JP2012192605A - Injection molding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding method that can suppress decrease of designability and quality due to mixing of cold slug in a molded article even if the composition is not provided with a runner that includes a cold slug well.SOLUTION: In an injection molding method to perform on a base material 1, injection molding of a resin member 4 that integrally including an anchor part 44 for preventing dropout by astriding and engaging a through-hole 11 of the base material 1 by contacting the molds 2 and 3 to a plate like base material 1 on which a through-hole 11 is formed, by forming a cavity C limited with the base material 1 and the molds 2 and 3, and injecting the molten resin in the cavity C, injection of the molten resin is carried out through the anchor molding part C2 that forms the anchor part 44 among the cavity C and the injection pressure is set so that the tendency of dispersing rather than straight advancement may appear in the flowability of resin.

Description

  The present invention relates to an injection molding method for injection molding a resin member on a base material.

  Conventionally, a mold is brought into contact with a preformed base material (hereinafter simply referred to as a base material), a molten resin is injected into a cavity limited by a part of the base material and the mold, a clip, a rib, etc. There is known an injection molding method (hereinafter referred to as direct molding) in which a resin member is fixed to a base material while being molded. According to this direct molding, there is an advantage that a resin member having a desired shape can be freely molded at any location on the substrate without changing the mold for molding the substrate. It is also possible to integrally mold an anchor portion for preventing the resin member to be molded from falling off the base material. As the resin material of the resin member, a resin such as polypropylene that melts at about 220 degrees is used.

  Now, in general, in injection molding, a part of the resin melted at the time of the previous injection is once solidified in the injection nozzle, and this can be injected as a cold slug at the initial stage of the next injection and mixed into the molded product. There is a problem that various defects occur in the molded product. For example, the appearance of cold slugs as dirt on the surface can reduce the design of the molded product. In order to solve such problems, conventionally, a slug reservoir (cold slug well) is provided at the turning point of the runner that connects the injection port of the injection nozzle to the gate of the mold. Using the momentum, cold slugs were accumulated there and restrained from being brought into the mold. The technique described in Patent Document 1 below is an example.

JP 2009-208327 A

  However, in the case of direct molding in which the resin member is directly molded on the base material 100, generally, the injection nozzle 101 is directly applied to the gate 103 of the mold 102 as shown in FIG. That is, since it is the structure which does not provide a runner, the measure which provides a slug pool at the turning point of a runner like the past is impossible, and if cold slug generate | occur | produces, it will mix in a molded article reliably. Here, a case where the anchoring portion 104 for preventing dropout as shown in FIG. 3A is integrally formed with the resin member main body 105 by direct molding will be considered. Considering only the filling efficiency of the molten resin, it is preferable to inject the gate 103 as close to the center of the cavity C as possible as shown in FIG. However, since the temperature in the vicinity of the molding surface 106 of the mold 102 is low, the molten resin containing a large amount of cold slug that is initially injected is shown in the enlarged view of FIG. And adheres sequentially in the vicinity of the molding surface 106 shown surrounded by a two-dot chain line. For this reason, it is not preferable to set the gate 103 at a location that becomes the design surface of the resin member main body 105.

  Therefore, next, as shown in FIG. 4A, the gate 107 is set on the back side of the portion where the anchor portion 104 is formed with respect to the base material 100, and the molten resin containing a large amount of cold slug is passed through the through hole of the base material 100. It has been considered that the cavity C is accumulated in the portion C5 of the cavity C through 108 through which the anchor portion 104 is formed. However, when the gate 107 is set at this position, the injection pressure of the molten resin is directly applied not only to the mold 102 but also to the base material 100 during the injection molding. For this reason, the injection pressure has to be set lower than the injection molding in which the base material 100 is not damaged by the high-temperature molten resin. As shown by the arrow in the enlarged view of FIG. 4B, the fluidity of the molten resin under such a low injection pressure setting has a strong tendency to disperse radially rather than going straight in the direction of the through hole 108. appear. For this reason, the molten resin containing a large amount of cold slug injected at an early stage immediately disperses, and sequentially adheres to the vicinity of the molding surface 109 having a low temperature surrounded by a two-dot chain line in the figure. The problem that designability and quality deteriorate was confirmed. As a result, the portion C5 for forming the anchor portion 104 in the cavity C could not function as a slug reservoir.

