Metal mold for runnerless molding

Abstract

To provide a mold for runnerless molding capable of shortening a cycle time and capable of suppressing the occurrence of snotty-nosed, stringing and cold slug.SOLUTION: The mold for runnerless molding has a gate hole material heating means 1 which is arranged in one mold 3 so as to face a gate hole 53 provided in the other mold 2 to be opened and closed and heats a material in the gate hole 53 directly from the outside of the gate hole 53. The gate hole material heating means 1 may heat only the material in the gate hole 53 or may heat the nozzle 5 and the mold 2 around the gate hole 53.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mold for runnerless molding, and more particularly to a mold for temperature-controlled runnerless molding. [Background technology]

[0002] A temperature-controlled runnerless molding die opens and closes a gate hole by repeatedly melting and solidifying the solidified film inside the gate hole (this repetition of action is referred to as "opening and closing") by heating or cooling the material inside the gate hole in the die. Unlike pin-opening and closing types that open and close gate holes by inserting a pin into the runner through which the material flows, this type of temperature-controlled runnerless molding die not only ensures a sufficient flow path for the material within the runner, but also has the advantage of simplifying the die structure and making it easier to maintain by eliminating the need for pins, which are consumable items, and a drive mechanism to move the pins.

[0003] For example, in the technology described in Patent Document 1 by the applicant of the present application, an injection nozzle 1 is provided inside a mold, and a coil 14 for induction heating is wound around the outer periphery of this injection nozzle 1 up to the vicinity of the gate hole. With the mold of Patent Document 1, by switching the voltage applied to the coil 14 between high and low, the material in the runner and gate hole can be rapidly heated or cooled by induction heating, which has the advantage of shortening the cycle time in addition to the above advantages. On the other hand, the temperature-controlled type has problems such as stringiness and dripping due to insufficient cooling because the gate opening and closing is controlled by temperature control, and cold slugs are easily generated due to insufficient heating of the material and the low temperature of the mold around the gate opening.Cold slugs are a fatal defect, especially in the molding of small, precision molded products, which have seen an increase in demand in recent years. To solve this problem, the material in the runner and gate hole can be heated sufficiently to completely melt the material in the gate hole before injection, and then the material in the gate hole can be slowly cooled after injection is complete. However, if one tries to ensure sufficient time for heating and cooling, a new problem arises: the injection molding cycle time becomes longer, resulting in higher molding costs. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 58-39427 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0005] The present invention provides a temperature-controlled runnerless molding mold that can solve the problems of stringiness, dripping, and molding defects due to cold slugs all at once, and that can significantly reduce cycle time even more than the mold described in Patent Document 1. [Means for solving the problem]

[0006] After extensive research, the inventors of the present invention found that, in temperature-controlled runnerless molding dies, the material inside the gate hole is solidified by natural heat dissipation, preventing drooling and stringiness, but the longer it takes for natural heat dissipation, the slower the formation of the gate seal (solidified film) becomes, and the slower the molding cycle becomes. Furthermore, with previous technology, a large amount of heat is input to melt the small amount of material that forms the gate seal. This is because the material that forms the gate seal is indirectly heated by heating mold components such as the torpedo tip and the nozzle itself.

[0007] If the material that makes up the gate seal (solidified film) could be heated directly, the gate seal could be heated and melted in a short time with a small amount of heat, and the time required for cooling could be significantly reduced. In other words, if the material that makes up the gate seal could be heated and melted directly and with pinpoint precision, the above problem could be solved, and even if cold slug were to be generated, it could be melted along with the material. Then, when heating is stopped, the material inside the gate hole is rapidly cooled by the low-temperature mold surrounding the gate hole, which also prevents stringiness and dripping.

[0008] Based on the above findings, the present invention, as described in claim 1, is configured such that a runnerless molding die has a gate hole material heating means that is placed in one die that opens and closes the die opposite to the gate hole, and that directly heats the material of the gate hole from outside the gate hole. In the invention described in claim 2, the gate hole material heating means heats only the material of the gate hole.

