JP2006001145A - Injection molding mold and method for producing injection-molded component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the occurrence of burrs and the remainder of thin films during cutting when a molding is obtained by in-mold gate cutting. <P>SOLUTION: This mold has a fixed mold 11, a movable mold 12 which is installed to be able to approach or to separate from the fixed mold 11 and forms a cavity 30 for injection molding with the fixed mold 11, and a cut pin 20 having a gate part 22 which is installed between a runner 32 of the inflow side of a resin in the cavity 30 and a product part 31 defining a product shape in the cavity 30, has a surface extending in the direction crossing the resin inflow direction, and makes the resin flow from the runner 32 to the product part 31 by boring a hole in the intermediate part of the surface. The cut pin 20 separates the product part 31 from the runner 32 by moving the position of the gate part 22 in the crossing direction. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an injection mold used for molding a resin material, and more particularly to an injection mold that performs in-mold gate cutting.

  2. Description of the Related Art Conventionally, in molding processing of various resin materials, in-mold gate cutting is performed for a resin injected into a cavity in a mold, in which the resin gate portion is cut in the mold. According to this in-mold gate cut, when the solidified resin is taken out from the mold by opening the mold, the molded product part and the unnecessary resin part such as the gate part are already separated. There is no need to perform a gate cutting operation after taking out the solidified resin. Further, there is an advantage that the gate can be cut before the resin is completely solidified, and the cut surface is smooth and the post-processing of the cut surface is not required.

  4 (a) to 4 (c) are diagrams showing an example of an injection molding die in the prior art described in the publication (for example, see Patent Document 1). FIG. 4A shows a state before the gate cut by the injection mold, and FIG. 4B shows a state after the gate cut by the injection mold. FIG. 4C shows the shape of a molded product or the like obtained by the injection mold shown in FIG. In the injection mold shown in FIG. 4A, a movable mold 201 is provided on the opposite surface side of the fixed mold 200, and a cavity 202 that defines the product shape, and a resin is introduced into the cavity 202. A side gate 203 to be used and a runner 204 to be a resin flow path are formed. A resin reservoir 205 and an inclined surface 206 are formed on the fixed mold 200, and a pressure pin 207 for cutting the resin at the position of the side gate 203 is provided. By projecting the pressure pin 207 into the side gate 203, as shown in FIG. 4B, the resin in the cavity 202 and the gate side are cut by the pressure pin 207. As a result, the molded product 210 and the resin 211 in the sprue runner portion as shown in FIG. 4C are taken out from the mold in a completely separated state.

JP-A-7-52205 (page 3, FIGS. 1 to 3)

  Heretofore, as a general method for performing in-mold gate cutting, there has been a method using gate compression by a square pin or a cutting pin edge. However, the former gate compression by the square pin is a method in which the gate is compressed in the product portion, and the tip of the cut compression pin is worn and burrs are likely to occur. In the latter method using the cutting pin edge, the cutting is performed with the cutting pin abutting, so that the pin is easily bent and deformed, and the thin skin remains at the time of cutting, making adjustment difficult.

  Patent Document 1 shown in FIG. 4 can also be said to be the same classification as any of these gate cutting methods. However, in the technique of Patent Document 1, the resin material is compressed by the pressure pin 207 to form the cavity 202 and the resin reservoir 205. Is disconnected. However, basically, since the volume of the resin material does not change, the resin material moves in any direction. When this resin material moves, the moved part remains as burrs. The applicants repeated the experiment using the technique shown in FIG. As a result, it was possible to obtain an optimum value so that no burrs remained, but even in such a case, the cavity 202 and the resin reservoir 205 are connected by a film of several tens of μm, and a preferable molded product can be obtained. could not.

The present invention has been made in order to solve the technical problems as described above, and the object of the present invention is to generate burrs and to reduce the thin skin at the time of cutting when a molded product is obtained by in-mold gate cutting. It is to suppress the rest.
Another object is to obtain a good cut surface when a molded product is obtained by in-mold gate cutting.
Yet another object is to satisfactorily treat the cut gates when the gate is cut by shearing.

  For this purpose, in the gate cutting method according to the present invention, a hole is formed in a square pin, which is a cut pin, to form a gate portion. And it is comprised so that a cut pin may be moved within a type | mold after completion | finish of pressure holding, and the resin of a gate part may be cut | disconnected from a product. Accordingly, it is possible to suppress a problem that the pin is easily broken when the gate is cut, and it is possible to suppress a trouble such as a thin skin remaining at the time of cutting. That is, an injection mold to which the present invention is applied has a predetermined thickness and a mold that forms a cavity for injection molding including a runner on the resin inflow side and a product portion that defines a product shape. And a cut pin that cuts the product part of the cavity at the side gate position by sliding in the mold, and this cut pin forms a gate part that allows the resin to flow from the runner to the product part. The product part is cut at the side gate position by cutting the gate part with the thickness of the cut pin while maintaining the volume of the gate part.

