JPH09174607A - Method for injection molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate occurrence of a weld line in a molded article. SOLUTION: Resin passing through a first runner 26 is filled in a cavity space 23 through a first gate 27, while the resin passing through a second runner 28 is filled in the cavity space 23 through a second gate 29 provided at a different position from the first gate 27. The timing at which the filling is started through the second gate 29 is set to be later than that at which the filling is started through the first gate 27. The pressure of the resin filled through the second gate 29 is higher than that of the resin filled through the first gate 27, and when a pressure difference occurs, the resin joins in the part of a weld line in a state wherein the pressure difference is present. The direction of molecular orientation in the part of the weld line is changed to the direction of flow from the direction perpendicular thereto and the resin flows.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to an injection molding method.

[0002]

2. Description of the Related Art Conventionally, in an injection molding machine, a resin is heated and melted in a heating cylinder of an injection device and is injected from an injection nozzle. Then, the injected resin passes through the sprue and runner of the mold and fills the cavity space through the gate. Next, a molded product is molded by cooling and solidifying the resin in the cavity space.

[0003]

However, in the above-mentioned conventional injection molding method, since a weld line is generated, the appearance of the molded product is deteriorated. Therefore, painting is required to improve the appearance of the molded product. Further, if a weld line occurs, the strength of the molded product will be reduced accordingly.

FIG. 2 is a first diagram showing a flow front in a mold in a conventional injection molding method, and FIG. 3 is a second diagram showing a flow front in a mold in a conventional injection molding method. In the figure, 10 is a sprue, 11 is a runner,
12 is a gate, 13 is a cavity space, and Ff is a resin flow front. Arrow A from the injection nozzle (not shown)
The resin injected in the direction passes through the sprue 10 and the runner 11, and is filled in the cavity space 13 in the direction of the arrow B through the gate 12.

By the way, when there is an obstacle, for example, the core pin 15 in the cavity space 13, the resin is divided into two parts in front of the core pin 15, flows so as to wrap the core pin 15, and joins again. At this time, a weld line 14 is generated at the resin merging portion. After that, the resin is completely filled in the cavity space 13. In the injection molding method having the above structure, the weld line 14 is adjusted by adjusting the speed of filling the cavity space 13 with resin.
Can be suppressed, but not completely eliminated.

Next, an injection molding method in which the cavity space is filled with resin through the two gates will be described. FIG. 4 is a first diagram showing a flow front in a mold in another conventional injection molding method, and FIG. 5 is a second diagram showing a flow front in a mold in another conventional injection molding method.
FIG. 6 is a third diagram showing a flow front in a mold in another conventional injection molding method.

In the figure, 11a is a first runner and 11b.
Is a second runner, 12a is a first gate, 12b is a second gate, 13 is a cavity space, 15 is a core pin, and Ff is a resin flow front. The resin injected from the injection nozzle (not shown) passes through the first runner 11a on the one hand and is filled in the cavity space 13 in the direction of the arrow C via the first gate 12a, while passing through the second runner 11b on the other hand and The cavity space 13 is filled in the direction of arrow D through the two gates 12b.

By the way, an obstacle such as the core pin 1 is provided on the side of the second gate 12b in the cavity space 13.
When there is 5, the resin filled in the cavity space 13 through the second gate 12b is divided into two before the core pin 15, flows so as to wrap the core pin 15, and joins again.
At this time, a weld line 14 is generated at the resin merging portion.

Then, the resin merges with the resin filled in the cavity space 13 through the first gate 12a to generate a weld line 16 at the merged portion. SUMMARY OF THE INVENTION It is an object of the present invention to provide an injection molding method that solves the problems of the conventional injection molding method described above and can eliminate the occurrence of weld lines in a molded product.

[0010]

Therefore, in the injection molding method of the present invention, the resin that has passed through the first runner is filled in the cavity space through the first gate and the resin that has passed through the second runner is filled. , The cavity space is filled through a second gate arranged at a position different from the first gate.

