JP2010046975A - Mold for injection molding and method of injection molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology which efficiently prevents weld lines on resin moldings. <P>SOLUTION: A cavity 13 for molding resin in a mold is formed in a mold body 1. One end 21 of a pin member 2 is arranged in of the cavity 13. The other end 22 of the pin member 2 is substantially exposed outside the mold body 1. A light source 3 irradiates the other end 22 of the pin member 2 with a laser beam for heating. The pin member 2 is locally heated by irradiating the other end 22 of the pin member 2 with the laser beam. Preferably, the heat conductivity of the pin member 2 is substantially larger than that of the mold body 1 contacting the pin member 2. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a mold used for injection molding and a method for producing a molded product using the mold.

  A technique using a pin to form a hollow portion in a resin molded product is known. In this technique, pins are arranged in advance in the cavity. Next, the cavity is filled with molten resin. After the molten resin is solidified, the pin is removed and the molded product is taken out from the cavity. Thus, a hollow part can be formed in a molded article.

  By the way, when the pin is arranged in a direction intersecting with the resin flow direction in the cavity, a part of the molten resin is divided by the pin, passes through the side of the pin, and then merges again. Here, the molten resin in contact with the pin surface is solidified by heat exchange with the pin surface. For this reason, in the molten resin that has joined again, linear traces called weld lines may occur.

  The weld line not only causes the appearance of the molded product to be impaired, but also can cause a lack of strength in some cases.

  Conventionally, various techniques for preventing weld lines have been proposed. For example, in the techniques described in Patent Documents 1 and 2 below, the mold is heated using a heat medium to prevent the resin from solidifying during flow. If the separated resin can be joined again in the molten state, it is considered that the weld line can be prevented.

  However, in the technique of heating a mold or a pin using a heat medium, there is a problem that the apparatus becomes large and the cost is high. In addition, the heat medium tends to dissipate its own heat in a wide range in the flow path and the mold during the flow. For this reason, there also exists a problem that energy consumption will become large. Furthermore, in order to solidify the resin filled in the cavity, it is necessary to lower the mold temperature to a predetermined value or less. However, if the entire mold is heated, there is a problem that the time until cooling becomes longer and the production efficiency of the molded product is lowered.

On the other hand, in the technique described in Patent Document 3 below, solidification of the molten resin during flow is prevented by using a heat insulating member. However, when a heat insulating member is used, the apparatus becomes large and the cost becomes high. In addition, there is a problem that it is generally difficult to apply the heat insulating member to a microstructure mold.
JP 2005-119181 A JP 2006-76276 A JP 2002-210781 A

  The present invention has been made in view of such circumstances. The objective of this invention is providing the technique which can prevent the weld line in a molded article efficiently.

  The present invention can be expressed as items described below.

(Item 1)
It has a mold body, a pin member, and a light source.
A cavity for molding a resin is formed inside the mold body,
One end side of the pin member is disposed inside the cavity,
The other end side of the pin member is substantially exposed to the outside of the mold body,
The said light source becomes a structure which irradiates the laser beam for a heating to the other end side of the said pin member. The injection mold characterized by the above-mentioned.

  Here, the pin member may be a member for forming a hollow portion in a molded product, and the shape thereof is not particularly limited. In this invention, a pin member can be heated locally by irradiating a laser beam to the other end side of a pin member. The other end of the pin member only needs to be exposed to the outside of the mold to such an extent that it can be heated by laser light irradiation. It is possible that the surface of the pin member is covered with some member, for example, a film for promoting absorption of laser light.

(Item 2)
The mold for injection molding according to item 1, wherein the thermal conductivity of the pin member is substantially higher than that of the mold body that contacts the pin member.

  In the invention of this item, heat given by laser irradiation to the other end side of the pin member can be efficiently transmitted to one end side of the pin member. For this reason, the pin member arrange | positioned in a cavity can be heated efficiently.

(Item 3)
The injection mold according to item 1 or 2, wherein a gap for separating the other end side from the mold body is formed around the other end side of the pin member.

  By providing the gap, the contact area between the mold body and the pin member can be reduced. Thereby, the amount of heat transmitted from the pin member to the mold body can be reduced, and the pin member can be efficiently heated.

(Item 4)
Furthermore, it has a heat transfer member,
The heat transfer member is configured to allow heat conduction between the other end side of the pin member and the mold body by being filled in the gap.
Furthermore, the heat transfer member can be attached to and detached from the gap. The injection mold according to item 3.

