JP3745204B2 - Injection molding method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an injection molding method performed using an injection mold provided with a plurality of gates, and in particular, molten resin injected and injected from a preceding gate into a cavity flows into a subsequent gate to generate an air pool. It relates to measures to avoid this.
[0002]
[Prior art]
For example, as described in JP-A-11-58478, a plurality of gates are provided when injection molding a relatively thin and large resin molded product such as a resin bumper of an automobile. It is known that the injection molding order of the molten resin is determined in advance for each gate, and the molten resin is injected and injected from each gate into the cavity according to the order. .
[0003]
Then, after the flow of molten resin injected and injected from the preceding gate into the cavity reaches the rear gate, the gate valve corresponding to the subsequent gate is opened, and the cavity is opened from the gate via the sprue portion. The molten resin is injected and injected.
[0004]
At this time, when the molten resin injected and injected from the previous gate flows into the rear gate, the air in the rear gate passes through the parting line (mating surface) of the injection mold. Accordingly, it is assumed that air is not entrained when the molten resin is injected and injected from the downstream gate.
[0005]
[Problems to be solved by the invention]
However, in the conventional case, as shown in FIG. 4, the outlet of the sprue part b is blocked by the molten resin J injected and injected from the preceding gate and flowing into the succeeding gate a. The air K may be trapped in the portion b. For this reason, when the molten resin J is injected and injected from the succeeding gate a to the cavity d by opening the gate valve c, as shown in FIG. The air K in the portion b is mixed into the molten resin J and enters the cavity d. As a result, not only the strength of the molded product is lowered, but also the surface of the molded product is “blown” and “skin rough”. This causes a problem that the appearance is also reduced.
[0006]
The present invention has been made in view of such a point, and the main purpose thereof is to use an injection mold having a plurality of gates, and inject and inject molten resin into the cavities from the prior gates, and the flow front is In the injection molding method in which the molten resin is injected and injected into the cavity from the rear gate after reaching the rear gate, injection injection is performed from the front gate by utilizing the gate valve of the rear gate. This prevents the trapped air from being trapped in the sprue part of the rear gate by the molten resin, and the deterioration of the strength of the molded product and the appearance of the molded product surface due to the air being mixed into the molten resin. It is to be able to prevent it.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, before the molten resin injected into the cavity from the leading gate reaches the trailing gate, the trailing gate valve is opened at least for a while. The sprue portion was filled with molten resin, so that no air pool was generated in the sprue portion.
[0008]
Specifically, in the invention of claim 1, a plurality of gates provided along the parting line provided to communicate with the common cavity, a plurality of sprue portions communicating with the corresponding gates, Using an injection mold having a plurality of gate valves provided upstream of the corresponding sprue parts, the injection order of the molten resin is determined in advance for the plurality of gates, and the molten resin is injected into the cavity from the gate of the previous order. An injection molding method in which molten resin is injected and injected from the rear gate to the cavity after the flow head reaches the rear gate after injection.
[0009]
Then, before the flow of the molten resin injected and injected from the preceding gate into the cavity reaches the rear gate, the gate valve corresponding to the rear gate is temporarily opened to allow the molten resin to flow in the vicinity of the gate cavity. The gate valve is closed after injection injection so as to be filled to the position .
[0010]
In the above configuration, of the plurality of gates of the injection mold, the molten resin injected and injected from the preceding gate into the cavity eventually reaches the subsequent gate. At that time, before the flow of the molten resin reaches the downstream gate, the gate valve corresponding to the downstream gate is once opened so that the molten resin is filled from the gate to a position near the cavity of the gate. The gate valve closes after injection injection. As a result, when the flow of molten resin injected and injected from the preceding gate reaches the rear gate, at least the sprue portion of the rear gate is already filled with the molten resin. The situation where air stagnation occurs is avoided. Furthermore, the air in the rear-order gate can pass through the injection-molding parting line to the outside of the injection-mold, and hardly remains. Compared with the case where the molten resin injected and injected flows into the downstream gate to discharge the air in the downstream gate, the molten resin injected and injected from the downstream gate into the downstream gate Air is less likely to enter and enter the cavity.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0012]
1 and 2 show an injection molding process according to an embodiment of the present invention, and this injection molding process is used for manufacturing a resin front bumper for an automobile shown in FIG.
[0013]
In this injection molding process, an injection mold A having three gates is used. The injection mold A includes a first mold 1 as a movable mold provided so as to be movable in the opening / closing direction of the injection mold A (left and right direction in FIGS. 1 and 2), and a fixed provided so as not to move. The mold 2 comprises a second mold 2 as a mold, and the injection mold A is opened and closed by moving the first mold 1 in the opening and closing direction relative to the second mold 2 by a mold clamping device (not shown). It has come to be.
