JP2018114729A - Method for producing injection-molded article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an injection-molded article, capable of controlling the generation of gas remainder and improving an appearance quality of the injection-molded article.SOLUTION: This invention relates to a method for producing an injection-molded article which includes two or more board parts extending in parallel and a frame part for connecting them mutually, wherein the injection-molded article is formed by solidifying the resin after cavities inside a pair of molds separated by a parting line are filled with a molten resin; the cavity includes a board part cavity corresponding to the board part; when the cavity is filled with the resin, the resin flows toward the center of the board cavity from both sides thereof along a longitudinal direction of the board cavity. The board cavity is configured so asa to form a flow rate distribution of the resin in which, before the filling of the resin, a gas existing inside the board cavity is guided toward the parting line in connection with the filling of the resin.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an injection molded body.

  As shown in Patent Document 1, a lower grill of an automobile includes a configuration including a plurality of plate portions extending in parallel and a frame portion for connecting them together. Such a lower grill may be formed by injection molding.

  Injection molding is performed by solidifying a resin after filling a molten resin into a cavity of a split mold having a cavity having the same shape as a desired injection molded body. The cavity is provided with a plate cavity corresponding to the plate portion of the injection-molded body, and the resin is usually flowed from both ends of the plate cavity toward the center along the longitudinal direction of the plate cavity. The inside of the partial cavity is filled with resin.

JP, 2006-030522, A

  As resin fills the plate cavity, the gas in the plate cavity is usually discharged through the parting line of the split mold, but depending on how the resin flows, the gas is not properly discharged and the plate In some cases, gas is sandwiched by the resin from both ends of the part cavity and remains in the plate part cavity (gas residue is generated). Appearance defects such as generation of gas residue, deterioration of the resin due to compression and high temperature of the gas, and formation of traces of gas on the injection-molded body are likely to occur.

  This invention is made | formed in view of such a situation, and provides the manufacturing method of the injection molded body which can suppress the generation | occurrence | production of a gas residue and can improve the external appearance quality of an injection molded body.

  According to the present invention, there is provided a method of manufacturing an injection molded body comprising a plurality of plate portions extending in parallel and a frame portion for connecting them together, wherein the injection molded body is a pair of divisions divided by a parting line. The resin is formed by solidifying the resin after filling the cavity in the mold with molten resin, and the cavity includes a plate part cavity corresponding to the plate part, and the resin is filled when the resin is filled. Is flowed from both end sides of the plate portion cavity toward the center along the longitudinal direction of the plate portion cavity, and the plate portion cavity has a gas existing in the plate portion cavity before filling with the resin. Provided is a method of manufacturing an injection molded body configured to form a flow velocity distribution of the resin that is guided toward the parting line as the resin is filled. That.

  The present inventor has intensively studied the cause of the residual gas, and in the prior art, the thickness of the plate portion cavity is almost constant over the width direction (direction perpendicular to the longitudinal direction) of the plate portion cavity. Therefore, the flow rate of the resin is almost constant over the width direction of the plate portion cavity, and as a result, the resin in the plate portion cavity is prevented from being pushed out toward the parting line due to slight fluctuations in the molding conditions. It was discovered that there may be gas residue due to flow.

  Based on this knowledge, the plate portion cavity is formed so that the gas flow distribution in the plate portion cavity is guided toward the parting line as the resin is filled before the resin is filled. It is found that the gas in the plate portion cavity can be reliably guided toward the parting line, and the generation of the remaining gas can be suppressed thereby, and the present invention has been completed. It was.

