JP7217849B1 - Injection mold and molding method - Google Patents

Abstract

[PROBLEMS] To provide an injection mold and a molding method using the same, which can reduce the frequency of mold maintenance related to the removal of dirt on a gas vent, at a low cost. SOLUTION: An overflow cavity is provided at a position facing the gate side of the cavity, and the cavity and the overflow cavity are communicated with each other by a groove having a width of 0.5 to 30.0 mm and a height of 0.3 to 3.0 mm. . The molded product filled in the cavity and the overflow molded product filled in the groove and overflow cavity are cut with a cut pin before cooling and solidifying, and the cut pin constitutes a part of the inner wall of the cavity, so is difficult to see. In addition, since the fixed-side return pin provided at a position facing the cut pin is provided with a concave portion, only the groove portion is cut off and can be prevented from adhering to the sliding portion of the mold. It does not interfere with the opening and closing operation of the mold. [Selection drawing] Fig. 1

Description

The present invention relates to a mold for injection molding, and more particularly to a mold for injection molding that can reduce the frequency of maintenance related to cleaning of gas vents, and a molding method using the mold.

Injection molding is a process in which a hollow part called a cavity carved into a mold is filled with a thermoplastic polymer material that has been melted by heating, under high pressure, and then cooled and solidified to obtain a molded product, resulting in high productivity. have and are widely practiced. Some of them are also used for molding thermosetting polymeric materials.

In injection molding, when a cavity is filled with a molten polymeric material, it is necessary to quickly discharge the air in the cavity and the gas generated by heating the polymeric material to the outside. For this reason, it is essential to provide a groove, called a gas vent, which has a depth of several μm and communicates the cavity with the outside on the parting surface where the fixed side and the movable side of the mold are in contact with each other.

However, if molding is continued, the gas derived from the molten polymer material condenses, solidifies, and adheres to the gas vent. It needs to be cleaned, which is one of the causes of lower productivity.

As a solution to such problems, Patent Document 1 discloses injection molding of a thermoplastic resin composition at a mold temperature T° C. of 80° C. or higher using a mold equipped with a cavity and a gas vent. , In a method for manufacturing a molded product, the total amount of gas collected in the gas vent part during the injection molding is c; a; the amount of gas having a boiling point of (T-20) ° C. or higher among the gases collected in the gas vent portion is b; (here, the units of a, b and c are , μg/1 g of the thermoplastic resin composition), the value of the gas burn risk d represented by a specific formula is set to 35 or less. It is

However, the method disclosed here requires equipment such as a vacuum pump and parts for handling, which leads to the problem of complicating the structure of the mold and resulting in an increase in cost.

JP 2022-079945 A

Accordingly, an object of the present invention is to provide an injection molding die and a molding method using the same that can reduce the frequency of maintenance of the die described above at a low cost.

The present invention has been made as a result of intensive reexamination of the structure of injection molding dies in order to solve the above problems.

An injection mold according to an aspect of the present invention is an injection mold having a fixed side and a movable side, wherein the movable side is provided near a cavity and a position substantially facing a gate of the cavity. and a groove having a width of 0.5 to 30.0 mm and a height of 0.3 to 3.0 mm, which communicates the cavity and the overflow cavity, and the groove is arranged. A cut pin is arranged at a position adjacent to the cavity on the fixed side for separating the molded product formed in the cavity from the overflow molded product filled in the groove and the overflow cavity. A fixed-side return pin for returning the cut pin to its original position is provided at a position facing the cut pin, and the fixed-side return pin is provided with a concave portion on the opposite side of the cavity. do.

Further, in the injection mold according to an aspect of the present invention, the side surface of at least one of the cut pin and the fixed-side return pin on the side arranged in the cavity forms a part of the inner wall of the cavity. It is characterized by

Further, in the injection mold according to one aspect of the present invention, the surface of the cavity on which the groove is arranged is provided with a step forming a recess that is recessed from the connecting surface of the groove and the cavity. characterized by becoming

A molding method using an injection mold according to an aspect of the present invention is characterized in that the cut pin operates at a temperature at which the molten polymeric material filled in the cavity does not solidify.

In the injection mold according to the present invention, the overflow cavity is arranged at a position substantially opposite to the gate of the cavity filled with the molten polymer material through a groove having a larger cross-sectional area than a normal gas vent. Therefore, the frequency of maintenance for cleaning the gas vent can be reduced compared to an injection mold having a normal gas vent.

In addition, since this groove has a larger cross-sectional area than a normal gas vent, it is filled with molten polymeric material and becomes part of the overflow molding together with the molten polymeric material filled in the overflow cavity communicating with the groove. In the injection mold according to the present invention, since the cut pin cuts the molded product before it is solidified and ejected, it is ejected separately from the molded product.

Moreover, since the cut pin is a structure that constitutes a part of the side wall of the cavity and cuts before the molded product is solidified, it is possible to make the cut marks on the surface of the molded product invisible. . The width of the groove is limited to 0.5 mm to 30.0 mm and the height is limited to 0.3 mm to 3.0 mm. If the width exceeds 30 mm and the height exceeds 3.0 mm, cutting with a cut pin becomes difficult.