  Here, this mold has a puddle that opens toward the slide surface of the cut pin on the runner side of the cavity, and this cut pin moves the resin separated from the product part to the position of the puddle. It is preferable that the resin contained in the cut pin can be attached to the runner and discharged, and the resin (gate resin) in the separated gate portion can be easily disposed.

  On the other hand, an injection mold to which the present invention is applied is a fixed mold and a movable side which is provided so as to be able to contact with and separate from the fixed mold and forms a cavity for injection molding together with the fixed mold. It has a surface that extends between the mold and the runner on the resin inflow side in the cavity and the product part that defines the product shape in the cavity. And a cut pin having a gate that allows a resin to flow from the runner to the product part by making a hole in the middle part of the surface, and the cut pin separates the product part by moving the gate position in a crossing direction. It is characterized by doing.

  Here, if the gate formed on the cut pin is provided with a draft that gradually increases the hole size from the product part side toward the runner side, it is separated from the product part. It is excellent in that the resin (gate resin) is easily welded to the runner side and the gate resin is not left in the cut pins. The “intermediate portion of the surface” does not mean the complete middle, but includes the meaning of the middle relative to the end portion of the surface.

  From another point of view, the present invention relates to a method of manufacturing an injection molded part for producing a resin product using a mold, a filling step for filling the resin in the mold cavity, and the resin to be filled In the semi-molten state, change the volume of the resin filled in the gate, which is the path for the resin to flow from the runner on the resin inflow side into the cavity to the product part provided in the cavity. And a separation step of separating the product part.

Here, the separation step can be characterized in that the gate is moved by sliding the cut pin with respect to the gate drilled in the cut pin.
Further, in this separation step, the resin filled in the gate is moved to the puddle portion formed in the runner, the resin filled in the gate is welded to the puddle portion, and then the resin filled in the gate. The method may further include a step of removing the together with the runner.

  According to the present invention, when a molded product is obtained by in-mold gate cutting, it is possible to suppress the generation of burrs and the remaining thin skin at the time of cutting.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
FIGS. 1A to 1C are diagrams showing a configuration of a gate cut mold to which the present embodiment is applied. Fig.1 (a) has shown the whole block diagram of the gate cut metal mold | die. As shown in FIG. 1A, the gate cut mold to which this embodiment is applied is, for example, a fixed mold 11 attached to a fixed platen of an injection molding machine, and the fixed mold 11 is opposed to the fixed mold 11. A movable side mold 12 provided at a position, for example, provided on a movable platen of an injection molding machine, and a cut pin 20 for cutting resin are provided. The movable mold 12 is provided so as to be able to contact and separate from the fixed mold 11. The fixed mold 11 and the movable mold 12 form a cavity 30 that is a space for filling the resin. The cavity 30 is formed with a product portion 31 in which a product shape is defined, and a runner 32 serving as a resin flow path filled in the product portion 31. On the fixed mold 11 side of the runner 32, a puddle 33 cut into a wide concave shape is provided to facilitate the welding of the resin.

  Furthermore, the runner 32 and the product part 31 at the time of resin injection are connected by the gate part 22 formed by a hole formed in the cut pin 20. More specifically, the cut pin 20 is provided between the runner 32 on the resin inflow side in the cavity 30 and the product portion 31 that defines the product shape in the cavity 30, and in the direction in which the resin flows. On the other hand, it has a surface extending in the intersecting direction. The cut pin 20 forms a gate portion 22 by making a hole in an intermediate portion of this surface. The product part 31 can be cut at the side gate position 31a by sliding the cut pin 20 in the direction in which the surface extends (upward in the figure).

  FIG. 1B shows a cut pin 20 used in a gate cut mold, and FIG. 1C shows a CC cross section of the cut pin 20 shown in FIG. The main body of the cut pin 20 is a square pin, and a hole that becomes the gate portion 22 is formed in the main body. As shown in FIG.1 (c), the gate part 22 is provided with the R-shaped draft 23, It is comprised so that the resin formed in the gate part 22 may be easily discharged | emitted from the cut pin 20. As shown in FIG. Yes. The dimensions of the cut pin 20 are, for example, about 3 mm in width and about 0.6 mm in thickness. Thus, the cut pin 20 has a predetermined thickness, and acts so as to separate the gate portion 22 with this thickness. The gate portion 22 has a width of 1.5 mm, a height of about 0.8 mm at the largest opening, and a height of about 0.5 mm at the smallest opening. The R shape of the draft angle 23 is R = 0.5 mm. Degree. Thus, the gate portion 22 is provided with the draft 23 in which the hole size gradually increases from the product portion 31 side of the cavity 30 toward the runner 32 side. In addition, the gate part 22 vacated by this cut pin 20 is formed by, for example, electric discharge machining.

