JP2006007617A - Injection molding device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding device which can mass-produce a molded object of high shape precision free from inverted blister, residual stress and distortion by controlling the timing of starting an injection of a molten resin based on a mold temperature, and an injection molding method. <P>SOLUTION: This injection molding device comprises a temperature detection means 71 which detects temperatures near the cavity C of a mold, a control means 72 which outputs a signal when the mold temperature reaches a preset target temperature level based on the detection results of the temperature detection means 71 and an injection means 8 which begins injecting the molten resin into the cavity C based on a signal from the control means 72. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an injection molding apparatus for plastic products, and more particularly to an injection molding apparatus and an injection molding method suitable for manufacturing plastic products that require extremely high accuracy.

  Conventionally, when mass-producing plastic products by injection molding, mold closing process → molten resin injection filling process → mold and molded product cooling process → mold opening process → molded product release process → mold closing process → melting The cycle of resin injection and filling process is repeated.

Here, FIG. 5 is a graph showing the relationship between mold time and temperature in a general injection molding cycle. As shown in the figure, the mold temperature during one cycle is the lowest at the mold closing start t ₁ temperature T _MIN (° C.) at the start of molding, and then the molten resin is injected into the mold cavity. (T ₂ ), the temperature T _MAX (° C.) at the filling completion t ₃ becomes the highest. And after completion of filling, the molten resin is cooled and solidified by heat conduction to the cavity wall surface of the mold.

  In this way, injection molding of plastic products involves cooling and solidifying high-temperature molten resin by heat conduction to the cavity wall of the mold, so the temperature of the mold and molten resin during molding is the final molded product. It is closely related to the shape accuracy. For example, if the molten resin is rapidly cooled, distortion is left inside the molded product due to uneven cooling, resulting in birefringence, sink marks, or deformation. Since the cooling rate of the molten resin is determined by the temperature difference between the molten resin and the cavity wall surface, it is necessary to control the temperature of the molten resin and the mold with high accuracy. An injection molding apparatus or injection molding method has been proposed.

For example, in JP-A-6-254929, in order to prevent deformation of a molded product due to knockout at the time of mold release, a mold temperature is measured by a thermistor temperature sensor, and a cooling time required for the molded product based on the mold temperature. An injection molding machine has been proposed in which the mold is opened when the cooling time elapses. According to such a configuration, the molded product can be cooled to a heat deformation temperature or lower at the start of mold opening, and deformation of the molded product due to knockout can be prevented.
JP-A-6-254929

Here, FIG. 6 is an enlarged graph of the portion A in FIG. In the figure, after the mold opening start t ₄ , the parting surface of the mold is affected by the atmospheric temperature and gas flow, so that the mold opening state is 5 to 15 (° C.) between t ₄ and t ₁ . There is a variation of 1 to 10 (° C.) between t _{1 and} t ₂ , and the minimum cycle temperature T _MIN (° C.) varies within the range of L _{1 in} the figure. Linked to this, the temperature T ₂ (° C.) of the injection start t ₂ varies from 2 to 10 (° C.) (see L _{2 in the} figure), and eventually the maximum molding temperature T _MAX (° C.) is shown. The reality is that it varies in the middle L ₃ range.

In particular, after the mold opening start t ₄ , the outside air in contact with the parting surface of the mold is suddenly heated and expands, and an upward air flow is generated from below the mold. The uneven decrease in temperature has a great influence and cannot be ignored.

However, in the conventional injection molding machine described above, considering only the mold temperature T ₄ at the mold opening start t _4, the mold temperature T _MIN after mold opening _{(℃), T 2 (℃} ) and T _MAX ( (° C.) and the like. For this reason, the timing of the mold closing start t ₁ and the injection start t ₂ after the mold opening start t _{4 is} determined by simple time control. That is, after the mold opening start t ₄ is without considering any mold temperature, the time from the mold opening start t ₄ was measured by a counter, etc., mold closing after a predetermined time has elapsed started t ₁ or injection start t I only performed ₂ .