Hereinafter, various embodiments of the present invention will be exemplified. The following embodiments can be combined with each other.
Preferably, the plate part cavity is provided with a pair of parting lines, and the plate part cavity is configured such that the flow rate of the resin increases as the distance from any one of the parting lines increases.
Preferably, the plate portion cavity has one side edge and another side edge which is the opposite side edge, and the parting line is provided at a position adjacent to the one side edge, and the plate portion cavity In the cross section perpendicular to the longitudinal direction of the plate portion cavity, the thickness on the other side edge side is larger than the thickness on the one side edge side.
Preferably, the cavity includes a frame portion cavity corresponding to the frame portion, and the frame portion cavity includes a pair of short side cavities and a pair of long side cavities, and the short side cavity and the long side cavities. Side frame cavities are connected to each other to form the frame part cavity, and both ends of the plate part cavity are connected to the short side cavity.
Preferably, columnar cavities are provided between the pair of short side cavities to connect the plurality of plate cavities, and both ends of the columnar cavities are coupled to the long side cavities.
Preferably, the frame cavity is provided with a groove over the entire circumference.
Preferably, the split mold includes a gate for allowing the resin to flow into the cavity, and the gate is provided in the same plane as the plate portion cavity.
Preferably, the cavity includes a frame cavity corresponding to the frame, and the gate is connected to the frame cavity.

It is a perspective view of the injection molded object 1 of one Embodiment of this invention. It is the perspective view which looked at the injection molded object 1 of FIG. 1 from another angle. 3A is a cross-sectional view taken along the line AA in FIG. 2, and FIG. 3B is an end view of the plate portion 2. It is a perspective view which shows the division molds 21 and 22 used for injection molding of the injection molding body 1. FIG. It is a perspective view which shows the shape of the cavity 11 comprised by the division molds 21 and 22. FIG. It is sectional drawing in the same cross section as FIG. 3A in the state which closed the division molds 21 and 22. FIG. 7A is an enlarged view of a region A in FIG. 6, and FIG. 7B is a perspective view of the plate portion cavity 12. 8A is a cross-sectional view passing through the center of the plate cavity 12 in the thickness direction, and FIG. 8B is an enlarged view of a region B in FIG. 8A. It is a perspective view of the plate part cavity 12 of a prior art.

  Hereinafter, embodiments of the present invention will be described. Various characteristic items shown in the following embodiments can be combined with each other. In addition, the invention is independently established for each feature.

1. Injection Molded Body As shown in FIGS. 1 to 3B, an injection molded body 1 according to an embodiment of the present invention is a lower grill of an automobile and is formed by injection molding. The injection-molded body 1 includes a plurality of plate portions 2 extending in parallel and a frame portion 3 that couples them together. The frame portion 3 has a rectangular shape with rounded corners, and includes a pair of short side portions 3a and a pair of long side portions 3b. The short side portion 3a and the long side portion 3b are connected to each other to form the frame portion 3. It is configured. Both ends of each plate portion 2 are connected to the short side portion 3a. Between the pair of short side portions 3a, a plurality of column portions 5 that connect the plurality of plate portions 2 are provided. Both ends of each column part 5 are connected to the long side part 3b. The plurality of plate portions 2 and the plurality of column portions 5 are arranged in a lattice shape. Therefore, the injection-molded body 1 of the present embodiment is configured such that a lattice constituted by a plurality of plate portions 2 and a plurality of column portions 5 is provided in the frame portion 3. The frame part 3 is provided with a groove 4 over the entire circumference.

  As shown in FIG. 3B, the plate portion 2 has one side edge 2f and the other side edge 2r which is the opposite side edge. The injection-molded body 1 is installed in an automobile such that the side edge 2f side is directed to the front side (design side) of the automobile. The plate portion 2 has a thickness Tf on the side edge 2f side larger than a thickness Tr on the other side edge 2r side. Tr / Tf is, for example, 0.2 to 0.95, and preferably 0.5 to 0.9. This value is specifically 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, for example, It may be within a range between any two of the exemplified numerical values. When the plate part 2 has such a shape, it becomes difficult to generate a gas residue when the injection molded body 1 is manufactured. Details will be described later.

