JP2009241463A - Injection molding die and injection molding method - Google Patents

Abstract

In a resin molded product integrally having a first part and a second part made of different materials, a parting line between the first part and the second part is clarified.
A rough surface 31a is formed along a surface forming a boundary portion between a first portion and a second portion (front portion 3) of a first forming surface 31 for forming a first portion (upper surface portion 2). Is provided. The rough surface 31a is set so that the surface roughness is larger than that of the smooth surface 31b provided in a region away from the boundary portion from the rough surface 31a.
[Selection] Figure 2

Description

  The present invention relates to an injection mold of a resin molded product integrally having a plurality of parts made of different materials, and an injection molding method using this mold.

  For example, in a vehicle instrument panel 1 (hereinafter referred to as an instrument panel 1) as shown in FIG. 1, the upper surface portion 2 and the front portion 3 may be formed of different color materials from the viewpoint of design. Further, the upper surface portion 2 that is easily exposed to direct sunlight is formed of a material having excellent heat resistance, and the front portion 3 that is not easily exposed to direct sunlight is formed of a relatively low cost material, thereby reducing the material cost. is there. Such an instrument panel 1 is formed, for example, by separately forming the upper surface portion 2 and the front surface portion 3 or by painting a part after molding. In these cases, since a process of joining separately formed parts and a painting process are required, the manufacturing cost increases.

  In view of this point, for example, FIG. 10 of Patent Document 1 shows a method of integrally forming a first portion (over fender) and a second portion (protector) made of different materials. The method includes injecting material into a cavity to form a first portion, and after the first portion has solidified, contacting the second portion of the injection material with the first portion, Are integrally formed.

  However, in this method, there is a case where a gap is formed between the first portion and the mold due to molding shrinkage of the previously formed first portion. When the injection material of the second part enters such a gap, the boundary line (parting line) between the first part and the second part in the finished product becomes unclear and the appearance is deteriorated.

  Therefore, Patent Document 1 discloses a method of suppressing molding shrinkage of the first part by causing an extrusion pin provided on the mold to bite into the first part.

JP-A-7-124990

  However, as described above, if the extrusion pin is bitten into the first portion, an undercut may occur between the mold and the molded product, which may make it difficult to release the mold. In addition, when the extrusion pin is bitten into the first part in this way, the thickness of the first part is partially thinned or thickened. Unevenness may occur. In particular, in the case of a thin product such as an instrument panel of a car, there is a high possibility that such unevenness is generated, and there is a risk that the strength of the product is reduced or the appearance is deteriorated.

  Further, in the method of Patent Document 1 described above, molding shrinkage around the portion where the extrusion pin is disposed can be suppressed to some extent, but it is difficult to suppress molding shrinkage in the region between adjacent extrusion pins, and the part that is unclear in the parting line Is likely to occur. In particular, in the case of a product having a relatively long boundary line between the first part and the second part, such as an instrument panel of a car, it is extremely difficult to clarify the parting line over the entire length of the boundary line by the above method. It becomes difficult.

  An object of the present invention is to clarify a parting line between a first part and a second part in a resin molded product integrally having a first part and a second part made of different materials.

  In order to solve the above-mentioned problems, the present invention provides a mold for injection molding a resin molded article having a first part and a second part made of different materials, the first part for molding the first part. Having a molding surface and a second molding surface for molding the second portion, bringing the first portion and the second portion together by bringing the injection material of the second portion into contact with the solidified first portion In the injection mold to be molded, the surface roughness of the first molding surface in the region along the surface forming the boundary portion between the first portion and the second portion is larger than the region farther from the boundary portion than the region. A large rough surface is provided.

  “Different materials” refer to materials having different properties, for example, materials having different colors and types of materials (types of base resins and fillers or blending ratios). “Along the surface forming the boundary” is not limited to the state in contact with the surface forming the boundary, but may be separated from the boundary. “Surface roughness” refers to the average height roughness Rc defined in JIS B 0601: 2001.

  As described above, when a rough surface having a surface roughness larger than that of the other region is provided on the first molding surface, the fixing force between the molded product and the mold in a direction orthogonal to the molding surface varies depending on the location. That is, on the rough surface, since the injection material enters the minute concave portion formed on the surface, the fixing force between the molded product and the mold in the direction orthogonal to the molding surface becomes relatively strong. On the other hand, in a region having a relatively small surface roughness (hereinafter referred to as a smooth surface), the fixing force between the molded product and the mold in the direction orthogonal to the molding surface is relatively weak. Accordingly, when molding shrinkage occurs in the first part of the molded product, the part of the first part that is in contact with the rough surface is fixed to the mold, and the part that is in contact with the smooth surface is peeled off from the mold. As a whole, molding shrinks from a smooth surface to a rough surface. Therefore, if this rough surface is provided along the surface of the first molding surface along which the boundary portion between the first portion and the second portion is molded, the first portion can be molded and contracted toward the boundary portion. it can. As a result, the first portion and the mold can be fixed in the vicinity of the boundary line, so that a situation in which a gap is formed between the first portion and the mold in the vicinity of the boundary line can be prevented.

