JP2008290258A - Injection molding die and resin molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein, since the corners of a nest to hold a gate cut pin have circular curves and the gate cut pin needs to be provided with chamfering for the positions (four corners) corresponding to these circular curves, a burr is formed in the gate cut part of a resin molding due to the chamfering provided on the gate cut pin. <P>SOLUTION: In the injection molding die having a gate cut pin of a rectangular cross-sectional shape installed retractably into the inside of the fixed die or the movable die to the direction intercepting the gate and retreating therefrom, the gate cut pin is built to be freely slidable in a nest having a penetrated pin hole and part of the gate cut pin is protruded to the cavity when the gate cut pin intercepts the gate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an injection mold having a gate cut function and a resin molded product injection-molded by the injection mold.

  Molding of a resin molded product is generally performed by injecting molten resin injected from an injection molding apparatus into a cavity through a gate from a mold runner, and cooling and solidifying the molten resin.

  The resin solidified by cooling in the runner, the gate and the cavity is taken out from the mold, and an unnecessary resin is cut at the gate portion to obtain a desired resin molded product.

  Since such a gate cutting operation requires a lot of man-hours, a die with a gate cut mechanism that automatically performs cutting at the gate portion of the die has been proposed (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 07-223243

  The gate cut pins constituting the gate cut mechanism are inserted into pin through holes provided so as to penetrate through the movable type or fixed type inserts. Since the gate cut pin has a rectangular shape, the pin through hole must be drilled by wire electric discharge machining or the like. If it does so, the corner | angular part of the pin penetration hole of a nesting will be attached | subjected circular arc-shaped curve.

  For this reason, the corner portion of the gate cut pin to be inserted into the pin through hole has to be chamfered along with the arcuate curve, and the corner portion of the gate cut pin cannot be used with a sharp edge.

  When such a gate cut pin is used in an injection mold, as described in paragraph 0008 of Patent Document 1, the corner cut of the gate cut pin is deteriorated, and the position corresponding to the corner of the gate cut pin However, there is a problem that burrs adhere to the molded product.

  In order to solve this problem, in the invention described in Patent Document 1, the pin through hole is formed in a concave groove shape by facing the cavity on the side surface of the nest and opening along the sliding direction of the gate cut pin. The corner of the pin through hole on the cavity side is used with a sharp edge.

  However, if the side surface of the insert is formed in a concave groove shape, a part of the surface of the gate cut pin on the cavity side needs to be supported by another insert or mold part. For this reason, if resin pressure is applied to the cavity, the clearance between the cavity-side surface of the gate cut pin and the other inserts or mold parts described above changes, so when the clearance increases, molten resin flows into this clearance. The problem occurs. Further, when the clearance is increased, there is a problem that sliding of the gate cut pin is deteriorated.

  The present invention has been made to solve all of these problems. An injection mold and a resin molded product in which a burr generated in a molded product is eliminated by projecting a part of a gate cut pin into a cavity. Is to provide.

  In the present invention, a cavity, a gate, and a runner are formed between a fixed mold and a movable mold that are separable on the parting line surface, and can enter and exit in the fixed mold or the movable mold in a direction to block the gate. The present invention relates to an injection mold having a gate cut pin having a rectangular cross section.

  And since this gate cut pin is slidably incorporated in a nest having a penetrating pin through hole, the inner peripheral surface of the pin through hole formed in the nest and the sliding surface of the gate cut pin ( The clearance of the outer peripheral surface is always constant. For this reason, since the clearance between the inner surface of the pin through hole formed in the insert and the sliding surface of the gate cut pin does not change due to the resin pressure of the molten resin, the molten resin does not flow into this clearance. Moreover, since the clearance between the inner surface of the pin through hole formed in the insert and the sliding surface of the gate cut pin does not change, the slidability of the gate cut pin does not deteriorate. That is, according to the present invention, the maintenance frequency of the injection mold can be reduced.

  The molten resin flowing from the runner of this injection mold passes through the gate and is filled into the cavity. Then, after the molten resin has cooled and solidified, when the gate cut pin submerged in the fixed mold or movable mold is projected to the gate and the gate is shut off, a part of the gate cut pin is projected to the cavity Is a feature of the present invention.

  That is, when the gate cut pin protrudes from the movable mold or the fixed mold, a part of the side surface of the gate cut pin projects into the cavity. If it does so, a recessed part will be formed in the position corresponding to the gate cut pin of the resin molded product in a cavity, and generation | occurrence | production of the burr | flash to a resin molded product can be eliminated by this recessed part.