  The present invention has been made in view of such points, and even when a runner having a cold slug well is not provided, it is possible to suppress deterioration in design and quality due to mixing of cold slug into a molded product. It is an object to provide a simple injection molding method.

In order to solve the above problems, an injection molding method according to the present invention is configured as follows. In the first aspect of the present invention, a die is brought into contact with a plate-like base material in which a through hole is formed, a limited cavity is formed between the base material and the die, and molten resin is injected into the cavity. An injection molding method for injection molding a resin member integrally provided with an anchor part for preventing dropout to be locked across the through hole of the substrate,
Injection of the molten resin is performed through an anchor molding portion that molds the anchor portion of the cavity, and the injection pressure is set so that a tendency to disperse rather than straight travel appears in the fluidity of the resin. And

  According to this configuration, the molten resin is injected into the anchor molding portion in the cavity and flows so as to be dispersed. Therefore, most of the cold slug injected into the cavity in the initial stage of injection does not pass through the through-hole and is accumulated in the anchor molding part in the cavity, so that the designability and quality of the molded resin member are deteriorated. Can be suppressed.

  A second invention of the present invention is the injection molding method according to the first invention, wherein the cavity has a slug reservoir for accumulating cold slugs, and the slug reservoir is opposite to the anchor molding portion with respect to the base material. On the side, it is on the axis of the through hole of the substrate and is limited by the mold so as to form a dead end in the direction away from the substrate.

  According to this configuration, even when the cold slug cannot be accumulated at the anchor forming portion in the cavity and passes through the through hole, it can be accumulated in the slug reservoir on the axis thereof. Accordingly, it is possible to further suppress the deterioration of the design and quality of the molded resin member.

Sectional drawing which shows the 1st form for implementing the injection molding method of this invention. Sectional drawing which shows the 2nd form for enforcing the injection molding method of this invention. Sectional drawing for demonstrating the conventional 1st injection molding method. Sectional drawing for demonstrating the conventional 2nd injection molding method.

  A first embodiment for carrying out the present invention will be described below with reference to FIG. In the present invention, a new resin member 4 (hereinafter simply referred to as “resin member 4”) is secondarily injection-molded with respect to a plate-shaped substrate 1 that is primarily molded as shown in FIG. The present invention relates to an injection molding method for fixing while fixing.

  First, the base material 1 will be described. The substrate 1 is made of resin and is molded by a normal injection molding method (not shown). A through hole 11 that is a part of the cavity C filled with the molten resin is formed in the base material 1 when the base material 1 is molded. The cross-sectional view of FIG. 1A is cut along a plane including the axis of the through hole 11. In the state shown in FIG. 1A, the upper and lower surfaces of the substrate 1 are referred to as an upper surface 12 and a lower surface 13, respectively. FIG. 1B is a partially enlarged view showing the vicinity of the through hole 11 in FIG. The peripheral part where the through-hole 11 opens in the upper surface 12 of the base material 1 is an anchor coupling surface 14 to which the anchor part 44 of the resin member 4 to be molded is coupled. A part of the edge 15 and the lower surface 13 of the base material 1 is a main body coupling surface to which a molded resin member main body 41 is coupled.

  Next, a part of an injection molding machine used for injection molding will be briefly described. As shown in FIG. 1A, an injection molding machine including an injection-side mold 2 and a receiving-side mold 3 is used. As shown in FIG. 1B, the injection-side mold 2 has a flat molding surface for molding a portion of the resin member main body 41 extending from the base material 1 to the left in the figure, and the resin member 4. Among them, an anchor forming surface 21 for forming the anchor portion 44 of the rivet 42 is formed. The anchor molding surface 21 is a concave surface that is recessed in a substantially hemispherical shape (the bottom surface is a flat surface) having a diameter of about 5 mm from the surface that contacts the upper surface 12 of the substrate 1. The receiving mold 3 is formed with a body molding surface 31 that is a surface for molding the resin member body 41.