  For example, in the mold as described above, a partition portion that can be advanced and retracted is provided in the cavity, the partition portion is advanced to form a first cavity for forming the first portion, and the partition portion is retracted to form the second cavity. A second cavity can be formed for molding the portion. When the first part is formed by the end face (hereinafter referred to as the front end face) of the partition part in the advance direction, after the first part is solidified, the partition part is retracted to peel the front end face from the first part. There is a need to. At this time, if the strong force between the front end surface of the partition part and the first part in the advancing / retreating direction of the partition part is strong, the first part is pulled along with the retreat of the partition part, and the first part and the mold are A gap may be formed. Therefore, when the rough surface is provided on the front end surface of the partition portion, the releasability between the partition portion and the first portion in the advancing / retreating direction of the partition portion can be improved, and thus the above-described problems can be avoided.

  As described above, according to the present invention, since it is possible to prevent a gap from being formed between the first part and the mold, the injection material of the second part enters between the first part and the mold. In this case, the parting line between the first part and the second part can be made clear.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows an instrument panel 1 as an example of a resin molded product that can be formed by a molding die according to the present invention. The instrument panel 1 has an upper surface portion 2 as a first portion and a front portion 3 as a second portion, and the upper surface portion 2 and the front portion 3 are formed of different materials (for example, materials having different colors). . A parting line 10 between the upper surface portion 2 and the front surface portion 3 is provided linearly over the entire length in the width direction of the instrument panel 1. In the following description, the direction in which the parting line 10 of the instrument panel 1 extends is referred to as the width direction.

  The molding die of the instrument panel 1 shown in FIG. 2 includes a fixed mold 20, a movable mold 30, and a partition portion 40, and the cavity 50 is formed by clamping the fixed mold 20 and the movable mold 30. . The partition unit 40 includes a partition member 41 and a cylinder 42, and the partition member 41 can be advanced and retracted into the cavity 50 by expansion and contraction of the cylinder 42. The partition member 41 has a shape extending in the width direction (a direction perpendicular to the paper surface), and is disposed in a groove 33 formed over the entire length of the movable mold 30 in the width direction. When the cylinder 42 is extended, the partition member 41 is advanced into the cavity 50, and a part of the front end surface of the partition member 41 is brought into contact with the fixed mold 20, the cavity 50 is divided and the first cavity that molds the upper surface portion 2. 51 is formed (see FIG. 2). The molding surfaces of the fixed mold 20, the movable mold 30, and the partition member 41 facing the first cavity 51 are referred to as first molding surfaces 21, 31, 411, respectively. Specifically, the first molding surface 21 of the fixed mold 20 is used to mold the front surface of the upper surface portion 2 (the surface visible in FIG. 1), and the first molding surface 31 of the movable mold 30 and the partition member 41. In step S411, a surface on the back side of the upper surface portion 2 (a surface on the side not visible in FIG. 1) is formed. Among these, the 1st shaping | molding surface 411 of the partition member 41 becomes a surface which shape | molds the boundary part of the upper surface part 2 and the front part 3. FIG.

  When the cylinder 42 is retracted and the partition member 41 is retracted from the cavity 50, a second cavity 52 for forming the front portion 3 is formed (see FIG. 3). The molding surfaces of the fixed mold 20, the movable mold 30, and the partition member 41 that face the second cavity 52 are referred to as second molding surfaces 22, 32, and 412, respectively. Specifically, the surface on the front side of the front portion 3 is molded with the second molding surface 22 of the fixed die 20, and the surface on the back side of the front portion 3 with the second molding surfaces 32, 412 of the movable die 30 and the partition member 41. Is molded. The front end surface of the partition member 41 functions as the first molding surface 411 when the first cavity 51 shown in FIG. 2 is formed, and functions as the second molding surface 412 when the second cavity 52 shown in FIG. 3 is formed.

  Of the first molding surface of the mold, a rough surface is provided in a region along a surface that forms a boundary portion between the upper surface portion 2 and the front surface portion 3. In the present embodiment, as shown in FIGS. 2 and 3, a rough surface 31 a is formed on the first molding surface 31 of the movable mold 30 along the first molding surface 411 of the partition member 41. Specifically, as shown in FIG. 4, a rough surface 31 a is formed over the entire length in the width direction in a region along the edge P on the partition member 41 side of the first molding surface 31 of the movable mold 30. The rough surface 31a is formed by roughening the mold surface by, for example, corrosion processing, and the surface of the first molding surface 31 is more than the smooth surface 31b separated from the edge P than the rough surface 31a. The roughness is increased. 2 and 3, the unevenness of the rough surface 31a is exaggerated for easy understanding. Further, in FIG. 4, the rough surface 31 a is provided slightly apart from the edge P, but the present invention is not limited to this, and the rough surface 31 a may be provided in contact with the edge P.

