JP2000141411A - Injection mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection mold, with which the same effect as a dwelling is given to a flow terminal, resulting in preventing sinkmarks from developing. SOLUTION: In this injection mold, a cavity 2 corresponding to the shape of a molded product to be molded is formed between a movable mold 11 and a fixed mold 12, at least one or more resin well parts 13 are provided near the flow terminal apart from the resin gate 21 of the cavity 2. In addition, a piston 14 is provided movably to each resin well part 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for injection molding.

[0002]

2. Description of the Related Art When molding a molded article by injection molding,
Even with the same shape, sink marks are less likely to occur near the gate where the pressure is maintained, and sink marks may be noticeable at the flow end. In this case, 1) increase the injection pressure, extend the dwell time,
Modify the molding conditions such as lowering the resin temperature or lowering the mold temperature. 2) Increase the thickness of the gate and runner. 3) Add the runner where sink marks occur. 4) Equalize the thickness of the molded product. 5) Mold shrinkage. Use a material with a low ratio [Cost reduction of injection molded products and troubleshooting (issued by Plastic Age Co., Ltd.) 131].

[0003]

However, even with the above measures, sinks may not be eliminated depending on the shape of the cavity (particularly in the case of a direct gate). The present invention has been made in order to solve the conventional problems as described above, and provides an injection mold capable of giving the same effect as a dwelling pressure to a flow end and preventing the occurrence of sink marks. It was done for the purpose of doing.

[0004]

According to the present invention, there is provided an injection mold, wherein a cavity corresponding to the shape of a molded product to be molded is formed between a movable mold and a fixed mold. A mold having at least one or more resin pools near a flow end remote from a resin gate in a cavity, and a piston provided to be able to advance and retreat with respect to the resin pools. It is. Examples of a method for moving the piston include a hydraulic cylinder and an air cylinder, and a hydraulic cylinder is preferable because sufficient pressure can be applied.

[0005]

The injection molding die of the present invention can give the same effect as the dwelling pressure to the flow end, and can prevent the occurrence of sink marks. This is particularly effective in a direct gate where the gate position is limited.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of an injection mold according to the present invention. As shown in FIG. 1, the injection mold of the present invention includes a movable mold 11 and a fixed mold 12, and a cavity 2 corresponding to the shape of a molded product is formed when the mold is closed. . In addition, a resin reservoir 13 is provided in the cavity 2 in the vicinity of the flow terminal far from the resin gate 21. Further, a piston 14 is provided so as to be able to advance and retreat with respect to the resin reservoir 13, and has a hydraulic cylinder 15 for moving the piston 14.

FIGS. 2 to 4 are enlarged cross-sectional views in which the portion A in FIG. 1 is enlarged. FIG. 2 shows a state at the time of completion of injection, FIG. 3 shows a state when the hydraulic cylinder advances, and FIG. I have. When the injection is completed, as shown in FIG.
Is receded, and a heat insulating material 16 is provided between the fixed mold 11 and the piston 14 so as not to be affected by heat from the fixed mold 11. To prevent sink marks,
As shown in FIG. 3, the hydraulic cylinder 15 is advanced,
Accordingly, the piston 14 is advanced. Thereafter, the hydraulic cylinder 15 is retracted, and when the mold is opened, the state shown in FIG. 4 is obtained.

[0008]

The present invention will be described below with reference to examples. Example In the molded article shown in FIG. 5, a resin pool 13 was provided on a tapping screw mounting boss 32 that is distant from the gate 31 and easily sinks, and injection molding was performed under the following conditions to obtain a molded article. There was no sink mark in the obtained molded article. The setting conditions of the embodiment are as follows. Distance from gate 31 to boss 32: 400 mm Distance from resin reservoir 13 to boss 32: 70 mm Dimensions of resin reservoir 13: φ20 mm × length 20 mm Piston 14 diameter: φ15 mm Resin: ABS Piston 14 and resin reservoir 13 contact The surface temperature rises to 150 ° C. (using heat insulating material) Operating speed of the piston 14: 1 mm / sec Stroke of the piston 14: 10 mm Piston pressure by the hydraulic cylinder 15: 400 kg
/ Cm ² Comparative Example A molded article was obtained in the same manner as in Example except that the resin pool was not provided. In the obtained molded product, sink was generated at a portion 33 shown in FIG.

[0009]

Since the injection mold of the present invention is constructed as described above, the same effect as the dwelling can be given to the flow end, and the occurrence of sink marks can be prevented. In particular, it is effective for a direct gate where the gate position is limited.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an injection mold according to the present invention.

FIG. 2 is an enlarged sectional view of a portion A in FIG. 1 showing a state at the time of completion of injection.

FIG. 3 is an enlarged cross-sectional view of a portion A in FIG. 1 showing a state in which the hydraulic cylinder moves forward.

FIG. 4 is an enlarged sectional view of a portion A in FIG. 1 showing a state when the mold is opened.

FIG. 5 is a perspective view showing an example of a state of a molded article of the present invention.

FIG. 6 is an enlarged cross-sectional view taken along a line BB in FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Injection mold 2 Cavity 11 Fixed mold 12 Movable mold 13 Resin pool 14 Piston 15 Hydraulic cylinder 21 Resin gate

Claims (1)

[Claims] 1. An injection molding mold having a cavity corresponding to the shape of a molded product to be molded, wherein the cavity is formed between a movable mold and a fixed mold. An injection mold, wherein at least one or more resin pools are provided near the flow end, and a piston is provided so as to be able to advance and retreat with respect to the resin pools.