For this reason, in the above-described conventional injection molding machine, when the mold temperature becomes excessively high or low between the mold opening start t ₄ and the injection start t _2, it is not possible to cope with it at all. where the mold temperature should start of injection t ₂ when the target temperature O (° C.), there was no addition to the injection start t ₂ at this higher temperature P (° C.) or cold Q (° C.).

  In particular, when a high temperature molten resin is injected and filled into a mold that has become excessively low in temperature, the molten resin is rapidly cooled, and the amount of shrinkage of each part of the molded product differs due to such uneven cooling. In other words, molded products that require extremely high shape accuracy such as lenses, mirrors, and prisms have a problem in that desired shape accuracy cannot be obtained due to sinks, residual stress, and deformation.

  The present invention has been made in view of the above problems, and by controlling the injection start timing of the molten resin on the basis of the mold temperature, mass-produced molded products having high shape accuracy free from sink marks, residual stress, and deformation. An object of the present invention is to provide an injection molding apparatus and an injection molding method that can be used.

  In order to achieve the above object, the first injection molding apparatus of the present invention detects the temperature of a mold cavity closed or its vicinity in a cycle of injection molding of a plastic product, and the mold temperature is determined in advance. When the set target temperature is reached, the injection of molten resin into the cavity is started.

  Preferably, a temperature detection means for detecting the temperature of the mold cavity or the vicinity thereof, and a signal is output when the mold temperature reaches a preset target temperature based on the detection result of the temperature detection means And a control unit for starting the injection of the molten resin into the cavity based on a signal from the control unit.

  In order to achieve the above object, the second injection molding apparatus of the present invention detects the temperature of two or more cavities of a closed mold or the vicinity thereof in a cycle of injection molding a plastic product, When the mold temperature reaches a preset target temperature and the difference between the mold temperatures falls within a preset predetermined temperature difference, the injection of the molten resin into each cavity is started.

  Preferably, the temperature detection means for detecting the temperature of each cavity of the mold or the vicinity thereof, and each mold temperature becomes a preset target temperature based on the detection result of the temperature detection means, and each mold temperature Control means for outputting a signal when the difference between the two is within a predetermined temperature difference set in advance, and injection means for starting injection of molten resin into each cavity based on the signal from the control means The configuration.

  More preferably, in the first and second injection molding apparatuses, the control means outputs a signal when the mold temperature does not reach a preset target temperature based on a detection result of the temperature detection means. In addition, the temperature control means for adjusting the temperature of the mold is provided based on a signal from the control means.

  On the other hand, in order to achieve the above object, the first injection molding method of the present invention detects the temperature of the mold cavity closed or its vicinity in the cycle of injection molding of a plastic product, and the mold temperature When the temperature reaches a preset target temperature, injection of the molten resin into the cavity is started.

  In order to achieve the above object, the second injection molding method of the present invention detects the temperature of two or more cavities of a closed mold or the vicinity thereof in a cycle of injection molding a plastic product, When the mold temperature reaches a preset target temperature and the difference between the mold temperatures falls within a preset predetermined temperature difference, the injection of the molten resin into each cavity is started.

  According to the injection molding apparatus or the injection molding method of the present invention, since the injection start timing of the molten resin is controlled based on the mold temperature when the mold is closed, the mold always has the target temperature or the target temperature range. The molten resin can be injected when inside. This makes it possible to correct the mold temperature that has become excessively high or low due to mold opening, preventing sudden cooling of the molten resin, etc., and producing molded products with high shape accuracy without sinks, residual stresses, and deformation. Mass production is possible.

  In addition, when the mold has two or more cavities, if the temperature of each cavity or its vicinity is detected and the mold temperature is within a predetermined temperature difference, the injection start condition is The shape accuracy of all molded products formed by two or more cavities can be increased, and the product yield and productivity can be improved.

  Hereinafter, an injection molding apparatus and an injection molding method according to an embodiment of the present invention will be described with reference to the drawings. First, an injection molding apparatus and an injection molding method according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a partial sectional side view showing an injection molding apparatus according to the first embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes an injection molding apparatus according to this embodiment, which performs injection molding of a concave meniscus lens that is an optical element. The injection molding apparatus 1 includes a movable side platen 2 and a fixed side platen 3 that face each other in the horizontal direction. A movable side mold 4 is fixed to the movable side platen 2, and the fixed side platen 3. The fixed side mold 5 is fixed to.