  When the mold is cooled, the heat transfer member can be filled in the gap. Then, heat can be released from the pin member to the mold body, and the cooling time can be shortened.

(Item 5)
A tapered surface is formed on the outer peripheral surface on the other end side of the pin member,
5. The injection according to any one of items 1 to 4, wherein the mold body is formed with a contact surface for contacting the tapered surface to prevent the pin member from moving. Mold for molding.

  When the molten resin flows into the cavity, a pressing force from the molten resin is applied to the pin member. In the invention of this item, by forming a tapered surface on the pin member, it is possible to reduce the possibility that the pin member moves even when the molten resin flows.

(Item 6)
6. The concave portion for introducing laser light from the light source into the pin member is formed on the other end side of the pin member. Injection mold.

  By forming the recess, the heat generated by the laser beam can be efficiently transmitted toward one end side (cavity side) of the pin member. For this reason, even when the surface area on the other end side of the pin member is small, the pin member can be efficiently heated by laser irradiation.

(Item 7)
The injection molding die according to any one of items 1 to 6, wherein the pin member is made of any one of aluminum, copper, magnesium, tungsten, and alloys thereof.

(Item 8)
An injection molding method using the mold according to any one of items 1 to 7,
Irradiating the other end side of the pin member with laser light to heat the pin member;
Introducing molten resin into the cavity;
Removing the resin from the cavity after the resin is cured. An injection molding method comprising:

  ADVANTAGE OF THE INVENTION According to this invention, the technique which can prevent the weld line in a molded article efficiently can be provided.

  Hereinafter, an injection mold according to a first embodiment of the present invention will be described with reference to FIG.

  The injection mold in this embodiment includes a mold body 1, a pin member 2, and a light source 3 as main elements.

  The mold body 1 includes an upper mold 11, a lower mold 12, and a cavity 13.

  The upper mold 11 includes a resin flow path 111 for supplying molten resin to the cavity 13.

  The lower mold 12 includes a cavity surface 121. The cavity surface 121 forms a cavity 13 for resin molding inside the mold body 1.

  The lower mold 12 is formed with an insertion hole 122 for arranging one end side of the pin member 2 inside the cavity 13.

  As the material of the upper mold 11 and the lower mold 12 in this embodiment, a metal such as stainless steel can be used, but is not particularly limited.

  In this embodiment, the pin member 2 is formed in a cylindrical shape. However, the shape of the pin member 2 may be other shapes such as a prismatic shape, and is not particularly limited.

  Moreover, as a material of the pin member 2, an aluminum alloy is used in this embodiment. However, as the material of the pin member 2, the pin member 2 can be composed of any one of aluminum, copper, magnesium, tungsten, and alloys thereof. It is also possible to configure the pin component 2 with a material other than these. The pin member 2 preferably has a higher thermal conductivity than that of the lower mold 12 (particularly a portion in contact with the pin member 2).

  The pin member 2 is inserted into an insertion hole 122 formed in the lower mold 12. One end side 21 of the pin member 2 is disposed inside the cavity 13. The other end 22 of the pin member 2 is substantially exposed to the outside of the lower mold 12 of the mold body 1. Here, “substantially exposed” is sufficient as long as the pin member 2 can be irradiated with laser light from the light source 3. For example, the other end 22 can be covered with a transparent film. .

  The light source 3 is configured to irradiate the other end 21 of the pin member 2 with a laser beam 31 for heating the pin member 2. Here, the wavelength band of the laser light is, for example, the infrared band, but is not particularly limited as long as the pin member 2 can be heated.

  The configuration of the injection mold in the present embodiment may be basically the same as that of the prior art except for the points described above, and thus detailed description thereof will be omitted.

(Injection molding method in the first embodiment)
Next, an injection molding method using the injection mold described above will be described with further reference to FIG.

  First, the other end side 22 of the pin member 2 is irradiated with laser light from the light source 3. Thereby, the other end side 22 of the pin member 2 is heated. Furthermore, since the heat applied to the other end side 22 of the pin member 2 is transmitted to the one end side 21, the one end side 21 can be heated.

  In this embodiment, since the pin member 2 is locally heated using a laser beam, there is an advantage that energy use efficiency is higher than when the heat medium is brought into contact with the pin member 2.

