JPH0436848B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synthetic resin molding die, and particularly to a synthetic resin molding die having a nested structure that prevents the occurrence of burrs.

Molded product A shown in Figure 1 and molded product B shown in Figure 2
When molding two molded products that have the same basic external shape but differ only in recesses a and b, conventionally, replaceable inserts are used to form recesses a and b, and the rest are made of the same metal. It is molded with a mold. For example, in order to mold molded product A, use the nest shown in C in Figure 3B.
To obtain the molded product B, the nests shown in D in FIG. 4B are used on the core side.

Here, we will consider the case where molded products A and B are obtained using nests in which the vertical and horizontal maximum lengths e and f of the recess shown by c in Figure 3A and the recess shown by d in Figure 4A are equal, respectively. . First, to form the recess c using the nest C, the upper surface E of the nest C is abutted against the mold F on the upper side, that is, on the cavity side, as shown in FIG. 5, to prevent burrs from forming. For this reason, when a large number of molds are molded, the upper mold F wears out (Figure 6). When molding is performed using the insert D (FIG. 4B) on the worn upper mold F, the insert D is attached in a raised state by the amount of wear of the upper mold F, as shown in FIG. For this reason, as shown in FIG. 4A, the bridging portion between the two recesses of the molded product swells, and a step (line G) is formed there, which significantly impairs the appearance.
In order to avoid this problem, conventionally the upper surface E has been set within a range of, for example, 0.01 to 0.01, which is the range where burrs do not occur, as shown in Figure 8.
Nested with clearance i lowered by 0.02mm
A method using C′ is often adopted. However, even though a clearance i of 0.01 to 0.02 mm is provided, if a large number of moldings are performed, the clearance i becomes large due to mold wear etc., and burrs are generated all around the hole of the molded product. For this reason, it cannot be applied to uses such as keyholes in electronic desktop calculators, where formed holes are used for precise fitting or sliding.

The present invention has been proposed in view of the above-mentioned shortcomings of the prior art, and its object is to use a synthetic resin that does not cause undesired lines, steps, or burrs on the products even when a large number of products are molded. It is located in a place that provides molding molds.

Typical embodiments of the present invention are shown below.
This will be explained in detail according to the drawings.

FIG. 9 shows a nest C'' according to an embodiment of the present invention, in which a groove having a dimension J equal to the dimension indicated by H in FIG. 4 B and a depth K is provided.
It corresponds to the bridging portion b' between the two recesses b. nesting
C'' is C in Figure 3 A and 8, excluding the groove part.
It has the same external dimensions as the nest shown in Figure C'.
The value of K, that is, the clearance is selected to be a size that does not cause burrs, for example, 0.01 to 0.02 mm. In this case, since a clearance is provided in the portion having the dimension J, the molds will not come into close contact with each other, and no marks will be left on the mold on the cavity side even after a large number of moldings are performed. Therefore, lines, steps, etc. are not formed on the molded product, resulting in a good appearance. Furthermore, since the molds are in close contact with each other in the portions other than the dimension J, burrs will appear only between the dimensions J after multiple moldings. Therefore, the range in which burrs occur is significantly reduced compared to the conventional method, and reliability is improved when constructing a keyboard or the like.

In addition, although the above-mentioned embodiment shows an example of molding a keyhole of an electronic desktop calculator, the present invention can be applied to any synthetic resin molding die used to mold a hole having substantially the same shape.

As described above, the present invention provides a first molded product A having a single opening hole C, a plurality of opening holes b, b within the outline formed by the opening hole C, and each of the opening holes b, In a synthetic resin molding die for molding a second molded product B having a bridging part connecting b in the same mold by replacing the nest, on the upper surface of the nest for molding the first molded product A, It is characterized in that a shallow groove is formed in a range corresponding to the bridging portion of the second molded product B. For this reason, when molding many types of molded products with holes, etc. with the same general external shape and dimensions using a mold with an exchangeable nesting structure, the nesting mold used to mold the largest recess is Since we have made the same as the cavity and formed a shallow groove on the top surface of the nest in the area corresponding to the bridging part that separates the recess, we have eliminated the level difference that conventionally occurs in molded products when molding with other nests. In addition to preventing the occurrence of , it also has the following effects.

A wide variety of molded products with a significantly reduced range of burr generation can be molded using the same mold.

Even if burrs occur on the molded product, the amount is negligible, so the molded product can be used for precise fitting and sliding parts without problems.

[Brief explanation of drawings]

Figures 1 to 8 are diagrams for explaining the background of the present invention, of which Figures 1 and 2 are perspective views showing an example of a molded product molded with the same mold that can be nested and replaced. , Fig. 3 A, B and Fig. 4 A, B are perspective views of the nesting part of the molded product and each nest, Fig. 5 is a cross-sectional view showing the state in which the nest C is used, and Fig. 6 is a diagram showing a state in which a large number of nests C are used. 7 is a sectional view showing the state in which the insert D is used after mold F has worn out, and FIG.
A cross-sectional view showing the state of use of the nest C′ with milled millimeters,
9 and 10 are a perspective view and a sectional view of an embodiment of the present invention. Here, A, B...molded product, C, C', C'', C
,D... are nested.

Claims (1)

[Scope of Claims] 1. A first molded product A having a single opening hole C, a plurality of opening holes b, b within the outline formed by the opening hole C, and each of the opening holes b, In a synthetic resin molding die for molding a second molded product B having a bridging part connecting b in the same mold by replacing the nest, on the upper surface of the nest for molding the first molded product A, A synthetic resin molding die, characterized in that a shallow groove is formed in a range corresponding to the bridging portion of the second molded product B.