  The movable mold 4 includes, in order from the movable platen 2 side, a movable mounting plate 41, a spacer block 42 fixed to the plate surface of the movable mounting plate 41, and a nested protrusion housed in the spacer block 42. Means 43, a movable side receiving plate 44 fixed to the plate surface of the spacer block 42, and a movable side mold plate 45 fixed to the plate surface of the movable side receiving plate 44.

  An insert 46 having a convex molding surface is incorporated in the center of the movable side mold plate 45 so as to be able to advance and retreat in the horizontal direction. The insert 46 is directed toward the fixed mold 5 by the insert projecting means 43. And projecting. The nest projection means 43 includes a pair of projecting plates 43 a and 43 b slidably provided in the internal space of the spacer block 42, and the movable receiving plate 44 extends from the pair of projecting plates 43 a and 43 b to the nest 46. During sliding of a pair of projecting plates 43a and 43b, a telescoping projection pin 43c that contacts, a projecting rod 43d that penetrates the movable platen 2 and the movable mounting plate 41 and contacts one projecting plate 43b, and a pair of projecting plates 43a and 43b The guide pin 43e that prevents rattling is provided.

  On the other hand, the fixed-side mold 5 includes, in order from the fixed-side platen 3 side, a fixed-side mounting plate 51, a fixed-side receiving plate 52 fixed to the plate surface of the fixed-side mounting plate 51, and the fixed-side receiving plate 52. It has a fixed side mold plate 53 fixed to the plate surface. An insert 54 having a concave molding surface is incorporated in the center of the fixed-side mold plate 53, and the movable-side platen 2 is driven forward to abut the movable-side mold plate 45 against the fixed-side mold plate 53. As a result, a cavity C for forming a molded product is formed between both the inserts 46 and 54.

  The movable mold plate 45 and the fixed mold plate 53 are respectively provided with heating / cooling water channels 45a, 53a, and the heating / cooling water channels 45a, 53a are temperature control means capable of switching supply of hot water or cold water. 6 is connected. The temperature in the mold or cavity C can be adjusted by circulating hot water or cold water supplied by the temperature control means 6 in the heating and cooling water channels 45a and 53a.

  Here, in this embodiment, the temperature in the vicinity of the cavity C when the movable side mold 4 and the fixed side mold 5 are closed is measured by the temperature measuring instrument 7, and the mold temperature is a preset target temperature. Then, the injection of the molten resin into the cavity C is started.

  The temperature measuring instrument 7 has a temperature detecting means 71, a control means 72 and a display means 73. The temperature detecting means 71 detects the temperature in the vicinity of the molding surface of the movable die 4 by means of a temperature sensor (thermocouple) 71a embedded in the vicinity of the molding surface of the movable member 4 in the movable portion 4. Is amplified and then A / D converted and output to the control means 72.

  The control means 72 outputs the detection result of the temperature detection means 71 to the display means 73, and the display means 73 displays the current mold temperature by a liquid crystal digital display or the like. Further, the control means 72 determines whether or not the mold temperature detected by the temperature detection means 71 is a preset target temperature, and outputs an operation signal when the mold temperature reaches the target temperature. (The specific contents are not shown). The target temperature set in the control means 72 is determined in consideration of ensuring the shape accuracy of the molded product. For example, when extremely high shape accuracy is required, one temperature is set to some extent. If sufficient shape accuracy can be ensured even within this temperature range, a certain range of temperature is set.

  The injection means 8 that has received the operation signal from the control means 72 starts injection of the molten resin into the cavity C via the runner portion 81 and the gate portion 82 based on the preset filling pressure and pressurization time.

  The temperature sensor 71a described above may be embedded not only in the vicinity of the molding surface of the insert 46 but also in the vicinity of the molding surface of the movable side mold plate 45 (see the chain line portion in FIG. 1). Moreover, as long as the shape accuracy of the molded product is not affected, the temperature in the cavity C may be directly detected.