  The width W of the plate part 2 is preferably larger than the thickness Tf, and the value of Tf / W is, for example, 0.05 to 0.5, preferably 0.1 to 0.3. Specifically, this value is, for example, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, and is within the range between any two of the numerical values exemplified here. It may be.

2. Method for Manufacturing Injection Molded Body The injection molded body 1 is manufactured by injection molding using a pair of split molds 21 and 22, as shown in FIG. The split molds 21 and 22 are provided with recesses 21a and 22a. As shown in FIG. 6, when the split molds 21 and 22 are closed, the cavity 11 is formed by the recesses 21a and 22a. The contact surfaces of the divided molds 21 and 22 become parting lines PL. The split mold 21 is provided with a gate 16 communicating with the recess 21a. The injection-molded body 1 is formed by filling a molten resin into the cavity 11 through the gate 16 and then solidifying the resin.

  As shown in FIG. 5, the cavity 11 has the same shape as the injection molded body 1. That is, the cavity 11 includes a plurality of plate portion cavities 12 that extend in parallel and a frame portion cavity 13 that connects them together. The plate portion cavity 12 and the frame portion cavity 13 correspond to the plate portion 2 and the frame portion 3, respectively.

  The frame cavity 13 has a rectangular shape with rounded corners, and includes a pair of short side cavities 13a and a pair of long side cavities 13b. The short side cavities 13a and the long side cavities 13b are connected to each other. A frame cavity 13 is formed. Both ends of each plate cavity 12 are connected to the short side cavity 13a. Between the pair of short side cavities 13a, a plurality of column part cavities 15 that connect the plurality of plate part cavities 12 are provided. Both ends of each columnar cavity 15 are connected to the long side cavity 13b. The plurality of plate portion cavities 12 and the plurality of column portion cavities 15 are arranged in a lattice shape. Therefore, the cavity 11 according to the present embodiment is configured by providing a lattice constituted by a plurality of plate part cavities 12 and a plurality of column part cavities 15 in the frame part cavity 13. The frame part 3 is provided with a groove 14 over the entire circumference. A gate 16 is communicated with the short side cavity 13a.

  As shown in FIG. 7A, the split mold 21 has a shape corresponding to the one side edge 12f and the upper surface 12t of the plate cavity 12, and the split mold 22 includes the other side edge 12r and the lower surface of the plate cavity 12. The plate cavity 12 is formed by combining the divided molds 21 and 22 with a shape corresponding to 12b. The upper surface 12t is parallel to the opening / closing direction S of the divided molds 21 and 22. The lower surface 12b is inclined so that the distance from the upper surface 12t increases as the distance from the other side edge 12r increases. As described above, since there is no reverse tapered portion in the plate portion cavity 12, it is easy to mold the injection molded body 1.

  In FIG. 7A to FIG. 7B, of the parting lines PL between the divided molds 21 and 22, the upper part and the lower part of the plate part cavity 12 are indicated as parting lines PL 1 and PL 2, respectively. The parting line PL1 is provided at a position adjacent to the other side edge 12r, and the parting line PL2 is provided at a position adjacent to the one side edge 12f. The parting lines PL1 and PL2 correspond to a pair of parting lines in the claims.

  As shown in FIG. 7A, the plate portion cavity 12 has a thickness Tf on the one side edge 12f side larger than a thickness Tr on the other side edge 12r side. Tr / Tf is, for example, 0.2 to 0.95, and preferably 0.5 to 0.9. This value is specifically 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 0.95, for example, It may be within a range between any two of the exemplified numerical values.

  The width W of the plate portion cavity 12 is preferably larger than the thickness Tf, and the value of Tf / W is, for example, 0.05 to 0.5, preferably 0.1 to 0.3. Specifically, this value is, for example, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, and is within the range between any two of the numerical values exemplified here. It may be.

