JP2007283505A - Mold and gate residue preventing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold capable of preventing the occurrence of the so-called gate residue remaining in the pin shape on the side of a product of a resin solidified at a gate part. <P>SOLUTION: The periphery 11 of the opening part of the pin gate 4 opened in a cavity 3 is formed into a protruded shape which forms an almost semispherical shape recessed on an obtuse angle recessed part to the resin product. Further, the inner peripheral surface of the leading end part of the pin gate 4 is formed into a rough surface having an almost star shape on a plan view so as to concentrate stress to the leading end part of the pin gate 4 coming into contact with the resin product. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a mold used for injection molding and a gate remaining prevention method.

  Conventionally, a mold for molding a resin product has a so-called gate residue in which the resin solidified at the gate portion remains in the form of a pin on the product side. The rest was excised.

  Since this is extremely troublesome, means for preventing the occurrence of the remaining gate itself has been proposed.

  For example, there is a pin gate type resin molding die in which the gate diameter of the pin gate is set to 0.4 to 0.6 mm and the land length of the pin gate is set to approximately 0 mm. In addition, this mold can prevent the generation of the remaining gate by applying the above-described configuration when molding a molded product having a volume of 0.5 to 2.5 cm 3 using PS resin containing silicon. , And.

JP 2001-315170 A (first page, FIG. 1)

  In the prior art described above, the external shape of the pin gate itself is the same as the conventional one, and the gate diameter, land length, and gate land angle in the pin gate are optimized, and further, the resin material is limited so that the gate remaining from the conventional pin gate is reduced. The incidence is reduced. Therefore, if the size of the product or the resin material is different, a gate residue may occur or the injection time may increase, which may not be applicable.

  Accordingly, the present invention has been made in view of such a situation, and an object thereof is to provide a mold and a gate remaining prevention method capable of solving the above-described problems.

In order to achieve the above technical problem, the mold and the gate remaining prevention method according to the present invention employ the following technical means.
That is, the mold according to claim 1 is a mold for injecting molten resin from a gate having a draft angle into a cavity formed by a pair of molds to mold a resin product, and the mold is opened in the cavity. The periphery of the opened opening of the gate is formed in a convex shape such that a substantially hemispherical concave portion is formed in the resin product, or a convex shape such that an obtuse concave portion is formed in the resin product. And the inner peripheral surface of the tip of the gate is rough.
According to a second aspect of the present invention, the metal mold according to the first aspect is characterized in that the inner peripheral surface of the tip of the gate is formed in a substantially star shape in a plan view.
According to a third aspect of the present invention, there is provided a method for preventing a remaining gate of a resin product by injection molding, wherein the gate is formed so that a component surface of the resin product has an acute angle or a concave curve with respect to a center line of the gate. And the inner peripheral surface of the tip of the gate is roughened.

  According to the present invention, a convex shape that forms a substantially hemispherical concave portion in the resin product, or a convex shape that forms an obtuse concave portion in the resin product, around the opening of the gate opened in the cavity. In addition, the inner peripheral surface of the tip of the gate is roughened so that stress concentrates on the tip of the gate in contact with the resin product. As a result, the remaining gate can be completely prevented.

Next, an embodiment of a mold according to the present invention will be described.
As shown in FIG. 1, the mold according to the present embodiment includes a cavity plate 1 that forms a design surface of a resin product W (see FIG. 3), and a resin plate W that is disposed to face the cavity plate 1. And a core plate 2 for forming the back surface.

  For example, as shown in FIG. 3, the cavity plate 1 and the core plate 2 are defined in a plate-like main body so as to be cut out in a substantially U shape in plan view, and the top portion in the defined region. In addition, a switch member formed with a cap-shaped convex portion, that is, a cavity 3 for molding the resin product W is formed.

  As shown in FIG. 1, a pin gate 4 for injecting molten resin to a midway portion in the defined area is provided in the cavity plate 1.

  The pin gate 4 is formed with a draft that gradually decreases in diameter toward the cavity 3, and the inner peripheral surface of the tip is flat so that the inner peripheral surface becomes a rough surface as shown in FIG. 2. It is formed to have a substantially star shape.

  In addition, this rough star-shaped rough surface forming method in plan view can be easily formed by carrying out a normal pin gate 4 processing and then carrying out a tearing. Therefore, even if it is referred to as a substantially star shape in plan view, it is not a strict shape, and it is sufficient if the inner peripheral surface is uneven.

  Further, the cavity plate 1 is formed in a convex shape such that a substantially hemispherical concave portion w <b> 1 is formed in the resin product W around the opening portion 11 of the pin gate 4 opened in the cavity 3. That is, the pin gate 4 is formed so that the constituent surface of the resin product W is not a right angle with respect to the center line of the pin gate 4 but an acute angle or a concave curve.

  In the mold according to the present embodiment configured as described above, when the molten resin injected into the cavity 3 through the gate solidifies in the same manner as a general mold, the cavity plate 1 in a mold-clamped state immediately. And the core plate 2 are separated from each other, and the resin product W is pushed up by an ejector pin (not shown) to be removed.

  At this time, the inner peripheral surface of the tip portion of the pin gate 4 is rough, and the periphery 11 of the opening of the pin gate 4 is formed in a convex shape, that is, the resin product W with respect to the center line of the pin gate 4. Since the component surface is an acute angle or a concave curve, the tensile stress is concentrated on the tip of the gate in contact with the resin product W, and the solidified resin is surely cut from the portion. As a result, the remaining gate can be completely prevented. In addition, although the recessed part w1 as shown in FIG. 3 is formed in the position corresponding to the pin gate 4 in the resin product W, this recessed part w1 is a thing of the grade which does not have any problem as a product.

  As mentioned above, although the metal mold | die concerning this Embodiment was demonstrated, embodiment mentioned above shows an example of suitable embodiment of this invention, and this invention is not limited to it, The Various modifications can be made without departing from the scope of the invention.

  For example, a gate remaining prevention method may be employed in which the pin gate 4 is formed so that the constituent surface of the resin product W has an acute angle or a concave curve with respect to the center line of the gate, and the inner peripheral surface of the tip of the gate is roughened. .

It is a longitudinal cross-sectional view in the principal part of the metal mold | die concerning this Embodiment. It is a XX arrow directional view in FIG. It is a perspective view around the principal part of the resin product shape | molded with the metal mold | die concerning this Embodiment.

Explanation of symbols

1 Cavity plate 11 Around the opening 2 Core plate 3 Cavity 4 Pin gate W Resin product w1 Recess

Claims (3)

A mold that molds a resin product by injecting molten resin from a gate having a draft in a cavity formed by a pair of molds,
Around the opening of the gate opened in the cavity is a convex shape that forms a substantially hemispherical concave portion in the resin product, or a convex shape that forms an obtuse concave portion in the resin product. The metal mold | die characterized by the above-mentioned. WHEREIN: The internal peripheral surface of the front-end | tip part of the said gate is a rough surface.   2. The mold according to claim 1, wherein an inner peripheral surface of a tip portion of the gate is formed to have a substantially star shape in a plan view. A method for preventing gate residue of resin products by injection molding,
The gate is formed so that the component surface of the resin product has an acute angle or a concave curve with respect to the center line of the gate, and the inner peripheral surface of the front end portion of the gate is roughened to prevent remaining gates. Method.

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