Next, an injection molding method according to this embodiment will be described with reference to FIGS. FIG. 2 is a graph showing the relationship between the mold time and temperature in the injection molding cycle of the injection molding apparatus. As shown in FIG. 2, one cycle of injection molding (see FIG. 5) is completed, and the mold temperature T _MIN (° C.) at the time of the mold closing start t ₁ is excessively, for example, L _{1 in} the figure. In the case of lowering, after the movable side mold 4 and the fixed side mold 5 shown in FIG. 1 are closed, the temperature near the cavity C is detected by the temperature detecting means 71, and the temperature O ′ near the cavity C is set in advance. not initiate injection of the molten resin until a target temperature O was (see t ₂ in FIG. 2). Thereafter, when the temperature O ′ of the cavity C rises to the target temperature O by the temperature control means 6, the control means 72 outputs an operation signal to the injection means 8, and the cavity is passed through the runner portion 81 and the gate portion 82. Injection of molten resin is started in C (see t ₂ ′ in FIG. 2). Thus, no variations occur in the start of injection temperature, such as L ₂ in FIG. 6, always cavity C can perform injection filling of molten resin when it becomes the optimum temperature.

  According to the injection molding apparatus and the injection molding method of this embodiment, since the injection start timing of the molten resin is controlled based on the temperature near the cavity C when the mold is closed, the cavity C is always When the target temperature is reached, the molten resin can be injected and filled. This makes it possible to correct the temperature of the cavity C that has become excessively high or low due to mold opening, and prevents rapid cooling of the molten resin, and has high shape accuracy without sinks, residual stresses, and deformation. It becomes possible to mass-produce molded products.

  Next, an injection molding apparatus and an injection molding method according to the second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a partial sectional side view showing an injection molding apparatus according to the second embodiment of the present invention. In addition, in this embodiment, about the location similar to 1st embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the figure, the injection molding apparatus 1 of the present embodiment simultaneously molds two biconvex lenses. The movable side mold plate 45 has nests 46A and 46B, and the fixed side mold plate 53 has a nest 54A. , 54B are incorporated. These inserts 46A, 46B and 54A, 54B form two cavities C1, C2 when the movable side mold 4 and the fixed side mold 5 are closed.

  Here, temperature sensors 71a and 71b are embedded in the inserts 46A and 46B of the movable side mold plate 45, respectively, and the temperature in the vicinity of the cavities C1 and C2 is detected by the temperature detecting means 71, and the temperature of each mold is detected. Becomes a preset target temperature, and when the difference between the mold temperatures falls within the range of the preset predetermined temperature difference, the control means 72 outputs an operation signal to melt into the cavities C1 and C2. Resin injection is started.

  As a range of the predetermined temperature difference between the cavities C1 and C2, there is a temperature difference of about 0 to 2 ° C. for the lens as in the present embodiment and about 0 to 4 ° C. for the prism (including a case where there is no temperature difference). However, it is possible to sufficiently ensure the shape accuracy of the molded products that are simultaneously molded.

  According to the injection molding apparatus and the injection molding method of this embodiment, when the mold has two or more cavities C1 and C2, the temperatures near the cavities C1 and C2 are detected, and the mold temperatures are Since the conditions for starting injection are within a predetermined temperature difference from each other, the shape accuracy of all molded products molded by the cavities C1 and C2 can be increased, and the product yield and productivity can be improved. be able to.

  Next, an injection molding apparatus and an injection molding method according to a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a partial sectional side view showing an injection molding apparatus according to the third embodiment of the present invention. In addition, in this embodiment, about the location similar to 1st and 2nd embodiment mentioned above, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  In the figure, in the injection molding apparatus 1 according to the present embodiment, in addition to the configuration of the second embodiment described above, the control means 72 of the temperature measuring device 7 determines the mold temperature based on the detection result of the temperature detection means 71. When the temperature is not the preset target temperature, an operation signal is output to the temperature adjustment means 6, and the temperature adjustment means 6 determines the temperature of the movable side mold plate 45 and the fixed side mold plate 53 based on the operation signal from the control means 72. Adjustments are made. Specifically, the temperature adjustment means 6 performs switching between hot water and cold water based on an operation signal from the control means 72, and this is applied to each heating / cooling water channel 45 a of the movable side mold plate 45 and the fixed side mold plate 53. 53a to adjust the temperature of the movable side mold plate 45 and the fixed side mold plate 53 or the cavities C1 and C2.

