JPH1177757A - Mold for molding ring-shaped molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To dispense with deburring by allowing the outer peripheral side surface of the terminal part of the sprue provided to one template to communicate with the inner peripheral surface of a ring-shaped cavity over the entire periphery thereof through film gate parts of fine length so as to leave fine gaps. SOLUTION: The outer peripheral side surface of the terminal part of a sprue 9 along the PL surface of both templates of inner and lower molds 3, 4 is allowed to communicate with the inner peripheral surface of a ring-shaped cavity 6 centering around the sprue 9 over the entire periphery thereof through film gate parts 10 of fine length so as to leave fine gaps. In the same way, film gate parts 12 are also provided to the outer peripheral side surface of the ring-shaped cavity 6 along the PL surface over the entire periphery thereof to be allowed to communicate with the gaps 13 of both templates of the inner and lower molds 3, 4. A filled material passes through the sprue 9 to fill the ring-shaped cavity 6 through the film gate parts 10 and the overflow material flows out to the gaps 13 through the film gate parts 12 to become outer burr. The material in a large number of sprues 9 is solidified to become inner burr and both of them can be simply taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding a ring-shaped molded article, and more particularly to a mold useful for transfer molding and injection molding which does not require deburring in post-processing.

[0002]

2. Description of the Related Art Conventionally, a molding method for obtaining a ring-shaped molded product includes two openable and closable molding dies b and c in which a plurality of cavities a are arranged as shown in FIG. Filling the material d along the gap, closing the mold, and filling the material d into the cavity a from within the mold is generally a so-called compression molding method, and the equipment such as a mold and a molding machine is inexpensive. Widely used from.

[0003]

However, in compression molding, it is necessary to charge several sheets of material d preformed in the form of a sheet in accordance with the number of cavities a in the mold. In addition to the cause of defects such as scorch and unfilled (insufficient capacity of the material with respect to the cavity capacity), the molded product f has an inner burr as shown in FIGS. 6B and 6C. Since it is molded together with g and the outer burrs h, it is necessary to separate the molded product f from these burrs in post-processing, and a great deal of labor has been required (e in the figure is bleeding air).

Accordingly, an object of the present invention is to provide a mold for molding a ring-shaped molded product which does not require deburring in post-processing.

[0005]

SUMMARY OF THE INVENTION A mold for molding a ring-shaped molded article according to the present invention is a molding mold having a pair of mold plates forming a ring-shaped cavity, provided on one of the mold plates. The outer peripheral side surface of the end portion of the sprue communicates with the inner peripheral side surface of the ring-shaped cavity over the entire circumference, particularly along the PL surface of both mold plates, through a film gate portion having a minute gap and a minute length. It is characterized by becoming.

The film gate portion has a gap and a length within a range of 0.01 to 0.5 mm, and the ring-shaped cavity has an inner peripheral diameter (in a cross section) of 1 to 20 mm and a vertical sectional diameter of the ring. Is preferably in the range of 0.5 to 15 mm.

[0007] The above molding die has three mold plates of an upper die, a middle die and a lower die, and has a plunger at the center of the lower surface of the upper die to compress the material and fill the cavity. A structure in which a material pot is provided at the center of the upper surface of the container and the sprue penetrates the middle mold plate from the bottom of the material container pot to reach the upper surface of the lower mold is particularly preferably used for transfer molding.

[0008] Transfer molding does not require charging the preformed material in accordance with the number of cavities in the mold as compared with compression molding, and is less likely to cause defects such as scorch and unfilled. However, since the material loss is large and the molding operation is slightly more complicated than the compression molding of the upper and lower two-piece molds, the molding is generally limited to molding of complicated shapes and those having strict dimensional accuracy. The merit of eliminating the need for deburring during processing is great.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of a molding die according to the present invention as a transfer molding die.
This will be described with reference to FIG. FIG. 1A is an exploded perspective view of the whole, FIG. 1B is an exploded longitudinal sectional view thereof, FIG. 2 is an enlarged longitudinal sectional view of the vicinity of a sprue end when the middle mold and the lower mold are closed,
FIG. 3 is a perspective view showing the state of the obtained molded product and burrs, and FIG.
2 is a longitudinal sectional view showing the film gate portion of FIG. 2 further enlarged, and FIG.