  Because the gate cut pin is put in the pin through hole that passes the gate cut pin provided in the movable type or fixed type insert, the corner of the gate cut pin to be put in the pin through hole is chamfered However, this is because the chamfered portion is located in the concave portion formed in the resin molded product.

  Therefore, the injection mold according to the present invention does not have a problem that the corner of the gate cut pin is cut off and burrs adhere to the resin molded product at a position corresponding to the corner of the gate cut pin. .

  The gate cut pin may be subjected to a surface treatment such as Ta-C (tetrahedral amorphous carbon) having a high hardness, a low friction coefficient, and a low processing temperature. The reason why the hardness is increased is to reduce wear, and the reason why the coefficient of friction is decreased is that the gate cut pin slides through the pin through hole. The reason for lowering the processing temperature is to eliminate the risk of deformation of the gate cut pin.

  In addition, the resin molded product molded with the above-described injection mold has a recess formed on the gate side of the cavity, but a resin molded product free of burrs can be obtained at low cost.

  According to the present invention, the frequency of maintenance of the injection mold can be reduced, and a resin molded product free from burrs can be obtained at a low cost.

  Hereinafter, the present invention will be described in detail using examples.

A first embodiment according to the present invention will be described with reference to FIGS.
1 is a side sectional view of an injection mold before gate cut, FIG. 2 is a side sectional view of an injection mold after gate cut, and FIG. 3 is a front end portion of a gate cut pin 4 in FIG. 4 is a plan view of the insert (movable side), FIG. 5 is a plan view showing the state of the insert (movable side) when the gate cut pin protrudes and cuts the resin, and FIG. 6 is injection molding. It is the perspective view which expanded a part of resin molded product shape | molded with the metal mold | die.

(Injection mold)
As shown in FIG. 1, the injection mold 14 includes a movable mold 1 and a fixed mold 2, and can be separated by a parting line surface 13. A runner 6, a gate 7, and a cavity 8 are formed between the movable mold 1 and the fixed mold 2, and molten resin injected from an injection molding apparatus (not shown) passes the runner 6 and the gate 7 from the sprue 3. Through which it is injected into the cavity 8.
Here, the gate 7 refers to a portion where the molten resin is cut by a gate cut pin 4 described later.

(Gate cut pin)
The movable die 1 is provided with a gate cut pin 4 whose tip can protrude and retract with respect to the runner 6 on the upstream side of the gate 7. The gate cut pin 4 has a rectangular cross section, and is inserted into a pin through hole 19 provided through the insert (movable side) 20 as shown in FIGS. 4 and 5. And the rear-end part of the gate cut pin 4 is connected to the cylinder 5 as a drive device, as shown in FIG.

  When the cavity 8 is filled with the molten resin and the pressure holding of the molten resin is completed, the gate cut pin 4 operates the cylinder 5 to project the runner 6 in the direction of blocking as shown in FIG. Is.

  And the front-end | tip part of the gate cut pin 4 has the front-end | tip surface 10 parallel to the parting line surface 13, as shown in FIG. 3, A part of this front-end | tip surface 10 is diagonally chamfered by the runner side. (Chamfer 11).

  The chamfer 11 is provided so that the molten resin does not flow to the cavity 8 side but flows to the runner 6 side when the gate cut pin 4 protrudes. The tip surface 10 is provided to prevent the tip of the gate cut pin 4 from being worn and to prolong the life of the gate cut pin 4.

  Note that a chamfer 12 having a chamfer dimension smaller than the chamfer 11 (for example, C0.5) may be provided also on the gate side of the distal end surface 10 of the gate cut pin 4. The chamfer 12 may be R (Radius) 0.5 having a radius of about 0.5 mm, for example.

  In this embodiment, as shown in FIG. 3, when the length dimension of the gate cut pin 4 is B, and the dimension of the portion parallel to the parting line surface 13 on the tip surface 10 of the gate cut pin 4 is D. Further, a chamfer 11 is provided so that D = 0.5 × B.

(Nesting)
The movable mold and the fixed mold of the injection mold 14 are provided with at least a nested (movable side) 20 and a nested (fixed side) 21.