[0009] Here, "only" includes cases where only the material of the gate hole is heated and melted by concentrating heating light such as laser light or infrared light, which is a means for heating the gate hole material, as well as cases where the diameter of the heating light is slightly larger than the diameter of the gate hole, and as a result most of the irradiated heating light is reflected by the shiny parts of the metallic nozzle or mold around the gate hole, resulting in only the material of the gate hole being heated and melted. As an example of the gate hole material heating means, as described in claim 3, there can be mentioned a means for irradiating laser light or infrared rays as heating light. By concentrating such heating light with a lens, it is possible to heat the material solidified in the gate hole directly and in a pinpoint manner. Note that the heating light such as laser light may be irradiated continuously or in an intermittent pulsed manner.

[0010] Furthermore, if the temperature of the mold around the gate hole is low, the material in contact with the inner periphery of the gate hole is difficult to melt. Materials that transmit a large amount of heating light, such as transparent / semitransparent materials, are also difficult to melt. In such cases, it is advisable to simultaneously heat not only the gate hole material but also the periphery of the gate hole in the mold partially using the gate hole material heating means, as described in claim 4. When using heating light such as laser light or infrared light, if the injection nozzle or mold is made of a glossy material such as metal, reflection of the heating light can be suppressed by partially coloring the periphery of the gate hole, as described in claim 5.

[0011] As described in claim 6, the gate hole material heating means for irradiating heating light such as laser light or infrared light can be configured to include a lens arranged opposite the gate hole, a heating light source that supplies the heating light to the lens via light guiding means, and gate material heating control means that controls the driving of the heating light source so that the heating light is irradiated onto the gate hole material through the lens.

[0012] In the present invention, the material of the gate hole may be heated only by the gate material heating means, but as described in claim 7, the material of the gate hole may be heated by a combination of heating by the gate material heating means and heating by another heating means that heats the material in the gate hole. An example of the other heating means is an induction heating coil as described in Patent Document 1. [Effects of the Invention]

[0013] The effects of the mold of the present invention are as follows. (i) By irradiating the solidified film with heating light such as laser light directly and pinpointly, the time required for melting the solidified film can be reduced, thereby shortening the cycle time. (ii) By irradiating the solidified film with heating light such as laser light directly and pinpointly, the cold slag contained in the solidified film can be melted together with the solidified film, thereby suppressing the occurrence of molding defects due to cold slag and enabling even small molded products to be molded with high precision and good yield in a short cycle time. (iii) During injection, the solidified film in the gate hole can be heated and melted with pinpoint precision, eliminating or reducing the need to heat and increase the temperature of the material in the runner using a separate heating method such as an induction heating coil. This allows the temperature of the mold around the gate hole to be kept low, and by rapidly cooling the material in the gate hole after injection and forming a solidified film in a short period of time, the timing for mold opening can be shortened while also suppressing defects such as stringiness and dripping. (iv) By combining irradiation of heating light such as laser light with heating and temperature increase of the material in the runner using induction heating coils, even fine molded products can be molded precisely with a high yield. BEST MODE FOR CARRYING OUT THE INVENTION

[0014] Hereinafter, preferred embodiments of the mold of the present invention will be described in detail with reference to the drawings. FIG. 1 is an enlarged cross-sectional view of the main parts of a runnerless molding die according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the tip of the injection nozzle according to another embodiment of the present invention. FIG. 3 is an enlarged cross-sectional view of the main parts to explain the operation of this embodiment. FIGS. 4 and 5 are graphs to explain the operation of this embodiment, showing the relationship between the temperature of the material at the gate hole and the timing of various commands.