The mold 1 for transfer molding shown in FIG.
Consists of three mold plates of an upper mold 2, a middle mold 3, and a lower mold 4. The upper mold 2 is provided with a plunger 7 at the center of the bottom surface for compressing the material 5 and filling the ring-shaped cavity 6. The middle mold 3 is provided with a material container pot 8 for filling the material 5 at a position for receiving the plunger portion 7 at the center of the upper surface, and penetrates the mold plate from the bottom of the material container pot 8 to reach the upper surface of the lower mold 4. A sprue 9 is provided. As shown in FIG. 2, the outer peripheral side surface of the end portion (lower end portion in the figure) of the sprue 9 along the PL surfaces of both the mold 3 and the lower mold 4 has a film gate portion 10 having a minute gap and a minute length. Through the sprue 9
And the inner peripheral side surface of the ring-shaped cavity 6 around the entire periphery. Similarly, a film gate portion 12 is provided on the entire outer peripheral side surface of the ring-shaped cavity 6 along the PL surface, and a gap between both the mold plates of the middle mold 3 and the lower mold 4 is provided.
Communicates with 13.

In the transfer molding die 1, the material 5 filled in the material container pot 8 of the middle die 3 is
It is compressed by the plunger portion 7 of the upper die 2, passes through the sprue 9, and is filled into the ring-shaped cavity 6 through the inner film gate portion 10 provided on the outer peripheral side surface of the lower end portion over the entire periphery. The material 5 that has overflowed the ring-shaped cavity 6 flows through the outer film gate portion 12 provided over the entire outer peripheral side surface into the gap 13 between the mold surfaces of the middle mold 3 and the lower mold 4, and as shown in FIG. As shown, since it becomes the sheet-shaped outer burr 14, it can be easily removed at the end of molding. On the other hand, the material 5 in many sprues 9
Is solidified together with the material 5 in the material container 8 and the inner burr 15
Thus, it can be similarly easily taken out at the end of molding. Since only the ring-shaped molded product P remains on the lower mold 4 in this manner, it can be efficiently collected by means such as suction.

The gap S and length L (see FIG. 4) of the inner film gate portion 10 (between the sprue 9 and the ring-shaped cavity 6) should be 0.01 to 0.5 mm, especially 0.03 to 0.3 mm. Is preferred. If this is less than 0.01 mm, the material will not flow easily, which may cause unfilled material.
Exceeding the limit will cause poor cutting when separating the molded product from the burrs at the end of molding, and the burrs may remain on the molded product or a part of the molded product may be removed along with the burrs. Will be impaired.

(Gap 13 between ring-shaped cavity 6 and mold surface)
The gap and length of the outer film gate portion 12 are preferably 0.01 to 0.5 mm, particularly preferably 0.03 to 0.3 mm, as in the case of the inner film gate portion 10 described above. If the thickness is less than 0.01 mm, the material is difficult to flow, so that it is difficult for the overflowing material to escape, and there is a problem that air that should be discharged simultaneously with the material remains in the cavity. On the other hand, if it exceeds 0.5 mm, a part of the molded product may be cut off during deburring as in the case of the inner side.

The longitudinal cross-sectional shape of the ring of the ring-shaped cavity 6 can be selected from arbitrary shapes such as a circle, a square, and an irregular shape in accordance with the shape of a desired molded product. ) And the vertical cross-sectional diameter (or vertical cross-sectional area) of the ring. In other words, when the inner diameter of the ring (in the cross section) is less than 1 mm, the sprue becomes thinner accordingly, and the strength of the vulcanized and hardened material in the sprue decreases. Breaks, impairing the deburring workability, and
If it exceeds 20 mm, the inner diameter of the sprue becomes large, so that the material loss increases, and the cost increase due to the material loss increases more than the effect of eliminating the deburring step. As a result,
The preferable inner diameter of the ring is 1 to 20 mm. On the other hand, if the vertical cross-sectional diameter of the ring is less than 0.5 mm, the workability at the time of removing the molded product from the mold is deteriorated. For this reason, the vertical section diameter of the ring is 0.5 to 15 mm (average vertical section area is 0.2 to 176.
6mm ² ), especially 2-5mm (3.14-19.62m in average longitudinal sectional area)
m ² ) is preferred. From the inner diameter and the vertical cross-sectional diameter of the ring, the outer diameter of the ring is preferably 2 to 50 mm.

It is preferable that the number of ring-shaped molded products in the molding die of the present invention is 16 or more. If the number is less than 16, the time required for deburring is shortened even in compression molding. The demerit due to material loss is greater than the labor for performing deburring work after normal compression molding.
On the other hand, when the number of moldings is large, there are no restrictions on the number of moldings, as long as restrictions on equipment such as the capacity of the molding machine (molding pressure, adaptive mold size) are allowed. The greater the number of moldings, the greater the effect.