2A to 2C are views for explaining the state of the gate cut mold before and after cutting the gate portion. The operation of the mold will be described with reference to FIGS. 2 (a) to 2 (c). In addition, the effect | action of the metal mold | die demonstrated below corresponds also to the method of manufacturing an injection molded part using the metal mold | die for injection molding.
First, using a mold clamping device of an injection molding machine, the movable mold 12 is pressed against the fixed mold 11 and the mold is clamped. At this time, as shown in FIG. 2A, the runner 32 and the product portion 31 are connected by the gate portion 22. In the next step, the resin melted in the heating cylinder is injected into the mold, and the product part 31 is filled with the resin via the runner 32 and the gate part 22. The resin to be filled flows in from a large opening portion of the gate portion 22 (for example, a portion having a height of 0.8 mm) and fills the product portion 31. Then, the resin is further pushed into the product portion 31 to increase the resin pressure and hold the pressure.

  After completion of the pressure holding, the cut pin 20 is basically slid in the direction of the arrow in the figure (upward in the figure) as shown in FIG. 2B in a semi-molten state before cooling. The product part 31 is cut by the movement of the cut pin 20 at a small part of the opening of the gate part 22 (for example, a part having a height of 0.5 mm), that is, at the side gate position 31a. Due to the movement of the cut pin 20, the large portion of the opening of the gate portion 22 is positioned in the portion of the puddle 33 of the runner 32, and the cut pin 20 stops in the state shown in FIG. Due to the movement of the cut pin 20, the product portion 31 is completely separated from the gate portion 22 of the cut pin 20. After a certain period of time has elapsed in this state, the fixed mold 11 and the movable mold 12 are separated, the product is taken out, and the runner 32 is moved in the right direction in the figure, thereby allowing the gate portion 22 to move. The resin is pulled out. Thereafter, the cut pin 20 moves back in the direction opposite to the arrow direction in the figure. Thus, in the present embodiment, the gate portion 22 is separated from the product portion 31 by the thickness of the cut pin 20 while maintaining the volume of the gate portion 22.

  FIG. 2 (c) shows the molded product and the runner resin taken out. A cut gate (gate resin) is welded to the taken-out runner resin at the welded portion, and the welded gate resin is integrated with the runner resin. R of the draft angle 23 shown in FIG. 1C is effective for facilitating welding of the cut gate resin. Also, the draft angle R is meaningful in order to make it easy to discharge the gate resin from the cut pin 20 together with the runner resin. Furthermore, in the present embodiment, since the runner 32 is partially thickened and the puddle 33 is provided, the gate resin is easily welded to the runner resin, and the gate resin is disposed of separately after the gate cut by welding. There is no need to do. Furthermore, in the present embodiment, the gate portion 22 is separated from the product portion 31 by the thickness of the cut pin 20 while maintaining the volume of the gate portion 22 as described above. Maintaining the volume of the gate portion 22 is almost "maintaining the volume of the gate resin as it is". Strictly speaking, the volume of the gate resin slightly changes, but such a slight change is considered as an error, and “maintaining the volume of the gate resin as it is” is close to the idea of the present embodiment.

In addition, the inventors confirmed the effect in this Embodiment using various resin materials. The materials used in the experiment were POM (polyacetal), PA (polyamide), PC (polycarbonate), elastomer, PPE (polyphenylene ether), PMMA (polymethyl methacrylate), glass 30% PC, ABS (acrylonitrile butadiene styrene) , PBT (polybutylene terephthalate).
As a result of these sharp examinations, depending on the material, there was a case where the resin remained on the gate portion 22 in the cut pin 20 due to the delay of the protrusion of the cut pin 20. In addition, there are cases where cut projections are formed on the cut surface of the product portion, the cut surface feels torn, or the cut surface becomes dull. As a result of experiments, it has been found that, for example, a material with good fluidity causes problems such as burrs. Preferred materials include ABS and PBT. Good results can be obtained by devising cutting conditions for other materials. In addition, as a whole, a better cut surface can be obtained when the protruding speed is faster. However, if it is too early, the resin is stretched and drooping occurs greatly. Therefore, it is preferable to select an appropriate ejection speed according to the material. As the ejection speed, for example, 0.8 seconds to 1.1 seconds or the like can be selected.