  As shown in FIG. 4, the insert (movable side) 20 is provided with a pin through hole 19 through which the gate cut pin 4 is inserted. Since this pin through hole is drilled by wire electric discharge machining or sculpture electric discharge machining, the corner portion 22 has an arcuate curve. For this reason, the four corners of the gate cut pin 4 are subjected to R chamfering processing corresponding to each portion 22.

  As shown in FIGS. 4 and 5, when the gate cut pin 4 protrudes, a part of the gate cut pin 4 protrudes (enters) into the cavity 8. ) That is, the right side of the dotted line 23 shown in FIG. 4 is the cavity 8, but when the gate cut pin 4 protrudes, a part of the side surface of the gate cut pin 4 enters the cavity 8.

  Then, as shown in FIG. 6, a recess 26 is formed at one end 25 of the resin molded product 24 molded by the injection mold 14 at a position corresponding to the gate cut pin 4. However, if the amount of protrusion of the gate cut pin 4 into the cavity 8 (dimension E in FIG. 4) is 0.5 mm, for example, if the concave portion 26 has no problem in terms of the function of the resin molded product 24, the gate cut portion has a burr It is possible to mold the resin molded product 24 that does not exist.

  Further, the insert (fixed side) 21 is provided with a recess 9 into which the tip of the gate cut pin 4 enters. The recess 9 has a depth A of 2 mm, and a clearance of 0.5 mm is provided between the distal end surface 10 of the gate cut pin 4 and the bottom 15 of the recess 9.

  The length C of the recess 9 is set to 1.5 times the length B of the gate cut pin 4, and a slope 16 is formed on the runner 6 side (upstream side) of the recess 9.

  The inclined surface 16 has a function of smoothing the flow of the molten resin and preventing the occurrence of turbulent flow in the recess 9 when the molten resin is injected into the cavity 8. In addition, the slope 16 has a function of allowing the molten resin to easily flow (easily escape) to the runner side when the gate cut pin 4 protrudes, and to easily release the resin solidified in the recess 9 from the movable mold 2. Also have.

  In addition, the depth dimension A of the recessed part 9 must be 2 mm or less. This is because if the depth A of the concave portion 9 is larger than 2 mm, the amount of the molten resin that enters the concave portion 9 increases when the molten resin is injected into the cavity 8, so that a turbulent flow occurs in the molten resin or the molten resin melts. This is because air is mixed in the resin, so that silver streaks are generated in the molded product or bubbles are generated in the molded product.

  Further, the depth A of the recess 9 is desirably 0.5 mm or more. This is because the tip of the gate cut pin 4 must be inserted into the recess 9 in order to ensure the gate cut by the gate cut pin 4. Even in this case, the clearance between the tip surface 10 of the gate cut pin 4 and the bottom 15 of the recess 9 must be about 0.2 mm. This is for avoiding a collision between the distal end surface 10 of the gate cut pin 4 and the movable die 2 and extending the life of the gate cut pin 4.

A second embodiment according to the present invention will be described below with reference to FIGS.
FIG. 7 is a side sectional view of the injection mold before gate cutting, and FIG. 8 is a side sectional view of the injection mold after gate cutting.
Only differences from the first embodiment will be described, and description of the same parts as those of the first embodiment will be omitted.

  The difference from the first embodiment is only that the gate cut pin 4 is provided in the fixed die 2 and the recess 9 is provided in the movable die 1.

  That is, when the molten resin is injected into the cavity 8, the gate cut pin 4 is immersed in the insert (fixed side) 21 provided in the fixed mold 2 as shown in FIG. 7. Then, the cavity 8 is filled with molten resin, and after completion of the pressure holding, the gate cut pin 4 is protruded as shown in FIG.

  At this time, the tip of the gate cut pin 4 is inserted into the recess 9 provided in the insert (movable side) of the movable mold 1, so that the gate cut in the gate 7 is reliably performed. Further, since the depth A of the recess is set to any value within the range of 0.5 mm to 2 mm, even when the molten resin collides with the recess 9 during the injection of the molten resin, the depth A Turbulent flow does not occur and air does not enter the molten resin. In this example, the recess A was set to a depth A = 0.5 mm.

A third embodiment according to the present invention will be described below.
Only differences from the first embodiment will be described, and description of the same parts as those of the first embodiment will be omitted.

The difference from the first embodiment is only that the surface of the gate cut pin 4 is coated with Ta-C. Here, Ta-C coating means tetrahedral amorphous carbon (Tetrahedral
(Amorphous Carbon) is a surface treatment, and a material to which such a coating is applied has heat resistance, wear resistance, and releasability.