  Moreover, in this embodiment, since the thermal conductivity of the pin member 2 is higher than that of the mold body 1, the heat applied to the other end side 22 of the pin member 2 is efficiently transmitted to the one end side 21. Can be communicated to.

  After sufficiently heating the pin member 2, the molten resin is injected into the cavity 13 through the resin flow path 111 of the upper mold 11. The flow of the molten resin is indicated by reference numeral 100 in FIG. Then, the molten resin comes into contact with the pin member 2, is divided into a flow 101 and a flow 102, and merges again after passing through the pin member 2. Here, when the surface temperature of the pin member 2 is lower than the solidification temperature of the resin, there is a possibility that a weld line is formed in the molded resin.

  In this embodiment, since the pin member 2 can be heated sufficiently, there is an advantage that the possibility that a weld line is generated in the resin molded product can be reduced.

_Assuming that the temperature of the pin member 2 is T _pin , the temperature at which the resin is solidified is T ₀ , and the temperature of the _mold body 1 is T _mold , the relationship between them is preferably expressed by the following formula (1). .
T _mold <T ₀ <T _pin (1)

Here, T ₀ <T _pin is a suitable condition for preventing weld lines. However, if T ₀ ≈T _pin , the weld line can be prevented.

T _mold <T ₀ is a suitable condition for rapidly curing the resin. When T _{mold ≈T 0} is set, it takes a long time to cool the mold, resulting in a decrease in manufacturing efficiency and an increase in cost.

  In the present embodiment, since the pin member 2 can be locally heated by the laser light from the light source 3, there is an advantage that it is easy to achieve the relationship of the above-described formula (1).

  The molten resin filled in the cavity 13 is solidified by heat exchange with the mold body 1. After the resin is sufficiently cured, the upper mold 11 and the lower mold 12 can be separated and the resin molded product can be taken out. Moreover, the hardening time of resin can be shortened by cooling the metal mold body 1 as necessary.

  In the present embodiment, since the pin member 2 can be locally heated by the laser light from the light source 3, as described above, the temperature of the mold body 1 can be kept low. For this reason, the time required for cooling the mold main body 1 can be shortened. Furthermore, there is an advantage that the equipment for cooling the mold body 1 can be simplified and the cost of the equipment can be reduced.

  In the above-described embodiment, the laser light emitted from the light source 3 is transmitted to the free space and applied to the pin member 2. However, the present invention is not limited to this, and it is also possible to guide the laser light to the pin member 2 via a waveguide such as an optical fiber.

  In the above-described embodiment, a film for promoting the absorption of the laser beam can be formed on the other end side 22 of the pin member 2 (that is, the portion irradiated with the laser beam). If it does in this way, the pin member 2 can be heated efficiently.

  Since the injection molding method in the present embodiment can be the same as the conventional method in points other than those described above, further detailed description is omitted.

(Second Embodiment)
Next, an injection mold according to a second embodiment of the present invention will be described with reference to FIG. In the description of the second embodiment, the same reference numerals are used for constituent elements that are basically the same as those of the first embodiment described above, thereby simplifying the description.

  In the second embodiment, a gap 123 that separates the other end side 22 and the lower mold 12 of the mold body 1 is formed around the other end side 22 of the pin member 2.

  The mold according to the second embodiment further includes a heat transfer member 4. The heat transfer member 4 is configured to enable heat conduction between the other end side 22 of the pin member 2 and the lower mold 12 of the mold body 1 by filling the gap 123. Furthermore, the heat transfer member 4 can be attached to and detached from the gap 123. Specifically, the heat transfer member 4 is formed in a ring shape. Further, as the material of the heat transfer member 4, it is preferable to use a material having a high thermal conductivity, like the pin member 2. Further, the material of the heat transfer member 4 may be the same as or different from that of the pin member 2.

  In the mold according to the second embodiment, the contact area between the lower mold 12 of the mold body 1 and the pin member 2 can be reduced by providing the gap 123. Thereby, the amount of heat transferred from the pin member 2 to the mold body 1 can be reduced, and there is an advantage that the pin member 2 can be efficiently heated.

  Moreover, when cooling the metal mold | die of 2nd Embodiment, the heat-transfer member 4 can be filled into the space | gap part 123. FIG. Then, heat can be released from the pin member 2 to the mold body 1, and the time required for cooling the resin can be shortened.