The timing at which filling is started via the second gate is set later than the timing at which filling is started via the first gate. In another injection molding method of the present invention, further, an opening / closing pin is provided in the second runner, and the opening / closing pin is opened,
Filling is started via the second gate.

In yet another injection molding method of the present invention, the opening / closing pin is opened while vibrating. In still another injection molding method of the present invention, the opening / closing pin is opened / closed by a drive source different from the drive source of the ejector pin. In yet another injection molding method of the present invention, a cold slag well is further formed in the resin flow direction downstream of the opening / closing pin in the second runner.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 1 is a cross-sectional view of a mold according to an embodiment of the present invention, FIG. 7 is a vertical cross-sectional view of a mold according to an embodiment of the present invention, and FIG. 8 is a schematic program diagram of a mold according to the embodiment of the present invention. Is. In addition,
In FIG. 8, the horizontal axis represents time and the vertical axis represents the input signal of the proportional pressure reducing valve.

In the figure, 51 is a fixed side mounting plate,
The fixed mold 52 is attached to a fixed platen (not shown) via the fixed side attachment plate 51. The injection nozzle of the injection device (not shown) is advanced in the injection process, and the tip of the injection nozzle is brought into contact with the sprue bush 53 of the fixed mold 52. On the other hand, the movable platen (not shown) is moved back and forth (moved in the left-right direction in the figure) by a mold clamping device (not shown) to bring the movable mold 54 into and out of contact with the fixed mold 52. Therefore, the movable mold 54 is
It is attached to the movable platen via a movable side attachment plate 55 and a spacer block (not shown).

The resin injected from the injection nozzle passes through the sprue 21, flows through the first runner 26 in the direction of arrow E, and is filled in the cavity space 23 through the first gate 27. Then, it flows in the direction of arrow F through the second runner 28 and is filled in the cavity space 23 through the second gate 29. Therefore, the second gate 2
9 is arranged at a position different from the first gate 27, for example, at a position facing the first gate 27.

When the injection process is completed, a pressure holding process is subsequently performed to increase the resin pressure in the cavity space 23, the resin cooling is started, and after a certain period of time, a molded product (not shown) is formed on the movable mold 54 side. The mold is opened while leaving the mark, and the molded product is pushed down. Therefore, the sprue lock pin 57 and the ejector pin 58 are provided. The sprue lock pin 57 has the sprue 21
And the molded product is held when the mold is opened and left on the movable mold 54 side. In addition, the ejector pin 58
Is disposed with the tip facing the cavity space 23, and the molded product is pushed down from the movable mold 54 after the mold is opened.

The sprue lock pin 57 and the ejector pin 58 penetrate the movable mold 54 and extend rearward (toward the mold clamping device), and the head portions formed at the rear end are narrowed by the ejector plates 61 and 62, respectively. Held and fixed. Then, a rod 63 can be brought into contact with the ejector plates 61, 62, and the sprue lock is moved as the rod 63 is advanced by an ejector cylinder (not shown) as a first drive source. The pin 57 and the ejector pin 58 are advanced.

In addition, in order to retract the sprue lock pin 57 and the ejector pin 58, four return pins 45 are provided, and a return spring 46 surrounding the return pin 45 is provided with an ejector plate 61 and a movable member. It is arranged between the mold 54. By the way, if there is an obstacle, for example, the core pin 25 on the second gate 29 side in the cavity space 23, the core pin 25
A weld line is generated in the resin merging portion on the further downstream side.

Further, the resin merges with the resin filled in the cavity space 23 through the first gate 27 to further generate a weld line in the merged portion. Therefore, the opening / closing pin 31 is arranged at a predetermined position of the second runner 28 so as to be movable back and forth. The open / close pin 31 is connected to the second runner 2
8 is disposed with its front end facing, and extends rearward through the movable mold 54 and the ejector plates 61 and 62, and the respective head portions formed at the rear ends are open / close plates 67 and 6.
It is clamped by 8 and fixed.