  The injection-side mold 2 is formed with a gate 22 that opens to the plane portion of the anchor molding surface 21. An injection nozzle 23 for injecting molten resin is inserted into the injection mold 2. The injection nozzle 23 includes a needle valve 24 that directly opens and closes the gate 22 of the mold 2 on the injection side. The injection pressure of the molten resin is set lower than when the resin member is molded alone. Specifically, the base material 1 is set so as not to be damaged by being hit with a high-temperature molten resin, and to tend to disperse radially rather than to move straight to the fluidity of the injected molten resin. . The injection molding machine also includes mold clamping means such as a hydraulic cylinder (not shown) for driving the mold 2.

  Next, formation of the cavity C by mold clamping will be described. First, the substrate 1 is set on the receiving mold 3, and the receiving mold 3 comes into contact with the lower surface 13 of the substrate 1. Next, the mold 2 on the injection side is driven by the mold clamping means and comes into contact with the upper surface 12 of the substrate 1 and the mold 3 on the receiving side. At this time, the gate 22 of the mold 2 on the injection side is positioned on the axis of the through hole 11. Thus, the molds 2 and 3 on the injection side and the receiving side are clamped so as to sandwich the base material 1. By this clamping, a cavity C having a molded shape of the desired resin member 4 is formed by the base material 1, the injection mold 2 and the receiving mold 3. The cavity C is a portion for molding the main body molding portion C1 which is a portion for molding the plate-shaped resin member main body 41, the inside of the through hole 11 which is a portion for molding the shaft portion 43 of the rivet 42, and the anchor portion 44. It consists of a certain anchor forming part C2. The main body molding portion C1 is formed into a plate shape by the main body bonding surface of the substrate 1, the molding surface of the injection-side mold 2 (excluding the anchor molding surface 21), and the main body molding surface 31 of the receiving-side mold 3. It is a limited space. The anchor molding part C2 is a space limited by the anchor molding surface 21 of the mold 2 on the injection side and the anchor coupling surface 14 of the substrate 1. The anchor forming portion C2 has, as a part thereof, a main slug reservoir C3 that accumulates cold slugs. The main slug reservoir C3 forms a dead end in the direction away from the axis of the through hole 11.

  Next, filling of the molten resin will be described. Molten resin is injected into the cavity C formed as described above from the injection nozzle 23 through the gate 22 of the mold 2 on the injection side. In the initial stage of injection, a large amount of cold slug generated by solidifying in the injection nozzle 23 is injected. However, as described above, the injection pressure of the resin is low, and the tendency to disperse appears more than the tendency to go straight to the fluidity of the injected molten resin. For this reason, the molten resin containing a large amount of cold slag injected in the initial stage is dispersed as shown by the arrow in FIG. It flows in the C3 direction. Further, since the temperature of the mold is low, the fluidity of the resin is inferior in the vicinity of the anchor molding surface 21 surrounded by the two-dot chain line shown in FIG. 1B in the main slug reservoir C3. For this reason, the molten resin containing the cold slug adheres sequentially from this location and starts to solidify, and is reliably accumulated in the main slug reservoir C3. After all the main slug reservoir C3 is filled with the resin, the molten resin which does not contain the cold slug is injected and filled into the main body molding portion C1 through the through hole 11. FIG. 1A shows a state in which the cavity C is completely filled with the molten resin. In addition, in the enlarged view of FIG. 1 (B), the expression of the filled resin is omitted. When filling of the molten resin is completed and the injection pressure is weakened, the needle valve 24 closes the gate 22 to shut off the molten resin.