  An injection molding method using the above mold will be described below. First, as shown in FIG. 2, the partition member 41 is advanced into the cavity 50 to form the first cavity 51. In this state, the material of the upper surface portion 2 is injected from the first gate 23 provided in the fixed mold 20. When the upper surface portion 2 is solidified, the partition member 41 is moved backward to form the second cavity 52 as shown in FIG. In this state, by injecting the material of the front portion 3 from the second gate 24 provided on the fixed mold 20 and bringing the injected material into contact with the solidified upper surface portion 2, the upper surface portion 2 and the front portion 3 are integrated. Molded. After the front portion 3 is solidified, the molded product is taken out from the mold, and the instrument panel 1 is completed.

  In the above process, when the material of the upper surface portion 2 injected into the first cavity 51 is solidified, molding shrinkage occurs in the upper surface portion 2. In particular, when the molded product is thin as in the present embodiment, molding shrinkage mainly occurs in a direction perpendicular to the molding surface (direction perpendicular to the thickness direction of the molded product). When the material of the upper surface portion 2 is injected into the first cavity 51, the injection material of the upper surface portion 2 enters the minute concave portion of the rough surface 31a of the movable mold 30. The material of the upper surface portion 2 that has entered the minute recess exhibits an anchor effect in a direction orthogonal to the first molding surface 31, that is, mainly in a direction in which molding shrinkage occurs, and restricts movement of the upper surface portion 2 due to molding shrinkage. Can do. On the other hand, in the smooth surface 31b, the anchor effect as described above is not exhibited, and the fixing force between the upper surface portion 2 and the mold in the direction orthogonal to the molding surface 31 is relatively weak. Therefore, molding shrinkage of the upper surface portion 2 occurs from the smooth surface 31b toward the rough surface 31a, and the material of the upper surface portion 2 flows toward the boundary portion side with the front surface portion 3. This prevents a situation in which a gap is formed between the upper surface portion 2 and the mold (first molding surface) in the vicinity of the boundary portion between the upper surface portion 2 and the front surface portion 3. The injection material of the front part 3 does not enter between the two, and the parting between the upper surface part 2 and the front part 3 can be made clear and the appearance of the product can be improved.

  In order to obtain such an effect, that is, in order to obtain a sufficient fixing force between the mold and the upper surface portion 2 in a direction perpendicular to the molding surface, the surface roughness of the rough surface 31a is, for example, in the range of 50 μm to 150 μm. Of these, it is desirable to set within the range of 80 μm to 120 μm, and more preferably within the range of 90 μm to 110 μm. Even if the surface roughness of the rough surface 31a is the same, the fixing force can be increased by increasing the area of the rough surface 31a. By the way, if the surface roughness of the rough surface 31a is too large with respect to the thickness, the unevenness of the rough surface 31a causes variations in the amount of molding shrinkage in the thickness direction of the upper surface portion 2, and the surface of the upper surface portion 2 is uneven. May occur. Therefore, it is desirable to set the surface roughness of the rough surface 31a as small as possible within a range in which molding shrinkage of the upper surface portion 2 in a direction orthogonal to the molding surface can be suppressed. For example, when the surface on the front side of the instrument panel 1 is a smooth surface, the surface roughness of the rough surface 31a is preferably suppressed to 10% or less of the wall thickness, and minute unevenness (so-called “texture”) is formed on the surface on the front side. When formed, the surface roughness of the rough surface 31a is preferably suppressed to 30% or less of the wall thickness.

  The shape of the rough surface 31a and the smooth surface 31b of the first molding surface 31 of the movable mold 30 is transferred to the instrument panel 1 thus formed. Specifically, in the surface on the back side of the upper surface portion 2, the roughness along the boundary portion (parting line 10) with the front part 3 is larger than the region farther from the parting line 10 than the region. A surface portion is formed (not shown). Thus, by providing the rough surface portion on the back side surface of the instrument panel 1, the width of the design design of the front side surface which becomes the design surface can be widened.