A fixed-side return pin having a concave portion provided on the opposite side of the cavity is arranged at a position facing the cut pin. This fixed-side return pin has the function of returning the cut pin protruding to cut the groove to its original position. It can be prevented from adhering to sliding parts of the mold. If such countermeasures are not taken, when the mold is opened and the molded product is ejected, the next mold clamping operation will be performed with the material of the separated groove portion still adhering to the cut pin, and there is a risk of damaging the mold.

1 is an overall cross-sectional view of an example of an injection mold according to the present invention; Enlarged view of portion A surrounded by a dashed line in FIG. Enlarged view of portion B surrounded by broken line in FIG. Perspective view showing the integrated overflow molded product and the molded product without grooves cut before being ejected. A diagram showing an example in which the positions of the cavity grooves are different

Next, embodiments of an injection molding die according to the present invention and a molding method using the die will be described with reference to specific drawings.

FIG. 1 is an overall cross-sectional view of an example of an injection mold according to the present invention. FIG. 2 is an enlarged view of a portion A surrounded by a dashed line in FIG. 1, and FIG. Furthermore, a state in which molten polymeric material is filled from the cavity 3 to the overflow cavity 6 via the groove 4 is shown.

In the injection molding process according to the present invention, as shown in FIG. It is actuated to separate the molten polymeric material filled in the grooves 5 from the molten polymeric material filled in the cavities 3, ie the molding. Further, in the example shown here, a step 11 indicated by reference numeral 13 in FIG. However, if there is no step 11, the surface of the fixed return pin 7 on the cavity 3 side must be designed to form part of the inner wall of the cavity 3.

FIG. 3 is an enlarged view of portion B surrounded by a dashed line in FIG. 2, and shows a state where the ends of groove 4 are cut 12 and separated from the molded product. Also, FIG. 4 is a perspective view showing a state in which the overflow molded article and the molded article are integrated before being ejected, with the groove 14 not cut. By making the overflow molded product 15 approximately the same size as the raw material plastic pellets, it can be used as a recycled material as it is.

Thereafter, the molded product is ejected to the outside of the cavity 3 by the ejector sleeve 9, and at the same time, the overflow molded product filled in the groove 4 and the overflow cavity 6 is ejected to the outside by the operation of the ejector pins 10a, 10b and fixed. The side return pin 7 is returned to its home position by a restraining spring (not shown).

In FIG. 1, the right side face of the cut pin 8 is in contact with a portion of the lower side of the left side face of the longitudinal perimeter of the cavity 3, which is the right side face of the cut pin 8. constitutes a part of the outer circumference of the cavity 3 . Due to such a structure and the synergistic effect of cutting the grooves before the molded article is solidified, the cut traces of the grooves in the molded product are difficult to visually recognize.

In addition, as shown in FIG. 2, the recess 5 is provided on the side of the fixed-side return pin facing the cut pin 8, so that only the material filled in the groove 4 is not separated, and the overflow cavity is formed. Since it is protruded integrally with the part, it is possible to prevent damage to the mold during the next mold clamping operation.

FIG. 5 shows an example in which the position of the groove 20 of the cavity 19 is different from that shown in FIG. In FIG. 5, 17 is a runner, 18 is a submarine gate, and 19 is a cavity. 20 is a groove, 21 is a recess, 22 is an overflow cavity, 23 is a fixed side return pin, 24 is a cut pin, and 25, 26a and 26b are ejector pins. In this case, the cut pin 24 forms part of the inner wall of the cavity 19 .

As described above, according to the present invention, the frequency of maintenance related to the removal of dirt on the gas vent of the injection molding mold can be reduced, and the injection mold and the molding method using the same contribute to productivity improvement. can provide It should be noted that the present invention is not limited to the above-described embodiments, and includes various modifications and modifications that can be conceived by those who have ordinary knowledge in the field of the present invention, without departing from the gist of the present invention. Even if there is a design change in the range, it is of course included in the present invention.

Reference Signs List 1, 17 runners 2, 18 submarine gates 3, 19 cavities 4, 14, 20 grooves 5, 21 recesses 6, 15, 22 overflow cavities 7, 23 Fixed side return pins 8, 24 Cut pins 9, 10a, 10b, 25, 26a, 26b Ejector pins 11, 13 Stepped portion 12 Cut portion 27 parting surface

Claims (4)

In an injection mold having a fixed side and a movable side, the movable side includes a cavity, an overflow cavity provided at a position facing a gate of the cavity, and a width that communicates the cavity and the overflow cavity. is 0.5 to 30.0 mm and has a height of 0.3 to 3.0 mm, and is formed in the cavity at a position adjacent to the cavity where the groove is arranged. A cut pin is provided for separating the molded product from the overflow molded product filled in the groove and the overflow cavity, and the cut pin is returned to its original position at a position facing the cut pin on the fixed side. A mold for injection molding, characterized in that a fixed-side return pin is provided for the purpose, and the fixed-side return pin is provided with a concave portion on the opposite side of the cavity. 2. The injection molding method according to claim 1, wherein a side surface of at least one of said cut pin and said fixed side return pin on the side arranged in said cavity forms a part of the inner wall of said cavity. Mold for molding. 2. The injection molding according to claim 1, wherein the surface of the cavity on which the groove is arranged is provided with a step forming a recess that is recessed from the connecting surface of the groove and the cavity. mold for. The cut pin is operated at a temperature at which the molten polymer material filled in the cavity does not solidify. A molding method for the molded product.

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