  As shown in FIG. 7B, molten resin flows from the both end sides of the plate portion cavity 12 toward the center along the longitudinal direction of the plate portion cavity 12, thereby causing the plate portion cavity 12 to flow. Is filled with resin. When there is no resin in the plate portion cavity 12, the gas G is present in the plate portion cavity 12, and the gas G is discharged from the plate portion cavity 12 through the parting line PL as the resin is filled. is necessary.

  From one end side of the plate portion cavity 12, the resin R1 flows in the arrow X1 direction, and from the other end side of the plate portion cavity 12, the resin R2 flows in the arrow X2 direction. In the present embodiment, since the plate portion cavity 12 has a thickness Tf on the side edge 12f side larger than a thickness Tr on the other side edge 12r side, the resins R1 and R2 are made of the side edge 12f. The flow velocity on the side is larger than the flow velocity on the other side edge 12r side. For this reason, the front end surfaces f1 and f2 of the resins R1 and R2 are inclined from the plane perpendicular to the longitudinal direction of the plate portion cavity 12, as shown in FIG. 7B. For this reason, the front end surfaces f1 and f2 first contact at the contact point CP on the one side edge 12f side, and then the contact surfaces of the front end surfaces f1 and f2 from the one side edge 12f side toward the other side edge 12r side. spread.

  When the contact surfaces of the front end surfaces f1 and f2 spread, the gas G in the plate portion cavity 12 is guided to the other edge 12r side as indicated by an arrow Y. And since the parting line PL1 is provided in the position adjacent to the other side edge 12r, the gas G is discharged | emitted out of the board part cavity 12 through the parting line PL1. For this reason, according to this embodiment, since it is suppressed that gas remains in the board part cavity 12, it is suppressed that the quality change of a resin and the trace of gas are formed in the injection molded object 1, and external appearance quality. Will improve. Further, since the other side edge 12r is not on the design side, even if a resin alteration or gas trace is formed on the injection molded body 1, it is not noticeable.

  Further, when the entire front end surfaces f1 and f2 are in contact with each other at the same time, the trace of the contact surface (weld) is easily noticeable. Since it spreads toward the side, the weld is not noticeable.

  The angle α of the front end face f1 with respect to the longitudinal direction of the plate portion cavity 12 is preferably 45 to 85 degrees, and preferably 60 to 80 degrees. Specifically, the angle α is, for example, 45, 50, 55, 60, 65, 70, 75, 80, 85 degrees, and may be within a range between any two of the numerical values exemplified here. .

  As shown in the prior art of FIG. 9, when the thickness of the plate portion cavity 12 is substantially constant over the width direction of the plate portion cavity 12, the flow rate of the resin flowing through the plate portion cavity 12 is also substantially constant. In this case, if the flow velocity of the resin R1, R2 at both side edges 12f, 12r of the plate portion cavity 12 increases for some reason, the gas G is guided to the center in the width direction of the plate portion cavity 12, and is sandwiched between the resins R1, R2. And trapped. If it will be in such a state, resin will change in quality or a trace of gas will become easy to be formed in injection molding object 1, and appearance quality will fall. According to this embodiment, occurrence of such a problem is suppressed.

  As shown in FIGS. 8A to 8B, the gate 16 for pouring the resin into the plate portion cavity 12 is provided in the short side cavity 13 a of the frame portion cavity 13 in the same plane of each plate portion cavity 12. Yes. When the gate 16 is provided at such a position, the resin flowing in from the gate 16 is displaced only in the in-plane direction of the plate portion cavity 12 so as to go around the groove 14 as indicated by an arrow X in FIG. It is injected into the partial cavity 12. If the resin is displaced in the out-of-plane direction of the plate portion cavity 12, the loss of the injection pressure of the resin tends to increase, but in this embodiment, the resin is displaced only in the in-plane direction of the plate portion cavity 12 and the plate portion Since it is injected into the cavity 12, the loss of injection pressure is suppressed. For this reason, since a high pressure is applied to the resin also on the contact surfaces of the tip surfaces f1 and f2 of the resins R1 and R2, the weld is less noticeable.