The opening / closing plates 67 and 68 are arranged so as to be able to come into contact with and separate from the movable side mounting plate 55, and are moved forward and backward by two opening / closing cylinders 72. The opening / closing cylinder 7
The second pressure rod 73 penetrates the cross head 74 and the movable side mounting plate 55 and is in contact with the opening / closing plate 68, and the opening / closing pin 31 is operated by operating the opening / closing cylinder 72 as a second drive source. You can stick it out.

The hydraulic pressure supplied to the opening / closing cylinder 72 is controlled by a proportional pressure reducing valve or a servo valve (not shown). By electrically controlling the proportional pressure reducing valve or the servo valve, the opening / closing pin 31 can be moved forward to close the second runner 28, or can be moved backward to open the second runner 28. In addition, four return pins 69 are arranged to retract the opening / closing pin 31, and a return spring 70 surrounding the return pins 69 is arranged between the opening / closing plate 67 and the movable mold 54. To be done. The opening / closing pin 31 and the return pin 69 have head portions respectively formed at their ends, and the head portions are sandwiched and fixed by the opening / closing plates 67 and 68, respectively.

Reference numeral 30 is a bent portion P1 of the second runner 28.
It is a cold slag well formed in. The cold slug well 30 is formed downstream of the opening / closing pin 31 in the second runner 28 in the resin flow direction. Further, in FIG. 8, T _d is a forward start delay time, T _a is a forward time, T _b is a cycle time, T ₃ is a primary pressurizing time, and T ₃ is
₄ is the secondary pressurizing time, P ₁ is the initial exciting force, P ₂ is the final exciting force, P ₃ is the primary applying force, P ₄ is the secondary applying force, and ΔP is the depressurizing force.

In this case, the proportional pressure reducing valve generates hydraulic pressure in a pattern as shown in FIG.
When it is supplied to 2, the open / close pin 31 is opened while vibrating at a frequency of several to 10 [Hz]. The opening / closing pin 31 can be opened without vibrating. Further, although the open / close cylinder 72 is used as the second drive source in the present embodiment, an air cylinder, an electric motor, or the like may be used instead of the open / close cylinder 72.

Next, the operation of the mold having the above construction will be described. FIG. 9 is a first diagram showing a flow front in a mold according to an embodiment of the present invention, FIG. 10 is a second diagram showing a flow front in a mold according to an embodiment of the present invention, and FIG. 11 is a book. It is a 3rd figure which shows the flow front in a metal mold | die in embodiment of invention.

In the figure, 26 is a first runner, 28 is a second runner, 27 is a first gate, 29 is a second gate, and 23.
Is a cavity space, 25 is a core pin, and Ff is a resin flow front. The resin injected from the injection nozzle (not shown) passes through the sprue 21 (FIG. 1), then passes through the first runner 26, and is filled in the cavity space 23 in the direction of arrow G through the first gate 27. At this time, the opening / closing pin 31 is closed and the resin is not sent to the second gate 29.

When the resin flow front Ff reaches the front of the core pin 25, the opening / closing pin 31 is opened while vibrating. At this time, the resin (cold slag) in contact with the opening / closing pin 31 is pushed into the cold slag well 30, and only the molten resin passes through the second runner 28 and the cavity via the second gate 29. The space 23 is filled in the direction of arrow H.

By the way, the resin filled through the first gate 27 is divided into two before the core pin 25,
They are merged again to generate a weld line 81. However, the pressure of the resin filled through the second gate 29 is
Since the opening / closing pin 31 has just been opened, the pressure difference is higher than the pressure of the resin filled through the first gate 27 and reaching the downstream side of the core pin 25.

Therefore, in the portion of the weld line 81, the resin filled through the second gate 29 and the first
The resin filled through the gate 27 joins with a pressure difference. In this case, the direction of molecular orientation in the portion of the weld line 81 is changed from the direction perpendicular to the flow direction to the flow direction, and the resin flows. As a result, the weld line 81 can be eliminated.

