JP3088765B2 - Injection mold and injection molding method using the mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding die and an injection molding method using the die.

[0002]

2. Description of the Related Art As shown in FIG. 3, a conventional mold for injection molding comprises a mold piece 4 and a mold plate 5 having a draft 5a formed at an angle of 2 to 3 degrees inside. ing.

[0003] Regarding the ejection of molded articles,
Many eject mechanisms and mold structures using an ejector rod, an air blow, a mold piece, and the like have been proposed.

As an injection molding method, for example, as disclosed in Japanese Patent Application Laid-Open No. 64-36421, a gate seal injection molding method for obtaining a high-precision resin molded product using a pair of dies is known. ing.

[0005]

However, in the conventional injection molding technique, some eject mechanism is required for taking out a molded product. Generally, ejector rods are often used, but in this case, processing of the ejector pins and high-precision processing when fitting the pins into the mold are required. Further, the structure of the mold such as the ejector plate becomes very complicated. These things are
The same applies to other systems other than the ejector rod, and there is a problem that the cost is large in terms of both the mold processing and the mold structure.

On the other hand, when these eject mechanisms are not provided, in order to take out a molded product, a mold is provided with a taper called a draft angle. Without this draft angle, the molded product would bite into the mold and cannot be removed in normal molding. Providing a taper makes it easier to take out molded products, but requires taper processing costs,
Unless the finish of the taper is increased with high accuracy, there is a problem that it causes burrs and a misalignment occurs.

[0007]

In order to solve the above problems, an injection molding die according to the present invention comprises a die piece ,
There is no slope, and there is a concave portion where the die piece is engaged and held.
And a pair of mold plates that can abut and be adjacent to each other.

In the injection molding method, the injection mold is heated to a temperature exceeding the glass transition point of the resin to be injection-molded, the molten resin is injected into the cavity, and the gate is opened. The injection molding die is gradually cooled to a temperature lower than the glass transition point of the resin while the resin injected and closed is kept in the cavity, and then the pressure in the cavity prevents the molded product from being deformed and shrunk. In this case, the injection molded article is taken out at the time of.

[0009]

The mold for injection molding according to the present invention has a mold piece and a draft angle.
Having a concave portion in which the mold piece is engaged and held
Since it is composed of a mold plate, there is no need to process a taper for forming a draft angle, and a simple mold structure is obtained. In addition, in the injection molding method using the injection mold, the injection mold is heated to a temperature exceeding the glass transition point of the resin to be injection-molded, and the molten resin is injected into the cavity. injection, and gradually cooled the injection mold while the injected resin confined in the cavity by closing the gate to a temperature lower than the glass transition point of the resin, and then the pressure in the cavity, and deformation of the molded article The injection molded product was taken out when the pressure to prevent shrinkage was reached, so the pressure in the cavity was set to a pressure close to zero to prevent deformation of the molded product.
Pressure greater than zero to prevent shrinkage of the part
If the force is set to substantially zero, a state in which the molded product can be taken out is formed.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a partial cross-sectional view of an injection mold according to one embodiment of the present invention. A mold piece 1 is provided on a mold plate 2 having no draft inside to manufacture a mold 3 for injection molding. The injection molding dies 3 are brought into contact with each other to form a pair that can be separated from each other, and this pair of dies is heated to 170 ° C., which is higher than the glass transition point 140 ° C. of the polycarbonate resin, which is the raw material of the molded product. Next, the molten polycarbonate resin is injected into the cavity, which is a space in the pair of molds, and the mold is gradually cooled while closing the gate and closing the injected polycarbonate resin in the cavity. Was cooled to 130 ° C., which is lower than the glass transition point of 140 ° C.

FIG. 2 is a timing chart showing the cavity pressure and the temperature of the mold in the injection molding process along with the transition of time. Then, when the cavity pressure became substantially zero, the end of the molded product was picked up and taken out to prepare an fθ lens molded product of the scanning optical system. This fθ lens molded product has high molding accuracy and has no slope formed on the side surface, so that the lens itself can be easily fixed and positioned on a device.

[0012]

As described above, since the injection mold of the present invention has a structure without a draft, it is not necessary to perform high-precision taper processing, and has a simple structure and is inexpensive. It is possible to process with high precision. In addition, by adopting the above-described injection molding method using the injection mold, a desired molded product can be easily manufactured at low cost.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of an injection mold according to one embodiment of the present invention.

FIG. 2 is a diagram showing an example of a timing chart showing a cavity pressure and a temperature of a mold on a time axis in an injection molding method using the mold.

FIG. 3 is a partial sectional view showing an example of a conventional injection mold.

[Description of symbols] 1 Mold piece 2 Mold plate 3 Injection molding mold

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Suji Hatakeyama 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Akira Fukushima 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Toshihiro Kanematsu 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside Ricoh Co., Ltd. (72) Shinya Senoo 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. (56) References JP-A-55-158949 (JP, A) JP-A-62-60623 (JP, A) JP-A-63-37912 (JP, A) JP-A-1-200925 (JP, A) A) Japanese Utility Model Showa 60-51017 (JP, U) Japanese Utility Model Showa 63-21953 (JP, Y2) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84

Claims (2)

(57) [Claims] 1. The mold piece has no draft angle, and the mold piece is
And a mold plate having a recess that is engaged and held, and a pair of injection molds that can be in contact with and adjacent to each other. 2. The method according to claim 1, wherein the injection mold is heated to a temperature exceeding a glass transition point of a resin to be injection-molded.
The molten resin is injected into the cavity, the gate is closed, and the injected resin is gradually cooled to a temperature lower than the glass transition point of the resin while closing the injected resin in the cavity. pressure, change of the molded article
An injection molding method, wherein an injection-molded product is taken out when a pressure for preventing the shape and shrinkage is reached.