JPH06339949A - Runnerless mold - Google Patents

Abstract

PURPOSE:To make continuous molding properties excellent by providing a cavity forming a manifold and a molded product and setting the capacity of a molding material remaining in the manifold less than the specified ratio of the whole cavity capacity. CONSTITUTION:A manifold 1 is controlled to the temperature of retaining a molding material in the manifold not solidified nor cured and sufficiently fluid. The temperature control is carried out by a heater or a heating medium in a heater hole or a heating medium flow path 2. Mold clamping is carried out at the time of molding, and then the molten molding material is injected by a molding machine cylinder and passed through a sprue 4, a runner 5 and a subrunner 9 in the manifold 1 and filled in the cavity 7 through a gate 8. At that time, the quantity of the molding material remaining in the manifold 1 is set to 2/3 or less of the whole capacity of the cavity 7. The solidification (or curing) of the molding material in the runner 5 can almost be eliminated by the arrangement to improve the continuous molding properties.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a runnerless molding die used for injection molding of synthetic resin molding materials and the like.

[0002]

2. Description of the Related Art In injection molding, a runnerless molding die is often used to reduce waste of molding material. The runnerless molding die eliminates the loss of molding material in the flow path (sprue, runner) in which the molten molding material is injected into the cavity that forms the molded product, so this part is unitized as a manifold,
By setting the temperature independently of the cavity, the fluidity of the molding material is maintained and it is utilized for the next molding shot. A conventional runnerless molding die has a structure as shown in FIG. C is a fixed side mold, and D is a movable side mold. And, (21) is fixed to the fixed side mold A by a manifold. (22) is a heater hole or heat medium flow path for temperature control, (23) is an air gap for insulating the manifold from other molds, (24) is a sprue, and (25) is a runner. (26) shows a cavity and (27) shows a gate. (28),
(29) is a protruding pin.

The molding material injected into the molding die passes through the sprue and runner in the manifold and is filled in the cavity. After the molding material is hardened or solidified in the cavity, the mold is opened, the molded product is taken out, the mold is clamped, and then the molding process of the next shot is performed. At this time, a part of the molding material in the manifold is filled in the cavity. In this case, if the residence time of the molding material in the manifold becomes long, the molding material undergoes an unfavorable change under the influence of heat. In particular, in the case of a thermosetting molding material, the curing reaction proceeds, causing deterioration of the fluidity and causing molding failure.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides a runnerless molding die which is excellent in continuous moldability and hardly causes molding defects in injection molding.

[0005]

SUMMARY OF THE INVENTION The present invention includes a manifold for holding an injected molding material in a molten state in a sprue and a runner, and a cavity for forming a molded article, and a volume of the molding material retained in the manifold. Is less than ⅔ of the total volume of the cavity, and relates to a runnerless molding die. The runnerless molding die of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic sectional view of a runnerless molding die of the present invention. A is a fixed mold, and B is a movable mold. (1) is a manifold, which is fixed to the fixed mold A. (2) is a heater hole or heat medium flow path for temperature control,
(3) is an air gap for insulating the manifold,
(4) shows a sprue and (5) shows a runner. (7) is a cavity, (8) is a gate, (9) is a sub-runner continuing from the runner of the manifold, and (11), (12) and (13) are projecting pins, respectively. In addition, the runner tip of the manifold
It is preferable that (6) has a shape with a small cross-sectional area, and it is preferable to provide an undercut-shaped runner lock (10) on the movable mold surface of the sub runner.

Next, the case of injection molding using the runnerless molding die of the present invention will be described. Manifold
(1) The molding material in the manifold solidifies (or hardens)
The temperature is controlled to maintain sufficient fluidity. This temperature control is performed by the heater or the heat medium in the heater hole or the heat medium flow path (2). After the mold is clamped at the time of molding, the molten molding material is injected by the molding machine cylinder, passes through the sprue (4), the runner (5), and the sub-runner (9) in the manifold, and then through the gate (8) to the cavity (7 ) Is filled. After the molding material in the cavity (7) is solidified (or cured), the mold is opened. At this time, the molded product in the cavity and the material of the sub-runner (9) are attached to the movable mold B and separated from the material of the runner (3) of the manifold.

In the present invention, since the amount of the molding material staying in the manifold (1) is 2/3 or less of the total volume of the cavity, all the molding material in the manifold is refreshed for each molding shot. Therefore, while staying in the manifold, the molding material in that part undergoes a thermal change, especially in the case of a thermosetting molding material, the curing reaction is minimized, so that continuous molding can be performed easily and molding defects can occur. Is rarely generated. Furthermore, the temperature of the manifold is controlled, but the runner is affected by the heat from the mold body.
(5), especially near the runner tip (6), the molding material is likely to solidify (or harden). However, the smaller the volume of the molding material that stays in the manifold, that is, the larger the volume of the molding material that is directly injected from the molding machine cylinder into the cavity for each molding shot, the less the solidification (or hardening) is suppressed. . In the present invention, the manifold
By setting the amount of molding material retained in (1) to 2/3 or less of the total volume of the cavity, solidification (or hardening) of the molding material in the runner (5) can be almost eliminated, and continuous molding can be performed. It is possible to further improve the sex.

In the present invention, when the sub-runner (9) is provided with the runner lock (10), the material of the sub-runner (9) is completely attached to the movable mold B. Further, when the manifold has a shape in which the cross-sectional area of the runner tip portion (6) is narrowed, the material of the runner portion and the material of the sub-runner portion can be separated without any problem, and the runner tip portion (6) can be separated. There is no material leakage. Next, the material of the molded product and the sub-runner portion is taken out from the mold by the projecting pins (11) and (12). Then, the mold is clamped and the next shot is molded. At this time, all of the molding material in the manifold is filled in the cavity. Although the gate shape shows a side gate in the drawing, a submarine gate or the like can also be adopted.

[0010]

In the runnerless molding die of the present invention,
The amount of molding material retained in the manifold is not more than ⅔ of the total volume of the cavity. Therefore, all the molding material in the manifold is refreshed for each molding shot, and the solidification (or hardening) of the molding material near the runner, especially near the runner tip can be prevented, which facilitates continuous molding and Almost no defects occur.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a runnerless molding die of the present invention.

FIG. 2 is a schematic sectional view of a conventional runnerless molding die.

[Explanation of symbols]

 A Fixed-side mold B Movable-side mold 1 Manifold 2 Heater hole or heat medium flow path 3 Air gap 4 Sprue 5 Runner 6 Manifold runner tip 7 Cavity 8 Gate 9 Subrunner 10 Runner lock 11, 12, 13 Projecting pin C Fixed side mold D Movable side mold 21 Manifold 22 Heater hole or heat medium flow path 23 Air gap 24 Sprue 25 Runner 26 Cavity 27 Gate 28, 29 Projecting pin

Claims (1)

[Claims] 1. A manifold for holding the injected molding material in a molten state in a sprue and a runner, and a cavity for forming a molded article, and the volume of the molding material retained in the manifold is 2 / of the total volume of the cavity. A runnerless molding die characterized by being 3 or less.