[0015] [Configuration Description] As shown in FIG. 1 , the mold of this embodiment is provided with a manifold (not shown) and an injection nozzle (hereinafter, nozzle) 5 in a fixed mold 2, which is one of a pair of molds that open and close. A gate 52 of the nozzle 5, which injects molten material M such as resin, opens into a cavity 4 between the fixed mold 2 and the movable mold 3, which is the other mold. A nozzle runner 51, which is a hole through which the molten material M flows along an axis C, is formed inside the nozzle 5 and communicates with the gate 52. A gate hole 53 is formed at the boundary between the nozzle runner 51 and the gate 52, which separates the material M injected into the cavity 4. After injection is complete, the material M in the gate hole 53 cools and solidifies to form a solidified film Ma, sealing the material M maintained in a molten state within the nozzle runner 51 to prevent leakage.

[0016] Similar to the nozzle of Patent Document 1, an induction heating coil 54 is wound around the outer periphery of the nozzle 5 up to the vicinity of the gate hole 53, and by controlling the voltage applied to this induction heating coil 54, the nozzle 5 is constantly heated to a temperature at which the material M in the nozzle runner 51 is kept at a constant molten temperature while the mold is open, and the solidified state of the solidified film Ma in the gate hole 53 can be maintained. The induction heating coil 54 heats the nozzle 5 in a short time to a temperature at which the solidified film Ma melts during mold clamping, making it ready for injection. Reference symbol TS denotes a temperature sensor located near the gate hole 53, and a control unit (not shown) controls the magnitude of the voltage applied to the induction heating coil 54 based on the temperature detected by this temperature sensor TS. The above configuration is known from, for example, Patent Document 1.

[0017] In this embodiment, the gate hole material heating means is a laser irradiation device 1 that irradiates laser light. As shown in Figure 1, a laser irradiation device 1 is provided on the movable mold 3 side, and laser light is irradiated onto the solidified film Ma in the gate hole 53 from above the axis C of the nozzle 5. The solidified film Ma and cold slag can be heated and melted by a combination of heating the solidified film Ma with an induction heating coil 54 and irradiating it with laser light, or the solidified film Ma can be melted by irradiating it with laser light alone. In this case, the voltage applied to the induction heating coil 54 is set to a temperature that maintains the solidified film Ma when the mold is opened while keeping the material M in the nozzle runner 51 constantly molten.

[0018] The movable mold 3 has a hole 31 formed therein that penetrates from the cavity surface 4a to the other side, and an optical fiber 13 is inserted into this hole 31. A lens body 14a and a lens cover 14b are attached to one end of the optical fiber 13 on the cavity 4 side, and the surface of the lens cover 14b on the cavity surface 4a side is fixed to the cavity 4 so that it is flush with the cavity surface 4a.

[0019] The other end of the optical fiber 13 is connected to a laser light source 11. The intensity of the laser light emitted from the laser light source 11 and the ON / OFF timing of the irradiation are controlled by a control unit 12. The laser light may be emitted continuously or in the form of intermittent pulse irradiation. In this embodiment, the lens body 14a and the lens cover 14b constitute the lens 14 that converges the laser light toward the solidified film Ma. Various materials can be used for the lens body 14a and the lens cover 14b, but for example, since the melting temperature of the resin in resin injection molding is approximately 190°C to 320°C and the injection pressure is approximately 50 to 200 MPa, the lens body 14a and the lens cover 14b are formed from a material that can withstand these temperatures and pressures.

[0020] Examples of such materials include quartz (heat-resistant temperature of about 1200° C., pressure-resistant temperature of about 1130 MPa) and sapphire (heat-resistant temperature of about 2000° C., pressure-resistant temperature of about 2950 MPa). The lens 14a and the lens cover 14b may be made of the same material or different materials. In order to prevent the lens 14 from being pushed into the hole 31 by the pressure acting on the cavity surface 4a during injection molding, it is advisable to make the lens body 14a and the lens cover 14b slightly larger than the inner diameter of the hole 31, and to provide a step on the cavity surface 4a side of the hole 31 so that the outer edge of the lens body 14a engages with the step.