  Next, the molded product will be described. As described above, the resin filled in the cavity C is cooled, the mold is opened by the mold clamping device, and the molded product is taken out. The molded product includes a base material 1 and a resin member 4 newly formed on the base material 1. The resin member 4 includes a plate-shaped resin member main body 41 and a rivet 42 for preventing the resin member 4 from falling off. The resin member main body 41 is formed in such a shape as to extend the base material 1 to the left in the drawing from the portion joined to the lower surface 13 of the base material 1. The rivet 42 is formed in such a manner as to be locked from the resin member main body 41 in a state of straddling the through hole 11 of the base material 1, and the shaft portion 43 inside the through hole 11 and the upper surface 12 side from the base material 1. The anchor portion 44 protrudes into Since the resin member 4 including the rivet 42 is bonded to the bonding surface of the base material 1 due to the thermal action during molding, the locking of the rivet 42 only weakens this bonding and the resin member main body 41 falls off. It is for preventing. Since the cold slug injected at the time of molding is accumulated in the anchor portion 44 as described above, mixing into the resin member main body 41 is suppressed, and the design and quality are good. In addition, since the anchor portion 44 is provided at a place where the appearance quality is not important, there is no problem even if dirt due to cold slug or an irregular shape due to contact between the gate 22 and the needle valve 24 appears on the surface.

  The 1st form for implementing this invention is comprised as mentioned above. According to the configuration of the first embodiment, the injection of the molten resin is performed through the anchor molding portion C2 that molds the anchor portion 44 of the resin member 4 in the cavity C, and the injection pressure goes straight to the fluidity of the resin. It is set to show a tendency to be more dispersed. Therefore, since most of the cold slug injected into the cavity C in the initial stage of injection is accumulated in the anchor molding portion C2 in the cavity C before passing through the through hole 11, the design of the resin member to be molded Deterioration of quality and quality can be suppressed.

  Moreover, according to the structure of the 1st form, the gate 22 of the metal mold | die 2 of the injection | emission side is opening to the anchor molding part C2. Therefore, an irregular shape caused by the contact of the needle valve 24 of the injection nozzle 23 and the gate 22 of the mold 2 on the injection side occurs in the anchor portion 44, and the influence on the appearance of the molded resin member can be reduced.

  Next, a second embodiment for carrying out the present invention will be described with reference to FIG. In the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, the description thereof is omitted, and only different parts are described. As shown in FIG. 2 (A), a slug capturing surface 32 that is depressed in the same shape as the anchor molding portion C2 of the injection mold 2 is formed on the body molding surface 31 of the receiving mold 3. Yes. The slug capturing surface 32 forms a substantially hemispherical preliminary slug reservoir C4 for accumulating cold slugs that could not be accumulated in the main slug reservoir C3 of the mold 2 on the injection side. In addition, the “slug reservoir” described in the claims refers to the preliminary slug reservoir C4. The preliminary slug reservoir C4 is on the axis of the through hole 11 on the side opposite to the anchor forming portion C2 with respect to the substrate 1. Further, the preliminary slug reservoir C4 forms a dead end in the direction away from the base material 1. The cavity C formed by mold clamping includes a main body molding portion C1, the inside of the through hole 11, an anchor molding portion C2, and a preliminary slug reservoir C4.

  Most of the resin containing a large amount of cold slag injected at the beginning of the resin flows in the direction of the anchor molding surface 21 as described in the first embodiment, but a small amount passes through the through hole 11. It is impossible to completely prevent this. In addition, even when the number of cold slugs to be injected increases due to some cause, they cannot be accumulated in the main slug reservoir C3 of the mold 2 on the injection side and pass through the through holes 11. However, since the fluidity of the resin is set so that a dispersion tendency appears from the straight line, the molten resin exiting the through hole 11 toward the lower surface 13 is also dispersed as shown by an arrow in FIG. The ratio toward the slug pool C4 increases. Further, like the main slug reservoir C3 described in the first embodiment, as shown in FIG. 2B, the fluidity of the resin in the vicinity of the slug capturing surface 32 surrounded by the two-dot chain line is inferior. For this reason, the resin containing the cold slug sequentially adheres from this portion and starts to solidify, and is reliably accumulated in the preliminary slug reservoir C4. After all of the preliminary slug reservoir C4 is filled, the molten resin that hardly contains the cold slug is filled in the main body molding portion C1, which is the remaining cavity. FIG. 2A shows a state in which the cavity C is completely filled with resin. In addition, in the enlarged view of FIG. 2 (B), the expression of the filled resin is omitted.

