintain dimensional accuracy and shape accuracy within tolerances when manufacturing functional and structural parts with plastic, making it suitable for industrial applications. It is an object of the present invention to provide a plastic molded product that is sufficiently effective, does not cause "burrs" when released from the mold, and has a good design, and a method for molding the same.

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 3 to 5.

In the figure, 1 is a plastic molded product made of polyacetal, and this molded product 1 has a plate-like part 2, two cylindrical convex parts 3,
3 and two V-shaped grooves 4, 4.

The two convex portions 3, 3 are located near one end and the other end of the plate portion 2 in the longitudinal direction, and are spaced apart from each other by a predetermined distance;
This plate-shaped part 2 is provided to protrude perpendicularly to the Lee body, and the plate-shaped part 2 is provided with a circumferential direction of these protrusions 3, 3 in contact with the protruding parts of both convex parts 3, 3. along both the V-shaped grooves 4,
4 are formed respectively. These V-shaped grooves 4, 4 have side walls on the sides of the respective convex portions 3, 3, respectively.
The extended side wall of 3 is cut out perpendicularly to the plate-like portion 2, and the other side wall of 4 is cut out at a predetermined angle. Next, a method for molding the plastic molded product 1 configured as described above will be explained. First, a mold 5 corresponding to forming the molded product 1 having the above shape is
Manufacture.

That is, the forming portion 6 of the plate-like portion 2 is carved in one of the molds 5a, and the forming portion 6 of the double-convex portions 3, 3 is formed in this forming portion 6 in correspondence with the protruding portions of the respective convex portions 3. Forming portions 7, 7 are bored therein, and an inverted V having a shape corresponding to both the V-shaped grooves 4, 4 is provided in the plate-like portion forming portion 6 in contact with the location where the double convex portion forming portion 7 is formed. The letter-shaped protrusions 8, 8 are integrally protruded along the circumferential direction. Then, by employing, for example, an injection molding method, heated and molten polyacetal is injected into the cavity 9 formed by the one mold 5a and the other mold 5b, and the polyacetal is cooled and solidified. After that, the obtained molded product is demolded. The thus obtained molded product 1 undergoes shrinkage during and after molding, but the plate-shaped portion 2 of the molded product 1 has a V along the circumferential direction in contact with the protruding portions of the convex portions 3, 3. Since the V-shaped grooves 4, 4 are formed, even if the contraction occurs as described above, the contraction is buffered by these V-shaped grooves 4, 4, and the contraction of the plate-shaped part 2, especially in its longitudinal direction, is reduced. is the double convex portion 3
, 3 < and these double convex portions 3
, 3 do not influence each other, the convex portions 3, 3 are reliably prevented from falling down and tilting due to shrinkage of the molded product 1, and the convex portions 3, 3 are plate-shaped. It is maintained perpendicular to the part 2 as molded, and the double convex part 3
, 3 are kept parallel to each other.

Further, the plate-like portion 2 of the molded product 1 has the V-shaped grooves 4, 4.
are formed and these parts are hollowed out, but since this hollowing is V-shaped, the wall thickness of the plate-shaped part 2 increases as it goes toward the bottom of the grooves 4, 4 forming part. Since it is in a state where it gradually becomes thinner, after molding, a sudden difference in shrinkage may occur in the molded portion of these V-shaped grooves 4, as in the case of concave lightening, which is step-like and has a certain width due to conventional concave groove formation. This prevents the plate-like portion 2 from warping or twisting, and the plate-like portion 2 is reliably maintained in a flat state. Furthermore, as mentioned above, since the hollowed out part is V-shaped, there is no problem of "burrs" occurring when the mold is released from the mold 5, and the molded product 1 has a good design. As described above, since the V-shaped grooves 4, 4 are formed along the circumferential direction in the vicinity of the protruding portion of the convex portion 3, the above-mentioned shape can be molded using polyacetal having high molding shrinkage. Even when the product is molded, the convex parts 3, 3 are prevented from collapsing due to resin contraction, and their perpendicularity is reliably maintained, and these convex parts 3, 3 are reliably maintained parallel to each other, and the plate-like shape is maintained. This prevents bending of the portion 2, thereby improving the dimensional accuracy and shape accuracy of polyacetal molded products used for functional parts, etc. can be reliably maintained within prescribed tolerances,
Polyacetal is an effective material for use. For example, when used as a sleeve for a capstan bearing of a tape recorder, the shaft center does not become eccentric, making it extremely effective.