[0021] The irradiation diameter of the laser light irradiated onto the solidified film Ma can be set by changing the lens 14 to one with a different focal length. Basically, the irradiation diameter of the laser light should be the same as the diameter of the solidified film Ma. By doing so, the laser light can be irradiated only onto the material M (solidified film Ma) solidified in the gate hole 53. Since the temperature of the nozzle 5 near the gate hole 53 is low, even if the laser light is irradiated only onto the solidified film Ma, the heat is absorbed by the nozzle 5, and the material M does not melt easily at the contact point between the solidified film Ma and the inner surface of the gate hole 53, which may result in the generation of a small amount of cold slug. Furthermore, if the solidified film Ma is made of a transparent / semitransparent resin, much of the laser light, which is the heating light, may pass through the solidified film Ma, making it difficult to melt.

[0022] Therefore, in another embodiment shown in Figure 2, the irradiation diameter of the laser light is made slightly larger than the diameter of the solidified film Ma, so that not only the solidified film Ma but also the periphery of the gate hole 53 of the nozzle 5 is heated. If the nozzle 5 is made of a metal such as tool steel, its glossy surface will reflect much of the laser light, reducing the heating effect. Therefore, as shown in Figure 2, it is advisable to form a colored portion 55 around the periphery of the gate 52 in a color that suppresses reflection of the laser light. In this way, by also heating the periphery of the gate hole 53 by irradiating it with laser light, even if the solidified film Ma is transparent / semi-transparent or if heat is lost due to a low-temperature mold around the gate hole 53, the solidified film Ma can be heated and melted in a short time by heating the periphery of the gate hole 53.

[0023] [Explanation of action 1] The operation of the mold having the above configuration will be described with reference to FIGS. In the following description, a case will be described in which the solidified film Ma of the gate hole 53 is melted and ejected only by irradiating it with laser light. Figure 3 is a diagram explaining the operation of the mold having the above configuration, where (a) is a diagram explaining the initial state before injection (the state when the mold is opened), (b) is a diagram explaining the state when the mold is closed, and (c) is a diagram explaining the state at the time of injection. Figure 4 is a graph showing the relationship between the temperature of the material at the gate hole detected by the temperature sensor and each timing. 3(a), in the initial state before injection (when the mold is opened), material M in nozzle runner 51 of nozzle 5 is kept in a molten state by being maintained at a constant temperature (approximately temperature T2 in FIG. 4) by applying a constant voltage to induction heating coil 54. On the other hand, material M in gate hole 53, which is in contact with the outside air, solidifies into a film at temperature T1 and forms solidified film Ma, which prevents molten material M in nozzle runner 51 from leaking out of gate 52.

[0024] When a mold clamping start signal is output from a control device (not shown) of the injection molding machine (see FIG. 4), the movable mold 3 moves toward the fixed mold 2 and enters a mold clamping state. When a mold clamping completion signal is output by mold clamping, the control unit 12 (see FIG. 1) outputs an irradiation command signal for laser light L to the laser light source 11 of the laser irradiation device 1. As a result, the laser light L is irradiated onto the solidified film Ma. The laser light L may be irradiated only onto the solidified film Ma, or, as described in the other embodiments above, may also be irradiated onto the solidified film Ma and the periphery of the gate 52 of the nozzle 5.

[0025] When the temperature of the gate hole 53 reaches temperature T2 due to irradiation with the laser beam L, the solidified film Ma in the gate hole 53 melts. At this time, the cold slug contained in the material M also melts along with the solidified film Ma. This brings the gate into an open state, allowing the material M to be injected from the nozzle 2 into the cavity 4. When the temperature of the gate hole 53 reaches temperature T2, irradiation of the laser beam L is stopped, an injection command signal is output, and the molten material M is injected from the nozzle 5 into the cavity 4, as shown in FIG. 3(c). The subsequent cycle is the same as that of a known runnerless molding die.