  In the present embodiment, the gate 16 is provided at a position biased to the front side in the front-rear direction in the short side cavity 13a, but the position at which the gate 16 is provided is not particularly limited, and is a position biased toward the rear side in the front-rear direction. Alternatively, it may be provided at the center in the front-rear direction.

The present invention can also be implemented in the following modes.
In the above embodiment, due to the difference in the thickness of the plate portion cavity 12, the gas existing in the plate portion cavity 12 before the resin filling is guided toward the parting line PL1 along with the resin filling. Although the flow velocity distribution of the resin is formed, such a flow velocity distribution of the resin may be realized by another means. For example, a difference can be formed in the flow velocity of the resin by providing a difference in the temperatures of the divided molds 21 and 22 or providing a difference in the surface roughness of the inner surface of the plate cavity 12.
In the above embodiment, the gas is guided toward one of the pair of parting lines PL1 and PL2, but a resin that guides the gas toward both the pair of parting lines PL1 and PL2 is used. A flow velocity distribution may be formed. For example, by configuring the plate portion cavity 12 such that the flow rate of the resin near the center in the width direction of the plate portion cavity 12 is large and the flow rate of the resin decreases toward each of the parting lines PL1 and PL2. Can be realized.

1: Injection molded body 2: Plate part 2f: One side edge 2r: Other side edge 3: Frame part 3a: Short side part 3b: Long side part 4: Groove 5: Column part 11: Cavity 12: Plate part cavity 12t: Upper surface 12b: Lower surface 12f: One side edge 12r: Other side edge 13: Frame portion cavity 13a: Short side portion cavity 13b: Long side portion cavity 14: Groove 15: Column portion cavity 16: Gate 21: Split mold 21a: Recessed portion 22: Split mold 22a: Recessed portion CP: Contact point G: Gas PL: Parting line PL1: Parting line PL2: Parting line S: Opening / closing direction f1: Tip surface f2: Tip surface

Claims (8)

A method of manufacturing an injection-molded body comprising a plurality of plate portions extending in parallel and a frame portion for connecting them together,
The injection-molded body is formed by solidifying the resin after filling a molten resin into a cavity in a pair of split molds divided by a parting line,
The cavity includes a plate portion cavity corresponding to the plate portion,
When filling the resin, the resin is flowed from the both end sides of the plate portion cavity toward the center along the longitudinal direction of the plate portion cavity,
The plate cavity forms a flow velocity distribution of the resin such that a gas existing in the plate cavity is guided toward the parting line as the resin is filled before the resin is filled. A method for producing an injection-molded body, comprising: The plate cavity is provided with a pair of parting lines,
The method according to claim 1, wherein the plate portion cavity is configured such that the flow rate of the resin increases as the distance from any one of the parting lines increases. The plate portion cavity has one side edge and the other side edge that is the opposite side edge;
The parting line is provided at a position adjacent to the one side edge,
3. The method according to claim 1, wherein a thickness of the other side edge side of the plate part cavity is greater than a thickness of the one side edge side in a cross section perpendicular to the longitudinal direction of the plate part cavity. The cavity includes a frame cavity corresponding to the frame;
The frame cavity includes a pair of short side cavities and a pair of long side cavities, and the frame cavity is configured by connecting the short side cavities and the long side cavities to each other.
The method according to any one of claims 1 to 3, wherein both ends of the plate part cavity are connected to the short side cavity.   5. A column cavity that connects the plurality of plate cavities is provided between the pair of short side cavities, and both ends of the column cavity are connected to the long side cavities. The method described in 1.   The method according to claim 4 or 5, wherein the frame cavity is provided with a groove all around. The split mold includes a gate for allowing the resin to flow into the cavity,
The method according to claim 1, wherein the gate is provided in the same plane as the plate portion cavity. The cavity includes a frame cavity corresponding to the frame;
The method of claim 7, wherein the gate is coupled to the frame cavity.