Further, FIG. 6 shows a modification of the above embodiment, in which the V-shaped groove 4 is placed along the circumferential direction at a location slightly apart from the protruding portion of the convex portion 3 of the plate portion 2. At the same time, both side walls of the V-shaped groove 4 are inclined, and when the V-shaped groove 4 is formed in contact with the protruding portion of the convex portion 3 as described above, it can be effectively contracted. However, even if the V-shaped groove 4 is formed at a slight distance from the protruding portion of the convex portion 3, the same shrinkage buffering effect can be obtained.

FIG. 7 shows still another embodiment of the present invention, and this embodiment is a plastic molded product having a cylindrical convex portion 3 protruding from one longitudinal end of a plate portion 2. , the plate-shaped part 2 is formed in a state extending only to one side from the protruding part of the convex part 3, and the V-shaped groove 4 is formed in the above-mentioned convex part 3 of this plate-shaped part 2.
The V-shaped groove 4 is formed along the circumferential direction of the V-shaped groove 4 in such a manner as to divide the plate-shaped portion 2 at a location slightly apart from the protruding location. The V-shaped groove 4 is formed only partially surrounding the convex part 3, and the V-shaped groove 4 is not formed along the entire circumference of the convex part 3. Similar to the embodiment shown in the figure, both side walls are inclined. Note that the other configurations, operations, and effects are the same as those of the above-described embodiments, so their explanations will be omitted. Note that in the above embodiment, the convex portion is 2
Although the individual protrusions are provided and the V-shaped grooves are formed accordingly, the present invention is not limited to this, and three or more protrusions may be provided protrudingly. There is no problem even if only one protruding portion is provided, and by forming a V-shaped groove in accordance with the protruding portion, resin shrinkage can be reliably buffered.

In addition, although the above embodiment describes the case where polyacetal is used as the molding material, other thermoplastic resins such as high-density polyethylene, polypropylene, polyvinyl chloride, or thermosetting resins may be used, and molding materials may also be used. In addition to the injection molding method, an appropriate molding method such as transfer molding may be employed, and other configurations may be variously modified without departing from the gist of the present invention. As explained above, the present invention provides a plastic molded product that integrally has a convex portion projecting perpendicularly from a plate-like portion, in which V along the circumferential direction is formed in the vicinity of the protruding portion of the plate-like portion. Since the V-shaped groove is formed, even if the molded product shrinks during or after molding, the contraction of the resin is buffered by the V-shaped groove, thereby preventing the convex portion from collapsing. In this way, the convex portion can be reliably maintained with respect to the plate-like portion, the convex portions can be maintained parallel to each other, and a V-shaped groove is formed in the plate-like portion. Since the wall thickness of the flat plate part in this part gradually changes, sudden shrinkage due to the corner cutting is prevented, and there is no risk of warping or the like occurring in the plate part. .

Furthermore, in order to obtain a molded product having the shape described above, an inverted V-shaped protrusion corresponding to the V-shaped groove described above is simply provided on the mold for molding the molded product, and this mold is used. Since all you need to do is molding, you can easily obtain a molded product with almost no change in shape due to resin shrinkage, and there is no inconvenience caused by "゜curvature" when the mold is released, and the shape accuracy and dimensional accuracy are reliably acceptable. It has the advantage that it can be maintained within a certain range, has a good design, and is particularly effective when used in engineering plastics.

[Brief explanation of the drawing]

1 and 2 are longitudinal cross-sectional views, with some parts omitted, showing conventional plastic molded products, respectively. FIG. 3 is a perspective view showing an embodiment of the present invention, and FIG. 5 is a partially omitted longitudinal sectional view showing an example of a mold used for molding of the same example, and FIG. 6 is a partially omitted longitudinal sectional view showing another embodiment of the present invention. FIG. 7 is a partially omitted perspective view showing still another embodiment of the present invention. ]... Plastic molded product, 2... Plate-shaped part, 3... Convex part, 4... V-shaped groove, 5... ... Mold, 6... Plate-shaped part forming part,
7...Protrusion forming portion, 8...Inverted V-shaped protrusion.

Claims (1)

[Scope of Claims] 1. In a plastic molded product integrally having a convex portion projecting perpendicularly from a plate-like portion, a V-shape is provided along the circumferential direction near the protruding portion of the plate-like portion. A plastic molded product characterized by forming grooves. 2. In a method for molding a plastic molded product that integrally has a convex part that projects perpendicularly from a plate part, the convex part is formed in the plate part molding part of the mold for molding the molded product. An inverted V-shaped protrusion is provided protruding along the circumferential direction near the part, and a predetermined molding material is fed into the mold to form a V-shaped protrusion along the circumferential direction near the protruding part of the convex part of the plate-shaped part. A method for molding a plastic molded product, characterized by molding a molded product in which a character-shaped groove is formed.