[0026] [Experimental Example 1] The material injection experiment was carried out under the following conditions. I. Experimental Example Specific experiments of the present invention were carried out in a runnerless molding die under the injection conditions shown in Table 1 below.

[0027] [Table 1]

[0028] In this experiment, we measured the irradiation time and the extent to which the material inside the gate hole 53 was heated by laser light irradiation. In this experiment, a dummy nozzle was used to represent the nozzle 5, and the material inside the nozzle runner was not heated by an induction heating coil. Therefore, the temperature of the material solidified inside the gate hole of the dummy nozzle before laser light irradiation was 25°C, almost the same as room temperature. When laser light was irradiated onto the solidified material inside the gate hole, the temperature of the material rose to 300°C and melted within 0.2 seconds. The results of this experiment are shown in Table 2 below.

[0029] [Table 2]

[0030] This shows that the solidified material can be heated and melted from 25°C to 300°C in an extremely short time of less than 0.2 seconds by irradiating it with laser light alone. In an actual nozzle 5, the material in the nozzle runner 54 is maintained at about 180°C by induction heating using the induction heating coil 54, and the temperature of the solidified material (solidified film Ma) in the gate hole 53 is also about 90°C, so heating by about 50°C is sufficient to bring it up to the injection temperature of about 140°C. Therefore, in an actual nozzle 5, the solidified film Ma can be brought to an injection-ready state almost "simultaneously" with irradiation of the laser light. As will be explained in the comparative example below, conventional heating using induction heating coil 54 involves indirect heating of the material via nozzle 5, and therefore requires a long time (approximately 5 seconds) from the start of heating until the material is ready for injection. However, direct heating of the material by irradiating it with laser light, as in the present invention, allows the material to be heated and melted in an extremely short time, and it is clear that, in principle, heating of the material by induction heating coil 54 for injection is not necessary.

[0031] II Comparative Example As a comparative example, conventional injection molding was carried out using an existing runnerless molding die under the following conditions: The nozzle material, gate hole diameter, injection molding material, etc. were the same as in the above experimental example. The glass transition point of ABS resin, the material used in the experiment, is unclear, but it is fluid at temperatures above 140°C and can be injected. Therefore, to maintain the solidified film Ma, the temperature of the material in the nozzle runner 51 is set so that the temperature of the material in the gate hole 53 is lower than 140°C. In this experimental example, the temperature of the material in the nozzle runner 51 is adjusted to about 180°C so that the temperature of the material in the gate hole 53 is about 90°C. In order to raise the temperature of the material in the gate hole 53 to 140°C during injection, the temperature of the material in the nozzle runner 51 needs to be heated to about 220°C by induction heating, and it took about 5 seconds from the start of heating until injection was possible.

[0032] [Table 3]

[0033] In the runnerless molding die of the present invention, the temperature of the solidified film Ma reached 300°C with laser irradiation for a short time of less than 0.2 seconds, making it ready for injection. In this experiment, the induction heating coil 54 was not required to heat the material in the nozzle runner 51, thereby shortening the mold clamping and injection time by nearly 5 seconds. Furthermore, because the material in the nozzle runner 51 was maintained at a low temperature, the material in the gate hole 53 was quickly cooled, allowing the solidified film Ma to form at the gate hole 53 in a short time, thereby shortening the mold opening time. Furthermore, because the material was sufficiently cooled in a short time, no stringiness or dripping was observed. Even if rapid cooling promoted the formation of cold slag, the solidified film Ma and cold slag were almost completely melted by laser irradiation, so there was no effect on the injection-molded product.