As shown in FIG. 1B, the shape of the sprue 9 is preferably a funnel having a taper downward so as to improve the releasability of the material inside. As shown in an enlarged view in FIG. 5, the diameter p on the inlet side of the sprue 9 is
And a taper shape such that the diameter q on the outlet side satisfies 0.5 ≦ q / p ≦ 1. When q / p <0.5, the shape of the ring-shaped cavity (the size of the longitudinal cross-sectional diameter of the ring) In some cases, the sprue 9 has a structure in which the sprue 9 cuts through the inner wall of the ring. In addition, the material loss increases, which is inconvenient. It would be contrary to purpose. The thickness t of the sprue portion of the middle mold 3 is 2 mm ≦ t ≦ 20.
mm, which is larger than 1/2 of the vertical cross-sectional diameter of the ring. At t <2, the strength of the medium size is insufficient, and at 20 <t, the material loss is large, and the medium size is heavy and workability is poor. Become.

As the molding material applied to the molding die of the present invention, various thermoplastic or thermosetting resins and elastomers are useful. Particularly, from the viewpoint of the flow of the material during molding, silicone rubber or the like is used. A material having a low green strength is suitable.

[0018]

Next, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples. (Example) 81 circular silicone rubber rings (inner diameter 3 mm, outer diameter 5 mm (vertical cross-sectional diameter 1 mm)) were molded in 810 (9 rows x 9 rows) transfer molding dies. The time required was 60 minutes. The dimensions of the sprue portion of this mold were p = 4 mm, q = 3 mm, r = 10 mm, and the gap and length of the film gate portion were 0.1 mm.

(Comparative Example) When 810 circular silicone rubber rings having the same shape as in the example were molded by using a 81-piece compression molding die, the time required for deburring was 121 minutes. Table 1 shows the results of the above Examples and Comparative Examples. Thus, the productivity of the transfer molding die was twice that of the compression molding die.

[0020]

[Table 1]

[0021]

According to the molding die of the present invention, the deburring work which is indispensable for the molded product by the ordinary compression molding becomes unnecessary, and the workability, the productivity and the quality are improved without the remaining burrs. Reduce fatigue.

[Brief description of the drawings]

FIG. 1 shows the entire molding die of the present invention,
(A) is an exploded perspective view and (b) is a longitudinal sectional view.

FIG. 2 is an enlarged longitudinal sectional view of the vicinity of a sprue end portion in FIG.

FIG. 3 is a perspective view showing a state of a molded product and burrs obtained by the molding die of FIG. 1;

FIG. 4 is a vertical cross-sectional view showing the film gate portion on the inside in FIG. 2 in a further enlarged manner.

FIG. 5 is an enlarged vertical sectional view of a main part of the medium-sized machine shown in FIG. 1;

6 (a) is a perspective view showing a conventional compression molding die, FIG. 6 (b) is a perspective view showing a state of the obtained molded product and burrs, and FIG. 6 (c) is a state in which a mold plate is closed. FIG.

[Explanation of symbols]

1 ‥ Transfer molding mold, 2 ‥ Upper mold, 3 ‥
Medium, 4 lower, 5 ‥ material, 6 ‥ ring cavity, 7 ‥ plunger, 8 ‥ material pot, 9 ‥ sprue, 10 ‥
(Inside) film gate, 12 mm (outside) film gate, 13 mm gap, 14 mm outer burr,
15mm inner burr, P ‥ molded product (ring shaped product), S ‥ gap, L ‥ length,
p ‥ sprue inlet side diameter, q ‥ sprue outlet side diameter, t ‥ medium thickness.

Claims (2)

[Claims] 1. A molding die having a pair of mold plates forming a ring-shaped cavity, wherein an outer peripheral side surface of an end portion of a sprue provided on one of the mold plates has a minute gap with a minute gap. A molding die for a ring-shaped molded product, which is communicated with the inner peripheral side surface of the ring-shaped cavity through a portion over the entire circumference. 2. A molding die has three mold plates of an upper die, a middle die, and a lower die, and a plunger for compressing a material and filling a cavity in a central portion of a lower surface of the upper die, The ring-shaped molded product according to claim 1, further comprising a material pot at a central portion of the upper surface of the middle mold, and a sprue extending from the bottom of the material pot to the upper surface of the lower mold through the middle mold plate. Mold for molding.