  The resin member 4 molded in this manner includes a resin member main body 41 and a rivet 42 and a projection 45 formed by a depression of the slug capturing surface 32. The protruding portion 45 is formed to protrude from the resin member main body 41 in an opposite direction to the anchor portion 44 on an extension line passing through the through hole 11 from the anchor portion 44. Since the cold slug injected at the time of molding as described above is accumulated in the anchor portion 44 and the protrusion 45, mixing into the resin member main body 41 is suppressed, and the design and quality are good. Further, since the protrusion 45 is provided in a place where the appearance quality is not important, there is no problem even if dirt due to cold slug appears on the surface. Further, since the protrusion 45 has a small curved surface shape similar to the anchor portion 44, this dirt is not noticeable.

The 2nd form for implementing this invention is comprised as mentioned above. According to this configuration, the same effect as in the first embodiment can be obtained.
Further, according to this configuration, the cavity C has a preliminary slug reservoir C4 for accumulating cold slugs, and the preliminary slug reservoir C4 penetrates the base material 1 on the opposite side of the anchor molding portion C2. It is on the axis of the hole 11 and is limited by the receiving die 3 so as to form a dead end in the direction away from the base material 1. Therefore, even when the cold slug cannot be accumulated in the anchor molding portion C2 in the cavity C and passes through the through hole 11, it can be accumulated in the preliminary slug reservoir C4 on the axis, and the design of the resin member to be molded In addition, deterioration in quality can be further suppressed.

  The contents described above are merely examples of embodiments for carrying out the present invention, and do not mean that the present invention is limited to the above contents. First, in Embodiments 1 and 2 described above, the base material 1 is a plate-shaped resin material, and the resin member body 41 to be molded is also a plate-shaped material. However, the present invention is not limited to this. Moreover, in said Embodiment 1 and 2, the anchor shaping | molding surface 21 and the slug capture | acquisition surface 32 were hollow in the substantially hemispherical shape of about 5 mm in diameter. However, it is of course not limited to this, and depending on various conditions such as the dimensions and shape of the base member 1 and the resin member 4 to be molded, and the type of resin used, the anchor molding surface 21, the slug capturing surface 32, and the through hole 11 Each size, shape, and relative arrangement can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 Base material 11 Through-hole 12 Upper surface 13 Lower surface 14 Anchor coupling surface 15 Edge 2 Injection side mold 21 Anchor molding surface 22 Gate 23 Injection nozzle 24 Needle valve 3 Receiving side mold 31 Main body molding surface 32 Slug capture surface 4 Resin Member 41 Resin member main body 42 Rivet 43 Shaft portion 44 Anchor portion 45 Projection portion C Cavity C1 Main body molding portion C2 Anchor molding portion C3 Main slug reservoir C4 Preliminary slug reservoir

Claims (2)

The mold is brought into contact with the plate-like base material on which the through holes are formed, a limited cavity is formed between the base material and the mold, and the molten resin is injected into the cavity. It is an injection molding method in which a resin member integrally provided with an anchor part for preventing falling off that is locked over is injection molded on a base material,
Injection of the molten resin is performed through an anchor molding portion that molds the anchor portion of the cavity, and the injection pressure is set so that a tendency to disperse rather than straight travel appears in the fluidity of the resin. An injection molding method. 2. The injection molding method according to claim 1, wherein the cavity has a slug reservoir for accumulating cold slugs, and the slug reservoir is on the opposite side of the anchor molding portion with respect to the substrate, and the through hole of the substrate. An injection molding method characterized by being limited by a mold so as to form a dead end in a direction away from the base material.

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