[0034] [Another experimental example] In the above experimental example, black ABS was used as the material, but it is estimated that resins other than ABS or materials other than black would require 0.2 seconds or more under the same conditions. The table below shows Experimental Result 2, an example of another experiment using ivory LCP (liquid crystal polymer) as the material under the same conditions as the above example. In this example, the material temperature was able to be heated from 30°C, which is almost the same as room temperature, to 350°C within 0.5 seconds. This suggests that although the heating time may be slightly longer depending on the color and material, it is possible to essentially melt the solidified film Ma almost simultaneously with the irradiation of the laser light and make it ready for injection.

[0035] [Table 4]

[0036] [Explanation of action 2] Next, a case where the gate is opened and closed by the cooperation of the irradiation of the solidified film Ma with the laser light L and the heating of the solidified film Ma by the induction heating coil 54 will be described. In the explanation of the experimental results above, it was stated that in principle it is not necessary to heat and increase the temperature of the material in the nozzle runner 51 using the induction heating coil 54, but when the molded product is relatively large, it is thought that it becomes difficult to sufficiently heat and melt the material in the gate hole 53 using only the laser light irradiation. Therefore, in such cases, it is advisable to use a combination of laser light irradiation and heating and increasing the temperature of the material in the nozzle runner 51 using the induction heating coil 54 to increase the fluidity of the material. Hereinafter, another effect when laser light irradiation and heating / temperature increase of the material in the nozzle runner 51 by the induction heating coil 54 are used in combination will be described.

[0037] 5 is a timing chart for explaining this other action. When a mold clamping start signal is output from a control device (not shown) of the injection molding machine, the movable mold 3 moves toward the fixed mold 2 and enters a mold clamping state. When a mold clamping completion signal is output by mold clamping, a voltage is applied to the induction heating coil 54 (heating timing signal output), which causes the induction heating coil 54 to heat the nozzle 5 and increase its temperature, thereby raising the temperature of the molten material M and the solidified film Ma. In explaining this action 2, the laser light source 11 is driven at the same time as the voltage application, and laser light L is irradiated toward the gate hole 53 via the lens 14.

[0038] As a result, the heating and temperature increase of the material in the nozzle runner 51 by the induction heating coil 54 and the heating of the solidified film Ma by the irradiation of the laser light L work together to heat and increase the temperature of the solidified film Ma in the gate hole 53. When the temperature of the gate hole 53 rises to T2, the solidified film Ma melts. At this time, the cold slag contained in the material M melts along with the solidified film Ma. This opens the gate, allowing the material M to be injected from the nozzle 2 into the cavity 4. When the temperature of the gate hole 53 reaches temperature T2, the voltage application to the induction heating coil 54 is stopped, the laser beam irradiation is stopped, an injection command signal is output, and the material M is injected from the nozzle 5 into the cavity 4, as shown in FIG. 2(c). The subsequent cycle is the same as that of a known runnerless molding die.

[0039] In injection molding using the mold of the present invention, sagging and stringiness can be suppressed by rapidly cooling the material M in the gate hole 53 when the mold is opened, and even if cold slugs are generated, they can be melted by irradiating them with laser light. Furthermore, the cycle time of injection molding can be shortened by combining heating by the induction heating coil 54 and irradiation with laser light.

[0040] 4 and 5, the laser irradiation command signal is output simultaneously with the output of the mold clamping completion signal, but the laser irradiation command signal may be output immediately before the mold clamping completion signal is output. By doing so, the cycle time can be further shortened. The timing immediately before the mold clamping completion signal is output may be determined by, for example, measuring in advance the time from the output of the mold clamping start command signal to the output of the mold clamping completion signal (mold clamping time: for example, 2 seconds), setting a timer for a time shorter than the mold clamping time (for example, 1.8 seconds), and outputting the laser irradiation command signal. Alternatively, a sensor may be provided that measures the distance between the fixed mold and the movable mold, and when the distance between them during mold clamping movement becomes equal to or less than a certain value, the laser irradiation command signal may be output. Furthermore, the irradiation of heating light such as laser light may be at the same output from the start of irradiation until the material melts, but the output may vary in strength, and the irradiation may be intermittent pulse irradiation rather than continuous irradiation.