  The present invention is not limited to the above embodiment. Hereinafter, other embodiments of the present invention will be described. In the following description, portions having the same configuration and function as those of the above-described embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the above embodiment, the case where the rough surface 31a is formed only on the first molding surface 31 of the movable mold 30 is shown, but the present invention is not limited to this. For example, as shown in FIGS. 5 and 6, a rough surface 41 a may be provided on the tip surface of the partition member 41 in addition to the first molding surface 31 of the movable mold 30. Thus, by providing the rough surface 41a on the front end surface of the partition member 41 that forms the boundary portion between the upper surface portion 2 and the front surface portion 3, the upper surface portion 2 and the gold in the direction orthogonal to the molding surface at the boundary portion. Since the fixing force with the mold can be increased, it is possible to more reliably prevent a situation in which a gap is generated between the mold and the upper surface portion 2 due to molding shrinkage of the upper surface portion 2.

  Incidentally, after forming the upper surface portion 2 with the first molding surface 411 of the partition member 41 as shown in FIG. 5, when the partition member 41 is retracted from the cavity 50 as shown in FIG. The upper surface portion 2 is fixed, the upper surface portion 2 is pulled as the partition member 41 is retracted, and a gap may be formed between the upper surface portion 2 and the fixed mold 20. Since the rough surface 41a is formed on the front end surface of the partition member 41 as in the present embodiment, the releasability between the partition member 41 and the upper surface portion 2 in the advancing / retreating direction of the partition member 41 can be improved. Such problems can be avoided. Moreover, a rough surface part is formed in the boundary part with the front part 3 among the upper surface parts 2 by shape | molding the upper surface part 2 with the rough surface 41a of the partition member 41 as mentioned above (refer FIG. 6). When the material of the front surface portion 3 enters the minute concave portion of the rough surface portion, the bonding force between the upper surface portion 2 and the front surface portion 3 can be increased.

  In the above embodiment, the front surface portion 3 is injected after the upper surface portion 2 is solidified. However, the present invention is not limited to this, and as long as the injection material of the front surface portion 3 comes into contact after the upper surface portion 2 is solidified, the upper surface portion 2. And the material of the front part 3 may be injected simultaneously. For example, by appropriately setting the positions of the first gate 23 and the second gate 24, the melting point and the solidification speed of the injection material, the timing at which the solidified upper surface portion 2 and the injection material of the front portion 3 come into contact with each other is adjusted. be able to.

  Moreover, in said embodiment, although the case where the resin molded product consists of a 1st part (upper surface part 2) and a 2nd part (front part 3) is shown, it is not restricted to this, For example, three or more several It may be a molded product having a portion (not shown).

  Moreover, although the case where this invention is applied to the injection molding of the instrument panel of a vehicle is shown in said embodiment, it can apply not only to this but another injection molded product. In particular, the present invention can be suitably applied to an injection-molded product having a long parting line between the first part and the second part and a thin wall thickness, and can be applied to instrument panel injection molding as in the above embodiment. In addition, for example, the present invention can be applied to injection molding of a car bumper.

It is a perspective view which shows the instrument panel of a vehicle. It is sectional drawing which shows the injection mold which concerns on embodiment of this invention. It is sectional drawing which shows the injection mold which concerns on embodiment of this invention. It is a perspective view which shows the movable 1st molding surface. It is sectional drawing of the injection mold which concerns on other embodiment. It is sectional drawing of the injection mold which concerns on other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Instrument panel 2 Upper surface part 3 Front part 10 Parting line 20 Fixed type | mold 21 1st shaping | molding surface 22 2nd shaping | molding surface 23 1st gate 24 2nd gate 30 Movable type | mold 31 1st shaping | molding surface 31a Rough surface 31b Smooth surface 32 1st 2 molding surface 40 partition part 41 partition member 411 first molding surface 412 second molding surface 42 cylinder 50 cavity 51 first cavity 52 second cavity

Claims (3)

A mold for injection-molding a resin molded article having a first part and a second part made of different materials, and a first molding surface for molding the first part, and a mold for molding the second part In an injection mold having a second molding surface and integrally molding the first part and the second part by bringing the injection material of the second part into contact with the solidified first part,
Of the first molding surface, a rough surface having a larger surface roughness than the region separated from the boundary part is provided in a region along the surface forming the boundary part between the first part and the second part. An injection mold characterized by that.   A partition part which can be moved forwards and backwards is provided in the cavity, and a first cavity for forming the first part by forming the partition part is advanced, and a second cavity for forming the second part by retracting the partition part The injection mold according to claim 1, wherein the rough surface is provided on an end surface of the partition portion on the leading side in the advance direction. When injection molding a resin molded product having a first part and a second part made of different materials, after the material of the first part is solidified, the injection material of the second part is brought into contact with the first part, thereby An injection molding method for integrally molding a first part and a second part,
Of the first molding surface, a rough surface having a larger surface roughness than the region separated from the boundary part is provided in a region along the surface forming the boundary part between the first part and the second part. An injection molding method characterized by the above.

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