  FIG. 3 is a diagram showing an overall configuration of the movable side in the in-mold gate cut. The in-mold gate cut mold shown in FIG. 3 is configured such that the protruding portion of 3 mm shown on the left side of the figure jumps into the fixed mold 11. Then, a gate cut pin 101 for sliding the cut pin 20 for gate cutting, a cut plate 102 for pushing out the gate cut pin 101, a coil spring 103 for pushing the gate cut pin 101 back and then returning, and a cut plate Limit sleeve 104 for preventing 102 from moving backward (right side) more than necessary, GC return pin 105 for protecting the gate cut pin 101 in the event that the gate is cut and slid beyond the design value It has. In the in-mold gate cut mold shown in FIG. 3, the cut plate 102 is operated to secure a cut stroke of about 1 mm, thereby enabling gate cut in the mold.

  As described above in detail, according to the present embodiment, when a molded product is obtained by in-mold gate cutting, it is possible to suppress the generation of burrs and the remaining thin skin at the time of cutting. Here, in the present embodiment, a hole is formed in the moving cut pin 20 itself to form the gate portion 22 that is a flow path of the molten resin. In addition, the parallel movement of the cut pin 20 moves the resin portion (gate resin) filled in the hole portion of the gate portion 22 formed in the cut pin 20 by using the thickness of the cut pin, and this gate The resin is separated from the product. Thus, according to the present embodiment, it is possible to reliably separate the product from the runner 32 at the side gate position in the mold, and there is no need to separate the molded product after molding as in the prior art. . Further, even when the gate portion is cut by the cut pin 20, the volume of the resin in the mold does not change. As a result, an unnecessary stress is not generated in the mold and the product, and a good gate cut can be performed. Furthermore, since the cut gate is welded to the runner side, there is no occurrence of cutting residue at the gate portion.

  INDUSTRIAL APPLICABILITY The present invention is used for an injection mold that adopts an in-mold gate cut method, a method for manufacturing an injection molded part using this injection mold, and / or a molded product obtained by such a manufacturing method. be able to.

(a)-(c) is the figure which showed the structure of the gate cut metal mold | die to which this Embodiment is applied. (a)-(c) is a figure for demonstrating the state of the gate cut metal mold | die before and after cutting | disconnection of a gate part. It is the figure which showed the whole movable side structure in the gate cut in a type | mold. (a)-(c) is the figure which showed the example of the metal mold | die for injection molding in the prior art (for example, refer patent document 1) of publication.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Fixed side metal mold, 12 ... Movable side metal mold, 20 ... Cut pin, 22 ... Gate part, 23 ... Draft, 30 ... Cavity, 31 ... Product part, 31a ... Side gate position, 32 ... Runner, 33 ... Hot spring, 101 ... Gate cut pin, 102 ... Cut plate

Claims (7)

A mold that forms a cavity for injection molding including a runner on the resin inflow side and a product part that defines a product shape;
A cut pin having a predetermined thickness and cutting the product portion of the cavity at a side gate position by sliding in the mold;
The cut pin forms a gate part for allowing resin to flow from the runner into the product part, and the product part is separated by cutting the gate part with the thickness of the cut pin while maintaining the volume of the gate part. Is cut at the side gate position. The mold includes a puddle that is opened toward the slide surface of the cut pin on the runner side of the cavity,
The injection mold according to claim 1, wherein the cut pin moves the resin cut from the product part to the position of the puddle. A fixed mold,
A movable side mold that is detachably provided on the fixed side mold and forms a cavity for injection molding together with the fixed side mold;
A surface extending in a direction intersecting the direction in which the resin flows in, provided between the runner on the resin inflow side in the cavity and the product portion defining the product shape in the cavity; With a cut pin having a gate for making resin flow from the runner to the product part by making a hole in the middle part of the surface,
The cut pin separates the product part by moving the position of the gate in the intersecting direction.   4. The injection molding according to claim 3, wherein the gate formed on the cut pin is provided with a draft that gradually increases the hole size from the product portion side toward the runner side. Mold. A method of manufacturing an injection molded part that generates a resin product using a mold,
A filling process for filling the mold cavity with resin;
When the resin to be filled is in a semi-molten state, a gate that is a path through which the resin flows into the product portion provided in the cavity from the runner on the resin inflow side in the cavity is filled in the gate. A method of manufacturing an injection-molded part including a separation step of separating the product part by moving the resin without changing the volume.   6. The method of manufacturing an injection-molded part according to claim 5, wherein the separating step moves the gate by sliding the cut pin with respect to the gate drilled in the cut pin. In the separation step, the resin filled in the gate is moved to a puddle portion formed in the runner,
6. The method of manufacturing an injection molded part according to claim 5, further comprising a step of removing the resin filled in the gate together with the runner after the resin filled in the gate is welded to the puddle portion. Method.

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