  Other configurations and advantages of the second embodiment are the same as those of the first embodiment described above, and thus detailed description thereof is omitted.

(Third embodiment)
Next, an injection mold according to a third embodiment of the present invention will be described with reference to FIG. In the description of the third embodiment, the same reference numerals are used for constituent elements that are basically the same as those of the first embodiment described above, thereby simplifying the description.

  In the third embodiment, a tapered surface 221 is formed on the outer peripheral surface of the other end 22 of the pin member 2.

  Further, the lower mold 12 of the mold body 1 is formed with a contact surface 124 for contacting the tapered surface 221 and preventing the pin member from moving.

  Furthermore, a concave portion 222 for introducing laser light from the light source 3 into the pin member 2 is formed on the other end side 22 of the pin member 2.

  When the molten resin flows into the cavity 13, a pressing force from the molten resin is applied to the pin member 2. In the mold of this embodiment, since the taper surface 221 is formed on the pin member 2 and the contact surface 124 is formed on the mold body 1, the pin member 2 moves even when molten resin flows. The possibility can be reduced.

  Further, in the third embodiment, by forming the recess 222 on the other end side 22 of the pin member 2, heat generated by the laser light can be efficiently transmitted toward the one end side 21 of the pin member 2. For this reason, even when the surface area on the other end side 22 of the pin member 2 is small, the pin member 2 can be efficiently heated by laser irradiation. That is, when the taper surface 221 is provided on the pin member 2, the exposed area on the other end side 22 of the pin member 2 is reduced. Even in this case, there is an advantage that the pin member 2 can be efficiently heated by forming the recess 222.

  Other configurations and advantages of the third embodiment are the same as those of the first embodiment described above, and thus detailed description thereof is omitted.

  In addition, this invention is not limited to the said embodiment, Of course, a various change can be added in the range which does not deviate from the summary of this invention.

1 is a schematic cross-sectional view showing a configuration of an injection mold according to a first embodiment of the present invention. It is explanatory drawing for demonstrating the flow of the molten resin in a cavity, Comprising: It is a figure corresponded to the principal part expanded horizontal sectional view of FIG. It is a schematic sectional drawing which shows the structure of the injection die concerning 2nd Embodiment of this invention. It is a schematic sectional drawing which shows the structure of the injection die concerning 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold body 11 Upper mold 111 Resin flow path 12 Lower mold 121 Cavity surface 122 Insertion hole 123 Cavity part 124 Contact surface 13 Cavity 2 Pin member 21 One end side 22 Other end side 221 Tapered surface 222 Recessed part 3 Light source 31 Laser light 4 Heat transfer member

Claims (8)

It has a mold body, a pin member, and a light source.
A cavity for molding a resin is formed inside the mold body,
One end side of the pin member is disposed inside the cavity,
The other end side of the pin member is substantially exposed to the outside of the mold body,
The said light source becomes a structure which irradiates the laser beam for a heating to the other end side of the said pin member. The injection mold characterized by the above-mentioned. The injection mold according to claim 1, wherein the thermal conductivity of the pin member is substantially higher than that of the mold body that contacts the pin member. The injection mold according to claim 1 or 2, wherein a gap for separating the other end side from the mold body is formed around the other end side of the pin member. Furthermore, it has a heat transfer member,
The heat transfer member is configured to allow heat conduction between the other end side of the pin member and the mold body by being filled in the gap.
Furthermore, the heat-transfer member is detachable with respect to the said space | gap part. Injection mold of Claim 3 characterized by the above-mentioned. A tapered surface is formed on the outer peripheral surface on the other end side of the pin member,
The contact surface for contact | abutting to the said taper surface and preventing the movement of the said pin member is formed in the said mold main body. The any one of Claims 1-4 characterized by the above-mentioned. Injection mold. The recessed part for introducing the laser beam from the said light source into the inside of the said pin member is formed in the other end side of the said pin member. The any one of Claims 1-5 characterized by the above-mentioned. Mold for injection molding. The injection molding mold according to any one of claims 1 to 6, wherein the pin member is made of any one of aluminum, copper, magnesium, tungsten, and alloys thereof. An injection molding method using the mold according to any one of claims 1 to 7,
Irradiating the other end side of the pin member with laser light to heat the pin member;
Introducing molten resin into the cavity;
Removing the resin from the cavity after the resin is cured. An injection molding method comprising:

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