[0014]
The mating surface of the first mold 1 with the second mold 2 communicates with a cavity for forming the cavity 3 along the parting line L between the molds 1 and 2 and the cavity 3. Each of the recesses for forming the three gates 4, 4,... (FIG. 1 and FIG. 2 shows only one later-order gate 4 to be described later) along the parting line L is also provided. ing.
[0015]
On the other hand, a hot runner block 5 is attached to a side of the second mold 2 opposite to the first mold 1 (left side in FIGS. 1 and 2). A hot runner 6 for guiding the molten resin J supplied from the injection molding machine to the injection mold A to each gate 4 is formed. The downstream side of the hot runner 6 in the resin passage direction is branched into three so as to correspond to each gate 4, and a gate valve 7 is provided at each downstream end of the hot runner 6. Each of these gate valves 7 communicates with a corresponding gate 4 via a sprue portion 8.
[0016]
Specifically, the nozzles 10 are respectively arranged on the downstream end sides of the hot runner 6. Each nozzle 10 is provided in the second molding die 2 so as to penetrate the molding die 2 in the opening / closing direction of the injection molding die A, and the end surface upstream of the resin passage direction is the second molding of the hot runner block 5. The end surface on the downstream side is flush with the mating surface of the second mold 2 with the first mold 1 while being joined to the surface on the mold 2 side. A valve seat 11 having a small-diameter resin passage hole 11a is provided in the center of each nozzle 10 in the resin passage direction. The upstream side of the valve seat 11 in the nozzle 10 has a cross-sectional shape that is substantially constant in the resin passage direction, and the downstream end portion of the hot runner 6 is configured by this upstream side portion. On the other hand, the downstream side in the nozzle 10 is formed in a tapered cross section whose inner diameter gradually increases in the resin passage direction, and the sprue portion 8 is constituted by this downstream side portion.
[0017]
A valve body 12 for opening and closing the resin passage hole 11 a of the valve seat 11 is disposed on the upstream side of each valve seat 11. The valve body 12 penetrates the hot runner block 5 and is provided so as to be movable back and forth with respect to the valve seat 11. The gate valve 7 is configured by the valve seat 11 and the valve body 12. Further, on the opposite side of the hot runner block 5 from the second mold 2, drive means 13 (for example, an electromagnetic type, a hydraulic type, a vacuum type, etc.) for moving the valve body 12 back and forth is installed. Then, as shown by the left-pointing arrow in FIG. 1, the valve body 12 moves backward to open the resin passage hole 11 a of the valve seat 11, so that the molten resin J in the hot runner 6 passes through the gate 4. While being injected and injected into the cavity 3, as indicated by a right-pointing arrow in FIG. 2, the valve body 12 moves forward to close the resin passage hole 11a, thereby allowing the molten resin J to pass through the resin passage hole 11a. It comes to stop.
[0018]
In the injection mold A, the gates 4, 4,... Are arranged so as to correspond to the central portion and both side portions of the resin front bumper as schematically shown in FIG. It is a rear view showing only the right side portion of the front bumper, and the left side portion is not shown). In these three gates 4, 4,..., The order of injection and injection of the molten resin J is determined in advance, the gate 4 in the central part is determined in the first order, and the gates 4 in both side parts are determined in the subsequent order. ing.
[0019]
In the present embodiment, before the flow front of the molten resin J injected and injected into the cavity 3 from the prior gate 4 reaches the rear gate 4, the gate valve 7 corresponding to the rear gate 4. The gate valve 7 is closed after the injection valve is injected and injected so that the molten resin J is filled up to the position near the cavity 3 in the succeeding gate 4.
[0020]
Here, the procedure for injection molding a resin front bumper using the injection mold A configured as described above will be described.
[0021]
After the first mold 1 is moved in the closing direction by the mold clamping device and the mold is clamped, first, the molten resin J is supplied to the hot runner 6 of the injection mold A by the injection molding machine. At the same time, the corresponding gate valve 7 is opened in the leading gate 4 corresponding to the central portion of the resin front bumper, and the molten resin J is injected and injected into the cavity 3. Thereby, the molten resin J injected and injected into the cavity 3 is gradually filled from the central part of the cavity 3 toward both side parts as shown by arrows in FIG.
[0022]
At this time, the gate valve 7 corresponding to the rear order gate 4 is temporarily opened before the flow of the molten resin J injected and injected from the previous order gate 4 reaches the rear order gate 4. As a result, first, the molten resin J is filled in the sprue portion 8 corresponding to the rear rank gate 4, and then, when the molten resin J is filled to the position near the cavity 3 in the rear rank gate 4, The gate valve 7 is closed. Then, after the flow of molten resin J injected and injected from the leading gate 4 reaches the trailing gate 4, the gate valve 7 corresponding to the trailing gate 4 is opened again. The molten resin J is injected and injected from the gate 4 into the cavity 3.