  According to the injection molding apparatus and the injection molding method of this embodiment, the cavities C1 and C2 can be actively heated or cooled, and the time until the cavities C1 and C2 reach the target temperature. As a result, the injection molding cycle can be shortened.

It is a partial section side view showing the injection molding device concerning a first embodiment of the present invention. It is a graph which shows the relationship between the time and temperature of the metal mold | die in the injection molding cycle of the said injection molding apparatus. It is a partial cross section side view which shows the injection molding apparatus which concerns on 2nd embodiment of this invention. It is a fragmentary sectional side view which shows the injection molding apparatus which concerns on 3rd embodiment of this invention. It is a graph which shows the relationship between the time and temperature of a metal mold | die in a general injection molding cycle. It is the graph which expanded the A section in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Injection molding apparatus 2 Movable side platen 3 Fixed side platen 4 Movable side metal mold 41 Movable side mounting plate 42 Spacer block 43 Entry protrusion means 43a, 43b Protrusion plate 43c Entry protrusion pin 43d Protrusion rod 43e Guide pin 44 Movable side receptacle Plate 45 Movable side plate 45a Heating / cooling channel 46, 46A, 46B Nest 5 Fixed mold 51 Fixed plate mounting plate 52 Fixed side receiving plate 53 Fixed side plate 53a Heating / cooling channel 54, 54A, 54B Nest 6 Temperature Adjustment means 7 Temperature measuring instrument 71 Temperature detection means 71a, 71b Temperature sensor (thermocouple)
72 Control means 73 Display means 8 Injection means 81 Runner part 82 Gate part C, C1, C2 Cavity

Claims (7)

  In the cycle of injection molding of plastic products, the temperature of the mold cavity closed or in the vicinity thereof is detected, and when the mold temperature reaches a preset target temperature, the molten resin is injected into the cavity. An injection molding apparatus characterized by starting.   Temperature detection means for detecting the temperature of the mold cavity or the vicinity thereof, and control means for outputting a signal when the mold temperature reaches a preset target temperature based on the detection result of the temperature detection means 2. An injection molding apparatus according to claim 1, further comprising: injection means for starting injection of molten resin into the cavity based on a signal from the control means.   In the cycle of injection molding of plastic products, the temperature of two or more cavities of the closed mold or its vicinity is detected, each mold temperature becomes a preset target temperature, and the difference between each mold temperature is preset An injection molding apparatus characterized by starting injection of molten resin into each cavity when the difference is within the predetermined temperature difference.   Temperature detecting means for detecting the temperature of each cavity in the mold or the vicinity thereof, and based on the detection result of the temperature detecting means, each mold temperature becomes a preset target temperature, and the difference between the mold temperatures is A control unit that outputs a signal when a predetermined temperature difference is set in advance is provided, and an injection unit that starts injection of molten resin into each cavity based on the signal from the control unit. The injection molding apparatus according to claim 3.   The control means outputs a signal based on the detection result of the temperature detection means when the mold temperature does not reach a preset target temperature, and based on the signal from the control means, the mold The injection molding apparatus according to claim 2 or 4, further comprising a temperature adjusting means for adjusting the temperature of the temperature.   In the cycle of injection molding of plastic products, the temperature of the mold cavity closed or in the vicinity thereof is detected, and when the mold temperature reaches a preset target temperature, the molten resin is injected into the cavity. An injection molding method characterized by starting. In the cycle of injection molding of plastic products, the temperature of two or more cavities of the closed mold or its vicinity is detected, each mold temperature becomes a preset target temperature, and the difference between each mold temperature is preset An injection molding method characterized by starting injection of molten resin into each cavity when the difference is within the predetermined temperature difference.

Images