If the opening / closing pin 31 is opened while vibrating, the resin in the weld line 81 will flow further, so that the weld line 81 can be completely eliminated. In the present embodiment, when the resin flow front Ff reaches the front of the core pin 25, the opening / closing pin 3
1 is opened while vibrating, but the open / close pin 31 is opened at a predetermined timing from when the filling of the resin into the cavity space 23 is started to when the pressure holding is started.
Can also be opened.

Further, by changing the timing of opening the open / close pin 31, it is possible to suppress the generation of the weld line 81 and change the position of the weld line 81 without completely eliminating the weld line 81. You can also It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention.

[0031]

As described above in detail, according to the present invention, in the injection molding method, the resin passing through the first runner is filled into the cavity space through the first gate, and the second runner is filled. The resin that has passed through is filled in the cavity space through a second gate arranged at a position different from the first gate.

The timing at which the filling is started via the second gate is set later than the timing at which the filling is started via the first gate. In this case, first, the resin passing through the first runner is , The cavity space is filled through the first gate, and then the resin that has passed through the second runner is filled in the cavity space through the second gate.

At this time, the pressure of the resin filled through the second gate is higher than the pressure of the resin filled through the first gate, and a pressure difference is generated. The resin filled through the gate and the resin filled through the first gate join together with a pressure difference. Then, the direction of the molecular orientation of the weld line portion is changed from the direction perpendicular to the flow direction to the flow direction, and the resin flows, so that the weld line can be eliminated.

In another injection molding method of the present invention, an opening / closing pin is further provided in the second runner, and by opening the opening / closing pin, filling is started via the second gate. In this case, by changing the timing of opening the open / close pin, it is possible to suppress the occurrence of a weld line in the molded product or change the position of the weld line.

In still another injection molding method of the present invention, the open / close pin is opened while vibrating. In this case, the resin in the weld line portion further flows due to the vibration of the opening / closing pin, so that the weld line can be completely eliminated. In yet another injection molding method of the present invention, a cold slag well is further formed in the resin flow direction downstream of the opening / closing pin in the second runner.

In this case, when the open / close pin is opened, the cold slag can be pushed into the cold slag well to fill only the melted resin into the cavity space.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold according to an embodiment of the present invention.

FIG. 2 is a first diagram showing a flow front in a mold in a conventional injection molding method.

FIG. 3 is a second diagram showing a flow front in a mold in a conventional injection molding method.

FIG. 4 is a first diagram showing a flow front in a mold in another conventional injection molding method.

FIG. 5 is a second diagram showing a flow front in a mold in another conventional injection molding method.

FIG. 6 is a third diagram showing a flow front in a mold in another conventional injection molding method.

FIG. 7 is a vertical cross-sectional view of a mold according to the embodiment of the present invention.

FIG. 8 is a schematic diagram of a mold program according to the embodiment of the present invention.

FIG. 9 is a first diagram showing a flow front in the mold according to the embodiment of the present invention.

FIG. 10 is a second diagram showing the flow front in the mold according to the embodiment of the present invention.

FIG. 11 is a third diagram showing the flow front in the mold according to the embodiment of the present invention.

[Explanation of symbols]

 23 Cavity space 26 1st runner 27 1st gate 28 2nd runner 29 2nd gate 30 Cold slug well 31 Open / close pin 58 Ejector pin 72 Open / close cylinder

Claims (5)

[Claims] 1. A resin that has passed through a first runner is
The cavity space is filled through a gate, and (b) the resin that has passed through the second runner is filled in the cavity space through a second gate arranged at a position different from that of the first gate. ) The injection molding method, wherein the timing of starting the filling through the second gate is set later than the timing of starting the filling through the first gate. 2. An opening / closing pin is provided in the second runner,
The injection molding method according to claim 1, wherein filling is started via the second gate by opening the opening / closing pin. 3. The injection molding method according to claim 2, wherein the opening / closing pin is opened while vibrating. 4. The injection molding method according to claim 2, wherein the opening / closing pin is opened / closed by a drive source different from a drive source of the ejector pin. 5. The injection molding method according to claim 2, wherein a cold slug well is formed in the resin flow direction on the downstream side of the opening / closing pin in the second runner.