[0023]
As described above, after the molten resin J filled in the cavity 3 is solidified, the first mold 1 is moved in the opening direction by the operation of the mold clamping device. Then, the resin front bumper as a molded product is removed in a state where the cured resins in the gates 4, 4,... And the sprue portions 8, 8,.
[0024]
Therefore, according to the present embodiment, there are three gates 4, 4,..., One gate 4 in the first order, and the remaining two gates 4, 4 in the second order. Injection molding of a resin front bumper in which the molding resin A is used to inject and inject the molten resin J from the preceding gate 4 to the cavity 3 and then inject and inject the molten resin J from each succeeding gate 4 to the cavity 3. In the process, before the flow of the molten resin J injected and injected from the prior gate 4 reaches the rear gate 4, the gate valve 7 corresponding to the rear gate 4 is temporarily opened to remove the molten resin J. Since the gate valve 7 is closed after filling the position in the vicinity of the cavity 3 in the rear-order gate 4, the sprue of each rear-order gate 4 by the molten resin J injected and injected from the front-order gate 4. In addition to avoiding the occurrence of air stagnation in the portion 8, when the molten resin J injected and injected from the preceding gate 4 flows into the succeeding gate 4, the succeeding gate It is also possible to avoid a situation in which the air K in the nozzle 4 remains from the parting line L between the molding dies 1 and 2 to the outside of the injection molding die A. When the molten resin J is injected and injected from 4, the strength of the front bumper made of resin and the appearance of the surface are prevented from being deteriorated due to the air K entering the molten resin J and entering the cavity 3. be able to.
[0025]
In the above embodiment, the case of the injection mold A having three gates 4, 4,... Is explained. However, the present invention is an injection molding in which two gates or four or more gates are provided. The present invention can also be applied to an injection molding method that uses a mold.
[0026]
Furthermore, in the above-described embodiment, the case of injection molding of a resin-made front bumper for automobiles has been described. However, the present invention is applicable to various molded products such as instrument panels, door trims, and air spoilers in the field of automobiles. It can be applied to an injection molding method.
[0027]
【The invention's effect】
As described above, according to the first aspect of the present invention, the injection mold having a plurality of gates is used, and the molten resin is injected and injected from the preceding gate to the cavity and then melted from the subsequent gate to the cavity. In the injection molding method in which resin is injected and injected, before the flow of molten resin injected and injected from the previous gate reaches the rear gate, the gate valve corresponding to the rear gate is temporarily opened. since so as to fill the molten resin to a cavity near the position of the gate Te, if the destination by ranking injection injected molten resin from the gate of it is possible to avoid a situation that the air reservoir is generated within the sprue portion Runomi First, when the molten resin injected and injected from the first-order gate flows into the second-order gate, the air in the gate is discharged from the parting line of the injection mold. It is possible to avoid a situation that remains not completely escape the parts, therefore, due to the fact that the air in the molten resin is injected injected from the subordinated gate from entering the cavity by mixing the molten resin It is possible to prevent the strength of the molded product from being reduced and the appearance of the molded product from being lowered.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 temporarily opens a gate valve of a rear-order gate before the flow of molten resin injected into a cavity from a prior-order gate reaches a rear-order gate in an injection molding process according to an embodiment of the present invention. It is a principal part expanded sectional view of the injection mold which shows the state.
FIG. 2 shows a state in which the gate resin corresponding to the rear order gate is closed before the rear order gate is filled with molten resin and the molten resin injected and injected from the front order gate reaches the rear order gate. FIG.
FIG. 3 is a rear view schematically showing the arrangement of a first-order gate and a rear-order gate with respect to an automotive resin front bumper.
FIG. 4 shows a state in which molten resin injected and injected from a prior gate in a conventional injection molding process flows into a rear gate and an air pool is generated in the sprue portion of the rear gate. FIG.
FIG. 5 is a view corresponding to FIG. 1 showing a state in which air in the sprue portion enters the molten resin and enters the cavity when the molten resin is injected and injected from the rear-order gate.
[Explanation of symbols]
3 Cavity 4 Gate 7 Gate valve 8 Sprue part A Injection mold L Parting line J Molten resin K Air

Claims (1)

A plurality of gates formed along the parting line and connected to a common cavity, a plurality of sprue portions communicating with the corresponding gate, and provided upstream of the corresponding sprue portion Using an injection mold having a plurality of gate valves, the injection order of the molten resin is determined in advance in the plurality of gates, and the molten resin is injected and injected into the cavity from the preceding gate. In the injection molding method in which the molten resin is injected and injected from the rear gate to the cavity after reaching the rear gate,
Before the flow of molten resin injected and injected into the cavity from the preceding gate reaches the latter gate, the gate valve corresponding to the latter gate is temporarily opened to allow the molten resin to flow into the latter gate. An injection molding method characterized in that the gate valve is closed after injection injection so as to fill up to a position near the cavity .

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