  The gate cut pin 4 has to be plunged into the concave portion 9 with high accuracy so that the burr does not adhere to the resin molded product. Therefore, the gate cut pin 4 is processed with high accuracy.

  Further, the gate cut pin 4 is operated each time the resin molded product is molded, and the gate cut pin 4 needs to have wear resistance because it frequently appears and disappears from the runner 6. As a method for imparting wear resistance to the gate cut pin 4, surface treatment is generally used. For example, in order to apply DLC (diamond-like coating), the gate cut pin 4 is heated from 200 ° C. to 300 ° C. Heated. Then, there is a problem that the gate cut pin 4 processed with high accuracy is thermally deformed.

  Therefore, in the third embodiment, the gate cut pin 4 itself is not heated to a high temperature, but is provided with a low temperature (about 100 ° C.) in order to impart heat resistance, wear resistance, and releasability to the gate cut pin 4 itself. And Ta-C coating.

(Ta-C coating)
The Ta—C coating applied to the gate cut pin 4 will be specifically described below.

  Since the material of the gate cut pin 4 is SUS, Fe or the like, first, a first binder layer made of titanium (Ti) is provided on the gate cut pin 4 with a thickness of 0.1 μm. Then, a second binder layer made of Ta—C with a high bias potential is provided on the first binder layer with a thickness of 0.1 μm. These two binder layers are provided to firmly attach the Ta—C coating to the surface of the gate cut pin 4.

  Next, an intermediate layer made of Ta—C is provided with a thickness of 2 μm on the second binder layer, and finally a wear-resistant layer made of Ta—C is provided with a thickness of 0.3 μm. Note that the magnitude of the bias potential is second binder layer> intermediate layer> abrasion resistant layer.

  By providing the Ta-C coating having such a layer structure on the surface of the gate cut pin 4, the gate cut pin 4 can be provided with wear resistance while maintaining high accuracy without being thermally deformed. For this reason, the lifetime of the gate cut pin 4 can be lengthened, and the maintenance frequency of the gate cut pin 4 can be reduced.

  The above-described embodiments are merely illustrative and are not intended to limit the present invention. The present invention can be recognized by those skilled in the art from the claims, the detailed description of the invention, and the drawings. Modifications and additions can be made without departing from the technical idea of the invention.

  For example, in the above-described embodiment, in FIG. 3, B = 0.5 × D and C = 1.5 × B are shown, but the present invention is not limited to this, and the gate cut pin 4 If the tip surface 10 is formed at the tip, B may not be 0.5 × D. Moreover, since it is necessary to let the molten resin in the recessed part 9 escape to the runner 6 side (upstream side) by protrusion of the gate cut pin 4, C> 1.5 * B may be sufficient.

  The present invention is applied to an injection mold used for molding a resin molded product and a resin molded product manufactured using the injection mold.

Side cross-sectional view of injection mold before gate cut (Example 1) Side sectional view of injection mold after gate cut (Example 1) Partial enlarged view of the tip of the gate cut pin (Example 1) Top view of the insert (movable side) (Example 1) A plan view showing a state of a nest (movable side) when the gate cut pin protrudes and cuts the resin (Example 1) An enlarged perspective view of a part of a resin molded product (Example 1) Side sectional view of injection mold before gate cut (Example 2) Side sectional view of injection mold after gate cut (Example 2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Movable type | mold 2 Fixed type | mold 3 Sprue 4 Gate cut pin 5 Drive device 6 Runner 7 Gate 8 Cavity 9 Recess 10 End surface 11 Chamfering 13 Parting line surface 14 Injection mold 15 Bottom
19 Pin through hole 20 Nesting (movable side)
21 Nesting (fixed side)
24 resin molded products

Claims (3)

Cavities, gates, and runners are formed between fixed and movable molds that can be separated on the parting line surface.
In the injection mold having a gate cut pin having a rectangular cross section provided so as to be able to protrude and retract in the fixed mold or the movable mold in the direction of blocking the gate,
The gate cut pin is slidably incorporated in a nest having a pin hole therethrough,
An injection mold characterized in that a part of the gate cut pin protrudes into the cavity when the gate cut pin blocks the gate.   The injection mold according to claim 1, wherein the gate cut pin is subjected to a surface treatment.   A resin molded product molded by the injection mold according to claim 1 or 2.

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