[0041] Although the preferred embodiments of the present invention have been described, the present invention is not limited to the above embodiments. For example, although a laser irradiation device has been cited as the heating means, other heating means such as an infrared irradiation device may be used as long as it can melt the solidified film Ma of the material M. Furthermore, the laser irradiation device is not limited to a semiconductor laser device and may be other laser irradiation devices. Furthermore, the nozzle heating means is generally an induction heating coil, but other heating means such as a heater may also be used as long as they can be used in temperature-controlled runnerless molding. Furthermore, by accommodating the optical fiber 13 in a metal tube and making the metal tube movable back and forth, the metal tube and the lens 14 can function as an ejector pin. Furthermore, the position of the lens is not limited to within the cavity, but may be in a runner portion that communicates with the cavity. In addition, in the above embodiment, one of the molds that opens and closes the mold is described as a fixed mold and the other mold is a movable mold, but the present invention also covers cases where one mold is a movable mold and the other mold is a fixed mold, or where both molds are movable molds. [Industrial Applicability]

[0042] The present invention is applicable not only to molds for resin injection molding, but also to those for injection molding of metals such as magnesium and glass, as long as the mold is a temperature-controlled runnerless molding mold. [Brief explanation of the drawings]

[0043] [Figure 1] FIG. 1 is an enlarged cross-sectional view of a main part according to a first embodiment of the present invention. [Figure 2] FIG. 10 is an enlarged cross-sectional view of a nozzle tip portion according to another embodiment of the present invention. [Figure 3] FIG. 2 is an enlarged cross-sectional view of a main part for explaining the operation of the present invention. [Figure 4] 10 is a graph illustrating the relationship between the temperature of the gate hole detected by the temperature sensor and each timing, for explaining the first effect of the present invention. [Figure 5] 10 is a graph illustrating the relationship between the temperature of the gate hole detected by the temperature sensor and each timing, for explaining the second effect of the present invention. [Explanation of symbols]

[0044] 1. Laser irradiation device (gate hole material heating means) 11 Laser light source 12 Control Unit 13 Optical Fiber 14 Lenses 15 Cover 2 Fixed mold 3 Movable mold 31 holes 4 cavities 4a Cavity surface 5 nozzles 51 Nozzle Runner Gate 52 53 Gate hole 54 Induction heating coil 55 Coloring section C Nozzle axis M Material Ma solidified membrane L Laser light (heating light) TS Temperature Sensor

Claims

1. In runnerless molding dies, a gate hole material heating means disposed in one mold opposite to a gate hole provided in the other mold during mold opening and closing, for directly heating the material of the gate hole from outside the gate hole; Runnerless molding mold characterized by:

2. 2. The die for runnerless molding according to claim 1, wherein the gate hole material heating means heats only the material of the gate hole.

3. A runnerless molding die as described in claim 2, characterized in that the gate hole material heating means irradiates laser light or infrared rays as heating light, and a lens focuses the laser light or infrared rays only onto the gate material.

4. 2. The mold for runnerless molding according to claim 1, wherein the gate hole material heating means heats the material of the gate hole and the mold around the gate hole.

5. A runnerless molding mold as described in claim 4, characterized in that the gate hole material heating means irradiates laser light or infrared light as heating light, and colors the periphery of the gate hole in the mold and irradiates the vicinity of the gate with the heating light to heat it.

6. The gate hole material heating means is a lens disposed opposite the gate hole, a heating light source that supplies the heating light to the lens via a light guide, and a gate material heating control means that controls the driving of the heating light source so that the heating light is irradiated onto the material of the gate hole through the lens; The mold for runnerless molding according to claim 3 or 5, characterized in that:

7. heating the material in the gate hole by a combination of heating by the gate material heating means and heating by a separate heating means for heating the material in the gate hole; The mold for runnerless molding according to any one of claims 1 to 5, characterized in that

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